Displays

We urgently need to wake up to the role that climate change will be playing in the phosphorus cycle.  The paper will attempt to address the complexities, controversies and uncertainties of estimating the effects that climate change is having on the phosphorus cycle.  Citing an example from three UK catchments, the effect of climate change on average winter phosphorus loads is predicted to increase by up to 30% by the 2050s, and these effects will only be off-set by large-scale agricultural changes (e.g. a 20–80% reduction in phosphorus inputs).  Achieving phosphorus-related quality water in diverse and productive agricultural landscapes under a changing climate is going to be a massive challenge.  It is less than a century since we started mining rock phosphate, but in the context of a 4.5-billion-year-old earth and the acceleration due to climate, we are living through a switching point for phosphorus in the earth system.

How to cite: Haygarth, P.: Time to wake up to climate change and the accelerating phosphorus cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10238, https://doi.org/10.5194/egusphere-egu2020-10238, 2020.

Phosphorus (P) as a key element in DNA, RNA as well as ATP and phospholipids is essential for the growth, functioning and reproduction of all life on earth. However, if fertilization with animal wastes or human excreta is not available or not organized, P fertilizers stem from nonrenewable geological P deposits, which are an increasingly limited resource. The potential threats of a global P limitation due to “peak phosphorus” have been discussed intensively in the recent past  including the socio economic as well as political consequences which will be dramatic. While a deficit in available soil P leads to a loss of agricultural yield, an excess of total P in soils triggers aquatic eutrophication, loss in biodiversity and wildlife habitat in surrounding water bodies in other regions of the world.

We calculated global soil P balances considering input from atmosphere and plant management (as sum of manure and residue input minus plant uptake) versus depletion due to soil erosion in coupling P fluxes from (Ringeval et al., 2017) with soil erosion rates from (Borrelli et al., 2017).

The world’s soils are currently being depleted in P in spite of high chemical fertilizer input. Considering the current high chemical fertilizer inputs most continents result in slightly positive P balances (e.g. net P input to soils). Exception are Africa with very low chemical fertilizer input of 1.7 kg ha^-1yr^-1 paired with high losses due to soil erosion of 2 kg ha^-1yr^-1 and Europe (the latter is the average for the geographic Europe including eastern European countries with very low chemical fertilizer input). Results indicate negative balances globally as well as for all continents (depletion between 4 and 19 kg P ha^-1yr^-1 ) if input of chemical fertilizers is neglected.

Parallel to the distribution pattern and dynamics of global soil erosion by water (Borrelli et al., 2017), P losses from soils due to water erosion are most dramatic in countries and regions with intensive agriculture and/or extreme climates (e.g., high frequencies of heavy rain storm or droughts followed by significant rain events).

References

Borrelli, P., Robinson, D.A., Fleischer, L.R., Lugato, E., Ballabio, C., Alewell, C., Meusburger, K., Modugno, S., Schütt, B., Ferro, V., Bagarello, V., Oost, K.V., Montanarella, L. and Panagos, P., 2017. An assessment of the global impact of 21st century land use change on soil erosion. Nature Communications, 8(1): 2013.

Ringeval, B., Augusto, L., Monod, H., van Apeldoorn, D., Bouwman, L., Yang, X., Achat, D.L., Chini, L.P., Van Oost, K., Guenet, B., Wang, R., Decharme, B., Nesme, T. and Pellerin, S., 2017. Phosphorus in agricultural soils: drivers of its distribution at the global scale. Global Change Biology

How to cite: Alewell, C., Borrelli, P., Ringeval, B., Ballabio, C., Robinson, D. A., and Panagos, P.: Obvious but overlooked: soil erosion neglect in the global phosphorus cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9980, https://doi.org/10.5194/egusphere-egu2020-9980, 2020.

Despite the importance of phosphorus (P) as a nutrient for all life, its availability is highly constrained in terrestrial ecosystems. The availability of P to plants and microbes is regulated by abiotic processes (e.g. P sorption/desorption, precipitation/dissolution) and biological activities (microbial P immobilization/organic P mineralization). Due to the strong geochemical component of the P cycle, it can be expected that soil C, N and P cycling may differ in terms of effects of geology, climate and management. Despite advances in our understanding of physico-chemical controls on P availability, there is still little mechanistic understanding of large scale controls on soil P cycling and its relation to soil C and N cycling, due to a lack of broad scale studies using common methodologies.

Here we aimed to investigate soil physicochemical and biological factors that drive soil P cycling and may cause a (de)coupling of C, N and P processes. We therefore sampled mineral topsoils (0-10 cm, n=95) across a continental transect in Europe (Southern Spain to Northern Scandinavia), covering major geological, climatic and land use gradients. The soils derived from different land uses (cropland, grassland, forest/woodland) and bedrock types (silicate, sediment, calcareous). We analyzed a wide range of potentially relevant physico-chemical and biological properties and measured gross rates of soil N and P processes by short term (24 h) incubations of soils with ³³P and ¹⁵N following isotope pool dilution approaches.

(i) Across the whole transect land-use effects on soil P pools and processes exceeded those of geology, reflecting the accumulation of fertilizer P in soils of managed ecosystems. Cropland (and grasslands) had higher values of soil total P and soil inorganic P (Pi), available Pi (Olsen P), and gross Pi mobilization rates by abiotic and biotic processes compared to forests. Soil phosphatase activity did not vary between land-uses. Soils on silicate bedrock had significantly higher total and labile P than calcareous soils.

(ii) Climate differentially affected P pools and processes. Soil total P, dissolved organic P, and gross Pi desorption decreased with mean annual temperature (MAT; these properties were not sensitive to mean annual precipitation - MAP), while soil phosphatase activity and gross total Pi mobilization through abiotic and biotic processes increased with MAP but were insensitive to MAT. This clearly points to adverse climatic controls of biotic and abiotic soil P processes.

(iii) We found strong interlinkages between soil C, N and P pools (soil organic matter and microbial biomass) and soil enzymes (beta-glucosidase, chitinase, phosphatase) but not in related gross processes (respiration, N and P mineralization). Interestingly the slopes of C-P and N-P relations of pools and enzymes differed systematically between land-uses, indicating that land management causes a partial decoupling of P from C and N cycles, reflecting the P-richness of croplands.

How to cite: Wanek, W., Wasner, D., Püspök, J., Böckle, T., Noll, L., Zhang, S., Zheng, Q., and Hu, Y.: Continental scale climate, land-use and geological controls of soil P cycling and relations with soil C and N, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10893, https://doi.org/10.5194/egusphere-egu2020-10893, 2020.

