Review of Pesticide Retention Processes Occurring in Buffer Strips Receiving Agricultural Runoff1

Arora, Kapil, Steven K. Mickelson, Matthew J. Helmers, and James L. Baker, 2010. Review of Pesticide Retention Processes Occurring in Buffer Strips Receiving Agricultural Runoff. Journal of the American Water Resources Association (JAWRA) 46(3):618-647. DOI: 10.1111/j.1752-1688.2010.00438.x Abstract: Review of the published results shows that the retention of the two pesticide carrier phases (runoff volume and sediment mass) influences pesticide mass transport through buffer strips. Data averaged across different studies showed that the buffer strips retained 45% of runoff volume (ranging between 0 and 100%) and 76% of sediment mass (ranging between 2 and 100%). Sorption (soil sorption coefficient, K_oc) is one key pesticide property affecting its transport with the two carrier phases through buffer strips. Data from different studies for pesticide mass retention for weakly (K_oc < 100), moderately (100 < K_oc < 1,000), and strongly sorbed pesticides (K_oc > 1,000) averaged (with ranges) 61 (0-100), 63 (0-100), and 76 (53-100) %, respectively. Because there are more data for runoff volume and sediment mass retention, the average retentions of both carrier phases were used to calculate that the buffer strips would retain 45% of weakly to moderately sorbed and 70% of strongly sorbed pesticides on an average basis. As pesticide mass retention presented is only an average across several studies with different experimental setups, the application of these results to actual field conditions should be carefully examined.     

模拟车用工况下5kW燃料电池尾气净化系统

模拟了车用工况下燃料电池发动机脉冲式排氢的特点,设计开发了一套质子交换膜燃料电池的尾气净化系统,并以5 kW燃料电池的尾气排放为例,研究其净化效果。研究了电池阳极排放氢气缓冲前后尾气中氢气浓度的变化,以及不同空速条件下氢气的去除效果。结果表明：电堆阳极排放氢气经过缓冲处理后,尾气中氢气浓度趋于平稳,大部分工况下处在2%以下,达到了安全处理的要求;尾气中氢气的去除效果与空速密切相关。对自制的整体式催化剂而言,当空速低于20000 h^-1时,氢气的去除率能达到约95%,而当空速达到39270 h^-1时,氢气的去除率仅为10.9%。鉴于这一问题,提出通过采用尾排空气的分流手段调整催化燃烧反应器对空速的要求,以提高尾气中氢气的去除率。     

湖岸缓冲带反硝化作用的研究进展

反硝化作用是湖岸缓冲带去除硝酸盐的重要途径。湖岸缓冲带是联系陆地与湖泊生态系的纽带,不仅为许多动植物提供适宜生境,而且通过反硝化作用能去除地下水中的硝酸盐,提高湖泊水质。概述不同检测反硝化速率的方法,并对比各种方法的优点与缺点。阐述反硝化作用的影响因素：厌氧环境、有机碳、湖岸坡度、缓冲带坡度、pH与温度、硝酸盐浓度。介绍反硝化速率模型的研究开发状况。最后,提出了目前国内外反硝化研究中存在的不足及发展方向。     

实例分析卫生防护距离和大气环境防护距离设置条件

卫生防护距离、大气环境防护距离,其定义相近、设定途径相似,但两者又有不同。故在环境影响评价大气环境预测分析时对大气环境防护距离、卫生防护距离的概念极易混淆。本文以某县殡仪馆建设项目为例,详细分析建设项目设置防护距离的设置条件,帮助环评工作者理解防护距离设置原则,防止出现"在环境保护法规和导则要求下盲目划定、划大防护距离"的技术错误。     

“四沿”化工企业污水处理系统安全事故状态下负荷缓冲及安全环境(SE)联锁探讨

在对"四沿"(沿江、沿河、沿湖、沿海)化工行业污水处理方法及流程特点总结的基础上,归纳出应对水力和污染物冲击负荷的缓冲方法。为克服缓冲控制能力有限的缺点,提出一种新方法——SE(安全和环境)联锁,以期达到完善管理、提高控制效果的目的,并详细阐述了该方法在管理及技术层面的实施途径。     

Application of a GIS-based stream buffer generation model to environmental policy evaluation

In this article a GIS method is presented for riparian environmental buffer generation. It integrates a scientifically tested buffer width delineation model into a GIS framework. Using the generally available data sets, it determines buffer widths in terms of local physical conditions and expected effectiveness. Technical burdens of data management, computation, and result presentation are handled by the GIS. The case study in which the method was used to evaluate the stream buffer regulations in a North Carolina county demonstrates its capability as a decision support tool to facilitate environmental policy formulation and evaluation, and environmental dispute resolution.     

