减少氮,磷损失,控制其对环境污染的途径

本文从改进肥料施用技术,改性现有肥料,阻断农田氮磷损失的物理和化学措施,运用生物以及植物生长调节物质等方面这了当前提高氮,磷肥料利用效率,减少氮、磷对环境污染的途径。     

人工湿地脱氮除磷特性研究

针对流域水体富营养化加剧和二级处理水氮磷指标较高的问题,提出以人工湿地对二级出水继续低耗、理想地脱氮除磷。研究中通过对照不同进水水质条件下,不同结构人工湿地的脱氮除磷效能,探讨了人工湿地内的主要脱氮除磷途径。研究表明,表面流湿地内植物对氨氮吸收／吸附和硝化过程为主要氮转化途径,潜流湿地内直接反硝化过程为主要脱氮途径,脱氮效率30％～40％;磷在人工湿地内主要依赖除磷填料床的物化吸附、共沉淀去除,除磷效率达80％以上。     

纳米技术将风化煤制成多功能肥料

中国农业科学院土肥所完成“风化煤多功能肥料修复荒漠化土地技术”，该技术将风化煤和废弃塑料加工成纳米级腐殖酸类混聚物和纳米级的塑料胶团溶液，再加工成固沙保水剂，并与一定比例的氮、磷、钾加热混拌后制成多功能肥料。鉴定会的专家认为，该技术为原始创新技术，对荒漠化土地进行生物修复和废弃物资源化均有重要意义。     

厌氧氨氧化的研究及其应用

厌氧氨氧化是近年来发现的一种新的氮素转化途径。与部分硝化相结合,应用于污水脱氮,具有运行成本低、节约能源和资源等优点。厌氧氨氧化是一生物过程,已确定的细菌有2种:Candidatus Brocadia anammoxidans和Candida-tus Kuenenia stuttgartiensis。描述了其生理学特性、生物化学途径,介绍了其2种应用途径:全自养亚硝酸型脱氮(CANON)和SHARON-ANAMMOX。     

自由表面人工湿地脱氮效果中试研究

对自由表面人工湿地去除农业面源污水中氮的效果及途径进行了研究 ,结果表明 ,脱氮效率随水力停留时间(HRT)延长而增加 ,HRT为 0 5、1、2和 3d时 ,系统总氮去除率分别为 18 3 %、3 8 9%、84 9%和 85 6%。HRT <2d ,出水水质波动较大 ,2d以上 ,系统即可高效稳定运行。硝化 /反硝化是湿地脱氮的主要途径 ,挥发和填料吸附脱氮量可以忽略 ,依靠植物吸收可以去除一部分氮 ,茭草 (Zizaniacaduciflora)和芦苇 (Phragmitascommunis)的氮吸收量每年分别为 44 0和70 0kgN/hm2 。     

自由表面人工湿地脱氮效果中试研究

对自由表面人工湿地去除农业面源污水中氮的效果及途径进行了研究，结果表明，脱氮效率随水力停留时间（HRT）延长而增加，HRT为0.5、1、2和3d时，系统总氮去除率分别为18.3%、38.9%、84.9%和85.6%。HRT＜2d，出水水质波动较大，2d以上，系统即可高效稳定运行。硝化／反硝化是温地脱氮的主要途径，挥发和填料吸附脱氮量可以忽略，依靠植物吸收可以去除一部分氮，茭草（Zizania caduciflora）和芦苇（Phragmitas communis）的氮吸附量每年分别为440和700kg N/hm^2。     

高效脱氮除磷耦合技术物料平衡系统的构建

为了明确系统中反硝化脱氮的具体途径,在传统活性污泥工艺物料衡算方法的基础上,构建了基于短程硝化、同步硝化反硝化和反硝化除磷耦合技术的新型物料平衡系统。以AAO工艺为例,计算了系统稳定运行期间,碳、氮和磷的物料流向,量化了反硝化的5种脱氮途径。结果表明,通过物料衡算推导,系统短程硝化（PN）效率为64．36％。同步硝化反硝化（SND）效率为57．37％;反硝化除磷（DPR）效率为7．82％。对反硝化途径的分析发现,通过亚硝酸盐型同步硝化反硝化去除的氮占32．7％,而作为除磷电子受体得到去除的氮占11．4％。     

厌氧氨氧化的研究及其应用

厌氧氨氧化是近年来发现的一种新的氮素转化途径。与部分硝化相结合，应用于污水脱氮，具有运行成本低、节约能源和资源等优点。厌氧氨氧化是一生物过程，已确定的细菌有2种：Candidauas Brocadia anammoxidans和Candidatus Kuenenia stuttgartiensis。描述了其生理学特性、生物化学途径，介绍了其2种应用途径：全自养亚硝酸型脱氮(CANON)和SHARON-ANAMMOX。     

