Displays

Nitrogen oxides (NOx) and ammonia (NH₃) from anthropogenic and biogenic emissions are central contributors to particulate matter (PM) concentrations worldwide. Ecosystem productivity can also be strongly modulated by the atmospheric deposition of this inorganic "reactive nitrogen" nutrient. The response of PM and nitrogen deposition to changes in the emissions of both compounds is typically studied on a case-by-case basis, owing in part to the complex thermodynamic interactions of these aerosol precursors with other PM constituents. In the absence of rain, much of the complexity of nitrogen deposition is driven by the large difference in dry deposition velocity when a nitrogen-containing molecule is in the gas or condensed phase.

Here we present a simple but thermodynamically consistent approach that expresses the chemical domains of sensitivity of aerosol particulate matter to NH₃ and HNO₃ availability in terms of aerosol pH and liquid water content. From our analysis, four policy-relevant regimes emerge in terms of sensitivity: i) NH₃-sensitive, ii) HNO₃-sensitive, iii) combined NH₃ and HNO₃ sensitive, and, iv) a domain where neither NH₃ and HNO₃ are important for PM levels (but only nonvolatile precursors such as NVCs and sulfate). When this framework is applied to ambient measurements or predictions of PM and gaseous precursors, the “chemical regime” of PM sensitivity to NH3 and HNO3 availability is directly determined. 

The same framework is then extended to consider the impact of gas-to-particle partitioning, on the deposition velocity of NH₃ and HNO₃ individually, and combined affects the dry deposition of inorganic reactive nitrogen. Four regimes of deposition velocity emerge: i) HNO₃-fast, NH₃-slow, ii) HNO₃-slow, NH₃-fast, iii) HNO₃-fast, NH₃-fast, and, iv) HNO₃-slow, NH₃-slow. Conditions that favor strong partitioning of species to the aerosol phase strongly delay the deposition of reactive nitrogen species and promotes their accumulation in the boundary layer and potential for long-range transport. 

The use of these regimes allows novel insights and is an important tool to evaluate chemical transport models. Most notably, we find that nitric acid displays considerable variability of dry deposition flux, with maximum deposition rates found in the Eastern US (close to gas-deposition rates) and minimum rates for North Europe and China. Strong reductions in deposition velocity lead to considerable accumulation of nitrate aerosol in the boundary layer –up to 10-fold increases in PM2.5 nitrate aerosol, eventually being an important contributor to high PM2.5 levels observed during haze episodes. With this new understanding, aerosol pH and associated liquid water content can be understood as control parameters that drive PM formation and dry deposition flux and arguably can catalyze the accumulation of aerosol precursors that cause intense haze events throughout the globe.

How to cite: Nenes, A., Kanakidou, M., Pandis, S., Russell, A., Song, S., Vasilakos, P., and Weber, R.: Aerosol acidity as a driver of aerosol formation and nutrient deposition to ecosystems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21227, https://doi.org/10.5194/egusphere-egu2020-21227, 2020.

The inorganic composition of aerosol impacts numerous chemical and physical processes and properties. However, many chemical transport models show large variability in both the concentration of the inorganic aerosols and their precursors (up to 3 orders of magnitude differences) and the inorganic aerosol composition. Different models predict very different properties (e.g., aerosol liquid water concentration and aerosol acidity) and outcomes (e.g., heterogeneous uptake of gases or aerosols’ direct and indirect impacts on climate). Here, we use airborne observations from campaigns conducted around the world to investigate how the inorganic fine aerosol (PM₁) composition, and one of its key parameters, aerosol acidity, changes from polluted regions (Mexico City, Los Angeles, Northeastern US, and Seoul) to remote ocean basins (the Atmospheric Tomography campaigns 1 and 2) in order to provide constraints for the chemical transport models. I find that the empirical ammonium balance with major ions (ammonium balance = mol NH₄ / (2×mol SO₄ + mol NO₃)) rapidly decreases from ~1 at the highest inorganic PM₁ concentration to 0 at the lowest inorganic PM₁. The data indicate a robust trend for ammonium balance vs inorganic PM₁ at all altitude levels in the troposphere, suggesting that NH₃ emissions and subsequent neutralization of H₂SO₄ becomes negligible in the most remote (lowest inorganic PM₁) regions. Further, a robust trend for PM₁ pH (calculated with E-AIM) vs inorganic PM₁ is observed at all levels for these campaigns, as well, decreasing from a pH of ~3 to a pH of ~ –1 from the highest to lowest inorganic PM₁. The data overall implies very low NH₃ (and NH₄⁺) throughout most of the atmosphere, contrary to predictions of some models, implying different physical properties than predicted in models. We compare these trends of ammonium balance and pH vs inorganic PM₁ against 9 chemical transport models (CTMs), and we find that the CTMs show large variability for both the ammonium balance and pH vs inorganic PM_­1, compared to observations. Generally, we find a high bias in the ammonium balance and pH, likely due to too much NH_­3 in model (possibly too high NH₃ emissions over oceans or too long lifetime) and inclusion of externally mixed seasalt into the submicron pH calculation. These results overall would imply different aerosol properties in the models than observed, impacting the chemistry, optical properties, and cloud properties.

How to cite: Nault, B. A., Campuzano-Jost, P., Jo, D., Day, D., Bahreini, R., Bian, H., Chin, M., Clegg, S., Colarco, P., Kodros, J., Lopez-Hilfiker, F., Marais, E., Middlebrook, A., Neuman, A., Nowak, J., Pierce, J., Thornton, J., Tsigaridis, K., and Jimenez, J. and the ATom Science Team: Global Survey of Aerosol Acidity from Polluted to Remote Locations: Measurements and Comparisons with Global Models, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11366, https://doi.org/10.5194/egusphere-egu2020-11366, 2020.

The dependence of aerosol acidity on particle size, location and altitude over Europe during a summertime period is investigated using the hybrid version of aerosol dynamics in the chemical transport model PMCAMx. The pH changes more with particle size in northern and southern Europe owing to the enhanced presence of non-volatile cations (Na, Ca, K, Mg) in the larger particles. Differences of up to 1-4 pH units are predicted between sub- and super-micron particles, while the average pH of PM_1-2.5 can be as much as 1 unit higher than that of PM₁. Most aerosol water over continental Europe is associated with PM₁, while PM_2.5-5 and PM_5-10 dominate the water content in the marine and coastal areas due to the relatively higher levels of hygroscopic sea salt. Particles of all sizes become increasingly acidic with altitude (0.5-2 units pH decrease over 2.5 km) primarily because of the decrease in aerosol liquid water content (driven by humidity changes) with height. Inorganic nitrate is strongly affected by aerosol pH with the highest average nitrate levels predicted for the PM_2.5-5 range and over locations where the pH exceeds 3. Dust tends to increase aerosol water levels, aerosol pH and nitrate concentrations for all particle sizes. This effect of dust is quite sensitive to its calcium content. The size-dependent pH differences carry important implications for pH-sensitive processes in the aerosol.

How to cite: Pandis, S., Zakoura, M., Kakavas, S., and Nenes, A.: Size-resolved aerosol pH over Europe during summer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5739, https://doi.org/10.5194/egusphere-egu2020-5739, 2020.

The fourth phase of the Air Quality Model Evaluation International Initiative (AQMEII-4) is a regional air-quality model intercomparison for North American and European domains, with a focus on acidifying deposition. The study protocol includes enhanced model outputs for acidic gas deposition resistances and conductances, and particle and aqueous phase deposition, and hence will provide an unprecedented estimation both of the variability in model predictions for the deposition of acidifying species, and indications of the reasons for model variability. All models make use of common lateral boundary conditions and emissions data. Model simulations are being conducted for the years 2009 and 2010 for the European domain, and 2010 and 2016 for the North American domain. Model outputs were reported on a common grid 0.125^o grid cell size domain in each of these domains, as well as at the latitude and longitude locations of receptor observation stations in the ENSEMBLE database format, and are uploaded to a common database for comparison at the Joint Research Centre at Ispra.