The eutrophic lake Eichbaumsee, a ~ 1 km long and 280m wide (maximum water depth 16m) dredging lake southeast of Hamburg (Germany), has been treated for water quality improvements using various techniques (i.e. aeration plants, removal of dissolved phosphate by aluminium phosphate precipitation and by Benthophos adsorption) during the past ~ 15 years. Despite these treatments no long-term improvement of the water quality was observed and the lake water phosphate content continued to increase by e.g. ~ 350 kg phosphate per year between March 2016 and February 2019. As no creeks or rivers drain into the lake and hydrological groundwater models do not suggest any major groundwater discharge into the lake, sources of phosphate (and other nutrients) are unknown.

We investigated the phosphate fluxes from sediment pore water and groundwater into the water body of the lake. Sediment pore water was extracted from sediment cores recovered by divers in August 2018 and February 2019. Diffusive phosphate fluxes from pore water were calculated based on phosphate gradients using first Fick`s law. Stable water isotopes (δ²H, δ¹⁸O) were measured in the lake water, sediment pore water, interstitial waters in the banks surrounding the lake, the Elbe river and in three groundwater wells close to lake. Stable isotope (δ²H, δ¹⁸O) water mass balance models were used to compute water inflow/outflow to/from the lake.

Our results revealed pore-water borne phosphate fluxes between – 0.07 mg/m²/d (i.e. slight phosphate uptake by the sediments) and 2.6 mg/m²/d (i.e. phosphate release to the lake). Assuming that the measured phosphate fluxes are temporarily and spatially representative for the whole lake, about 100 kg/a to 220 kg/a of phosphate is released from sediments. This amount is slightly lower than the observed phosphate increase of the lake water. Stable isotope signatures indicate a water exchange between the aquifer and the lake water. Based on stable isotope mass balances (δ²H, δ¹⁸O) we estimate an inflow of phosphate from the aquifer to the lake between 190 kg/a and 1400 kg/a. This inflow indicates that groundwater-born phosphate is as or even more important than phosphate supply via sediment pore-water. Our study suggests that groundwater may have an important impact on lake nutrient budgets.

How to cite: Scholten, J., Förster, W., Schubert, M., Knöller, K., Classen, N., Lechelt, M., Richard, J.-H., Rohweder, U., and Zunker, I.: Phosphate supply to the eutrophic lake Eichbaumsee (Germany): Sedimentary versus groundwater sources, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4664, https://doi.org/10.5194/egusphere-egu2020-4664, 2020.

To understand current phosphorus (P) cycling, which encompasses disturbances caused by human activity, it is necessary to quantify the long-term natural P cycles on which modern drivers act. The shortness of monitored P records renders this difficult by only covering the post-disturbance period and therefore fail to capture pre-disturbance baselines. Target driven management of sensitive ecosystems suffering from eutrophication uses baselines for P that cannot be reliably quantified at present. Recovery will only be possible if P loadings can be brought under control and this requires an understanding of what water quality targets are both desirable and achievable on a site-specific basis. This matters because a well-functioning ecosystem will be more resilient under future climate change and increasing human pressure on the landscape.

Where lakes are present in the landscape, there is the opportunity to use the sediment archive to provide long records of past P concentration.  At present, these reconstructions rely on diatoms or related microfossil indicators. These require time and resource intensive tailored training sets and furthermore the records do not preserve in all lakes. Here we present a novel geochemical method for reconstructing water P concentrations based on lake sediment P burial fluxes, which in principle is universally applicable.

Tested at six published lake sites, the method produces results that agree very well with overlapping monitoring data for those lakes (r² = 0.8). We want to share our method with the research community to identify additional sites to further verify the general applicability.

To illustrate the value of this approach to site-specific management, we compare past lake water total P reconstructions at Crosemere (UK) with a record of Holocene land cover change to identify the drivers of acceleration in the P cycle. Wider application of this lake sediment geochemical method will allow more critical evaluation of the human and natural drivers of the P cycle and be of benefit to ‘systems understanding’ spanning terrestrial and aquatic ecosystems.

How to cite: Moyle, M., Boyle, J., and Chiverrell, R.: Reconstructing past lake water total phosphorus concentration using sediment geochemical records, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9777, https://doi.org/10.5194/egusphere-egu2020-9777, 2020.

Phytoplankton can accumulate polyphosphate (polyP) to alleviate the limitation of essential nutrient phosphorus (P). Yet polyP metabolisms in aquatic systems and their roles in P biogeochemical cycle remain elusive. Previously reported polyP enrichment in low-phosphorus oligotrophic marine waters contradicts the common view of polyP as a luxury P-storage molecule. Here, we show that in a P-rich eutrophic bay of Lake Ontario, planktonic polyP is controlled by multiple mechanisms and responds strongly to seasonal variations. Plankton accumulates polyP as P storage under high-P conditions via luxury uptake and uses it under acute P stress. Low phosphorus also triggers enrichment of polyP that can be preferentially recycled to attenuate P lost. We discover that picoplankton, despite their low production rates, are responsible for the dynamic polyP metabolisms. Picoplankton store and liberate polyP to support the high primary productivity of blooming algae. PolyP mechanisms enable and P exchange and efficient P recycling on the ecosystem and even larger scales.

How to cite: Dittrich, M., Li, J., Diane Plouchart, D., and Zastepa, A.: Recycling of Polyphosphate accumulated in picoplankton in coastal Lake Ontario, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12462, https://doi.org/10.5194/egusphere-egu2020-12462, 2020.

Phosphorus (P) is a development-limiting nutrient for crops, hence global food production relies on P fertilizer application. However, P mobility in soil depends on many abiotic and biological processes, most notably its chemical interactions with the soil particles. Optimizing the timing and amount of fertilization could lead to higher production efficiencies and also reduce P runoff and subsequent contamination of water bodies. Plants have developed strategies to improve P uptake by optimizing the root system architecture and exuding organic acids for enhancing P mining locally to the root tips. However, these adaptations are mainly a response to low P availability or to already immobilized P patches in soil, and little is known about the fate of P in the early stages of fertilization.

In this framework, we developed an experimental assay for investigating P release from the fertilizer pellets, and its movement through soil using non-invasive microdialysis sampling techniques and inductively coupled plasma - mass spectrometry (ICP-MS) analytical techniques. Microdialysis allowed for time resolved in-situ samplings and the small size of the probes also allows for a fine spatial resolution.

Results showed a very rapid release of the P from the fertilizer pellet (triple super phosphate, TSP), producing a high concentration pulse that lasts a few hours. P concentrations then decrease over time until reaching steady low concentrations after 6-8 days and P replenishment from the pellet was not observed after the first pulse. The experiments showed that the speed of P movement in soil is greatly influenced by soil particle size distribution, and that gravity plays an important role in promoting quick P movement in the downward direction, while diffusion can account for P observed in the upward direction. Modelling was also applied to data fitting for quantifying trends and deriving an effective P diffusion coefficient in saturated soil.

