Assessing seasonal nitrogen export to large tropical lakes.

Rivers are exporting increasing amounts of nitrogen (N) to lakes, which is leading to eutrophication. However, the seasonality apparent in nutrient loading, especially in tropical areas, is thus far only partially understood. This study aims to better understand the seasonality and the sources of dissolved inorganic nitrogen (DIN) inputs from sub-basins to tropical lakes. We integrated existing approaches into a seasonal model that accounts for seasonality in human activities, meteorology and hydrology, and we applied the model to the sub-basins of a representative tropical lake: Lake Tana, Ethiopia. The model quantifies the river export of DIN by season, source and sub-basin and also accounts for open defecation to land as a diffuse source of N in rivers. Seasonality parameters were calibrated, and model outputs were validated against measured nitrogen loads in the main river outlets. The calibrated model showed good agreement with the measured nitrogen loads at the outflow of the main rivers. The model distinguishes four seasons: rainy (July-September), post-rainy (October-December), dry (January-March) and pre-rainy (April-June). The river export of DIN to Lake Tana was about 9 kton in 2017 and showed spatial and temporal variability: It was highest in the rainy and lowest in the dry seasons. Diffuse sources from agriculture were important contributors of DIN to rivers in 2017, and animal manure was the dominant source in all seasons. Our seasonal sub-basins and rivers model provides opportunities to identify the main nutrient sources to the lake and to formulate effective water quality management options. An example is nutrient application level that correspond to the crop needs in the sub-basins. Furthermore, our model can be used to analyse future trends and serves as an example for other large tropical lakes experiencing eutrophication.

Environmental and health impact by dairy cattle livestock and manure management in the Czech Republic.

In this study we evaluate the potential environmental and health impact of dairy cattle livestock and manure management in the Czech Republic. We present a new approach for national assessments of the environmental impact of an agricultural sector. Emission estimates are combined with a country-specific set of indicators to assess the environmental impact in nine regions with specific environmental characteristics. We estimate the contribution of emissions of ammonia (NH3) and nitrogen oxides (NO) to acidification and terrestrial eutrophication, nitrate (NO3) and phosphate (PO4) to aquatic eutrophication, nitrogen oxides (NO), particulate matter (PM10) and (PM2.5) to human toxicity and methane (CH4) and nitrous oxide (NO) to global warming. We present large regional differences in the environmental and health impact per unit of agricultural production. The regional acidifying, eutrophying and global warming impact of dairy cattle is calculated to be up to three times the national average, depending on the dairy cattle intensity. Aquatic eutrophication is found to be a problem in regions with relatively high eutrophying emissions per hectare of so-called nitrate vulnerable zones. Human toxicity problems caused by dairy cattle livestock and manure management are problematic in regions with a high population density in rural areas. The strength of our approach is the use of country-specific characterisation factors to assess the potential environmental and health impact of agriculture at the sub-national scale. We were able to analyse the potential environmental impact without explicit quantification of specific effects on humans and ecosystems. The results can be used to identify the most polluted areas as well as appropriate targets for emission reduction.

Evaluation of methods for quantifying agricultural emissions of air, water and soil pollutants.

Integrated assessments that analyze global warming, acidification, eutrophication and ozone related problems simultaneously, need complete, detailed and consistent emission estimates that consider possible interrelations between different pollutants. We discuss three types of emission estimation methods: emission factor, regression analyses and process-based methods. Selected examples of these are reviewed to illustrate the large variety in methods available. We present an approach for the evaluation of emission estimation methods which follows three steps: (1) Comparison, (2) Scoring and (3) Multi-Criteria Analysis (MCA). We demonstrate the usefulness of this approach by applying it to a case study for the Czech Republic. Firstly we compare selected methods with respect to characteristics which we consider as requirements to quantify emissions of air, water and soil pollutants in an integrated way. We observe that none of the selected methods fully meet our defined characteristics. Secondly, we score the methods with respect to three types of criteria. This evaluation reveals large differences between the methods. We conclude that the following methods best meet our criteria: the IPCC Guidelines, methods from INITIATOR, and the detailed method of the EMEP/CORINAIR Guidebook. Finally, we perform a Multi-Criteria Analysis to analyze how our conclusions change if one considers certain criteria as more important than others. Based on this analysis we suggest that combining parts of each of the three methods forms a sound basis for a new emission estimation method for quantifying agricultural emissions of air, water and soil pollution simultaneously.

Cost-effective control of SO2 emissions in Asia.