黄河河口磷酸盐的缓冲作用探讨

河口区,磷酸盐浓度在很宽的盐度范围变化很小,甚至不变,对此提出悬浮物和沉积物对磷有缓冲作用。我们认为解吸吸附反应是其缓冲机制,从而进行了大量的模拟实验,并加以系统的分析。     

Contour Farming Based on Natural Vegetative Strips: Expanding the Scope for Increased Food Crop Production on Sloping Lands in Asia

In the agriculture of the future, there is a compelling place for agroecologically-based practices alongside practices based on the best available chemical, genetic, and engineering components. This paper explores this issue in the context of the development and spread of a conservation farming system based on natural vegetative contour buffer strips in smallholder production systems in southeast Asia. Farmers adapted contour hedgerow farming practices into a simpler, buffer-strip system as a labor-saving measure to conserve soil and sustain yields on steeply sloping cropland in Claveria, Mindanao, Philippines. Permanent-ridge tillage systems were also adapted to smallholder farming systems by researchers. Natural vegetative buffer strips resulted in gradually increasing yields, with an estimated benefit of 0.5t/ha/crop. They were seen to increase land values, facilitate investment in more intensive and profitable cropping systems, and expand the land base for food crop agriculture. They induced an institutional innovation of farmer-led Landcare organizations, which have spread this and other agroforestry practices to thousands of households in the southern Philippines.     

Efficacy of Vegetated Buffers in Preventing Transport of Fecal Coliform Bacteria from Pasturelands

An experimental study was conducted in Tillamook, Oregon, USA, to quantify the effectiveness of edge-of-field vegetated buffers for reducing transport of fecal coliform bacteria (FCB) from agricultural fields amended with dairy cow manure. Installation of vegetated buffers on loamy soils dramatically reduced the bacterial contamination of runoff water from manure-treated pasturelands, but the size of the vegetated buffer was not an important determinant of bacterial removal efficiency. Only 10% of the runoff samples collected from treatment cells having vegetated buffers exhibited FCB concentrations >200 colony forming units (cfu)/100 mL (a common water quality standard value), and the median concentration for all cells containing vegetated buffers was only 6 cfu/100 mL. The presence of a vegetated buffer of any size, from 1 to 25 m, generally reduced the median FCB concentration in runoff by more than 99%. Results for FCB load calculations were similar. Our results suggest that where substantial FCB contamination of runoff occurs from manure-treated pasturelands, it might be disproportionately associated with specific field or management conditions, such as the presence of soils that exhibit low water infiltration and generate larger volumes of runoff or the absence of a vegetated buffer. Buffer size regulations that do not consider such differences might not be efficient or effective in reducing bacterial contamination of runoff.     

基于气囊缓冲的某火箭炮着陆冲击分析

目的减小火箭弹着陆冲击加速度。方法基于LS-DYNA瞬态动力学分析软件和冲击动力学理论,采用有限元软件HYPERMESH建立火箭炮-气囊系统有限元模型,采用显式动力学方法对火箭炮-气囊系统的着陆冲击缓冲过程进行仿真。分析火箭炮在正常着陆工况下,火箭弹的着陆冲击响应,得出空投装备速度、加速度变化曲线,以及气囊的体积、压力曲线。结果在正常着陆工况下,火箭弹横向加速度的最大值为122 m/s2,小于安全的横向加速度;火箭弹纵向加速度的最大值为48.3 m/s2,小于安全的纵向加速度;火箭弹的最大轴向力为2640 N,小于安全闭锁力。结论在火箭炮着陆冲击过程中,气囊缓冲装置吸收了大部分冲击能量,起到了良好的缓冲作用,火箭弹的冲击加速度、闭锁力均在安全范围内。采用显式动力学方法对火箭炮的着陆冲击过程进行分析是可行的。