The Global Environmental Multiscale – Modelling Air-quality and CHemistry (GEM-MACH) is Environment and Climate Change Canada’s air-quality modelling system, and is a participant in AQMEII-4, with simulations taking place on a 10km grid cell size domain covering North America. Several GEM-MACH simulations are underway for the AQMEII-4 campaign, including both the model’s research and operational configurations, based on the most recent version of the model code (GEM-MACHv3). The operational version of the model is optimized for rapid computation, making use of a 2-bin particle size distribution with occasional rebinning to/from 12-bin when necessary for improved particle microphysics accuracy. The research version of the model incorporates fully coupled chemistry (direct and indirect effects) with the P3 cloud parameterization, forest canopy shading and turbulence, revised anthropogenic plume rise, emitted and transported methane, modulation of particle crustal material by meteorology, the KPP/RODAS3 gas-phase solver, ammonia bi-directional fluxes, satellite-derived leaf area index data, a 12-bin particle size distribution, a revised parameterizations for some of the gas-phase resistances, and six additional particulate species (base cations, iron and manganese).

In addition to providing a status update on the AQMEII-4 ensemble simulations, we focus here on the simulations of the research version of GEM-MACH, for the years 2010 and 2016. The annual total values of acidifying sulphur and nitrogen’s deposition components will be compared for this time period, and the AQMEII-4 diagnostics will be used to show the relative contributions of GEM-MACH’s gas-phase resistances and conductances towards total gas-phase deposition. The gas-phase values will also be compared to the annual average lowest model layer molar concentrations of the depositing species, to determine the extent to which acidity in the atmosphere tracks atmospheric concentrations. In addition, we will also examine the relative impact of base cations on average atmospheric acidity and deposition and the extent to which the transportable versus non-transportable fractions of fugitive dust emissions may influence net acidic deposition. We will also exceedances of critical loads based on the simulation totals of sulphur and nitrogen deposition and critical load ecosystem data.

How to cite: Makar, P. A., Akingunola, A., Zhang, J., Pabla, B., Zheng, Q., Moran, M. D., Cheung, P., Aherne, J., Clifton, O., Schwede, D., Bianconi, R., Bellasio, R., Hogrefe, C., and Galmarini, S.: Atmospheric Acidity over North America: GEM-MACH Simulations for AQMEII-4, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2774, https://doi.org/10.5194/egusphere-egu2020-2774, 2020.

Water soluble organic carbon (WSOC) is a ubiquitous and significant fraction of fine particulate matter.  Despite advances in aerosol thermodynamic equilibrium models, there is limited understanding on the comprehensive impacts of WSOC on aerosol acidity (pH).  We address this limitation by studying submicron aerosol that represent the two extremes in acidity levels found in the atmosphere: strongly acidic aerosol from Baltimore, MD, and weakly acidic conditions characteristic of Beijing, China. These cases are then used to construct mixed inorganic/organic single-phase aqueous particles, and thermodynamically analyzed by the E-AIM and ISORROPIA models in combination with activity coefficient model AIOMFAC to evaluate the effects of WSOC on the H⁺ ion activity coefficients (γ_H+) and activity (pH).  We find that addition of organic acids and non-acid organic species concurrently increases γ_H+ and aerosol liquid water.  Under the highly acidic conditions typical of the eastern U.S. (inorganic-only pH ~1), these effects mostly offset each other, giving pH changes of < 0.5 pH units even at organic aerosol dry mass fractions in excess of 60%.  Under conditions with weaker acidity typical of Beijing (inorganic-only pH ~4.5), the non-acidic WSOC compounds had similarly minor effects on aerosol pH, but organic acids imparted the largest changes in pH compared to the inorganic-only simulations.  Organic acids affect pH in the order of their pKa values (oxalic acid > malonic acid > glutaric acid).  Although the inorganic-only pH was above the pK_a value of all three organic acids investigated, pH changes in excess of 1 pH unit were only observed at unrealistic organic acid levels (aerosol organic acid concentrations > 35 µg m^-3) in Beijing.  The model simulations were run at 70%, 80%, and 90% relative humidity (RH) levels and the effect of WSOC was inversely related to RH.  At 90% RH, WSOC altered aerosol pH by up to ~0.2 pH units, though the effect was up to ~0.6 pH units at 70% RH.  The somewhat offsetting nature of these effects suggests that aerosol pH is sufficiently constrained by the inorganic constituents alone under conditions where liquid-liquid phase separation is not anticipated to occur.

How to cite: Hennigan, C., Battaglia, Jr., M., Weber, R., and Nenes, A.: Effects of Water-soluble Organic Carbon on Aerosol pH, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2009, https://doi.org/10.5194/egusphere-egu2020-2009, 2020.

Aerosol acidity is an important parameter that affects gas-particle reaction rates, heterogeneous chemistry, human and ecosystem health, global biogeochemical cycles, and climate. Aerosol acidity is difficult to measure directly and remains poorly constrained in most of the troposphere. There is a further scarcity of measurements and/or proxy-estimates of aerosol acidity in the remote marine atmosphere, a region where aerosol acidity exerts strong control on the solubility, bioavailability, and toxicity of biogeochemically-relevant species that influence the productivity of the surface ocean. Here, we measure gas-phase ammonia, and aerosol phase (PM_2.5) ammonium, sulfate, nitrate, sodium, and chloride in the summertime Southern Ocean marine boundary layer every two hours across a latitudinal gradient from Cape Town (-34.11 °S, 18.03 °E) to Antarctica (-58 °S, -0.06 °W). A thermodynamic equilibrium model, i.e., ISORROPIA-II, was run in “forward” mode to calculate aerosol pH using the measured gas + aerosol concentrations, atmospheric temperature, and relative humidity as inputs. The model was able to accurately predict the observed concentration of gas-phase ammonia across the entire dataset (R² > 0.9). Aerosol pH ranged from 0.96 to 4.92 with pH generally increasing with distance away from Cape Town. Observed aerosol- and gas-phase concentrations were typical for the remote marine atmosphere and will be presented in full. Temperature varied significantly across the 8 day transect from 18.42 °C near Cape Town to a minimum of -2.13 °C. Factors that control aerosol pH across the time and space scales observed will be evaluated and discussed as well as implications for improving our understanding of atmospheric chemistry and biogeochemical cycling in remote marine atmospheres.

How to cite: Altieri, K., Spence, K., and Xokashe, S.: Thermodynamic predictions of aerosol pH in the summertime Southern Ocean marine boundary layer using high-resolution aerosol- and gas-phase observations from Cape Town to Antarctica , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22233, https://doi.org/10.5194/egusphere-egu2020-22233, 2020.

Atmospheric transport and the subsequent air-to-sea deposition of water-soluble iron (Fe_ws), an essential micronutrient for the phytoplankton growth, have a profound influence on the biogeochemical cycles of carbon and nitrogen. Sources of Fe_ws include contributions from poorly soluble natural mineral dust and highly soluble anthropogenic aerosols from biomass burning emissions and fossil-fuel combustion in the continental outflows. Apart from the source/emission contributions, atmospheric processing of aerosol iron (Fe_Tot) by inorganic acidic species (e.g., non-sea-salt or nss-SO₄^2- and NO₃^-) and/or organic acids also affect the supply of Fe_ws to the surface waters that are downwind of pollution sources. Among these, the least understood process is the oxalic acid-mediated photochemical cycling of Fe_ws. Laboratory studies have clearly demonstrated an enhancement in the fractional solubility of aerosol iron (i.e., Fe_ws (%) = Fe_ws/Fe_Tot ×100) via the oxalic acid complexation with Fe_Tot and subsequent photochemical reduction process. However, lacking support from the field measurements limits our ability to incorporate the proposed mechanism in the current biogeochemistry models. This study is designed with the overarching goal of investigating the role of oxalic acid on the Fe_ws (%) over a coastal ocean (i.e., the Bay of Bengal: BoB) influenced by the atmospheric outflow from the Indo-Gangetic Plain (IGP) and South-east Asia (SEA) during the winter season. We analysed 31 PM_2.5 samples for the mass concentrations of Fe_Tot, Fe_ws and other chemical composition including nss-SO₄^2-, NO₃^-, oxalic acid and related polar compounds as well as stable carbon isotopic composition of oxalic acid (δ¹³C_oxalic). Strong positive linear relationship of oxalic acid with Fe_Tot and significant inverse linear relationship between δ¹³C_oxalic and Fe_ws over the BoB clearly emphasize the role of oxalic acid on the Fe_ws (%).  These findings comply with the notion that oxalic acid formed from the precursor water-soluble organic acids in the deliquescent aerosols, is complexed with aerosol-Fe and undergoes through successive photochemical reactions, contributing to an overall increase in the Fe_ws (%). 

