Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures

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CLIMATE CHANGE IMPACTS ON NEW YORK CITY'S WATER SUPPLY SYSTEM1

ABSTRACT: It has been well established that the greenhouse gas loading of the atmosphere has been increasing since the mid 19th century. Consequently, shifts in the earth's radiative balance are expected with accompanying alterations to the earth's climate. With these anticipated, and perhaps already observable, changes in both global and regional climate, managers of regional water resources seek insight to the possible impacts climate change may have on their present and future water supplies. The types and degrees of impacts that climate change may have on New York City's water supply system were assessed in a study of a watershed at Allaben, New York. Hypothetical scenarios of future climate and climate change projections from three General Circulation Models (GCMs) were used in conjunction with the WatBal hydrological model and the Palmer Drought Severity Index (PDSI) to ascertain how runoff and soil moisture from this watershed may change in a warmer climate. For the worst case predictions, the results indicate that within the century of the 2000s, the watershed's air temperature may increase up to about 11°F, while its precipitation and runoff may decrease by about 13 and 30 percent, respectively. If this watershed is typical of the others within the New York City water supply system, the system's managers should consider implementing mitigation and adaptation strategies in preparation for the worst of these possible future conditions.     

豫北典型农田作物中重金属污染状况及健康风险评价

农产品污染引发的食品安全问题目前已经成为全社会关注的焦点,为了研究和评价农作物中重金属污染和健康风险状况,采集了焦作市武陟县玉米、水稻和花生三种大田作物样品,共计47个样品,其中玉米样品16个,花生样品4个,水稻样品27个。在测定作物籽粒中重金属Cr、Ni、As、Cd和Pb含量的基础上,分别采用单因子污染指数和综合污染指数法评价了作物籽粒中重金属的污染状况,并运用危险商（HQ）法评价了这些作物中的重金属对人体健康可能造成的风险,进而应用相关分析法、聚类分析法及主成分分析法,探讨了作物籽粒中重金属含量的分布特征及其污染来源。结果表明：武陟县农田作物籽粒中的Cr、Ni、As、Cd和Pb的平均含量分别为0.26±0.42、0.31±0.29、0.04±0.03、0.01±0.04和0.03±0.03 mg·kg^-1。其中,玉米籽粒中的Cr、Ni、As、Cd和Pb的平均含量分别为8.86×10^-2±0.21、9.41×10^-2±0.12、8.10×10^-3±5.29×10^-3、1.20×10^-5±4.92×10^-5和0.04±0.02 mg·kg^-1;水稻籽粒中的Cr、Ni、As、Cd和Pb的平均含量分别为0.38±0.49、0.44±0.31、0.07±0.02、4.60×10^-3±7.42×10^-3和0.03±0.03 mg·kg^-1;花生籽粒中的Cr、Ni、As、Cd和Pb的平均含量分别为0.13±0.22、0.32±0.16、0.02±3.05×10^-3、0.11±0.07和1.32×10^-2±1.70×10^-2 mg·kg^-1。农作物籽粒中各重金属元素的单因子污染指数评价结果显示,从总体上看,3种农作物籽粒中5种重金属的单因子污染指数均值均小于1,单因子污染指数均值大小顺序为：Ni＞As＞Cr＞Pb＞Cd;从作物类型来看,玉米和水稻中Ni超标的样品比率分别为6.67%和51.85%,水稻中Cr超标的样品比率为12%。农作物籽粒中各重金属元素的综合污染指数评价结果显示,重金属的平均综合污染指数为0.59,整体上处于安全等级。总体来看,14.89%的农作物受到不同程度的污染,其中轻度污染的农?     

季节性雪被对青藏高原东缘高寒草甸土壤氮矿化的影响

依据自然雪被分布的差异,在青藏高原东缘高寒草甸中设置3条样带(即深雪、中等厚度雪被和浅雪),于2008年的秋冬过渡期,连续监测各样带中的雪被厚度和土壤温度,并采用原位培养法测定每月的土壤氮素氨化、硝化和矿化速率,以研究不同厚度雪被对高寒草甸土壤氮矿化的影响.结果表明,月均土温、每月日最高土温均值分别与雪被厚度极显著相关,二次函数关系拟合较好(R2=0.576,0.685),且根据每月日最高土温均值与雪被厚度的二次函数关系方程可知,25 cm厚的雪被可以起到较好的隔绝效果;土壤含水量受雪被厚度和土壤温差两个因素的显著影响.在秋冬过渡期末,浅雪梯度下土壤硝态氮含量显著降低,且雪被下的净氮矿化速率与月均土温、每月日最高土温均值、每月日最低土温均值都分别呈极显著相关,二次函数关系拟合较好(R2=0.589,0.541,0.601).研究表明,不同厚度的雪被对土壤温度和含水量影响显著,从而显著地影响着土壤氮的矿化,深雪更有利于氨化、硝化和氮矿化.图7表2参36     

Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing

In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon (S_C) algorithm, in which the decomposition rate of S_C and input rate to S_C (through decomposition and humification of residues) depend on the current size of S_C. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation (S_x) that depends on texture and controls the turnover rate. It is shown in an analytical solution that S_x is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the S_C dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate S_C in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils.     

