A Sensitivity Analysis of Nitrogen Losses from Dairy Farms

International attention has focused on agricultural production systems as non-point sources of pollution affecting the quality of streams, estuaries and ground water resources. The objective of the current study was to develop a model of nitrogen management on the dairy farm, and to perform sensitivity analyses in order to determine the relative importance of manipulating herd nutrition, manure management and crop selection in reducing nitrogen (N) losses from the farm. The importance of the method of N input to the farm (purchased feed, legume fixation, inorganic fertilizer, imported manure) was investigated, and the potential to reduce N losses from dairy farms was evaluated. Nitrogen balance equations were derived, and related efficiency coefficients were set to reference values representing common management practices. Total farm N efficiency (animal product N per N input), and N losses per product N were determined for different situations by solving the set of simultaneous equations. Improvements in animal diet and management that increase the conversion of feed N to animal product by 50% would increase total farm N efficiency by 48% and reduce N losses per product by 36 to 40%. In contrast, reducing losses from manure collection, storage and application to improve the percentage of manure N that becomes available in soil by 100% would only improve total farm N efficiency by 13% and reduce total N losses by 14%. Selecting crops and management that can use soil nutrients 50% more efficiently would improve total farm efficiency by up to 59% and reduce N losses by up to 41% depending on the predominant nitrogen sources to the farm. Legume production would reduce N losses per product compared with non-legumes. There was more than a five fold difference in N losses per animal product N between the most extreme scenarios suggesting considerable opportunity to reduce N losses from dairy farms.     

浙产白术市售种子质量的鉴定

根据试验,浙江产白术种子的净度可分为3个等级：一级净度为95％以上,二级净度90％～95％,三级净度90％以下.其发芽率为45％～59％,与种子批次的千粒重密切相关.种子在室外阳光下晒干.含水量可控制在8％～10％,而在室内阴干则与环境的相对湿度密切相关.其千位重的差异与该种子批次内大.中、小粒种子的比例有关,一般种子千粒重为25.60～37.50g.     

IMPLICATIONS OF C.A.R.E. VS. SOUTHVIEW FARM ON THE U.S. LIVESTOCK AND POULTRY INDUSTRY1

ABSTRACT: On May 19, 1993, a jury in the U.S. District Court for the Western District of New York found Southview Farm and Richard H. Popp guilty of violating the Clean Water Act on five occasions. The violations were the result of storm water runoff from a site used for disposal of dairy cattle manure from an unpermitted concentrated animal feeding operation. The presiding District Court judge later dismissed the jury verdict, and subsequently a U.S. Court of Appeals for the Second Circuit reversed the dismissal. The Court of Appeals concluded that the discharges were not exempt as agricultural storm water discharges, and that the manure spreaders involved were point sources. Because the use of animal manures in crop production activities will result, unavoidably, in the discharge of some pollutants to adjacent surface waters, a rational and universally applicable basis is needed to determine when such discharges are point versus nonpoint source. Current statutes and regulations do not delineate clearly such a boundary. To address this lack of specificity, I propose that application rates be based on recommended crop nutrient needs.     

1996年2月3日云南丽江7.0级地震震害调查和损失评估

对1996年2月3日云南丽江7．0级地震进行了震害调查和损失评估，此次地震造成了重大灾害，死亡309人，重伤4070人，轻伤12987人。房屋破坏、室内财产和生命线工程的直接经济损失总计为30．49亿元。     

河流水质灾害中的S—P方程稳态分析和临界氧亏计算

污染物对水环境的影响主要发生在枯水期，此时水流状态处于稳态．Streeter－phelps（S－P）方程能预测简单稳态条件下的水质状况，并具有较高的计算织亏的精度．     

CUMULATIVE IMPACTS OF LANDUSE ON WATER QUALITY IN A SOUTHERN APPALACHIAN WATERSHED1

ABSTRACT: Water quality variables were sampled over 109 weeks along Coweeta Creek, a fifth-order stream located in the Appalachian mountains of western North Carolina. The purpose of this study was to observe any changes in water quality, over a range of flow conditions, with concomitant downstream changes in the mix of landuses. Variables sampled include pH, HCO₃^2?, conductivity, NO₃^?_?-N, NH₄⁺-N, PO₄^3?-P, C1^?-, Na, K, Ca²⁺, Mg²⁺, SO₄^2?, 5iO₂, turbidity, temperature, dissolved oxygen, total and fecal coliform, and focal streptococcus. Landcover/landuse was interpreted from 1:20,000 aerial photographs and entered in a GIS, along with information on total and paved road length, building location and density, catchment boundaries, hydrography, and slope. Linear regressions were performed to relate basin and near-stream landscape variables to water quality. Consistent, cumulative, downstream changes in water quality variables were observed along Coweeta Creek, concomitant with downstream, human-caused changes in landuse. Furthermore, larger downstream changes in water quality variables were observed during stormflow when compared to baseflow, suggesting cumulative impacts due to landscape alteration under study conditions were much greater during storm events. Although most water quality regulations, legislation, and sampling are promulgated for baseflow conditions, this work indicates they should also consider the cumulative impacts of physical, chemical, and biological water quality during stormflow.     

DENSITY CURRENT INTRUSIONS IN AN ICE-COVERED URBAN LAKE1

ABSTRACT: Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10 m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.     

系统安全性评价的AHP方法及在热处理作业系统中的应用

介绍了系统安全评价的ＡＨＰ方法，叙述了该方法的基本步骤，并以某公司热处理分厂评忏为实例，证明了该方法的有效性和实用性。     

矿井重大灾害危险性评价的改进灰色统计法

用灰色统计理论［１］研究了矿井四大灾害即冒顶、水灾、火灾和瓦斯爆炸的危险性预评价问题，提出了一种新的评价方法──灰色统计综合法。同时，从应用的角度出发对灰色统计的算法作了改进，改进后的算法便于记忆和应用。     

用事故树分析法进行炼厂油罐爆炸事故的环境风险评价

论述了风险、风险评价、环境风险评价的概念及其主要内容，说明利用事故树分析法进行工程环境风险评价的程序和方法。并运用这种方法对某炼厂油罐爆炸事故进行了大气环境风险评价。