氮肥运筹和少免耕对麦田氮素径流流失的影响

采用田间小区定位试验研究了自然降雨条件下氮肥运筹和少免耕措施对稻麦两熟农田麦季氮素径流流失特征的影响。结果表明：自然降雨后麦田耕层土壤平均水分质量分数26.34%为径流事件发生的临界土壤水分质量分数。常规施肥（T0）条件下,麦季径流水量达2185.05 m3·hm-2,径流侵蚀泥沙量达716.08 kg.hm-2,少免耕（T2）处理增加麦田径流水量达29.67%,减少径流侵蚀泥沙量达13.96%,而肥料运筹（T1）与T0处理差异不显著;就整个麦季而言,T0处理条件下,径流水全氮（TN）平均质量浓度和径流侵蚀泥沙TN平均质量分数分别为10.51 mg·L-1和1.19 g·kg-1,T1处理显著降低径流水TN质量浓度和侵蚀泥沙TN质量分数分别达11.63%和5.93%,T2处理显著降低径流侵蚀泥沙TN质量分数达7.95%;麦季氮素径流流失主要集中在小麦生育前期,包括径流水氮素流失量和径流侵蚀过程中由泥沙流失的氮素量。T0处理条件下,氮素流失总量达31.76 kg·hm-2,其中,径流水氮素流失量占麦季氮素总流失量95%以上,T1处理减少麦季氮素总流失量达9.25%,而T2处理则增加麦季氮素总流失量达16.75%。     

灾害损失定量评估的模糊综合评判方法

讨论了灾害损失的构成要素以及灾害损失定量评估的指标体系；依据灾害失评估指标体系的一般形式，给出了由灾害损失单一因子计算灾级的公式；基于笔者提出的模糊灾度概念，给出了可用于各类灾害损失的等级划分的模糊综合评判方法。     

Evaluation of greenhouse gas emissions from wetland and agriculture ecosystems in Sanjiang Plain

Carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄) are important greenhouse gases (GHGs). The objective of this study is to quantify the aggregate GHG (CH₄, N₂O and CO₂) emissions and estimate economic losses of three ecosystems (marsh, paddy field and upland) in the Sanjiang Plain, excluding the Muling-Xiangkai Plain, south of Wanda Mountain. The results indicate the economic losses from GHG emissions of marshes were from 6.40 to 7.75?×?10⁹ CNY (Chinese Yuan), those of paddy fields were from 1.41 to 3.20?×?10⁹ CNY; and from uplands were from 0.26 to 0.49?×?10⁹ CNY. Using linear trend analysis, the economic losses through GHG emissions of marshes fell between 1982 and 2005, but those from paddy fields and uplands increased. In our study, the sequence in magnitude of the economic losses from GHG emissions was: marshes > paddy fields > uplands. In fact, the economic value of GHG emissions was negative because of these adverse impacts on the environment. This article could provide a reference for calculation of GHG exchange. The results suggest that improvement of fertiliser use efficiency for more precise agricultural management and returning straw to cropland could mitigate GHG emissions and would help to achieve sustainable development.     

地震灾害损失预测的动态分析模型

本文提出了一个地震灾害预测的动态分析模型。这个模型基于概率理论基础,考虑了一个城市因建设的发展,新房屋日益增多,部分旧房屋被淘汰,对城市抗震能力引起的变化;和由于经济的发展,社会财富的增加,对地震损失的影响。为解决这—问题,文中提出了动态震害矩阵和动态损失矩阵的求解方法。根据这一方法可以预测未来不同年代的地震经济损失。     

A NEW APPROACH FOR ESTIMATING IRRIGATION CONVEYANCE LOSSES AND THEIR ECONOMIC EVALUATION1

ABSTRACT: In this paper a new methodology for estimating conveyance efficiency within irrigation systems is presented. Based on statistical analysis of daily water releases from the source of supply and deliveries to the farmers in an irrigation district in Mexico, a linear model is obtained for estimating conveyance efficiency and two component factors. One of these factors points out the relative importance of the operational losses (i.e., losses due to water management), and the second shows the importance of the fixed losses which can be attributed to the average flow through the canal network without variations. In the last part of this paper, an analysis of the expected benefits and costs accruing from system improvement permits derivation of a decision rule which may be used for analyzing the economic feasibility of lining in-place canals.     