How to cite: Petroselli, C., Williams, K., Ghosh, A., Scotson, C., McKay Fletcher, D., Ruiz, S., Walker, N., Sousa Dias, T. G., and Roose, T.: Monitoring early stages of P release from fertilizer pellets to bulk soil using non-invasive sampling techniques, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8677, https://doi.org/10.5194/egusphere-egu2020-8677, 2020.

In neutral to acidic soils, the availability of phosphorus (P) is affected by its strong affinity for mineral surfaces. Especially the interaction between P and iron- and aluminum-(oxy)hydroxides (Fe- and Al-hydroxides) plays a crucial role in the immobilization and hence, availability of P for plants. In this context, the fixation of P is mainly determined by processes of adsorption, desorption, and precipitation. In that sense, the kinetics and mechanisms of P desorption from synthetic well crystalline goethite (α-FeO(OH)) and gibbsite (γ-Al(OH)₃) as well as from amorphous ferrihydrite (Fe₂O₃·H₂O) and Al-hydroxide (Al(OH)₃) were characterized.

Different inorganic and organic desorption solutions were selected for these experiments. On the one hand, substance conversion processes take place in the soil system. High-molecular-weight organic compounds formed during humification and mineralization play an important role in soil environment and P mobilization. On the other hand, plants had developed a range of adaptive strategies in case of P demand. Plant roots excrete complex mixtures of organic compounds such as organic acids, amino acids, and sugars. Additionally, there are equilibrium reactions, which are determined by the respective ionic strength of the soil solution itself. For a comparison regarding the efficiency of P mobilization from synthetic Fe- and Al-hydroxides, the desorption solutions CaCl₂, and CaSO₄ were chosen as main components of the soil solution, and humic and citric acid were selected as organic ligands following humification or produced by organisms in the rhizosphere.

Previous P adsorption experiments revealed the formation of adsorbed P surface complexes on crystalline hydroxides by using Fourier-Transform Infrared spectroscopy. Amorphous Al-hydroxides, characterized by a less rigid crystal structure, revealed higher accessibility of P binding sites within the particle structure. The higher accessibility of binding sites was also observed for ferrihydrite. The amorphous character enabled the diffusion of P into the mineral particle, where stable surface complexes and precipitates were formed. Hence, the grade of crystallinity affects the extent of precipitated and low-soluble P complexes.

After 8 weeks of desorption time, the cumulative P desorption increased following the order CaCl₂ < CaSO₄ < humic acid < citric acid. Amorphous ferrihydrite exhibited much less desorption when exposed to inorganic solutions than goethite, gibbsite, or Al-hydroxide. Modeling of the desorption data suggested a diffusion-controlled desorption step for ferrihydrite with citric acid as sorptive. The determination of C_Total also indicated various release mechanisms of the organic acids: while the use of humic acid led to the accumulation of metal-organic complexes in the solution, citric acid dissolved the mineral phase and hence, also low-soluble precipitated P-complexes. The results suggest organic compounds, especially citric acid, are more important for the mobilization of P from both crystalline and amorphous Fe- and Al-hydroxides than inorganic ions present in the soil solution.

How to cite: Gypser, S. and Freese, D.: Mobilization of P from crystalline and amorphous Fe- and Al-hydroxides, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2871, https://doi.org/10.5194/egusphere-egu2020-2871, 2020.

Preventing dissolved phosphorus (P) accumulation in soils and its transport to water bodies has been subject of many studies. However, despite the continuous efforts and advances, excessive P is still a concern and it is especially problematic in freshwater systems: excessive dissolved P leads to eutrophic conditions, a threat for water quality and aquatic life. P removal structures are a novel technology used in urban and rural settings to intercept dissolved P in surface and subsurface flows. P sorption materials (PSMs), active media with high affinity for dissolved P, are the core components of these structures. Once the PSMs reach service life, replacing the spent media can be costly. The objective of this research is to assess potential regeneration techniques that will extend the lifetime of Aluminum (Al)/Iron (Fe)-rich PSMs. We are proposing a regeneration involving a continuous circulation of 1M KOH aiming to restore unavailable sorption sites on the PSMs. A series of flow-through experiments was conducted alternating between P sorption (0.5 and 50 mg/L input solution) and desorption with KOH (5 or 20 pore volumes), varying residence times (0.5 min and 10 min) and number of recirculations (0, 6 and 24). We tested the treatments in 3 manufactured PSMs, Alcan, Biomax and PhosRedeem. Across two cycles of sorption-desorption, Alcan, Biomax and PhosRedeem showed an average P recovery of 81%, 79% and 7%, respectively.  The comparative investigation of the tested treatments revealed that the most effective regeneration treatment is characterized by a larger KOH volume (20 pore volumes) and no recirculation, with up to 100% reported P recovery. This research demonstrates the ability of Al/Fe-rich PSMs regeneration to contribute to a circular economy of P, as P recovery enables a more sustainable P cycle in both terrestrial and aquatic environments.

How to cite: S P C Scott, I., J Penn, C., and Huang, C. H.: Development of a regeneration technique for aluminum-rich and iron-rich phosphorus sorption materials , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4211, https://doi.org/10.5194/egusphere-egu2020-4211, 2020.

In common with most national agricultural systems, phosphorus (P) inputs are essential for production of crops and livestock in Northern Ireland (NI). However, the negative environmental impacts on their aquatic environments of inappropriate P management both in agriculture and the wider food system are widely acknowledged. Recent gains in reducing P loading to fresh waters through regulatory intervention are now reversing (Northern Ireland Environmental Statistics Report, DAERA 2018) suggesting the need for additional approaches that improve the sustainability of P use in the NI food system. Such approaches should ensure that P entering the food system (e.g. as food, fertilisers and animal feed) is efficiently recycled back into the system to ‘close the P cycle’, and thus reduce the demand for imported P. Furthermore, minimising P losses from different stages of the food system are critical to mitigating negative environmental impacts. To effectively achieve this, the flows, stores and losses of P within the food system must first be understood. Here, we report on a P substance flow analysis (SFA) undertaken for NI for the year 2017, that provided a focus to empower stakeholders to explore options to change P stewardship in the NI food system. Total P import to the NI food system in 2017 as food, feed, fertiliser and chemical P was 19096 t (10.21 kg person^-1 yr^-1), total P exports were 8097 t (4.33 kg person^-1 yr^-1) leaving a system surplus of 10999 t (5.88 kg person^-1 yr^-1). Of this surplus, 923 t of P (0.49 kg person^-1 yr^-1 or 8%) was consumed in food by the population of NI, 7959 t (72%) accumulated in agricultural soil as excess application, 1528 t (14%) were lost to fresh and coastal waters and 1189 t (11%) were disposed in landfill, demonstrating the current imbalance of P use in NI. This P SFA model created a framework of understanding to engage key stakeholders, in scenario analysis, to explore opportunities for improving the sustainability of P use in the NI food system.