中国农业水土环境存在的问题及对策探讨

中国农业水土环境问题十分严重。水土流失、土地沙漠化、水资源日显短缺、水体过度开采和污染加剧、土壤污染和次生盐渍化是水土环境恶化的根本原因。积极恢复植被、实施虚拟水土战略、对水土资源进行优化调控、构建节约型水土资源综合体系提高水土利用效率、通过国家生态税收建立生态补偿机制等,是解决农业水土环境问题的根本途径。     

套种条件下混合螯合剂对污染土壤Cd淋滤行为的影响

为了研究螯合剂对污染土壤Cd向下迁移的影响,对采自广东省乐昌市和清远市的2种铅锌矿废水污染水稻土（分别为中性和酸性土壤）进行100 cm土柱室外淋溶试验,研究在玉米与东南景天套种系统中,在5 mmol.kg-1土的混合螯合剂[MC∶柠檬酸∶味精废液∶EDTA∶KCl（摩尔比）=10∶1∶2∶3]的强化作用下对2种污染土壤中Cd的淋滤行为的影响.结果表明,施加混合螯合剂后第2 d,混合螯合剂能明显提高2种土壤各土层淋滤液Cd浓度;施后第8 d混合螯合剂仍能继续提高中性土壤20 cm以下土层和酸性土壤60 cm以下土层淋滤液Cd的浓度,但其活化作用均已迅速下降.施后第2 d和第8 d,2种土壤各土层的套种＋MC处理的淋滤液Cd浓度均超过国家地下水质量标准（GB/T 14848-93）.施加混合螯合剂可降低中性土壤表层全Cd量.不同处理的土壤Cd均有向下层迁移的趋势,尤其是酸性土壤,在20 cm和40 cm处不同处理的全Cd量与起始值比较分别下降了40%～58%和39%～49%,经过100 d的修复即可达到土壤环境质量标准（GB 15618-1995）.上述结果表明,施用混合螯合剂对Cd污染土壤的地下水水质存在一定的潜在污染风险.     

海南岛半干旱区农用地土壤重金属富集因素、健康风险及来源识别

为了解海南岛半干旱区农业土壤中重金属富集因素和污染状况,在感城镇采集1818件表层土壤样品,测定其重金属含量和化学组成.采用相关分析、地累积指数（I_geo）、综合生态风险指数（RI）、危害指数（HI）、致癌风险指数（CR）和正定矩阵因子分析（PMF）开展重金属风险评价和来源识别.结果显示,重金属ω（As）、ω（Cd）、ω（Cr）、ω（Cu）、ω（Hg）、ω（Ni）、ω（Pb）和ω（Zn）的平均值分别为22.7、0.128、33.4、14.5、0.032、9.32、32.5和43.3 mg ·kg^-1,除Zn外,均高于海南岛土壤背景值.相关分析表明,重金属富集与土壤中Fe、Mn、Al和有机质含量密切相关.I_geo结果表明,研究区农业土壤主要受到As的污染,其次为Cd和Cu;RI结果显示,高风险以上的样品占比为29.4%,其中As是潜在生态风险的主要贡献者;健康风险评估结果显示,As、Cr和Ni对儿童存在致癌风险,需要引起注意.基于PMF模型,确定了研究区重金属的4种主要来源,其中Hg主要来自工业排放;As主要来自农业活动;Ni、Cu、Cr和Zn主要来自与成土母质密切相关的自然来源;Pb和Cd主要来自农业活动和机动车尾气的混合源.研究表明PMF模型与相关分析相结合,能够有效识别土壤重金属来源.     

垃圾污染质在天然黏土屏障中运移情况的调查

通过对杨府山垃圾卫生填埋场的实地调查,重点调查了距垃圾场外边缘以南500m土壤中重金属含量,与国家环保局给出的土壤背景值比较,发现对人类健康有较大影响的Pb,Mn,Cu,Cd的浓度值均大大超过国家规定标准,污染指数分别达到了5.9959,2.0974,4.2021,2.4864,9.2204,其中镉的污染最为严重,并讨论了天然黏土屏障在污染质运移过程中的控制作用,及今后屏障材料的发展方向。该研究结果对该地区进行环境治理的必要性提供了科学依据。     

江津市紫色土中N、P养分元素区域空间变异性研究

利用地统计学,结合GIS研究紫色土土壤表层(0～20cm)的全氮、碱解氮、全磷和速效磷4种养分含量的空间分布特征结果表明,全氮和速效氮为正态分布,全磷和速效磷为对数正态分布;通过半方差函数分析,发现全氮存在纯块金效应,块金值为0.2,其它养分在一定间距内(50m)存在空间相关性,且为中等强度的空间自相关性(块金值与基台值之比在25%～75%之间);用普通克立格法和对数正态克立格法进行最优内插,做各种养分含量的分布图.结合GIS可充分了解土壤中N、P养分的空间变异性规律,并可进一步应用于精确施肥和农业非点源污染预测和控制.