太湖流域北部潜在洪涝风险区分析及影响评估

太湖流域历来遭受严重的洪涝灾害,并且近年来有不断加重的趋势。本文选择太湖流域北部的无锡市作为典型研究地区,研究其洪涝的危险性并进行潜在损失评估。人类活动,包括修筑圩区、森林破坏、人口增长、城市化等,对这个地区的洪涝形势有较大的影响;自然条件的变化使河道水位升高,洪涝历时缩短,洪峰增高。本文选择不同回归年(2,5,10,20,50年),结合地理信息系统分析模型,计算了潜在洪涝危险区域和洪涝损失,主要结论为:(1)人类活动已经改变了自然的洪涝形势,增大了汇流和洪涝;(2)洪涝危险区与降雨中心有关;(3)筑圩成功地保护了圩内的土地,缩短了洪涝历时,增高了圩外河道的洪涝水位;(4)经济发展使洪涝损失增加。     

SIMULATING NITROGEN LOSSES FROM AGRICULTURAL LAND: IMPLICATIONS FOR WATER QUALITY AND PROTECTION POLICY1

ABSTRACT: EPIC, a soil erosion/plant growth simulation model, is used to simulate nitrogen losses for 120 randomly selected and previously surveyed cropland sites. Simulated nitrogen losses occur through volatilization, surface water and soil runoff, subsurface lateral flow, and leaching. Physical and crop management variables explain a moderate but significant proportion of the variation in nitrogen losses. Site slope and tillage have offsetting effects on surface and ground water losses. Nitrogen applications in excess of agronomic recommendations and manure obtained off the farm and applied to the sites are significant contributors to nitrogen losses. Farm characteristics such as production of confined livestock, total manure nitrogen available, and farm income per cropland acre explain a relatively large portion of the variability in manure nitrogen applied to survey sites. The results help to identify farm characteristics that can be used to target nutrient management programs. Simulation modeling provides a useful tool for investigating variables which contribute to agricultural nitrogen losses.     

西河污灌区环境污染对居民健康影响的调查研究

本文对污灌区居民健康状况及水样致突性的调查,显示污灌区居民消化系统主要疾病(慢性胃炎,急、慢性肠炎)患病率,肝肿大率以及总标化死亡率均显著高于对照区(P<0.01)。污灌区消化系恶性肿瘤标化死亡率高于对照区(P<0.01)。污灌区消化系恶性肿瘤标化死亡率高于对照区(P<0.05);水样紫露草微核率亦高于对照区,并有显著性差异(P<0.01)。污灌区居民由于受饮用水和食物等污染,每年的健康经济损失总计为127.2050万元。     

STATUS AND PROSPECTS OF KAREZ IRRIGATION1

ABSTRACT: The karez is a traditional irrigation water source, consisting of hand-dug horizontal wells, that is still used in parts of South Asia, the Middle East, and North Africa. This paper describes the construction, management, and current problems of karez irrigation systems based on investigations conducted in Baluchistan Province, Pakistan. While karezes have served irrigation needs well in the past, they are now threatened by high costs of labor for construction and maintenance, and by the encroachment of tubewells which lower the water tables on which the karez systems depend. Possible methods for improving karez performance and needs for research are discussed.     

我国沙漠化灾害的发展及其危害

沙漠化灾害是在特定自然环境背景下产生的,严重危及人类生产和生存。文章着重阐述沙漠化发展对农、牧业、工矿交通及环境等方面造成的经济损失。据初步统计,全国每年因沙漠化遭受的直接经济损失达36～45亿元,间接经济损失高达292亿元以上。同时,指出沙漠化的实质是从根本上毁损土壤肥力,丧失人类赖以生存的土地。因此,从沙漠化发生时间的频繁性、经常性,空间分布的广泛性,致害的多样性及造成的经济损失严重性看,沙漠化灾害是我国严重自然灾害之一。