How to cite: Rothwell, S., Forber, K., Johnson, C., Doody, D., and Withers, P.: Identifying opportunities for sustainable phosphorus management in Northern Ireland with substance flow analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5603, https://doi.org/10.5194/egusphere-egu2020-5603, 2020.

The sustainable management of phosphorus (P) includes recycling and enhancing P-use efficiency (PUE) in agriculture.  In this study, we compared plant yield and the PUE of lettuce growing with soil amendments of biosolids from three wastewater treatment plants in comparison to commercial fertilizer.  Furthermore, we used AVP1-transformed lettuce (Lactuca sativa cv. Conquistador), which is genetically improved to enhance its PUE, and compared its performance to non-transformed (wildtype, WT) lettuce in greenhouse conditions.  AVP1 lettuce produced higher yield than WT lettuce only with commercial-fertilizer treatments; the yield with biosolid treatments did not vary between the two lettuce types.  PUE did not differ between WT and AVP1 lettuce but was higher for commercial fertilizer than for biosolids.  WT lettuce had higher P content in below-ground biomass than AVP1 lettuce when both were treated with biosolids.  This suggests that capability of AVP1 lettuce to acidify the root zone may have mobilized heavy metals from biosolids and these toxins reduced the yield, P uptake, and PUE in AVP1 lettuce.  In particular, Cd and As contents were high in lettuce biomass from biosolid treatments and exceeded recommendations for human daily oral dose.

How to cite: Chan, N. I., Rittmann, B., and Elser, J.: Evaluating P sustainability using biosolids in comparison to commercial fertilizer for P-use efficient genetically transformed lettuce, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5870, https://doi.org/10.5194/egusphere-egu2020-5870, 2020.

Phosphate is known to absorb strongly to schwertmannite (Fe₈O₈(OH)₆(SO₄)·nH₂O)¹ and as such, schwertmannite has been proposed to limit phosphate in solution in acid mine drainage (AMD) environments. This in turn will limit phosphate availability to the micro-organisms that live in and propagate AMD². Here we have studied sediment samples from the Rio Tinto river in Spain collected during Europlanet field area visit to verify whether phosphate can be incorporated into sulphate-rich minerals in this river. The minerals were identified using X-ray diffraction. Our analyses show that the concentration of phosphate in the river is in the nM range. Digestion of modern sediments in nitric acid followed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis indicate that sites with sulphate-rich minerals are correlated with elevated phosphate concentrations. In addition, phosphate is also retained in ancient sediments that are dominated by goethite (FeO(OH)).

We have also conducted experiments to explore the competition between Fe³⁺, phosphate and sulphate ions in solution as well as the effect of this on schwertmannite nucleation. UV-Vis and Raman spectroscopy demonstrate that contact ion pairs form between Fe³⁺ and phosphate or sulphate in solution. Particularly, phosphate and sulphate compete for Fe³⁺ in solution consistent with predictions by the solution speciation modelling program PHREEQC. Our experiments also show that above a critical concentration, phosphate retards the nucleation of schwertmannite. As this critical concentration is above that found in Rio Tinto river fluids, phosphate is expected to have a limited role in schwertmannite precipitation, but, its concentration is regulated by its incorporation into schwertmannite and other sulphate-bearing phases in AMD systems.

References

¹Eskandarpour et al. 2006, Material Transactions, 1832. ²Chen et al. 2015, ISME, 1579.

How to cite: King, H. E., Bakker, S., Munnecom, G., and Gomez, F.: Regulation of dissolved phosphate through incorporation into schwertmannite , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6206, https://doi.org/10.5194/egusphere-egu2020-6206, 2020.

Phosphate (P) as an essential resource for food production is becoming scarce. Its uncontrolled loss from agricultural areas is in conflict with the principles of a circular economy. Enhanced loading of surface waters with P is the main cause for eutrophication and presents a key challenge in meeting the objectives of the EU Water Framework Directive. Understanding and controlling environmental P fluxes therefore is key to target both problems, to develop new methods and approaches to manage environmental P fluxes, and to improve surface water quality.

In March 2019 the EU Marie Sklodowska-Curie Innovative Training Network P-TRAP has been launched. P-TRAP establishes a framework of partners from multiple science and engineering disciplines. Integration of non-academic partners from various stakeholder groups into the P-TRAP consortium paves the way for direct implementation of the acquired knowledge. The project is targeting the diffuse flux of phosphate (P) into surface waters, i.e. the problems of understanding and controlling environmental P fluxes. P-TRAP aims to develop new methods and approaches to trap P in drained agricultural areas and in the sediments of eutrophic lakes. Trapping of P involves the application of iron(Fe)-containing by-products from drinking water treatment. P-TRAP aspires the ideas of a circular economy and aims at recovering the retained P in agricultural systems. Novel microbial technologies will be developed to convert P-loaded Fe-minerals into marketable fertilizers whose suitability will be evaluated. The P-TRAP technologies have in common that they rely on the naturally strong connection between P and Fe and the innovative P-TRAP strategies will be underpinned by process-orientated investigations on the behaviour of P during the transformation of Fe minerals. The latter are key in trapping and recycling of P in agricultural systems and lakes. The poster will present the structure and the planned research of the project, including a first overview of achievements of the first year.

How to cite: Walter, S. and Behrends, T. and the P-TRAP team: P-TRAP - Diffuse phosphorus input to surface waters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7857, https://doi.org/10.5194/egusphere-egu2020-7857, 2020.

^* Corresponding author. Tel: 886-62757575 ext65433; E-mail: BL93@cornell.edu; liangbq@mail.ncku.edu.tw