不同基质复合垂直流人工湿地对富营养化景观水的净化效果

研究了两套不同基质复合垂直流人工湿地小试装置在不同季节对富营养化景观水的净化效果,分析了温度变化对污染物去除效果的影响,考察了微生物的硝化强度和反硝化强度以及基质理化性质对植物生长状况的影响,并探讨了氮、磷的去除途径.结果表明:不同基质复合垂直流人工湿地随季节变化对浊度、COD和磷的去除效果差异不明显;温度降低对脱氮效果影响显著,对磷的去除影响不大.沸石-页岩湿地硝化强度和反硝化强度优于砾石湿地.采用沸石作为基质可以提高系统对氮的去除效率,促进湿地植物的生长.对氮、磷去除途径的分析表明:微生物的硝化反硝化作用以及基质对磷的吸附沉淀作用是复合垂直流人工湿地去除氮、磷的主要途径;植物吸收分别占湿地TN、TP去除量的16%和35%左右,也是个重要途径.     

氮素化肥的环境污染

氮肥的过量施用会引起一系列生态问题，植物摄取过多的氮会导致体内有硝酸盐的大量积累；土壤中多余的氮随径流输入河流、湖泊、海洋、致使地表水富营养化；部分经淋进入地下水，使其中硝酸盐富集，人类饮用或食用了富含硝酸盐的水及食品能够诱发疾病，硝酸盐对环境的污染程度与氮肥施用量呈正相关，为防止氮的污染，必须合理施肥，提高氮肥利用率，并对肥料施用与地表水，地下水养分富集及农产品硝酸盐含量相关的问题进行系统的调查     

上海郊区稻田氮素流失研究

通过测坑和大田小区试验，研究了上海郊区稻田氮素排水流失和渗漏流失的特征、相关因素和流失负荷。结果表明，稻田综合排水TN为6.55mg／L，流失负荷为16．68kg／hm^2，以铵态氮为主，稻田氮素的排水流失负荷为16．68kg／hm^2。稻田渗漏水氮浓度与前茬作物有关，草莓和蔬菜高，麦茬低，TN为5．73mg／L，渗漏负荷为22．92kg／hm^2，其中硝态氮占50％左右。稻田氮素总流失负荷占稻季化肥用量的13．23％。测坑和大田试验都证明，施用有机肥可较多地减少稻田氮素流失量。     

Ammonia emission factors for N fertilizers applied to two contrasting grassland soils

Ammonia volatilization from nitrogen (N) fertilizer applied throughout the year to two soil types was measured using a system of small wind tunnels. Losses from urea ranged from 12 to 46% of the applied N. Small losses, averaging <1%, were measured from ammonium nitrate (AN) and calcium nitrate applications. Factors influencing these losses are discussed. Using these results and those from other workers, emission factors for urea and AN applications to grassland in the UK were determined as 23.0 and 1.6% of the applied N, respectively. Emission factors for these fertilizers when applied to arable land were estimated as 11.8 and 0.8%, respectively. The emission factor for all other applied N (as straight and compound fertilizers) was assumed to be similar to that for AN. Calculations showed that fertilizer applications to agricultural land in the UK contributes 34 kt NH3-N per year, equivalent to 17% of the total annual NH3 emission.     

Dolomite phosphate rock (DPR) application in acidic sandy soil in reducing leaching of phosphorus and heavy metals—a column leaching study

A column leaching study was designed to investigate the leaching potential of phosphorus (P) and heavy metals from acidic sandy soils applied with dolomite phosphate rock (DPR) fertilizers containing varying amounts of DPR material and N-Viro soils. DPR fertilizers were made from DPR materials mixing with N-Viro soils at the ratios of 30, 40, 50, 60, and 70 %, and applied in acidic sandy soils at the level of 100 mg available P per kilogram soil. A control and a soluble P chemical fertilizer were also included. The amended soils were incubated at room temperature with 70 % field water holding capacity for 21 days before packed into a soil column and subjected to leaching. Seven leaching events were conducted at days 1, 3, 7, 14, 28, 56, and 70, respectively, and 258.9 mL of deionized water was applied at each leaching events. The leachate was collected for the analyses of pH, electrical conductivity (EC), dissolved organic carbon (DOC), major elements, and heavy metals. DPR fertilizer application resulted in elevations up to 1 unit in pH, 7–10 times in EC, and 20–40 times in K and Ca concentrations, but 3–10 times reduction in P concentration in the leachate as compared with the chemical fertilizer or the control. After seven leaching events, DPR fertilizers with adequate DPR materials significantly reduced cumulative leaching losses of Fe, P, Mn, Cu, and Zn by 20, 55, 3.7, 2.7, and 2.5 times than chemical fertilizer or control. Even though higher cumulative losses of Pb, Co, and Ni were observed after DPR fertilizer application, the loss of Pb, Co, and Ni in leachate was <0.10 mg (in total 1,812 mL leachate). Significant correlations of pH (negative) and DOC (positive) with Cu, Pb, and Zn (P?<?0.01) in leachate were observed. The results indicated that DPR fertilizers had a great advantage over the soluble chemical fertilizer in reducing P loss from the acidic sandy soil with minimal likelihood of heavy metal risk to the water environment. pH elevation and high dissolved organic carbon concentration in soils after DPR fertilizer application are two influential factors.     