How to cite: Bikkina, S., Kawamura, K., Sarin, M., and Tachibana, E.: Role of Oxalic acid on Fractional Solubility of Aerosol Iron over Coastal Ocean: Evidence from compound-specific stable carbon isotopic composition and diagnostic mass ratios , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-423, https://doi.org/10.5194/egusphere-egu2020-423, 2020.

It is often said that plastics, and particularly microplastics (<5mm), are all

around us, especially in the oceans where there is much concern about possible harmful

effects on marine life.  The route of entry for plastics to the marine environment is generally

seen to be via rivers acting as a conduit after their production on the land by a whole host of

processes and uses by our societies.   But in all the discussion on the

topic and rapidly growing research activity, the atmosphere barely gets a mention. 

But, recently published results show significant amounts of microplastics

in air at a remote terrestrial location in the Pyrenees (Allen et al., 2019, Nature Geoscience

12:339).  However, there appear to be no results from measurements over the oceans.   If

these results from the Pyrenees are representative of the marine atmosphere a simple

calculation indicates a significant atmospheric route for the distribution of microplastics and

their subsequent deposition to the oceans.  If correct such a pathway would lead to the

distribution of microplastics wider and faster than by ocean circulation alone.  It would also

more readily explain why microplastics have been reported recently in Arctic snow

(Bergmann et al., 2019, Sci. Adv. 5: eaax1157).  In addition, it would also lead to a reframing

of our understanding of the budget and distribution of microplastics globally.

How to cite: Liss, P. S.: Microplastics: All Up in the Air?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9684, https://doi.org/10.5194/egusphere-egu2020-9684, 2020.

Anthropogenic emissions of nitrogen and sulphur oxides and ammonia have altered the pH of aerosol, cloud water and precipitation, with significant decreases over much of the marine atmosphere. Some of these emissions have led to an increased atmospheric burden of reactive nitrogen and its deposition to ocean ecosystems. Changes in acidity in the atmosphere also have indirect effects on the supply of labile nutrients to the ocean. For nitrogen, these changes are caused by shifts in the chemical speciation of both oxidized (NO₃^- and HNO₃) and reduced (NH₃ and NH₄⁺) forms that result in altered partitioning between the gas and particulate phases that affect transport. Other important nutrients, notably iron and phosphorus, are impacted because their soluble fractions increase due to exposure to low pH environments during atmospheric transport. These changes affect not only the magnitude and distribution of individual nutrient supply to the ocean but also the ratios of nitrogen, phosphorus, iron and other trace metals in atmospheric deposition.  Since marine microbial populations are sensitive to nutrient supply ratio, the consequences of atmospheric acidity change include shifts in ecosystem composition in addition to overall changes in marine productivity. Nitrogen and sulphur oxide emissions are decreasing in many regions, but ammonia emissions are much harder to control. The acidity of the atmosphere is therefore expected to decrease in the future, with further implications for nutrient supply to the ocean.

This presentation will explore the impact of increased atmospheric acidity since the Industrial Revolution, and the projected acidity decreases, on atmospheric nutrient supply and its consequences for the biogeochemistry of the ocean.

How to cite: Baker, A., Kanakidou, M., Nenes, A., Croot, P., Duce, R., Gao, Y., Guieu, C., Ito, A., Jickells, T., Mahowald, N., Middag, R., Myriokefalitakis, S., Perron, M., Sarin, M., Shelley, R., and Turner, D.: Changing atmospheric acidity as a modulator of nutrient deposition and ocean biogeochemistry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19425, https://doi.org/10.5194/egusphere-egu2020-19425, 2020.

The Southern Ocean is known to be the largest High Nutrient Low Chlorophyll (HNLC) area of the global ocean, where algal development is mainly limited by iron (Fe) deficiency, except in few naturally Fefertilized areas (e.g. around Kerguelen plateau). The availability of different nutrients is unevenly distributed in this area. Thus, northwards the polar front, nitrogen and phosphorus (N and P) concentrations are high, but the scarcity of silicon (Si) limits the growth of diatoms (HN-LSi-LC). Further North, the Southern Indian Ocean is characterized by macronutrient limitation and low primary production (LNLC).

In these areas, atmospheric input could play a major role in the nutrient supply of primary producers. The main aim of this study is to assess the biological response of local phytoplankton communities to a deposition of two types of natural aerosols: desert dust and volcanic ash. Preliminary trace-metal clean laboratory experiments enabled us to quantify the abiotic dissolution of main macro- and micronutrients in dry and wet deposition mode of different natural aerosols of these types that yield us to choose Patagonia dust and ash from the Icelandic volcano Eyjafjallajökull for our experiment at sea.

We set up a series of on-board trace-metal clean microcosm experiments in the contrasted biogeochemical conditions of the South Indian Ocean and Southern Ocean with addition of realistic amounts of dust and ash of respectively 2 and 25 mg.L^-1. Experiments ran over 48 hours to evaluate the triggered primary production and cell abundances. Primary production was estimated by ¹³C spike and biogenic Si (bSi) uptake rates were assessed by ³⁰Si spike. Parallel experiments with nutrient addition (dFe, DIP, DIN and dSi) along with flux cytometry for estimation of pico- and nanophytoplankton cells enabled us to determine which element(s) dissolved from the aerosols was responsible for the enhanced algal growth.

The highest CO₂ fixation rate of 50 mg.m^-3.day^-1 was found at the natural Fe fertilized Kerguelen plateau station. Dust, ash and Fe addition triggered primary production, and CO₂ fixation doubled in these treatments. We recorded an enrichment of b³⁰Si, indicating an increase of Si uptake rate, mostly stimulated by Fe addition. At the different HNLC stations (high N - low Si and high N - high Si), Fe and aerosol addition induced as well increased CO₂ fixation. In the northern LNLC stations, algal growth was stimulated by nitrogen addition as expected, but Fe, Si and aerosol addition also triggered a biological response from Synechococcus cyanobacteria and pico- and nanoeukaryotes.

Noteworthy, in most experiments the two contrasted aerosol types (desert dust and volcanic ash) at particle charges which varied over more than an order of magnitude triggered very similar biological responses in all of the sampled areas, even with distinct elementary and mineral compositions (e.g. the Icelandic volcano ash is 64 % amorphous and contains roughly twice the amount of Fe, P, Mn and
Zn compared to the Patagonian desert dust which is only 48 % amorphous).

How to cite: Geisen, C., Ridame, C., Journet, E., Caron, B., Marie, D., and Cardinal, D.: Impact of desert and volcanic aerosol deposition on phytoplankton in the South Indian Ocean and Southern Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20767, https://doi.org/10.5194/egusphere-egu2020-20767, 2020.

Primary productivity in the upper ocean is a key driver of Earth’s carbon cycle. The supply of micronutrients such as iron (Fe) and manganese (Mn) to the ocean is now known to exert a controlling influence on net primary productivity. Fragmental volcanic material, or tephra, is enriched in such nutrients, highly reactive and regularly supplied to the upper ocean when eruptions occur. However, there are no existing estimates of the global magnitude of the volcanic supply of these (and associated) nutrients to the oceans. Here we present new data from ten volcanic provinces globally including the Aleutian Islands and Lesser Antilles to estimate depletion factors of both Fe and Mn in altered tephra. By comparing the concentration of altered tephra to unaltered protolithic compositions, we can estimate depletion factors, and thus the amount of each element supplied to the oceans via this method. Using a novel Monte Carlo approach, we estimate mean values of Fe and Mn to be on the order of 26.1 and 0.25 Gmol yr^-1, respectively. These values are broadly comparable to riverine and atmospheric dust fluxes to the ocean, indicating that volcanism plays a major role in Fe and Mn ocean cycles.