Abstract: Bone residue was found an important constituent of the miraculous Amazonian Dark Earth and considered as an effective supply of Ca and P nutrient to increase soil fertility. The application of bone-char to the soil as amendment is a favorable practice, yet more research is needed to understand the behavior and fate of bone hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) (HAp) in the natural environment over time. In our study, we explored Fourier Transform Infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) to study the physicochemical properties of bone and bone-char (300-1200 °C) under pyrolysis temperatures and their dissolution behavior at different pH (4 and 6). We observed the structural transformation from B-type CHAp to a higher level of disorder AB or A-type CHAp with increasing temperatures, which could be explained by the reaction CO₂ with 2 OH^- in the CHAp channel. A weak band of CO₃^2- at 700 °C implied thermal decomposition of inorganic CO₃^2- at above 700 °C, which partially contributed to the increasing crystallinity and stability of bone char. As the pyrolysis temperature increased up to 1100 °C, the centroid of v_3c PO₄^3- peak shifted to a higher wavenumber (1029-1051 cm^-1), resulting from the rearrangement of P-O bonds. The loss of water and organic component contributed to an increase in vacancy.  The amide and lipids decomposition occurred within 300-600 °C, rendering a better crystal symmetry. The signal of structural OH^- band increased with increasing temperature from 300 to 500 °C, due to the reaction of inorganic CO₃^2- and H₂O [CO₃^2- + H₂O ↔ 2(OH^-) + CO₂]. There was more A-type CHAp formation due to simultaneous reverse reaction, and the OH^- band became weaker at above 500 °C. The surface consolidation of bone char was obvious at 700 °C, according to observation by the Transmission X-ray Microscopy (TXM). The P dissolution was the highest for bone at pH 4 (11.82±0.98 ppm), compared to that at pH 6 (10.93±0.39 ppm). The dissolution was relatively low in 500 °C biochar, and the amount was comparable at pH 4 (7.08±0.16 ppm) and pH 6 (6.902±0.16 ppm) after 140 hours’ incubation. The lowest P dissolution was observed at 700 °C biochar, and a higher dissolution was observed at higher pH 6(6.03±0.03 ppm) when compared to that at pH 4 (3.489 ±0.07 ppm). There was a very large increase in pH after bone char addition, which increased from 4 to 8.12 and 6 to 8.14, respectively. The solution end pH was similar after bone char addition. Surface complex reaction (≡CaOH₂⁺+HPO₄^2–⇌≡OPO₃H^-+H⁺) explained the PO₄^3- re-adsorption to bone char surface within the pH range of 4.5 to 8.2. Charring of bone would lead to a longer lifetime in the natural environment and render a stable pool of P nutrient in infertile soils. The scale-up application of bone char offers new opportunities to restore degraded soil by waste recycling and management.

Keywords: Bone char, hydroxyapatite (HAp), CHAp, FTIR, TXM, Phosphorus dissolution, soil fertility. 

How to cite: Biswas, P. P., Weng, Y., Turner-Walker, G., and Liang*, B.: Physico-chemical transformation of bone char for soil amendment , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8267, https://doi.org/10.5194/egusphere-egu2020-8267, 2020.

Understanding the consequences of the interplay between land use and climate change is among the most pressing challenges of the 21^st century for river managers. Over the past decades, agricultural land use has altered nutrient concentrations and stoichiometric ratios in stream ecosystems, thereby affecting aquatic biogeochemical cycles and the coupling among carbon, phosphorus, and nitrogen. In addition, the frequency and duration of droughts has increased dramatically across Europe, causing perennial streams to shift to intermittency and changing the capacity of sediments for the uptake and storage of macronutrients.

Our study aims to understand the effects of drying and re-wetting on the uptake, storage, and release of phosphorus and organic carbon from the benthic and the hyporheic zone of headwater streams under the additional stressor of agricultural land use. In specific, we are interested in the potential coupling and decoupling of phosphorus and dissolved organic carbon cycling in autotrophic and heterotrophic benthic biofilms. We sampled headwater streams before, during, and after the dry period in 2018 and 2019 and performed laboratory experiments with artificial drying and re-wetting and additions of dissolved organic carbon. We measured nutrient uptake and release, microbial biomass, respiration, and the activity of extra-cellular enzymes. The first results show an increased phosphorus release from the sediments immediately after re-wetting, foolowed by a reduced uptake capacity. The uptake of DOC was correlated with phosphorus in autotrophic biofilms, but not in heterotrophic ones.

How to cite: Weigelhofer, G. and Pucher, M.: Effects of intermittency and land use on the in-stream phosphorus and organic carbon uptake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2337, https://doi.org/10.5194/egusphere-egu2020-2337, 2020.

To fully understand coupling between P and other macronutrients it is necessary to have both long-term data sets and process models, combining empirical reality with numerical simulation of coupling processes. Here, lake sediment records of N and P from four UK lakes are compared with model output from N14CP, a long-term, large-scale model of cycling and export of macronutrients from the landscape. The sediment records at the three lakes that have substantial lowland contributions reveal strongly increasing N and P loading through the late 19^th century, with steady increases through the twentieth century. Corresponding changes in N and C isotopes are observed. However, the one mountain lake show maximum N and P loadings in the 19^th century, with declines through the twentieth, consistent with a wholly different land use history. The N14CP model shows N and P increasing from mid 19^th century for average lowland sites, in agreement with the lowland sediment records. The implications of these results for our knowledge about the history of P and N coupling and leaching from UK soils are discussed.

How to cite: Boyle, J., Tipping, E., Davies, J., Rose, N., Turner, S., Toberman, H., Schillereff, D., and Chiverrell, R.: Comparing lake sediment records of landscape macronutrient loadings with N14CP model simulations: 200 years of change in British lakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9968, https://doi.org/10.5194/egusphere-egu2020-9968, 2020.

Hypolimnetic withdrawal (HW) is a restoration method for eutrophied lakes that aims to remove phosphorus (P) and other nutrients from the system. It is conventionally carried out by pumping or siphoning nutrient-rich bottom water to the discharge of the lake during periods of thermal stratification. However, there is growing interest in developing closed circuit modifications of HW in which nutrients could be captured and the purified water returned to the same lake. This would tackle some problematic aspects of conventional HW, and additionally enable the capture and recycling of P stored in lakes.
A pilot closed circuit HW system has been constructed at a eutrophic dimictic lake located in Southern Finland. This hypolimnetic withdrawal and purification circuit (HWPC) consists of a withdrawal pipe installed at the lake deep, a treatment and filtering unit on shore, and a wetland. In the treatment unit, P is first precipitated and then captured by sand filters, while the purified water flows subsequently through a wetland and finally back into the lake.
In the current study, we investigated the pool of potentially removable P in the study lake, the optimal timing of HW within the annual cycle, and the functioning of the HWPC. The P retention capacity of the purification unit and the composition of the precipitate trapped in the filters were both examined. The results showed that P accumulation in the near-bottom water of the study lake during thermal stratification is substantial, allowing significant amounts of P to be removed from the lake via HW. The concentration of total P of the water entering the HWPC was over 300 µg/L, of which the system captured more than 80%. The P content of the precipitate trapped in the filters varied between 6-12 g P/kg, and consisted of both iron and calcium-bound P phases. These results imply that it is possible to recover P accumulated in eutrophied lakes for potential recycling purposes.

How to cite: Silvonen, S., Niemistö, J., Nurminen, L., Aurola, A.-M., Malin, I., Kotakorpi, M., Horppila, J., and Jilbert, T.: Recovering P from a eutrophic lake via hypolimnetic withdrawal and purification, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12974, https://doi.org/10.5194/egusphere-egu2020-12974, 2020.

