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591.
P. J. Murray D. J. Hatch E. R. Dixon S. Granger C. OPrey R. J. Stevens R. J. Laughlin S. C. Jarvis 《Water, Air, & Soil Pollution: Focus》2004,4(6):45-52
Much work has been done on gaseous emissions and leaching of nitrogenous compounds from whole soil profiles and also from soil surface measurements which are assumed to be mainly due to topsoil activity. In soils with an impervious clay subsoil, the boundary between the topsoil and subsoil may provide an interface for microbial activity, including N transformations. In this study, we investigated movement and transformations of two reactive N species (nitrate and urea) at the subsoil interface using a series of replicate, intact soil blocks, under two contrasting watering regimes. We measured fluxes in both liquid and gaseous phases and demonstrated that nitrate reaching the subsoil interface does not necessarily leach into water systems, but may denitrify immediately and could, therefore, add to atmospheric pollution through N2O production. On the other hand, ammonium reaching the subsoil interface either directly, or after mineralization, appears to be more mobile than expected and has the potential to pollute watercourses. 相似文献
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H. Arriaga G. Salcedo S. Calsamiglia P. Merino 《Agriculture, ecosystems & environment》2010,135(1-2):132-139
Dietary modifications in dairy cattle have been reported as a useful strategy to alter the composition of manure. Many reports have been published on how changes in dietary crude protein content and forage-to-concentrate ratio reduces animal nitrogen (N) excretion, but little information exists about the effect of diet modification on nitrous oxide (N2O) and nitric oxide (NO) emission when the subsequent slurry is applied on grassland. Two diets differing in forage:concentrate ratio (high forage or HF diet, 75:25; low forage or LF diet, 55:45) were tested to detect the improvement of N use efficiency in milk and the reduction of urinary and fecal N excretion. Triticale silage and barley grain were used as the main forage and concentrate sources in the diets. The subsequent slurries were characterized for N and ammonium-N content (NH4+-N) and applied on grassland in order to study total and pattern of emission of N2O and NO.The HF diet reduced the voluntary dry matter intake of the cows, N intake and urinary and fecal N excretion. However, the reduction of N intake did not improve the N use efficiency in milk (NUE) (21.0%) and did not reduce N excretion per unit of milk produced (15 g N l−1) due to the lower milk yield. Slurries were similar in N content but differed in NH4+ content, being lower in HF. Therefore, different slurry amounts were needed to be applied on grassland to reach the correct fertilisation rate (120 kg NH4+-N ha−1). Total emissions of N2O (5.8 and 5.0 kg N2O-N ha−1) and NO (507.2 and 568.6 g NO-N ha−1), and the pattern of emissions were not affected by dietary treatments. When fertilisation management depends on the collected volume to empty the slurry pit, higher N2O and NO emissions per kg of slurry could be expected from LF slurry. Nevertheless, if slurry is applied following recommendation rates, N2O and NO emission per unit of milk produced might be slightly lower from LF slurry. Grass yield (1.5 t dry matter ha−1) and N uptake (50 kg N ha−1) did not vary due to the applications of different slurries, and was attributed to low rainfalls. The correct management of the slurries on grasslands may justify an adequate nutritional strategy of dairy herds from an environmental and productive point of view. 相似文献
594.
凹凸棒石/氧化锌纳米复合材料对亚甲基蓝的吸附性能 总被引:5,自引:1,他引:4
采用化学沉淀法在凹凸棒石的表面负载纳米氧化锌合成了凹凸棒石/氧化锌(ATP/ZnO)纳米复合材料.同时,研究了亚甲基蓝在纳米复合材料上的吸附行为,并从热力学和动力学角度探讨了吸附作用机理.吸附实验表明:纳米复合材料对亚甲基蓝有优异的吸附能力;纳米复合材料对亚甲基蓝的吸附热力学符合Langmuir等温吸附方程,最大吸附量可达110.50mg·g-1,吸附焓变为18.69kJ·mol-1,吸附自由能变为-33.06~-22.74kJ·mol-1,吸附熵变约为146J.mol-1.K-1,是一个自发的吸热过程;纳米复合材料对亚甲基蓝的吸附动力学符合准二级动力学方程,速率常数随着溶液初始浓度的提高而下降. 相似文献
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597.