How to cite: Longman, J., Palmer, M., and Gernon, T.: Quantifying the role of volcanic ash supply in the oceanic iron and manganese cycles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10721, https://doi.org/10.5194/egusphere-egu2020-10721, 2020.

Although it is commonly accepted that atmospheric deposition of Fe particles can fertilise phytoplankton, there is yet no clear evidence on how such a fertilisation effect takes place. Several studies have attempted to link individual dust events with surface chlorophyll responses but generally, they do not find a clear correspondence between dust deposition and its impact on chlorophyll. In this work, we use a biogeochemical model to show that the atmospheric deposition of Fe in high-latitude seas, rather than creating instantaneous phytoplankton responses, replenish the upper mixed layer of the ocean during the pre-bloom period, from winter to early summer. The Fe accumulated at the surface boosts the phytoplankton bloom of the following summer, resulting in surface chlorophyll accumulations of up to 3 times larger than the years without atmospheric deposition. We used this mechanism to explain the strong inter-annual variability of the phytoplankton bloom in sub-Antarctic iron-limited waters east of Australia. Putting together more than a 15-years-long record of ocean colour observations and atmospheric aerosols reanalysis we uncovered a strong correlation (r²>0.6) between the dust that crossed the region during the pre-bloom period and the magnitude of the surface chlorophyll bloom. Interestingly, the correlation increased when taking into account pyrogenic aerosols in addition to dust. Our study presents the first observational link between Climate Change-enhanced droughts and wildfires, atmospheric aerosols and primary production of iron-limited waters.

How to cite: Llort, J., Matear, R. J., Strutton, P. G., Bowie, A. R., and Chase, Z.: Dust and pyrogenic iron boost phytoplankton blooms in sub-Antarctic waters of the Tasman Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7809, https://doi.org/10.5194/egusphere-egu2020-7809, 2020.

The project MarParCloud (marine biological production, organic aerosol particles and marine clouds: a process chain) aims at achieving a better understanding of the biological production of organic matter (OM)in the oceans, its export into marine aerosol particles and finally its ability to act as ice and cloud condensation nuclei (INP and CCN). The core of MarParCloud comprised a field campaign at the Cape Verde Atmosphere Observatory (CVAO) in autumn 2017, where a variety of chemical, physical, biological and meteorological approaches were applied. The investigations included concerted measurements of the bulk water, the Sea Surface Microlayer (SML), ambient aerosol particles on the ground (30 m a.s.l.) and in mountain heights (744 m) as well as cloud water. Important aspects of the ocean atmosphere Interactions focusing on marine OM have been addressed through detailed observation and modeling approaches.

Key variables comprised the chemical characterization of the atmospherically relevant OM components (e.g. lipids, proteins, sugars) in the ocean and the atmosphere as well as measurements of INP and CCN. Moreover, bacterial cell counts, mercury species and trace gases were analysed. To interpret the results, the measurements were accompanied by various auxiliary parameters such as air mass back trajectory analysis, vertical atmospheric profile analysis, cloud observations and pigment measurements in seawater. Additional modelling studies supported the experimental analysis.

Here we show the proof of concept of the connection between organic matter emission from the ocean to the atmosphere and up to the cloud level. A link between the ocean and the atmosphere was clearly observed as (i) the particles measured at the surface are well mixed within the marine boundary layer up to cloud level and (ii) ocean-derived compounds can be found in the aerosol particles at mountain height and in the cloud water. The organic measurements will be implemented in a new source function for the oceanic emission of OM. However, from a perspective of particle number concentrations, the marine contributions to both CCN and INP are rather limited.

How to cite: van Pinxteren, M., Fomba, K. W., Triesch, N., Wex, H., Gong, X., Vogtländer, J., Barthel, S., Stolle, C., Bahlmann, E., Rixen, T., Schulz-Bull, D., Robinson, T.-B., Wurl, O., Stratmann, F., and Herrmann, H.: Marine organic matter in the remote environment of the Cape Verde Islands – An introduction and overview to the MarParCloud campaign, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3359, https://doi.org/10.5194/egusphere-egu2020-3359, 2020.

Biochemical responses of oligotrophic Adriatic Sea surface layers to atmospheric deposition inputs

Frka¹, A. Miliković¹, A. Penezić¹, S. Bakija Alempijević¹, B. Gašparović¹, S. Skejić², D. Šantić², S. Brzaj³, V. Džaja Grgičin³, S. Vidič³, I. Šimić⁴, I. Bešlić⁴, S. Žužul⁴, R. Godec⁴, G. Pehnec⁴

¹Division for marine and environmental research, Ruđer Bošković Institute, Zagreb, Croatia

²Institute of Oceanography and Fisheries, Split, Croatia

³Croatian Meteorological and Hydrological Service, Zagreb, Croatia

⁴Institute for Medical Research and Occupational Health, Zagreb, Croatia

The atmosphere is a significant pathway by which both natural and anthropogenic material is transported from continents to both coastal and open seas. Once deposited through atmospheric deposition (AD) processing, atmospheric particulate matter (PM) provides the aqueous ecosystems with an external source of nutrients and pollutants. This, in turn, influences the organic matter (OM) production by the phytoplankton, changes CO₂ uptake and indirectly affects the climate. The input of AD is especially important in oligotrophic environments and it is expected to increase in the future scenarios of a warmer atmosphere with increased PM emissions and deposition rates. While the majority of the data related to the AD impacts generated so far in the Mediterranean have been conducted on its western and eastern regions, the effects of the AD inputs to oligotrophic surface waters of the Adriatic Sea sub-basin are unknown. This work is designed to assess the impact of AD on complex biochemical responses of Adriatic oligotrophic systems, considering the sea surface microlayer (SML) at the air-water interface.

Field campaign was conducted during the period of retrieval of sea surface oligotrophic conditions (February-July 2019) at the Martinska, Central Adriatic, Croatia. On-line black carbon (BC) concentrations were measured while the PM₁₀, wet and total deposition samples as well as the SML and underlying water (ULW; 0.5 m depth) samples were collected simultaneously. The temporal dynamics of the SML biology as well as concentrations of  inorganic and organic constituents enabled the assessment of their sources and the nature of the enrichments taking place within the SML. The first comprehensive insight into concentration levels of macro nutrients (N, P), trace metals (eg. Cu, Pb, Cd, Ni, Zn, Co) and OM (including aromatic pollutants) in atmospheric samples, their transport history, source apportionment and deposition fluxes to the oligotrophic Adriatic area will be presented. Daily and seasonal variations of PM₁₀ composition were affected by local traffic and open-fire events as well as by local meteorological conditions and long-range transport. The BC contribution of biomass burning versus fossil fuel combustion changed seasonally. Source apportionment module of LOTOS-EUROS chemical transport model enabled identification and quantification of main source areas contributing to deposition of PM. The main PM contributor is a public power sector outside Croatia while other contributing sectors are energy production, traffic, residential combustion as well as shipping. First deposition fluxes estimates show reasonable agreement between model calculations and measured data, and could be used for more general assessments of atmospheric inputs.

Acknowledgment: This work has been supported by Croatian Science Foundation under the IP-2018-01-3105 project: Biochemical responses of oligotrophic Adriatic surface ecosystems to atmospheric deposition inputs.

How to cite: Frka, S., Milinković, A., Penezić, A., Bakija Alempijević, S., Gašparović, B., Skejić, S., Šantić, D., Džaja Grgičin, V., Brzaj, S., Vidič, S., Šimić, I., Žužul, S., Bešlić, I., Godec, R., and Pehnec, G.: Biochemical responses of oligotrophic Adriatic Sea surface layers to atmospheric deposition inputs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15108, https://doi.org/10.5194/egusphere-egu2020-15108, 2020.

pH is a fundamental aerosol property that affects ambient particle composition, concentration and toxicity, linking pH to all aerosol environmental impacts. Direct measurement of aerosol pH is highly challenging, and so indirect proxies are often used to represent particle acidity. Aerosol thermodynamic models, such as ISORROPIA-II, are able to calculate particle pH – based on concentrations of various aerosol species, temperature (T), and relative humidity (RH) – and offer a rigorous approach to obtain aerosol pH already tested in the past with ambient aerosol data. However not many long aerosol measurements datasets exist to understand the trend of particle acidity along the past decades in Europe as well as around the world. Long-term monitoring programs for cloud/fog composition and acidity are also lacking in the global scientific community, but there are a few locations around the world where such measurements have been made routinely or periodically over periods of a decade or more. One of these locations is the rural station of San Pietro Capofiume in the Po Valley (Italy), where a consistent long dataset of fog-water ionic composition exists spanning the last 25 years (1993-2018).