Phosphorus (P) availability may influence the response of terrestrial ecosystems to environmental and climate change. Soil biogeochemical (organic) and geophysical (inorganic) P cycling processes are the key players in this regulation. There has been a continuous effort to include P cycling processes into terrestrial biosphere models (TBMs) and many modelling studies agreed on the significance of organic P cycling processes to terrestrial ecosystems. However, the role of inorganic P cycling processes remains unclear. Although the model representations of inorganic P cycling in most TBMs are similar, their parameterisations differ greatly, and none of TBMs have been validated against soil P measurements.

In this study, we developed a new algorithm based on the two-surface Langmuir isotherm to describe the inorganic P exchange between soil solution and soil matrix in the QUINCY TBM, and tested both the novel and conventional models at five beech forest sites in Germany along a soil P stock gradient, which are the main study sites of the German Research Foundation (DFG) funded priority programme 1685.

We conducted a literature review on Langmuir P sorption parameters, which indicates that the P sorption capacity (S_max) is strongly correlated with soil texture and the Langmuir coefficient (k_m) is strongly correlated with soil pH and organic matter (OM) content. We divided soil P sorption sites into the OM-rich clay and silty sites and OM-poor sandy sites and extracted empirical equations to calculate their S_max and k_m.

The two-surface Langmuir isotherm approach was implemented to QUINCY, and both the novel and conventional (one-surface Langmuir isotherm) models were applied to the study sites. The models were evaluated with observed soil inorganic P fractionations, foliar N and P contents, and normalized vegetation carbon (C) without calibration. The novel model significantly improved the goodness of model fit to P fractionation measurements at all sites. Both models were able to adequately capture the observed foliar N and P contents, but only the novel one reproduced the observed pattern of vegetation C along the soil P gradient.

We further tested the effect of both models on the responses to CO₂ addition, P addition and C&P addition at all study sites. The conventional model showed stronger ecosystem responses to P and C&P additions than the two-surface Langmuir one, especially at P-poor sites. It is probably due to that plants store more added P in the conventional model than the novel one. We also tested the sensitivity of both models to the P cycling parameterisation at one low-P site. Despite better model fit to the observed soil P fractionation, the novel model also produced higher and more robust gross primary production, foliar P content and vegetation C than the conventional one.

In summary, we showed that the two-surface Langmuir isotherm approach adequately reproduced the observed soil P fractionations and the pattern of vegetation C along a soil P gradient, owing to its better representation of inorganic P cycling and thus C-P interactions, particularly at low-P ecosystems.

How to cite: Yu, L., Ahrens, B., Wutzler, T., Schrumpf, M., Helfenstein, J., Pistocchi, C., and Zaehle, S.: The exchange of inorganic phosphorus between soil solution and matrix might largely affect the model predictions of terrestrial carbon cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16112, https://doi.org/10.5194/egusphere-egu2020-16112, 2020.

Stringent environmental policies in many countries have played an extensive role in reducing external phosphorus (P) loading to lakes from agriculture and urban sources. Nonetheless, such reductions in external P loading to many eutrophic lakes have not resulted in the expected concurrent restitution of water quality. Such a delayed recovery of many lakes is blamed both on internal loading of legacy P from lake sediments (i.e., benthic recycling) and the amplification of such internal P loading processes due to the reduction in external P concentrations. Hence, a detailed process understanding of P cycling at the sediment-water interface (SWI) is critical to understand nutrient loading, water quality and associated effects on lake water quality. Much of the work on sedimentary P cycling has traditionally focused on inorganic processes of soluble phosphate, particularly sorption to metals (Fe, Mn, Al) oxyhydroxides and clays. However, there is increasing recognition that organic forms of P, along with interactions between phosphate and humic substances, also play a decisive role in controlling P fluxes between sediments and the overlying water column.

This study focused on gaining further understanding of the such processes through the collection of sediment cores from the oxygenated epilimnion and the mostly anoxic hypolimnion of Lake 227 of the Experimental Lakes Area (ELA) in Ontario, Canada. Since 1969, this unique experimental lake has been fertilized with phosphorus (P), which triggered a relatively rapid trophic transition from oligotrophic to eutrophic conditions. The cores contain a chronological record of changes in sediment burial rates and sediment P speciation across this trophic transition.

Interpretation of such changes was undertaken by coupling results of chemical extractions with ²¹⁰Pb sediment dating, ³¹P NMR, XANES and Mössbauer spectroscopy. The major sedimentary P fraction prior to lake enrichment starting in 1969 was organic P (P_Org). Fertilization of the lake in 1969 coincided with significant increases in the accumulation rate of sediment, total organic carbon (TOC) and total P (TP), in addition to a marked relative contribution of NaHCO₃ extractable P. The combined proportion of P_Hum and P_Org desposited since artificial fertilization in 1969 account for ≥70% of total P burial in the sediments. The anticipated composition of such P_Hum fractions was hypothesized to be ternary phosphate (PO₄) complexes with humic substances. In support of this, the strong linear correlation between P and iron (Fe) extracted by NaHCO₃ implies a close association of the two elements in the humic fraction. Furthermore, XANES and Mössbauer spectra indicate that most Fe in the post-1969 sediments is conserved in the +3 oxidation state, which may be ascribed to the stabilization of reducible Fe by organic matter, partially due to the formation of ternary PO₄-Fe(III)-humic complexes. Our findings suggest the artificial eutrophication of Lake 227 resulted in the accelerated accumulation of a large sedimentary reservoir of reactive sediment P that may drive continued internal P loading to the water column following the cessation of artificial fertilization. 

How to cite: O'Connell, D., Ansems, N., Kukkadapu, R., jaisi, D., orihel, D., Cade-Menun, B., Hu, Y., Wiklund, J., Hall, R., Chessell, H., Brehends, T., and Van Cappellen, P.: Sedimentary phosphorus speciation dynamics following artificial eutrophication of Lake 227, Experimental Lakes Area, Ontario, Canada, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16637, https://doi.org/10.5194/egusphere-egu2020-16637, 2020.

