Evaluating anthropogenic N inputs to diverse lake basins: A case study of three Chinese lakes

The environmental degradation of lakes in China has become increasingly serious over the last 30 years and eutrophication resulting from enhanced nutrient inputs is considered a top threat. In this study, a quasi-mass balance method, net anthropogenic N inputs (NANI), was introduced to assess the human influence on N input into three typical Chinese lake basins. The resultant NANI exceeded 10 000 kg N km⁻² year⁻¹ for all three basins, and mineral fertilizers were generally the largest sources. However, rapid urbanization and shrinking agricultural production capability may significantly increase N inputs from food and feed imports. Higher percentages of NANI were observed to be exported at urban river outlets, suggesting the acceleration of NANI transfer to rivers by urbanization. Over the last decade, the N inputs have declined in the basins dominated by the fertilizer use but have increased in the basins dominated by the food and feed import. In the foreseeable future, urban areas may arise as new hotspots for nitrogen in China while fertilizer use may decline in importance in areas of high population density.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0638-8) contains supplementary material, which is available to authorized users.     

Ecological modelling of nitrate pollution in small river basins by spreadsheets and GIS

With the increasing importance and awareness of water quality in the small basins, the modelling system is developed for monitoring and predictions of surface water pollution. The compartment model deals with basin characteristics extended by land cover attributes. The parameters of the model are estimated by experimental data of water quality together with land cover types that serve as nutrient detention media or transformers. The study examines methodology to determine the potential areas of nitrate pollution from point and non-point sources by remote sensing techniques. Classification of water, agricultural, forest and urban areas is processed with satellite images (LANDSAT 7). Whereas the agricultural and urban areas act as sources of pollution, forest zones operate as sinks. The nitrate levels are decreased downstream, if the proportion of the forest inside contribution zones increases. The modelling system is used to simulate amounts of nitrates in each compartment of the stream during the monitored period of one year. The number of compartments and their lengths are estimated on the basis of morphology of the basin. Simulation of the dynamic model is carried out with the TabSim. Geographic information system (GIS) and remote sensing tools are used to manage and estimate nitrate inflows from point and non-point sources of pollution. The article presents the spatial and time variation of the nitrate (NO₃⁻) within the basin of the stream Rakovnický (the west part of Bohemia, the whole area of 368 km²). It is shown that the model approach extended by the GIS and remote sensing can support decision-making process for better management practices in the basins.     

饮用水生物预处理除氮技术

依据饮用水中氮元素各种污染形式间的转化机量，介绍了国内外利用生物预处理技术除氮的工艺和经验，讨论了运行控制中的各种影响因素，对生物预处理技术的除氮发展进行了展望。     

Photocatalytic removal of nitrogen oxides via titanium dioxide

We studied the removal of nitrogen oxides pollutants via TiO₂ Degussa P25 powder by photocatalysis. Parameters such as mass of catalyst, geometric irradiated surface, catalyst morphology, and thermal treatment were tested to explain the photocatalytic concentration decrease of nitrogen oxides. According to our working conditions, the conversion rates increased until an optimal value of the TiO₂ weight, 35% of NO concentration and around 20% of NOx, was decomposed by the photocatalysis. The NOx removal increased proportionally with the irradiated geometric surface. The structural transformation of anatase to rutile performed by thermal treatment involved the decrease of the photocatalytic activity.     

双氰胺对不同形态氮在红壤中转化的影响

采用室内好气培养方法，研究了碳酸氢铵、尿素在红壤中的转化，加入硝化抑制剂(双氰胺)对尿素、碳酸氢铵的水解速率、硝化速率的影响，以及硝化抑制剂用量问题。结果表明，无论加入DCD与否，大部分尿素在4d内水解，各处理硝态氮质量分数于35d内出现峰值，铵态氮质量分数变化趋势基本相似，尿素态氮和铵态氮的形态差异主要存在于培养4d内。双氰胺的加入明显提高了相应处理的铵态氮质量分数，降低了硝态氮的质量分数；硝化抑制剂对高质量分数(≥50％)铵态氮、尿素态氮处理的抑制效果优于低质量分数(≤50％)处理。至培养结束时中壤土中仍存在较高质量分数的铵态氮，故铵的硝化时间、尿素水解产生铵的硝化时间有待进一步研究。     