In this study, assuming that fog acts as an efficient natural scavenger of aerosol particles, we use the inorganic composition of fog-water collected at SPC as a proxy for the chemical composition of atmospheric aerosol in pre-fog conditions. So, we apply ISORROPIA-II to calculate the pH associated with particles having the same chemical composition of fog-water. In this way we extend the analysis to the long-time record of fog-water measurements obtaining the aerosol pH trend of the last 25 years. A comparison with existing aerosol samples and parallel ammonia gas measurements allow us to validate the approach.

Our thermodynamic analysis suggests a decreasing trend of aerosol pH in Po Valley. Over the twenty-five-year period the aerosol pH decreased approximately 1.1-1.6 pH units, progressing also with an increasing rate of reduction, which corresponds to 0.18 pH units between the first and the second decades (1993-2002 and 2003-2012 respectively) and 0.44 between the decade 2003-2012 and the last 6 years (2013-2018).

A multiple linear regression analysis applied on the simulated aerosol pH reveals that the aerosol pH reduction trend is driven by the contemporary decrease of the main pollutants atmospheric concentration (possibly due to the European environmental policies) and by the changing meteorogical parameters (T and RH), possibly linked with climate change.

Our analysis suggests for the first time the possibility of calculating pre-fog aerosol pH using fog compositional data in a thermodynamically consistent way, which can be useful to evaluate long-term trend of particles acidity also in other region of the world for which data are available (e.g., Californian Central Valley).

Projecting the trend in the future it is possible to speculate a potential change in deposition of nitrate/nitric acid from aerosol-dominant (slow) to gas-dominant (fast) with very important consequences in air quality.

How to cite: Paglione, M., Decesari, S., Rinaldi, M., Manarini, F., Gilardoni, S., Brunetti, M., Facchini, M. C., Fuzzi, S., Bacco, D., Trentini, A., Pandis, S. N., and Nenes, A.: Aerosol pH 25-years trend predicted from fog composition in Po Valley, Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19558, https://doi.org/10.5194/egusphere-egu2020-19558, 2020.

The acidity of aqueous atmospheric solutions is a key parameter driving both partitioning of semi-volatile acidic or basic trace gases and their linked aqueous-phase chemistry. On the other hand, acidity of atmospheric aqueous phases, e.g. deliquesced aerosol particles, cloud and fog droplets, is conversely affected by aqueous-phase chemistry processes. Those feedbacks in acidity and chemistry have crucial implications for the (i) tropospheric lifetime of air pollutants, hence air quality and atmospheric aerosol composition, (ii) deposition input into other terrestrial and oceanic ecosystems, (iii) the visibility, (iv) climate and (v) human health. Due to their fundamental role, atmospheric research has gained substantial progress in the understanding in feedbacks of acidity and multiphase chemistry. In the present study, the current state of knowledge on the acidity-multiphase chemistry feedbacks has been summarized. From a wide range of topics, two selected issues focusing on impacts of acidity (i) on the hydration of organic carbonyl compounds and (ii) multiphase chemistry of dissociating organic compounds in aqueous particles and clouds will be presented.

Hydration processes are typically known to be acid- or base-catalyzed. Thus, the acidity of an aqueous solution can affect the hydration and all other processes linked to it. This comprehensive literature study revealed that the hydration of simple aldehydes and ketones as well as dicarbonyls is less affected by acidity. However, for multifunctional carbonyl compounds such as pyruvic acid, the hydration equilibrium constant of the carbonyl group is strongly influenced by the electronic effects of the adjacent group. The hydration of carbonyl groups in compounds that also contain pH sensitive moieties, such as α-oxocarboxylic acids, is highly influenced by the acidity of the surrounding environment. However, this acidity effect is often not considered in multiphase models.

Furthermore, oxidation reactions of dissociating organic compounds can be affected by acidity. To examine the effect of acidity on the chemical processing of dissociating organic compounds, kinetic data for their oxidation by OH, NO₃ and O₃ have been newly compiled in the present study. Kinetic reactivity data of both protonated and deprotonated organic compounds together with their reactivity ratio  have been investigated to identify possible acidity effects. The present study showed that, for OH reactions, the impact of acidity on the chemical kinetics is often quite small and only important for some specific compounds. On the other hand, for NO₃ reaction, particularly under cloud conditions, acidity can substantially affect the chemical NO₃-initiated processing of organic compounds. Less acidic conditions will enhance the degradation of dissociating compounds via NO₃ because of more rapid oxidation and possibility of additional ETR pathway. Furthermore, the present O₃ kinetic data analyses have demonstrated the role of acidity for ozonolysis processes, especially for phenolic compounds. Overall, the present study summarizes atmospheric implications and needs for future investigations, particularly with respect to changing aerosol and cloud acidity conditions in the future.

How to cite: Schaefer, T., Tilgner, A., Pye, H. O. T., McNeill, V. F., and Herrmann, H.: Impacts of acidity on multiphase chemistry in aqueous particles and clouds, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10045, https://doi.org/10.5194/egusphere-egu2020-10045, 2020.

Aerosol acidity (pH) plays a significant role in the chemical behaviour of atmospheric particles, since it affects their composition and toxicity. This study investigates the seasonal variability of submicron particles acidity at the Finokalia atmospheric observatory in the eastern Mediterranean from February to December 2014. Direct measurements of aerosol pH are challenging and thus very rare. Therefore, aerosol pH is generally derived from thermodynamic model calculations. Submicron aerosol chemical composition data along with NH₃ and HNO₃ gas phase concentrations measured at Finokalia are here used in the thermodynamic model ISORROPIA-II in order to predict the aerosol pH. The predicted pH values show clear seasonality and the expected dependence on temperature and relative humidity. Submicron aerosols at Finokalia have been found to be acidic with an average pH values over the studied period of 1.77 ± 0.67, with the highest values occurring in winter and the lowest in summer and a winter to summer ratio of about 1.4.

We acknowledge support of this work by the project “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

How to cite: Neroladaki, A. M., Stavroulas, I., Tsiodra, I., Myriokefalitakis, S., Nenes, A., Mihalopoulos, N., and Kanakidou, M.: Seasonal variability of submicron aerosol acidity at a coastal site in the Eastern Mediterranean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9562, https://doi.org/10.5194/egusphere-egu2020-9562, 2020.