Iron (oxyhydr)oxides (FeOx) such as ferrihydrite (Fh) and lepidocrocite (Lp) control the mobility of trace elements, contaminants and nutrients such as phosphorus (P) in aquatic systems. Conversely, the sorption of P can alter the structure and reactivity of FeOx. As such, elevated P concentrations in eutrophic, coastal aquatic systems may have far-reaching but currently poorly understood consequences for coupled Fe-nutrient cycling. Here, we present laboratory and field experiments to elucidate the effects of P incorporation on (i) FeOx structure and reactivity and (2) environmental FeOx transformations (crystallization, sulfidation). The structure of the FeOx, synthesized in the absence or presence of P (‘pure’ or ‘P-bearing’ respectively), was probed with synchrotron-based methods (X-ray absorption spectroscopy, high-energy X-ray scattering). Laboratory-based acidic and reductive dissolution experiments (abiotic and microbial) with pure and P-bearing FeOx were combined with novel in-situ field experimentation. The field experiments, which were conducted in freshwater and marine aquatic systems, involved gel-based diffusive samplers loaded with pure and P-bearing FeOx (Fh and Lp) to obtain detailed insight into FeOx chemistry and structure without interference from the sediment matrix. Results from FeOx synthesis experiments showed differences in the impact of P incorporation between FeOx. Ferrihydrite underwent only minor structural changes because of P sorption, yet these changes significantly destabilized the mineral, as evidenced by enhanced rates of reduction and dissolution. Incorporation of P during Lp formation resulted in FeOx precipitate that was significantly less structured than pure Lp. Field experiments in Fe(II)-rich freshwater sediment conducted with Fh showed relatively slow crystallization rates for Fh compared to published laboratory studies. This likely was the result of FeOx surface passivation by adsorption of pore-water P. In H₂S-rich sediment, the degree of sulfidation was higher for P-bearing Fh compared to pure Fh, while the opposite was observed for pure and P-bearing Lp. These findings may be related to differences in electron transfer characteristics and surface reactions with sulfide between Fh and Lp. The novel field experiments provide detailed insight into natural FeOx dynamics in relation to environmental conditions. Decreased stability of FeOx formed in the presence of high nutrient concentrations, leading to less efficient retention of these nutrients, may represent an important feedback mechanism in eutrophication.

How to cite: Kraal, P., Behrends, T., van Genuchten, C., and Lenstra, W.: Interaction with phosphate alters the environmental behavior of iron minerals: double eutrophication trouble?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18193, https://doi.org/10.5194/egusphere-egu2020-18193, 2020.

Crop production in semi-arid regions is often affected by nutrient (N and P) and water deficiency. Hence, crop selection and cropping sequences are mainly influenced by the water supply during the rainy season, which underlies severe annual fluctuations. Under these conditions sorghum cultivation is common practice in smallholder farming systems due to its high potential to cope with water scarcity.

To examine the adaptation potential of sorghum (Sorghum bicolor L. Moench) to water and P stress, we measured transpiration and N uptake of five different sorghum lines (two Indian sorghum landraces, two African landraces and an Indian elite line) under the impact of organic (cowpea root residues) and mineral N-15 inputs. The plants were cultivated in either a P depleted (100 mg P kg^-1 soil) or P enriched (320 mg P kg^-1) Alfisol with a well-watered (WW) or water-stressed (WS) treatment. The experiment was carried out in the lysimetric phenotyping system (ICRISAT, India).

Cowpea labelling was carried out by injecting liquid N-15-label into the plant stem on a weekly basis over the growth period to ensure a homogeneous N-15 distribution in all parts of the plant. Mineral N-15-label was applied after soil saturation on the soil surface approximately two weeks after sorghum sowing to ensure no leakage of the tracer. The sorghum growth period was from middle of September 2018 till beginning of February 2019.

Under WW conditions, the sorghum lines showed different transpiration rates irrespectively of the P supply, whereas biomass and yield production was affected positively by P supply and organic residues. All sorghum lines had reduced transpiration rates, biomass and yield production under WS conditions. However, the African landraces were less susceptible to water stress than the Indian lines and could still produce yield and biomass. Furthermore, N delivery from cowpea residues could be proven in all treatments, while an efficient water supply had a positive impact on the N uptake from residues.

Overall an efficient P supply had only a positive influence on sorghum biomass and yield in interactions with a sufficient water supply or crop residues.

We can conclude that yield and biomass production of sorghum is not only dependent on transpiration rates. The potential to overcome water stress is enhanced for landraces and most properly belowground traits can explain the variation. Furthermore, we could demonstrate that all sorghum lines used biopores at both P levels to cover part of their N demand from cowpea residues. 

In this experiment, African landraces showed improved drought adaptation mechanisms compared to the bread elite line. Further soil and plant analysis will unravel the underlying traits such as improved mycorrhization, root morphology or nutrient uptake.

How to cite: Halicki, S., Görk, E. M., Sauer, A., Sudhabindu, K., Erugoti, L. K., Kholova, J., Ahmed, M. A., and Dippold, M. A.: The potential of Sorghum landraces to overcome P and water limitation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18863, https://doi.org/10.5194/egusphere-egu2020-18863, 2020.

The effects of soil drying and rewetting history on phosphorus solubilisation and growth of maize (Zea mays) under contrasting agricultural soils in China

Nyamdavaa Mongol^1,2, Jianbo Shen², Philip M. Haygarth¹

¹Lancaster Environmental Centre, Lancaster University, Lancaster, LA1 4YW, United Kingdom.

²Department of Plant Nutrition, China Agriculture University, Key Laboratory of Plant-Soil Interactions, Beijing 100193, PR China

Abstract

This paper tested the hypothesis that agricultural soils with a recent history of drying and rewetting (DRW) can trigger P solubilisation in the rhizosphere and a subsequent growth response of maize (Zea mays).  Specifically, it aimed at investigating a possible delayed effect of soil DRW stresses by studying P solubilisation in the rhizosphere, plant P acquisition and performance, and root growth, all under the previous history of series of DRW events, combined with different types of agricultural soils of varied texture and pH.  The soils were collected from four different agricultural regions of China, Shandong, Chongqing, Heilongjiang and Beijing, treated with four varying cycles of DRW events prior to the experiment, to raise levels of soil biotic and abiotic activities and potential development of maize growth. A controlled small pot experiment was conducted to establish the Olsen P in the soil, maize shoot P concentrations, root morphology and other rhizosphere parameters, for the duration of 43 days after planting.   The results show a positive relationship between plant biomass, plant P concentration, and Olsen P. The effect was most clearly demonstrated by growth of plants and their biological performance in the rhizosphere, as the plants responded better in the soil with a DRW background than a soil that did not have a history of DRW in the past.  However, the soluble P concentration and plant growth response varied depending on soil types and P application rates, and the most positive was under Haplic Phaeozems soil from Heilongjiang, leading to an acceptance of hypothesis.  

How to cite: Mongol, N.: The effects of soil drying and rewetting history on phosphorus solubilisation and growth of maize (Zea mays) under contrasting agricultural soils in China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19920, https://doi.org/10.5194/egusphere-egu2020-19920, 2020.