模拟酸雨对红壤铝形态的影响

用动态淋洗试验，研究了不同pH的模拟酸雨对红壤中铝形态和性质的影响．结果表明，酸雨淋洗引起红壤中盐基离子的淋失和土壤铝的溶出．随着酸雨溶液pH的降低，盐基淋矢量和铝溶出量增加．酸雨淋洗影响土壤铝形态的转化，使红壤中交换态铝上升，吸附态羟基铝有所下降．这说明在酸雨长期作用下，羟基铝溶解，并转化为交换态铝和引起铝的溶出，使铝进入环境，危害生态系统．     

Nitrogen availability in relation to vegetation changes resulting from grass encroachment in Dutch dry dunes

The encroachment of some tall grass species in open dune vegetation, as observed in a Dutch dry dune area, is considered unfavourable from a conservation viewpoint. This paper investigates differences in vegetation and soil properties between grass-dominated and still existing open dune grassland plots at four locations along the coast. Soil properties studied include nitrogen and phosphorus pools and nitrogen availability by mineralization. Vegetation properties included are above and below-ground biomass and nitrogen and phosphorus concentrations in above-ground biomass. Systematic differences in N-pools between grass-dominated and open dune grassland plots were not observed. However, N-availability by mineralization and its turnover rates are higher in grass-dominated plots than in open dune grassland plots, as well as above and below-ground biomass. In open dune grassland plots, atmospheric N-input is an important source of N, whereas in grass-dominated plots mineralization largely exceeds atmospheric N-input. However, these observations do not explain the mosaic-like vegetation pattern. Grazing intensity is most likely the determinant factor in the dry dune system. It is concluded, that grass encroachment is probably triggered by atmospheric deposition and is enhanced by positive feedbacks in the N-cycle. The relevance of these results for restoration management is briefly discussed.     

二种高硫煤中硫氮化学形态的研究

利用ＸＰＳ技术研究了贵定煤和西班牙Ｍｅｑｕｉｅｎｚａ煤中硫和氮化学形态的分布，并结合硫Ｋ－边ＸＡＮＥＳ和Ｍｏｓｓｂａｕｅｒ谱着重考察贵定煤中硫化学形态。结果表明，贵定煤中含硫化合物主要以噻吩形态存在，其次为有机硫化物；而Ｍｅｑｕｉｅｎｚａ煤中以有机硫化物含量最大，噻吩硫次之，有关含氮化合物，Ｍｅｑｕｉｅｎｚａ煤以吡咯和吡啶氮为主，但在贵定煤中观察到较大浓度的氧化氮化合物。     

Ancillary benefits of reduced air pollution in the US from moderate greenhouse gas mitigation policies in the electricity sector

Actions to slow atmospheric accumulation of greenhouse gases also would reduce conventional air pollutants yielding “ancillary” benefits that tend to accrue locally and in the near-term. Using a detailed electricity model linked to an integrated assessment framework to value changes in human health, we find a tax of $25 per metric ton of carbon emissions would yield NO_x-related health benefits of about $8 per metric ton of carbon reduced in the year 2010 (1997 dollars). Additional savings of $4–$7 accrue from reduced investment in NO_x and SO₂ abatement in order to comply with emission caps. Total ancillary benefits of a $25 carbon tax are $12–$14, which appear to justify the costs of a $25 tax, although marginal benefits are less than marginal costs. At a tax of $75, greater total benefits are achieved but the value per ton of carbon reductions remains roughly constant at about $12.     

Application of a coupled ecosystem-chemical equilibrium model, DayCent-Chem, to stream and soil chemistry in a Rocky Mountain watershed

Atmospheric deposition of sulfur and nitrogen species have the potential to acidify terrestrial and aquatic ecosystems, but nitrate and ammonium are also critical nutrients for plant and microbial productivity. Both the ecological response and the hydrochemical response to atmospheric deposition are of interest to regulatory and land management agencies. We developed a non-spatial biogeochemical model to simulate soil and surface water chemistry by linking the daily version of the CENTURY ecosystem model (DayCent) with a low temperature aqueous geochemical model, PHREEQC. The coupled model, DayCent-Chem, simulates the daily dynamics of plant production, soil organic matter, cation exchange, mineral weathering, elution, stream discharge, and solute concentrations in soil water and stream flow. By aerially weighting the contributions of separate bedrock/talus and tundra simulations, the model was able to replicate the measured seasonal and annual stream chemistry for most solutes for Andrews Creek in Loch Vale watershed, Rocky Mountain National Park. Simulated soil chemistry, net primary production, live biomass, and soil organic matter for forest and tundra matched well with measurements. This model is appropriate for accurately describing ecosystem and surface water chemical response to atmospheric deposition and climate change.