Aerosol acidity plays an important role in influencing precipitation pH, which has impacts on the environment as well as human health. It also has significance in shaping aerosol chemistry, including the catalytic formation of water-soluble organic carbon (WSOC), which in turn affects the hygroscopicity of aerosols. Past studies on aerosol acidity in the Indian subcontinent, mostly conducted in biomass burning (BB) source regions in the northwestern and central Indo-Gangetic Plain (IGP) and in western India, have identified Ca²⁺ and Mg²⁺ sourced from desert dust to be the predominant neutralizing agents. However, the prevalence of desert dust decreases progressively along the IGP corridor and is potentially rendered insignificant in the eastern IGP (eIGP). As such, there exists a critical weakness in our understanding of the processes governing aerosol acidity and its neutralization in the eIGP. To address this, the present study reports the seasonal variability of ionic species, WSOC and associated aerosol acidity in ambient PM_2.5 from a rural receptor site in the eIGP. To this end, a total of 88 PM_2.5 samples collected during the summer, post-monsoon and winter seasons of 2018 were analyzed for SO₄^2-, NO₃^-, Cl^-, Na⁺, NH₄⁺, K⁺, Ca²⁺, Mg²⁺, F^-, PO₄^3- and WSOC, followed by estimation of strong acidity. Across all seasons, the aerosol phase was dominated by SO₄^2-, NH₄⁺ and NO₃^-, with values increasing by factors of 1.8-1.9, 1.4-2.9 and 1.8-11, respectively, for the regional BB-dominated post-monsoon and winter seasons as compared to summer. Significant positive Cl^- depletion in summer pointed towards the influx of marine air while negative depletion in post-monsoon and winter suggested a BB source, which was further supported by concentration-weighted trajectory analysis. The averaged pH of the aerosol extract decreased progressively from summer (5.5±0.4) to winter (4.5±0.2). NH₄⁺ was observed to be the major acid-neutralizing agent across all seasons, with dust-derived Ca²⁺ and Mg²⁺ playing only minor roles. In general, WSOC formation is known to be catalyzed by the presence of excess acidity; however, during winter, it appeared that the regional transport of organic acids in the BB plume contributed to aerosol acidity at this receptor site (r=0.92; p<0.01 for WSOC and H⁺). BB-derived K⁺ appeared to perform a dual function of neutralizing acidity as well as producing it via reactions with WSOC during atmospheric transport. The wintertime acidity was also strongly governed by aerosol NO₃^- sourced from BB emissions and possibly accentuated via nighttime atmospheric chemistry at lower ambient temperatures, resulting in the formation of haze. These observations of the NO₃^- and WSOC-driven wintertime acidity, the dual function of K⁺ and the dominant role of NH₄⁺ in neutralization points to complex atmospheric processing of the IGP outflow during its transport to the eastern end of the corridor, which warrants further investigation.

How to cite: Sharma, B., J. Polana, A., Rawat, P., and Sarkar, S.: Aerosol acidity and its neutralization in the eastern Indo-Gangetic Plain: implications for water-soluble organic carbon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-717, https://doi.org/10.5194/egusphere-egu2020-717, 2020.

Transition metal ions, such as water-soluble iron (WS-Fe), are toxic components of fine particulate matter (PM_2.5). In Atlanta, GA, from 1998 to 2013, WS-Fe was the PM_2.5 species most associated with adverse cardiovascular outcomes in a previous study. We examined this data set to investigate the sources of WS-Fe and effects of air quality regulations on ambient levels of WS-Fe. Insoluble forms of iron in mineral and traffic dust combined with sulfate from coal-fired electrical generating units (EGU) were converted to soluble forms by sulfate-driven acid-dissolution. Sulfate produced both the highly acidic aerosol (summer pH 1.5-2) and liquid water required for the aqueous phase acid-dissolution, but variability in WS-Fe was mainly driven by particle liquid water. These processes were more pronounced in summer when particles were most acidic, whereas in winter the relative importance of WS-Fe from combustion emissions increased. Although WS-Fe represents a minute mass fraction (0.15%) of PM_2.5, the observed high correlation between WS-Fe and PM_2.5 mass (r=0.67) may result from these formation routes and account for some association between mass and adverse health seen in past studies. Similar processes are expected in many regions, implying these unexpected benefits from coal-burning reduction may be widespread.

How to cite: Weber, R. J., Wong, J., Wang, Y., Fang, T., Mulholland, J., Russell, A. (., Sarnat, S., and Nenes, A. (.: Iron in Soils and Road Dust is Modulated by Coal-Fired Power Plant Sulfur Making Toxic PM2.5, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3611, https://doi.org/10.5194/egusphere-egu2020-3611, 2020.

We take moist air (and artificial air) at +0.35 ⁰C, variously doped with CO_2, and pass it through a chamber chilled to -3⁰C.  We record any depletion of CO₂ in the gas stream using differential NDIR spectrometers, and we then de-gas the melt-water to measure the captured CO₂, again with NDIR.  Preliminary results are consistent with published curves for the CO₂/hydrate equilibrium at partial pressures relevant to the petrochemical industry and to industrial carbon capture as determined by Raman microscopy (Chazallon and Pirim 2018).

Extension of the CO₂/ice curve to atmospheric partial pressures allows a review of a range of related issues in atmospheric water, one of the more accessible being its acidity. The dissociation of CO₂ in water at equilibrium with 400ppm CO₂ at Earth surface is quoted as pH5.6, but fresh rainwater (and snow-melt) can be significantly more acidic, decaying exponentially to equilibrium with a half life of around four hours. This observation is consistent with published analyses of [CO₂] in rainwater that are significantly higher than the Henry equilibrium (Warneck 2000).  Both would be explained if convection was resulting in CO₂/ice-formation in clouds within the boundary layer, in turn leading to deposition of supersaturated levels of CO₂ together with enhanced acidity.

This paper speculates on the local [H₃O⁺] delivered by the melting of an ice particle that had grown in an atmosphere of 400ppm CO₂ at an altitude of 1km, and its dissipation through dilution by neighbouring unfrozen water drops and by slow release from the residue of hydrate caging in liquid water. For Earth surface it has potential implications for acid rain, for the solution and redeposition of carbonate rocks, and for ocean acidification.  

How to cite: Durham, B. and Pfrang, C.: CO2 hydrate equilibria at atmospheric partial pressures, and implications for atmospheric acidity , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6107, https://doi.org/10.5194/egusphere-egu2020-6107, 2020.

Atmospheric deposition can be an important source of nutrients and trace elements for land and ocean ecosystems. Atmospheric acidity is an important driver of the solubility of nutrients and trace elements present in atmospheric aerosols. Using a global 3-dimensional chemical transport model, we summarize here human driven past and future changes in the aerosol acidity and the resulting changes in the nitrogen, phosphorus and iron atmospheric deposition and solubility. We present and discuss the acidity driven changes in the chemical speciation and geographic patterns of nutrient deposition. Areas of uncertainties and implications for ecosystems functioning are discussed.

This work has been supported by the project “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund) and by the University of Bremen Excellence Chair of MK.

How to cite: Kanakidou, M., Myriokefalitakis, S., Nenes, A., and Daskalakis, N.: The importance of atmospheric acidity for nutrient deposition on global scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17843, https://doi.org/10.5194/egusphere-egu2020-17843, 2020.

The atmosphere is considered as an important external nutrient source for the marine environment, especially in remote ocean waters or the oligotrophic Mediterranean Sea. Phosphorus (P) is a critical nutrient affecting primary productivity in large areas of oceanic ecosystems. Much has been placed on inorganic P, while the importance of organic P as potential pool of bioavailable P is not widely recognized. In this study we quantify and speciate the anthropogenic organic P in the West and East Mediterranean atmosphere. Several anthropogenic organophosphorus compounds are analyzed, including pesticides (Phosmet, Malathion, Ethoprophos, Diazinon, Chloropyrifos-Me, Chloropyrifos-e), organophosphorus flame retardants and plasticizers (OPEs) (Tris- (1-chloro-2-propyl) phosphate (TCPP), tris[2-chloro-1-(chloromethyl)ethyl]phosphate (TDCP), Tris-(2-chloroethyl)phosphate (TCEP), tri-n-butyl phosphate (TnBP), triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP)).

Our analysis applied to Total Suspended atmospheric Particles (TSP) collected in Eastern (Crete, n = 67) and Western (Marseille, n = 25) Mediterranean Sea by using high-volume air sampler. The analysis performed with the liquid chromatography coupled to mass spectrometry (Q–TOF–LC/MS) after optimization of the analytical protocol for the aerosol samples. Five pesticides were found during the sampling period in East Mediterranean in total of 27 samples. The most frequent were chlorpyrifos–e (n = 9) and phosmet (n = 10) with average concentration 0.24±0.38 pmol m^–3 and 0.24±0.45 pmol m^–3, respectively following by diazinon (n = 4) at 0.07±0.00 pmol m^–3. Higher concentration was estimated in chlorpyrifos-me at 0.91±0.93 pmol m^–3 (n = 3) while ethoprophos was detected only in one sample (0.002 pmol m m^–3), malathion was below detection limit. In the West Mediterranean, the most abundant organophosphate pesticides were phosmet (n = 3) with an average concentration of 0.07±0.04 pmol m^–3, followed by diazinon (0.05 pmol m^–3, n = 1) and chloropyrifos-e (0.04 pmol m^–3, n = 2). Malathion, chlorpyrifos-me and ethoprophos were not detected. The average contribution of organophosphate pesticides in atmospheric organic P detected during this study was 0.2% and 0.1% for East and West Mediterranean, respectively.