Modeling transport and fate of nitrogen from urea applied to a near-trench paddy field

A simple but comprehensive model is developed to quantify N losses from urea applied to a near-trench paddy field, considering all the N-transformations such as urea hydrolysis, volatilization, nitrification, denitrification, and all the important transportations like runoff, lateral seepage, vertical leaching and crop uptake. Seasonal average data of field observations for three crop seasons were used for model calibration and validation, which showed that ammonia volatilization accounted for 26.5-29.4% of the applied N and N uptake by crop occupied 38.2-44.8%, while N losses via surface runoff, vertical leaching and lateral seepage varied from 5.6-7.7%, 4.0-4.9% to 5.0-5.3% of the applied N, respectively. These observed results were well predicted by our model, indicating that the model performed effectively at quantifying N losses via individual processes in a wide range of urea application rates and benefit for developing water and fertilizer management strategies for near-trench paddy fields.     

Integrated analysis of the effects of agricultural management on nitrogen fluxes at landscape scale

The integrated modelling system INITIATOR was applied to a landscape in the northern part of the Netherlands to assess current nitrogen fluxes to air and water and the impact of various agricultural measures on these fluxes, using spatially explicit input data on animal numbers, land use, agricultural management, meteorology and soil. Average model results on NH₃ deposition and N concentrations in surface water appear to be comparable to observations, but the deviation can be large at local scale, despite the use of high resolution data. Evaluated measures include: air scrubbers reducing NH₃ emissions from poultry and pig housing systems, low protein feeding, reduced fertilizer amounts and low-emission stables for cattle. Low protein feeding and restrictive fertilizer application had the largest effect on both N inputs and N losses, resulting in N deposition reductions on Natura 2000 sites of 10% and 12%, respectively.     

Mitigation of nutrient losses via surface runoff from rice cropping systems with alternate wetting and drying irrigation and site-specific nutrient management practices

Resource-conserving irrigation and fertilizer management practices have been developed for rice systems which may help address water quality concerns by reducing N and P losses via surface runoff. Field experiments under three treatments, i.e., farmers’ conventional practice (FCP), alternate wetting and drying (AWD), and AWD integrated with site-specific nutrient management (AWD + SSNM) were carried out during two rice seasons at two sites in the southwest Yangtze River delta region. Across site years, results indicated that under AWD irrigation (i.e., AWD and AWD + SSNM), water inputs were reduced by 13.4?~?27.5 % and surface runoff was reduced by 30.2?~?36.7 % compared to FCP. When AWD was implemented alone, total N and P loss masses via surface runoff were reduced by 23.3?~?30.4 % and 26.9?~?31.7 %, respectively, compared to FCP. However, nutrient concentrations of surface runoff did not decrease under AWD alone. Under AWD + SSNM, total N and P loss masses via surface runoff were reduced to a greater extent than AWD alone (39.4?~?47.6 % and 46.1?~?48.3 % compared to FCP, respectively), while fertilizer inputs and N surpluses significantly decreased and rice grain yields increased relative to FCP. Therefore, by more closely matching nutrient supply with crop demand and reducing both surface runoff and nutrient concentrations of surface runoff, our results demonstrate that integration of AWD and SSNM practices can mitigate N and P losses via surface runoff from rice fields while maintaining high yields.     

Surface runoff and nitrogen (N) loss in a bamboo (Phyllostachys pubescens) forest under different fertilization regimes

Nitrogen (N) losses from agricultural fields have been extensively studied. In contrast, surface runoff and N losses have rarely been considered for bamboo forests that are widespread in regions such as southern China. The thriving of bamboo industries has led to increasing fertilizer use in bamboo forests. In this study, we evaluated surface runoff and N losses in runoff following different fertilization treatments under field conditions in a bamboo (Phyllostachys pubescens) forest in the catchment of Lake Taihu in Jiangsu, China. Under three different fertilization regimes, i.e., control, site-specific nutrient management (SSNM), and farmer's fertilization practice (FFP), the water runoff rate amounted to 356, 361, and 342 m³?ha^?1 and accounted for 1.91, 1.98, and 1.85 % of the water input, respectively, from June 2009 to May 2010. The total N losses via surface runoff ranged from 1.2 to 1.8 kg?ha^?1. Compared with FFP, the SSNM treatment reduced total nitrogen (TN) and dissolved nitrogen (DN) losses by 31 and 34 %, respectively. The results also showed that variations in N losses depended mainly on runoff fluxes, not N concentrations. Runoff samples collected from all treatments throughout the year showed TN concentrations greater than 0.35 mg?L^?1, with the mean TN concentration in the runoff from the FFP treatment reaching 8.97 mg?L^?1. The loss of NO₃ ^?–N was greater than the loss of NH₄ ⁺–N. The total loss of dissolved organic nitrogen (DON) reached 23–41 % of the corresponding DN. Therefore, DON is likely the main N species in runoff from bamboo forests and should be emphasized in the assessment and management of N losses in bamboo forest.     

