AS2.9

Phosphorus is an important nutrient for the growth of marine life in the East China Sea(ECS), where phosphorus is restricted. The external input of phosphorus may cause changes in primary productivity and result in harmful algal blooms. Previous studies emphasized the important contribution of diluted water from the Yangtze River and Kuroshio current. Few researches focus on the sudden and large atmospheric input. Supported by the National Natural Science Foundation of China Open Research Cruise, we collected seawater samples, measured the oxygen isotopes of phosphate and then quantitatively analyze the contribution rate of phosphate from different sources. The results are found that atmospheric input is the main source of phosphorus in the northeast of the East China Sea and the main source of phosphate is from Taiwan Warm Current in the southwest part of the ECS. This finding is helpful for exploring the influencing factors of harmful algal blooms in the ECS and providing some ideas of solution.

How to cite: Tian, R. and Zhao, X.: Contribution of phosphorus transported by atmosphere to the East China Sea in summer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-925, https://doi.org/10.5194/egusphere-egu22-925, 2022.

Long-range atmospheric transport and deposition of anthropogenically-sourced aerosol iron (Fe) affects surface ocean biogeochemistry far from the emission source. However, it is challenging to establish the integrated impact of anthropogenic aerosol Fe on surface ocean dissolved Fe (dFe) cycling, due to other Fe sources and in situ cycling processes. Previous work has used a distinctively-light Fe isotopic signature (δ⁵⁶Fe) associated with anthropogenic activity to track the contribution of anthropogenic Fe at the basin scale. However, this requires not only the determination of the δ⁵⁶Fe endmember of all potential Fe sources, but also the assessment of how upper ocean biogeochemical cycling modulates surface ocean dFe signatures (δ⁵⁶Fe_diss). Here we accounted for dust, fire and anthropogenic Fe deposition fields in a global ocean biogeochemical model with an integrated δ⁵⁶Fecycle to quantify the impact of anthropogenic Fe on surface ocean Fe and δ⁵⁶Fe, with a focus on the North Pacific. The effect of anthropogenic Fe is spatially distinct and seasonally variable in our model, depending on the biogeochemical state of the upper ocean. In the subtropical regions where Fe is not limiting, anthropogenic Fe input leads to increased dFe levels and, at times, phytoplankton Fe uptake. δ⁵⁶Fe_diss declines due to the very light anthropogenic δ⁵⁶Fe endmember, most prominently in low dFe areas of the subtropical North Pacific gyre. In Fe-limited systems, such as the subpolar gyre, anthropogenic Fe stimulates both primary production and Fe uptake with little change to summertime dFe levels. Moreover, the decrease in δ⁵⁶Fe_diss is amplified as extra Fe dampens the impact of the fractionation effects associated with Fe uptake and complexation, whereby the overall δ⁵⁶Fe_diss often remains positive. Overall, it is important to account for biological parameters, such as primary productivity or Fe limitation, when assessing the oceanic impact of anthropogenic Fe.

How to cite: König, D., Conway, T., Hamilton, D., and Tagliabue, A.: Surface ocean biogeochemistry regulates the impact of anthropogenic aerosol Fe deposition on iron and iron isotopes in the North Pacific, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1494, https://doi.org/10.5194/egusphere-egu22-1494, 2022.

It is known that mineral dust is the largest source of aerosol iron (Fe) to the offshore global ocean, but acidic processing of coal fly ash (CFA) may result in a disproportionally higher contribution of dissolved Fe to the surface ocean. In this study, we determined the Fe speciation and dissolution kinetics of CFA from Aberthaw (United Kingdom), Krakow (Poland), and Shandong (China) in acidic aqueous solutions which simulate atmospheric acidic processing. The CFA bulk samples were re-suspended in a custom-made chamber to separate the PM₁₀ fraction. The Fe speciation in the PM₁₀ fractions was determined using sequential extraction methods. In the PM₁₀ fractions, 8%-21.5% of the total Fe was as hematite and goethite (dithionite extracted Fe), 2%-6.5 % as amorphous Fe (ascorbate extracted Fe), while magnetite (oxalate extracted Fe) varied from 3%-22%. The remaining 50%-87 % of Fe was associated with aluminosilicates. At high concentrations of ammonium sulphate ((NH₄)₂SO₄) and low pH (2-3) conditions, which are often found in wet aerosols, the Fe solubility of CFA increased up to 7 times. The oxalate effect on the Fe dissolution rates at pH 2 varied considerably, from no impact for Shandong ash to doubled dissolution for Krakow ash. However, high concentrations of (NH₄)₂SO₄ suppressed this enhancement in Fe solubility. The modelled dissolution kinetics suggest that magnetite may also dissolve rapidly under acidic conditions, as the dissolution of highly reactive Fe alone could not explain the high Fe solubility at low pH observed in CFA. Overall, Fe in CFA dissolved up to 7 times faster than in Saharan dust samples at pH 2. These laboratory measurements were used to develop a new scheme for the proton- and oxalate- promoted Fe dissolution of CFA. The new scheme was then implemented into the global atmospheric chemical transport model IMPACT. The revised model showed a better agreement with observations of surface concentration of dissolved Fe in aerosol particles over the Bay of Bengal, due to the rapid Fe release at the initial stage at highly acidic conditions.

How to cite: Baldo, C., Ito, A., Krom, M. D., and Shi, Z.: Atmospheric dissolved iron from coal combustion particles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4315, https://doi.org/10.5194/egusphere-egu22-4315, 2022.

Atmospheric Ice nuclei particles regulate in cloud properties such as, cloud lifetime, precipitation rates and cloud’s radiative properties due to their ability to trigger ice heterogenous formation. Particles ejected into the atmosphere during bubble bursting through the sea surface microlayer, which is enriched in organic matter, are considered as the major precursors of INPs over the ocean. In addition, mineral dust particles that are considered as the most important precursor of INP in the mixed-phase cloud regime globally and terrestrial bioaerosols that have been also shown to have INP activity are transported over the ocean and contribute to the INP in the marine environment.

In the present study we present results from the global 3-D chemistry transport model TM4-ECPL that accounts for INPs concentrations from marine organic aerosols, terrestrial bioaerosol and K-rich feldspar and quartz mineral dust particles. The simulated distribution of INP concentrations over the global ocean agrees with currently available ambient measurements. The relative contribution of the various INP precursors in the different compartments of the marine atmosphere is discussed on the basis of simulated 3-dimensional number concentrations of INP, providing insight to the cloud glaciation processes in the marine environment.

Support from PANACEA (MIS 5021516) 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 the Excellence grant, the U Bremen Excellence Chair and the European Union Horizon 2020 project FORCeS under grant agreement No 821205.

How to cite: Kanakidou, M., Chatziparaschos, M., Daskalakis, N., Myriokefalitakis, S., and Kalivitis, N.: Organic aerosols and dust as contributors to ice nucleating particles formation in the marine atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7951, https://doi.org/10.5194/egusphere-egu22-7951, 2022.