OPEs analyses in the same samples revealed higher concentrations in the West than in East Mediterranean atmosphere especially for TCPP, TCEP and TDCP, which are considered as the most potentially hazardous. In the West Med. the most abundant detected OPEs were the EHDPP (3.04±4.17 pmol m^-3) and the TCPP (1.71±1.28 pmol m^-3). In East Mediterranean, the most abundant detected OPEs were the TCPP (0.36±0.29 pmol m^-3) and the TCEP (0.24±0.20 pmol m^-3) whereas the TDCP and the EHDPP were not detected. The percentage contribution of OPEs in atmospheric organic–P over the West Mediterranean was 9%, while over East was 0.4%.

The total anthropogenic organic P deposited in East Mediterranean during stratification period (June-September) was calculated at 8 tons, which was 4 times lower comparing with West Mediterranean (29 tons of P) during the same period. Overall, the above anthropogenic compounds represented only 0.4% of the total anthropogenic P deposited during stratification period, however their toxicity and fate to the marine environment warrants further investigations.

How to cite: Violaki, K., Tsagaraki, M., Nenes, A., Sempere, R., Jimenez, J. C., and Panagiotopoulos, C.: The role of Organophosphate Esters Flame Retardants (OPEs) and organophosphate pesticides in Phosphorus Cycle in the atmosphere of Mediterranean Sea., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14697, https://doi.org/10.5194/egusphere-egu2020-14697, 2020.

Atmospheric deposition of trace constituents of natural and anthropogenic origin act as a nutrient source into the open ocean, affecting the marine ecosystem functioning and subsequently the exchange of CO₂ between the atmosphere and the global ocean. Among other species that are deposited into the open ocean, nitrogen (N), iron (Fe), and phosphorus (P) are considered as highly significant nutrients that can limit marine phytoplankton growth and thus directly impact on ocean carbon fluxes in the ocean, particularly where the nutrient availability is the limiting factor for productivity. For this work, we take into account the up-to-date understanding of the effects of air quality on the atmospheric aerosol cycles to investigate the potential ocean biogeochemistry perturbations via the atmospheric input with the European Community Earth System Model EC-Earth (http://www.ec-earth.org/), which is jointly developed by several European institutes. In more detail, state-of-the-art N, Fe, and P atmospheric deposition fields are coupled to the embedded marine biogeochemistry model and the response of oceanic biogeochemistry to natural and anthropogenic atmospheric aerosols deposition changes is demonstrated and quantified. Model calculations show that compared to the present day, the preindustrial atmospheric deposition fluxes are calculated lower (~1.7, ~1.5, and ~1.4 times for N, Fe, and P, respectively) corresponding to a respective lower marine primary production. On the other hand, future changes in air pollutants under the RCP8.5 scenario result in a modest decrease of the bioaccessible nutrients input into the global ocean (~ -15%, ~ -16% and ~ -22% for N, Fe and P, respectively) and overall to a slightly lower projected export production compared to present day. Although the impact of atmospheric processing on atmospheric inputs to the ocean results in a relatively weak response in total global-scale simulated marine productivity estimates, strong regional changes up to 40-60% are calculated in the subtropical gyres. Overall, this study indicates that both the atmospheric processing and the speciation of the atmospheric nutrients deposited in the ocean should be considered in detail in carbon-cycling studies, since they may significantly affect the marine ecosystems and thus the current estimates of the carbon cycle feedbacks to climate.

This work has been financed by the National Observatory of Athens internal grant (number 5065), the “Atmospheric deposition impacts on the ocean system”, and the European Commission's Horizon 2020 Framework Programme, under Grant Agreement number 641816, the "Coordinated Research in Earth Systems and Climate: Experiments, kNowledge, Dissemination, and Outreach (CRESCENDO)".

How to cite: Myriokefalitakis, S., Gröger, M., Hieronymus, J., and Döscher, R.: A state-of-the-art parameterization of atmospheric nutrient deposition fluxes in the global ocean , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13075, https://doi.org/10.5194/egusphere-egu2020-13075, 2020.

Accurate quantification of the global budget of atmospheric carbonyl sulfide (COS) is needed given its role in atmospheric chemistry and the global carbon cycle. COS is the most abundant atmospheric sulfur gas. In the stratosphere, COS is photodissociated to provide a significant source of sulfate aerosol, a key agent of stratospheric ozone depletion.  In the troposphere, measurements of the COS variation have the potential to provide constraints on the rates of CO₂ assimilation by terrestrial plants and hence on primary productivity. Accurate knowledge of the global budget of COS and of its respective source and sink fluxes is therefore needed to understand its impact on ozone depletion and on the carbon cycle. Recent estimates of the global COS budget, however, reveal discrepancies between known sources and sinks. In particular the magnitude of the oceanic flux (the largest known source to the atmosphere) remains uncertain. The ocean provides a source of COS to the troposphere through direct emission, and potentially through emission of COS precursors such as carbon disulfide (CS₂). Here we assess the role of the ocean in the global COS budget using a global atmospheric transport model (GEOS-Chem) in combination with recent estimates of COS source and sink fluxes, and with available oceanic and atmospheric measurements of COS.  We compare different realizations of oceanic COS fluxes taken from ocean biogeochemistry models and from recent data syntheses, and assess their ability to reduce the uncertainty in the current global budget of COS.

How to cite: Suntharalingam, P., Chen, Z., Lennartz, S., and Buitenhuis, E.: Assessing the Contribution of Oceanic Fluxes to the Global Budget of Carbonyl Sulfide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12274, https://doi.org/10.5194/egusphere-egu2020-12274, 2020.

In a recent study, it was suggested based on the apparent correlation between multi-annual measurements of summertime maxima and wintertime minima temperature and calculated pCO₂ in the most eastern region of the Mediterranean Sea surface waters that they are a net source of atmospheric CO₂. Furthermore, it was predicted that the magnitude of this source would increase substantially in this region and that adjacent regions in the Eastern Mediterranean as well would turn into net sources of atmospheric CO₂ due to the fast warming of these waters. In order to confirm the underlying assumption that seasonal variations in pCO₂ in Eastern Mediterranean surface waters are primarily a strong function of seasonal variations in temperature, water samples were collected for the analysis of total alkalinity and pH during 12 monthly cruises from February 2018 to January 2019 at the shallow (THEMO1) and the deep (THEMO2) open water stations that are ca.10 and 20 NM off the Mediterranean coast of Israel. The data from all the cruises show that surface (< 30m depth) seawater pCO₂ has a strong positive linear relationship with temperature in both stations (n=56, r²=0.94, p<0.001). The calculated annual net flux of CO₂ from the surface to the atmosphere based on these measurements is ca.1.13 Tg C y⁻¹, which is ca.15% higher than the previously estimated flux, but within its range of uncertainty (± 30%). These results clearly demonstrate that surface water pCO₂ levels are indeed a strong positive function of the seasonal variations in sea-surface temperature and that the open water of the most eastern Mediterranean Sea is a net source of atmospheric CO₂. These results are also in agreement with the conclusions of observational and modelling studies of air-sea CO₂ fluxes in the centers of subtropical gyres and therefore globally relevant.

How to cite: Yu, J.: Air-Sea seasonal CO2 fluxes in a fast warming oligotrophic region – the Eastern Mediterranean case study , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6143, https://doi.org/10.5194/egusphere-egu2020-6143, 2020.