分析了中国石化扬子石化烯烃厂环氧乙烷/乙二醇装置主要环境污染源,介绍了装置采取的主要清洁生产技术及应用效果。 相似文献
598.
《Agriculture, ecosystems & environment》2009,133(3-4):139
The NitroEurope project aims to improve understanding of the nitrogen (N) cycle at the continental scale and quantify the major fluxes of reactive N by a combination of reactive N measurements and modelling activities. As part of the overall measurement strategy, a network of 13 flux ‘super sites’ (Level-3) has been established, covering European forest, arable, grassland and wetland sites, with the objective of quantifying the N budget at a high spatial resolution and temporal frequency for 4.5 years, and to estimate greenhouse gas budgets (N2O, CH4 and CO2). These sites are supported by a network of low-cost flux measurements (Level-2, 9 sites) and a network to infer reactive N fluxes at 58 sites (Level-1), for comparison with carbon (C) flux measurements.Measurements at the Level-3 sites include high resolution N2O, NO (also CH4, CO2) fluxes, wet and dry N deposition, leaching of N and C and N transformations in plant, litter and soil. Results for the first 11 months (1.8.2006 to 30.6.2007) suggest that the grasslands are the largest source of N2O, that forests are the largest source of NO and sink of CH4 and that N deposition rates influence NO and N2O fluxes in non-agricultural ecosystems. The NO and N2O emission ratio is influenced by soil type and precipitation. First budgets of reactive N entering and leaving the ecosystem and of net greenhouse gas exchange are outlined. Further information on rates of denitrification to N2 and biological N2 fixation is required to complete the N budgets for some sites. The quantitative roles played by CO2, N2O and CH4 in defining net greenhouse gas exchange differ widely between ecosystems depending on the interactions of climate, soil type, land use and management. 相似文献
599.
600.
P.J. Thorburn J.S. Biggs S.J. Attard J. Kemei 《Agriculture, ecosystems & environment》2011,144(1):1-12
There is concern about environmental impacts of cropping in catchments of Australia's Great Barrier Reef, especially losses of nitrogen (N) from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out from other crops/regions because it is grown with the highest applications of irrigation water and N fertiliser rates of any sugarcane producing region in Australia, attributes which may enhance losses of N. Little is known about N losses from sugarcane production systems, especially irrigated systems. We measured parts of the water and N balance over three sugarcane crops at three contrasting sites in different parts of the Burdekin region, covering a range of soil types/textures and irrigation managements. The experimental data were used to parameterise the APSIM-Sugarcane cropping systems model, and the model then used to ‘infill’ missing data and develop more complete water and N balances for each of the crops at the three sites. The model was also used to simulate long-term yields and N losses through runoff and leaching below the root zone at the sites under a range of N fertiliser and irrigation management practices. Unlike the experience in other cropping systems, N losses through runoff and leaching below the root zone were not higher at our sites than measured in rainfed sugarcane production systems. The long-term simulations showed there were clear opportunities for reducing N losses while maintaining yields through reducing N fertiliser application rates. Simulations results suggested that long-term N surpluses of 50 kg ha−1 yr−1, considerably less than those during the experiment or common in the study region, were sufficient to maintain yields but reduce N losses by 50-57%. So, N fertiliser management should aim to keep surpluses to that level. Improved irrigation management could also help reduce N losses but generally to a much lesser extent than reduced N fertiliser applications. Research is required to confirm these predicted benefits, and investigate potential interaction between N fertiliser and irrigation management practices, and impacts of other management practices. 相似文献