Phosphorus (P) is often a limiting nutrient in soils and aquatic systems, but excessive concentrations can lead to eutrophication. The chemical forms in which P is retained in soils and sediments determine its bioavailability. Under reducing conditions, the ferrous phosphate mineral vivianite has been shown to be a major P burial phase in various environments such as coastal sediments. Depending on the local environmental geochemistry, ferrous iron (Fe²⁺) can be substituted by other divalent cations such as magnesium (Mg²⁺) and manganese (Mn²⁺). The substitution of Fe²⁺ could alter mineralogical characteristics of vivianite, which influences its further reactivity and thus the P and iron (Fe) cycle. Despite the importance of divalent cation substitution in vivianite in the environment, questions remain if certain divalent cations are preferentially incorporated and how they compete for substitution.

Here, we assessed the competitive incorporation of Mn²⁺ and Mg²⁺ into vivianite by carrying out vivianite precipitation experiments in anoxic aqueous solutions at pH 7. Additionally, we explored how varying salinity simulating an estuarine gradient influences the incorporation of Mn²⁺ and Mg²⁺. Changes in mineralogy with different degrees of Mn²⁺/ Mg²⁺ substitution were studied with X-ray powder diffraction, Raman spectroscopy, total elemental dissolution and other techniques.

Based on 19 different vivianites, our results demonstrate that Fe²⁺ is replaced by up to 50% by Mn²⁺/ Mg²⁺ in the vivianite structure, with preferential incorporation of Mn²⁺ over Mg²⁺. Increases in salinity seem to slightly enhance divalent cation incorporation. Following from our results, we will discuss the factors influencing divalent cation incorporation into vivianite, and how divalent cation substitution alters mineralogical characteristics. Finally, we will highlight how the substitution of Fe²⁺ by other divalent cations potentially enhances P fixation in form of vivianite under Fe-limiting conditions.

How to cite: Kubeneck, L. J., ThomasArrigo, L. K., Rothwell, K. A., and Kretzschmar, R.: Competitive divalent cation incorporation in the ferrous phosphate mineral vivianite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20474, https://doi.org/10.5194/egusphere-egu2020-20474, 2020.

Phosphorus (P) is critical for food production but rising P inputs to agricultural land have contributed to eutrophication of fresh and marine waters. Concurrently, wastewater effluent from increasing populations has also become a major P input to natural waters, particularly in urbanised catchments. This study considers the long-term phosphorus budget of the River Thames catchment from 1867 to the present. We combine databases of agricultural land use, human population and river monitoring to develop a phosphorus budget model for the gauged catchment area (9,948 km²) and identify key inputs, outputs and transfers over the period. We quantify P imports and exports of fertilizer, food, feedstuffs, and industrial products (1867-2017), along with direct discharge of fluvial P at the tidal limit (1936-2017).

Net P input to land from animal production was essentially stable at ~1,700 tonnes P until 1940, after which there was a steady rise, peaking at approximately 3,800 tonnes P in the early 1970s. Since then, P inputs to land have fallen to a current stable level of ~2,200 tonnes P. This represents a cumulative net input to land of 350 kT P since 1867. Whilst this input is somewhat counterbalanced by losses to the fluvial system and crop harvest, there is nevertheless a large P legacy in catchment soils.

Net inputs from wastewater (urine and faeces) rose steadily from 0.8 kT in 1936 to 2 kT in 2010, whilst the marked change occurred in relation to P in detergents rising from zero in 1950 to a peak of ~2kT in 1987, since when there has been a gradual decline to <1 kT at present. The total wastewater effluent contribution rose from 0.8 kT in 1936 to a peak of 3.4 kT at the end of the 1980s. The Urban Waste Water Treatment Directive (91/271/EEC) enforced enhanced removal of P in wastewater from the early 1990s, which led to an immediate, sharp decrease in wastewater contribution of 1 kT P since when there has been a steady decline to 0.4 kT at present. This has shifted the environmental pathway of wastewater P from discharge to rivers to accumulation in sludge which is now largely disposed of by application to agricultural land thus adding to the P legacy in catchment soils.

Our analysis of the Thames P budget will end with a discussion of uncertainties in the P model, and the sensitivity of our overall conclusions to assumptions about model structure and parameters applied to our historical records.

How to cite: Howden, N., Worrall, F., Burt, T., Jarvie, H., and Pianosi, F.: A 150-year phosphorus budget for the Thames catchment, UK, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20652, https://doi.org/10.5194/egusphere-egu2020-20652, 2020.

Domestic wastewater (WW) is an important carrier of nutrients usually wasted away by current centralised sewage treatment plants. The Run4Life project proposes an alternative strategy for increasing circularity of WW treatment systems and improving nutrient recovery rates and material qualities. This is based on a decentralised treatment of segregated black water (BW), kitchen waste and grey water combining existing and innovative technologies.

Run4Life is currently improving innovative nutrient recovery technologies, these being: (i) an ultra-low flush vacuum toilet, which uses around 0.5L/flush, thus less water than conventional vacuum toilets, allowing concentration of BW compared to conventional toilets and vacuum toilets. (ii) Bio-electrochemical systems for nitrogen recovery, which recovers up to 12.8 g/m²*d of Nitrogen present in blackwater as liquid fertilizer (ammonium nitrate) iii) (Hyper-)thermophilic anaerobic digestion, which aims to recover the phosphorous and nitrogen in the hygienised effluent in a one-step treatment and ready for use as fertilisers.  

Nutrient recycling technologies from domestic WW are demonstrated at large scale in four demonstration sites where decentralised WW treatment systems are implemented: Ghent (Belgium, 430 houses), Helsingborg (Sweden, 320 apartments), Sneek (The Netherlands, 32 houses), and Vigo (Spain, 1 office building). This will result in solid and liquid NPK fertilizers being recovered in the form of struvite, ammonium nitrate, calcium phosphate, organic fertilizers and reclaimed water.

The environmental, economic and societal impact of the obtained fertilizers is being tested by means of ecotoxicology tests, pot experiments, field trials, and by a selection of key performance indicators based on European, national and regional legislation present in the four different countries. Life cycle assessments are being performed for each technology and demonstration site, and active measures such as knowledge brokerage activities are being developed as an engagement strategy to advocate the institutional, legal and social acceptance of the Run4Life nutrient recovery technologies and fertilizers produced.  In addition, new business models which can benefit from the Run4Life project are currently being assessed.

It is expected that, by the end of the project, more than 90% of the water will be reused, and that nutrient recovery rates will achieve 100%.

How to cite: Torres Sallan, G., Borras, E., Aliaguilla, M., Molognoni, D., Sanchis, S., van-Eekert, M., Moerland, M., Todt, D., Chatzopoulos, P., Meulman, B., Kjerstadius, H., Demolder, L., de-Smet, P., and Morales, N.: Run4Life project: A step forward in NPK recovery from source-separated wastewaters., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21600, https://doi.org/10.5194/egusphere-egu2020-21600, 2020.