One of the main goals in the regional biogeochemical research of East Asia is to evaluate the state of acid deposition and the related pollution within EANET region (EANET, 2019). In the south of the Russian Far East there are two networks developed to monitor the content of acidic substances in atmospheric fall-out. The first one is the Russian national precipitation chemistry stations operated for more than 30 years, and the second is the international atmospheric monitoring sites supervised by EANET and WMO-GAW (Yearbook, 2019). We calculate the total deposition of airborne sulfur and nitrogen in a large region to evaluate their atmospheric balances under the transboundary influence. The present study focuses on the development and application of the spatial interpolation method to estimate wet deposition fluxes based on the monitoring data for 2013-2018. On the first step of the algorithm, we analyze the correlation of pollution monitoring results between network stations and estimate the maximum radius of representativeness for each station. On the second step, we interpolate the precipitation chemistry data for the set of meteorological stations located in the region under the study and calculate the wet deposition fluxes of sulfur and nitrogen for these sites. The flux values obtained are further interpolated for the regular grid of 10-km by 10-km cells within the region under the study. Finally, the total wet sulfur and nitrogen deposition for the region is a sum of deposition fluxes calculated for each cell. Additionally, we compared the data obtained with the correspondent flux calculated on the basis of the national snow cover chemistry network for the same region and period.

References

1. EANET. Fourth Report for Policy Makers (RPM4): Towards Clean Air for Sustainable Future in East Asia through Collaborative Activities. 2019. 50 p.
2. Yearbook. State and pollution of the environment in the Russian Federation: 2018. Moscow: RosHydroMet, 2019. 227 p. [in Russian]

How to cite: Gromov, S. A., Galushin, D. A., and Zhadanovskaya, E. A.: Estimation of the total wet sulfur and nitrogen deposition as a part of pollution balance in the south of the Russian Far East based on the monitoring data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13871, https://doi.org/10.5194/egusphere-egu2020-13871, 2020.

Phytoplankton is closely related to the Arctic Amplification in a future caused by the biogeophysical feedback. In particular, the increase in nutrients, which is one of the limiting factors of phytoplankton, affected by the increased inflow of rivers due to the Arctic warming in the Arctic region. Since Arctic region is sensitive to the feedback, the biological feedback is still difficult to expect an accurate simulate in the modeling simulation. This study used the GFDL-TOPAZ model by prescribing a runoff nitrogen flux in the contemporary level to simulate the phytoplankton, then prescribing the nitrogen flux over the East Siberian-Chukchi Sea. The model results underestimate chlorophyll A concentration and nutrient compared to the ARAON ship observation. But, We showed that the experiment of prescribing a regional runoff nitrogen flux by the river is well simulatinges the chlorophyll A concentration and nutrients than the CTRL experiment. Also, a  model result showed that the sea ice concentration in the Chukchi-East Siberian Sea and Kara-Barents Sea decreased, and it suggests that the regional change of the nutrient could, directly and indirectly, affect that Arctic sea ice concentrations

How to cite: Park, J. H. and Kim, B.: Impact of the regional runoff Nitrogen Flux using the GFDL-TOPAZ simulation on the Arctic Ocean phytoplankton., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20893, https://doi.org/10.5194/egusphere-egu2020-20893, 2020.

Deep chlorophyll maxima (DCM) are productive layers widespread throughout the global ocean. In the DCM, marine phytoplankton are adapted to low light conditions at the cost of elevated cellular iron (Fe) requirements, leading to Fe deficient growth. To sustain productivity, nutrient demands must be met by sources such as the dissolution of sinking lithogenic particles, recycling of biogenic particles and physical transport from below. The GEOTRACES programme has expanded the global ocean datasets for a suite of trace metals and also noble gases. Here, we exploit helium measurements to derive a vertical flux estimate of nitrate (NO₃), phosphate (PO₄), silica (Si) and Fe into the DCM in the subtropical North Atlantic and equatorial Pacific. We apply the Si* relation to show differences in nutrient deficiency between waters in the DCM and the upward flux into the DCM. The offset in Si* between the DCM and upward flux may be enhanced or reduced by the dissolution of sinking particles or internal recycling. We show that the upward Fe flux to the DCM is of similar magnitude to Fe supplied through regeneration. In contrast, we show that the upward Fe flux outweighs estimates of Fe supplied to the DCM via recycling or lithogenic particles in the subtropical North Atlantic. The muted role of lithogenic particles in our estimates leads to the question: what assumptions must be made about aeolian deposition to increase the relevance of lithogenic particles at the DCM?

How to cite: Rigby, S., Williams, R., Achterberg, E., and Tagliabue, A.: Which Processes Sustain Biota in Open-Ocean Deep Chlorophyll Maxima?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19351, https://doi.org/10.5194/egusphere-egu2020-19351, 2020.

Planktonic foraminifera precipitate calcareous shells, which after the death of the organisms are exported from the sea surface to the sea floor, where they are preserved on geologically relevant timescales. The export flux of planktonic foraminifera shells constitutes globally up to a half, and in the studied region off Cap Blanc (Atlantic Ocean) about one third, of the marine pelagic calcite flux. Given their importance for the marine calcite budget and for the pelagic carbonate counter pump, which counteracts the biological pump in terms of oceanic capacity for intake of CO₂, it is crucial to gain an understanding of factors modulating the export flux of planktonic foraminifera calcite. In principle, variability in the export flux of planktonic foraminifera calcite could depend within one species on i) shell flux, ii) shell size and iii) calcification intensity, and where shell size and calcification intensity differ among species also on the species composition of the deposited assemblage. To assess the importance of these aspects in modulating the export flux of planktonic foraminifera calcite, we investigated two annual time series (from 1990-1991 and 2007-2008) from sediment traps moored in the Cap Blanc upwelling area. We assessed the predictability of foraminifera calcite flux variability on seasonal and interannual time scales, by determining the variability in species-specific shell fluxes, shell sizes and weights with bi-weekly resolution. We find a remarkable discrepancy in the contribution of the controlling factors between seasonal and interannual scales. On the seasonal time scale, 80% of the variability of the calcite flux is explained by shell flux. On the inter-annual time scale, on the other hand, variations in shell size and calcification intensity are key to explain the calcite flux, since the time series from 2007-2008 yielded 58% larger and 11% heavier specimens. These results imply that for the global estimate of planktonic foraminifera calcite flux, shell flux is likely the most relevant predictor. However, a prediction of the temporal evolution of the calcite flux will likely require estimates of changes in shell size and calcification intensity of the involved foraminifera species.

How to cite: Kiss, P., Jonkers, L., Hudáčková, N., Turid Reuter, R., and Kučera, M.: Determinants of calcite flux in planktonic foraminifera on seasonal and interannual time scales, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20613, https://doi.org/10.5194/egusphere-egu2020-20613, 2020.

How to cite: Seok, M., Mo, A., Park, S., Ko, Y. H., Yun, S., Kim, D., and Kim, T.-W.: Seasonal variation in inorganic carbon parameters in the southwestern Yellow Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3330, https://doi.org/10.5194/egusphere-egu2020-3330, 2020.

Differentiating microbial, anthropogenic, and thermogenic sources of carbon dioxide (CO₂) and methane (CH₄) in background air is an important element of understanding upper ocean ecosystem processes. Concentrations of these gases alone are not dispositive indicators of processes, so additional diagnostic parameters including meteorological data, related gas species measurements, and isotopic values can allow researchers to better investigate processes. Here we present data from the Fleur de Passion sailing research vessel which traveled from Dakar, Senegal to the Azores, and to Northwest Spain between early April and October of 2019 as part of the larger Ocean Mapping Expedition by the Geneva-based NPO Fondation Pacifique. The 33-meter-long ketch research vessel carried as part of its instrument suite a Picarro G2201-i high precision gas analyzer, measuring concentrations and ẟ¹³C values of CO₂ and CH₄. The high precision data collected by the isotopic carbon analyzer (which are being sampled as part of the University of Geneva’s Winds of Change program) allow for subtle differentiation of modalities separated by a per mil or less, signals that could be lost by infrequent flask measurements or low-precision analyzers. We present findings from this expedition, as well as a brief description of future efforts to measure underway dissolved gases.

How to cite: Hofmann, M. E. G., Donis, D., Bent, J. D., Lucic, G., Cesar, O., and McGinnis, D. F.: High-precision cavity ring-down measurements of ẟ13CO2 and 13CH4 along the Eastern North Atlantic onboard the sailing research vessel Fleur de Passion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18860, https://doi.org/10.5194/egusphere-egu2020-18860, 2020.