Despite recent efforts to limit the growth of SO(2) emissions in Asia, the negative environmental effects of sulphur emissions are likely to further increase in the future. This paper presents an extension of the RAINS-Asia integrated assessment model for acidification in Asia with an optimisation routine that can be used to identify cost-effective emission control strategies that achieve environmental targets for ambient SO(2) concentrations and sulphur deposition at least costs. Example scenarios developed with this optimisation module demonstrate a potential for significant cost savings in Asia, if emission controls are allocated to those sources that have the largest environmental impact and are cheapest to control. It is shown that strategies that simultaneously address harmful population exposure and the risk of vegetation damage from acid deposition result in the most cost-effective use of resources spent for emission controls.

Future trends in worldwide river nitrogen transport and related nitrous oxide emissions: a scenario analysis.

We analyze possible future trends in dissolved inorganic nitrogen (DIN) export by world rivers and associated emissions of nitrous oxide (N2O). Our scenarios either assume that current trends continue or that nitrogen (N) inputs to aquatic systems are reduced as a result of changes in agriculture practices and fuel combustion technologies. The results indicate that moderate changes in the human diet in North America and Europe, reducing worldwide fertilizer use by only 16%, relative to Business-as-Usual (BAU) levels, may reduce DIN export rates to the North Atlantic and European Seas by about one third and associated N2O emissions by 36 to 77%. We furthermore calculate that relatively large reductions in NOy deposition rates in Europe (of about 80%) may reduce DIN export by rivers by a moderate 8% or less, relative to BAU levels. The potential effect of reduced NOy deposition on riverine DIN export is moderate, because most N in European rivers stems from agriculture, and not from fuel combustion. Nevertheless, the calculated 9% reduction (relative to BAU) in DIN inputs to the North Sea as a potential side effect of air pollution control may help achieve the international policy targets for reduced N inputs to the North Sea.

Cost-effective emission abatement in europe considering interrelations in agriculture.

Agriculture is an important source of ammonia (NH3), which contributes to acidification and eutrophication, as well as emissions of the greenhouse gases nitrous oxide (N2O) and methane (CH4). Controlling emissions of one of these pollutants through application of technical measures might have an impact (either beneficial or adverse) on emissions of the others. These side effects are usually ignored in policy making. This study analyses cost-effectiveness of measures to reduce acidification and eutrophication as well as agricultural emissions of N2O and CH4 in Europe, taking into account interrelations between abatement of NH3, N2O, and CH4 in agriculture. The model used is based on the RAINS (Regional Air pollution INformation and Simulation) model for air pollution in Europe, which includes emissions, abatement options, and atmospheric source-receptor relationships for pollutants contributing to acidification and eutrophication. We used an optimisation model that is largely based on the RAINS model but that also includes emissions of N2O and CH4 from agriculture and technical measures to reduce these emissions. For abatement options for agricultural emissions we estimated side effects on other emissions. The model determines abatement strategies to meet restrictions on emission and/or deposition levels at the least cost. Cost-effective strategies to reduce acidification and eutrophication in Europe were analysed. We found that NH3 abatement may cause an increase in N2O emissions. If total agricultural N2O and CH4 emissions in Europe were not allowed to increase, cost-effective allocation of emission reductions over countries in Europe changed considerably.

Anthropogenic emissions of nitrous oxide (N2O) from Europe.

Anthropogenic nitrous oxide (N2O) emissions from Europe, and Asiatic Turkey, are estimated for the period 1960-2040. Between 1960 and 1985 these emissions are found to have doubled to 1059 kton N2O-N/year. For future emissions three scenarios are defined: a no reduction scenario, where current trends continue; an acid reduction scenario, reflecting the implementation of maximum feasible technology to reduce acidification; and an optimistic scenario, in which both N2O and acidifying emissions are strongly reduced. In the no reduction and acid reduction scenario anthropogenic N2O emissions increase to 1199 and 1274 kton N2O-N/year by 2040, respectively. Thus technologies to reduce acidification are calculated to cause a net increase in N2O emissions. In the optimistic scenario 534 kton N2O-N is emitted annually from 2020. A climate goal, aiming to limit future global warming to 0.1 degree C//decade, is calculated to require a stabilization of anthropogenic European emissions at 221 kton N2O-N/year (based on a pro rata contribution of greenhouse gases to emission reductions, and worldwide equal per capita N2O emissions). In all three scenarios N2O emissions exceed 221 kton N2O-N/year. In order to meet their goal, countries need to cut anthropogenic emissions by 59-90% relative to 1985, and by 40-63% relative to 2040 in the optimistic scenario.