Current Nitrogen Management Status and Measures to Improve the Intensive Wheat–Maize System in China

During the first 35 years of the Green Revolution, Chinese grain production doubled, greatly reducing food shortage, but at a high environmental cost. In 2005, China alone accounted for around 38% of the global N fertilizer consumption, but the average on-farm N recovery efficiency for the intensive wheat-maize system was only 16-18%. Current on-farm N use efficiency (NUE) is much lower than in research trials or on-farm in other parts of the world, which is attributed to the overuse of chemical N fertilizer, ignorance of the contribution of N from the environment and the soil, poor synchrony between crop N demand and N supply, failure to bring crop yield potential into full play, and an inability to effectively inhibit N losses. Based on such analyses, some measures to drastically improve NUE in China are suggested, such as managing various N sources to limit the total applied N, spatially and temporally matching rhizospheric N supply with N demand in high-yielding crops, reducing N losses, and simultaneously achieving high-yield and high NUE. Maximizing crop yields using a minimum of N inputs requires an integrated, interdisciplinary cooperation and major scientific and practical breakthroughs involving plant nutrition, soil science, agronomy, and breeding.     

Phosphorus in waters from sewage sludge amended lysimeters

In surface waters, phosphorus (P) concentrations exceeding 0.05 mg liter(-1) may cause eutrophic conditions. This study was undertaken to measure total P concentrations in runoff and tile drainage waters from land receiving either inorganic fertilizer or anaerobically digested sewage sludge. Total P was measured in runoff and tile drainage waters during 2 years of sample collections from instrumented, large-scale lysimeters planted to corn (Zea mays L.). During the 3 years prior to monitoring P concentrations, six of the lysimeter plots had been amended with anaerobically digested sewage sludge which supplied 5033 kg P per ha. Additional sludge applications supplied 1058 and 1989 kg P per ha during the first and second years of monitoring operations, respectively. Another six lysimeters were annually treated with fertilizer which included P applications amounting to 112 kg ha(-1). For years 1 and 2, respectively, annual losses from lysimeters treated with sewage sludge were 4.27 and 0.35 kg P per ha in runoff and 0.91 from 0.91 and 0.51 kg Per P per ha in drainage waters. Parallel annual losses of P from lysimeters treated with superphosphate were 2.15 and 0.17 kg ha(-1) in runoff and 0.53 and 0.35 kg ha(-1) in tile drainage waters. Sludge applications did not significantly change absolute soil contents of organic P, but did decrease the per cent of total P present in organic forms. Sludge and soil, respectively, contained 21 and 36% of their total P contents in organic forms. In sludge and soil about 85 and 64% of their respective total inorganic P contents were associated with the Al and Fe fractions. Sludge applications significantly increased soil contents of P in the saloid (water-soluble plus P extracted with 1 N NH(4)Cl), Al, Fe and reductant soluble P fractions, but contents of Ca-bound P were not changed. Total P contents of the soil below a depth of 30 cm were not affected by sludge incorporated to a depth of about 15 cm by plowing.     

Possibilities for reducing nitrate leaching from agricultural land

Agricultural soil is a contributor of nitrate to natural waters. High nitrate levels in water leached from soils are related to high nitrate concentrations in drinking water, and excess levels change the ecological balance of rivers and lakes. In this paper, sound solutions to the major environmental issue of limiting nitrate leaching by modifying agricultural practices are discussed. The causes of nitrate leaching from agricultural land are briefly explained and existing measures for the reduction of nitrate losses are described, analyzed and evaluated. Reduction of nutrient leaching is not a question of organic or conventional farming, but rather of the introduction and use of appropriate countermeasures. We propose the following guiding principles to minimize leaching from agricultural soils. To some extent these principles require a new way of thinking: i) environmental indexing of fields and consideration of spatial variability within fields in relation to their contribution to leaching losses within a catchment; ii) reduction of nitrogen inputs to soil to levels slightly below those expected to give the optimum yield by applying less nitrogen fertilizer and by a further reduction in animal density; and iii) use of a range of counter-measures (catch crops, minimum tillage, control of biological processes, etc.) depending on how sensitive the farming system, soil and climate are to the risk of nitrate leaching.