Article (refereed) -postprintTipping, E.; Benham, S.; Boyle, J.F.; Crow, P.; Davies, J.; Fischer, U.; Guyatt, H.; Helliwell, R.; Jackson-Blake, L.; Lawlor, A.J.; Monteith, D.T.; Rowe, E.C.; Toberman, H. 2014. Atmospheric deposition of phosphorus to land and freshwater. Environmental Science: Processes and Impacts, 16 (7). 1608-1617. 10.1039/c3em00641g Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. Oceania, and South-Central America. The deposition rates are log-normally distributed, 30 and for the whole data set the geometric mean deposition rates are 0.027, 0.019 and 31 0.14 g m -2 a -1 for TP, FTP and PO 4 -P respectively. At smaller scales there is little 32 systematic spatial variation, except for high deposition rates at some sites in Germany, 33 likely due to local agricultural sources. In cases for which PO 4 -P was determined as well 34 as one of the other forms of P, strong parallels between logarithmic values were found. 35Based on the directly-measured deposition rates to land, and published estimates of P 36 deposition to the oceans, we estimate a total annual transfer of P to and from the 37 atmosphere of 3.7 Tg. However, much of the phosphorus in larger particles (principally 38 primary biological aerosol particles) is probably redeposited near to its origin, so that 39 long-range transport, important for tropical forests, large areas of peatland and the 40 oceans, mainly involves fine dust from deserts and soils, as described by the simulations 41of Mahowald et al. (Global Biogeochemical Cycles 22, GB4026, 2008). We suggest that 42 local release to the atmosphere and subsequent deposition bring about a pseudo-43 diffusive redistribution of P in the landscape, with P-poor ecosystems, for example 44 ombrotrophic peatlands and oligotrophic lakes, gaining at the expense of P-rich ones. 45Simple calculations suggest that atmospheric transport could bring about significant local 46 redistribution of P among terrestrial ecosystems.Although most atmospherically 47 transported P is natural in origin, local transfers from fertilised farmland to P-poor 48 ecosystems may be significant, and this requires further research. 49 50

Are small lakes passive pipes transporting terrigenous organic carbon (dissolved organic carbon [DOC]), or chimneys for CO2 release in the landscape? Using a unique combination of 30‐yr measurements, sediment dating and modeling of a small humic lake and its catchment in southeast Norway, we calculated lateral DOC fluxes and in‐lake retention. Concentrations and fluxes rose significantly, driven by declining sulfur deposition and increased precipitation. In‐lake retention (% of inputs) declined because of higher discharge and lower residence times. DOC removal rates were not sensitive to residence time. Modeled in‐lake DOC removal was driven primarily by microbial metabolism and, secondarily, by flocculation, suggesting that the likely fate of lake‐retained DOC is CO2 evasion to the atmosphere. Precipitation was the overriding landscape control on DOC fluxes and retention. In a wetter climate, small northern lakes will, on balance, function more as pipes than chimneys, with increasing lateral DOC fluxes but little change in CO2 production.

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2016). The INtegrated CAtchment model of phosphorus dynamics (INCA-P): Description and demonstration of new model structure and equations. Environmental Modelling and Software, 83, 356-386. AbstractINCA-P is a dynamic, catchment-scale phosphorus model which has been widely applied during the last decade. Since its original release in 2002, the model structure and equations have been significantly altered during several development phases. Here, we provide the first full model description since 2002 and then test the latest version of the model (v1.4.4) in a small rural catchment in northeast Scotland. The particulate phosphorus simulation was much improved compared to previous model versions, whilst the latest sorption equations allowed us to explore the potential time lags between reductions in terrestrial inputs and improvements in surface water quality, an issue of key policy relevance. The model is particularly suitable for use as a research tool, but should only be used to inform policy and land management in data-rich areas, where parameters and processes can be well-constrained. More long-term data is needed to parameterise dynamic models and test their predictions.

Lake ecosystems across the world are under combined pressures of eutrophication and climate change, which increase the risk of harmful cyanobacteria blooms, reduced ecological status, and degraded ecosystem services. In Europe, the third cycle of river basin management plans (2021–2027) according to the Water Framework Directive must take into account the potential impacts of climate change on water quality, including effects on relevant biological indicators. Here, we applied a Bayesian network as a meta-model for linking future climate and land-use scenarios for the time horizon 2050–2070, via process-based catchment and lake models, to cyanobacteria abundance and ecological status of a eutrophic lake. Building upon previous applications of the model, a new version was developed to include relevant climatic variables such as wind speed. Explorative scenarios showed that the combination of low wind and high temperature gave the most synergistic effects on cyanobacteria under high levels of eutrophication (Chl-a concentration). Considering the management target of good ecological status, however, the climate-related promotion of cyanobacteria blooms contributed most to degrading the ecological status at intermediate levels of eutrophication. Future developments of this model will aim to strengthen the link between climate variables and ecological responses, to make the model also useful for seasonal forecasting.

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Catchment‐scale water quality models are increasingly popular tools for exploring the potential effects of land management, land use change and climate change on water quality. However, the dynamic, catchment‐scale nutrient models in common usage are complex, with many uncertain parameters requiring calibration, limiting their usability and robustness. A key question is whether this complexity is justified. To explore this, we developed a parsimonious phosphorus model, SimplyP, incorporating a rainfall‐runoff model and a biogeochemical model able to simulate daily streamflow, suspended sediment, and particulate and dissolved phosphorus dynamics. The model's complexity was compared to one popular nutrient model, INCA‐P, and the performance of the two models was compared in a small rural catchment in northeast Scotland. For three land use classes, less than six SimplyP parameters must be determined through calibration, the rest may be based on measurements, while INCA‐P has around 40 unmeasurable parameters. Despite substantially simpler process‐representation, SimplyP performed comparably to INCA‐P in both calibration and validation and produced similar long‐term projections in response to changes in land management. Results support the hypothesis that INCA‐P is overly complex for the study catchment. We hope our findings will help prompt wider model comparison exercises, as well as debate among the water quality modeling community as to whether today's models are fit for purpose. Simpler models such as SimplyP have the potential to be useful management and research tools, building blocks for future model development (prototype code is freely available), or benchmarks against which more complex models could be evaluated.