基于小波神经网络的芦苇潜流人工湿地水质预测

人工湿地系统对污水的处理效果好,工艺简单,投资运行费用低,但影响其出水水质的因素很多,并且往往是非线性的,因此目前很难将这些影响因素模型化并用于水质预测. 已有的预测方法不是过于复杂就是预测精度不高. 神经网络是一种具有较强预测能力的新方法,适用于各种非线性模型的预测. 在小试研究的基础上,使用3种不同的、经过训练的小波神经网络,对芦苇潜流人工湿地沿程各采样口的水温,ρ(DO),pH,Eh和ρ(COD_Cr)等水质指标进行了预测. 结果显示,各指标的平均相对误差分别为:水温≤4.21%,pH≤1.36%,ρ(DO)≤9.77%,Eh≤6.50%,ρ(COD_Cr)≤17.76%,表明小波神经网络模型适用于人工湿地模型的预测.      

基于SPOT5影像多辐射校正水平的植被绿量遥感估算

选用南京市SPOT5图像的灰度值(DN)、星上辐射率(SR)、表观反射率(TOA)和地物反射率(PAC)数据,提取了两种植被指数(VI),即归一化植被指数(NDVI)和比值植被指数(RVI),并与地面实测的绿量(LVV)进行相关分析,建立了165个关系模型.结果表明,LVV与VI呈极显著的相关关系,其相关系数多以相对均质植被高于植被总体,基于灰度值高于常用的地物反射率为主.LVV-VI关系模型的R~2均值以多元线性回归模型最高(0.821),指数模型最低(0.536),而1～3次多项式模型均接近0.7.每种植被样方优选出一个模型,即阔叶林LVV-7.802 RVI_(PAC)-2.455(R~2=0.827,RMSE=0.498);针阔叶混交林LVV=-15.421 RVI_(TOA)+26.971 RVI_(DN)-8.261(R~2=0.918,RMSE=0.356);灌木LVV=-342.591 NDVI_(DN)~3-20.553 NDVI_(DN)~2+14.013 NDVI_(DN)+1.509(R~2=0.764,RMSE=0.689);草地LVV=2.934 RVI_(PAC)+2.147 RVI_(TOA)-3.193(R2=0.903,RMSE=0.464);总体植被LVV=1.789RVI_(PAC)-6.814NDVIs+4.258NDVI_(PAC)+12.854 NDVI_(DN)-0.342(R~2=0.810,RMSE=0.638).这些优选模犁的自变量包括了4种辐射校正水平下提取的两种植被指数,显示基于不同辐射校正水平的植被指数在植被LVV遥感反演中具有一定的应用潜力.     

矿区砷污染对土壤线虫群落结构特征的影响

对湖南省石门县雄黄矿区不同As污染程度土壤线虫群落结构特征进行了研究.共获得线虫27属,食真菌线虫滑刃属(Aphelenchoides)在3种土壤中均为优势属.食细菌和食真菌线虫分别为低As和中As土壤的优势营养类群,而植物寄生线虫为高As土壤的优势营养类群.低As和中As土壤的自由生活线虫成熟度指数(IM)和瓦斯乐斯卡指数(IW)显著高于高As土壤,但植物寄生线虫成熟度指数(IPP)和IPP/IM比值则表现出相反的趋势.可见,高As土壤的食物网受到As污染的干扰较大,群落环境质量较差.因此,土壤线虫群落结构对土壤质量或生态系统的变化具有很好的生物指示作用.     

土地经济密度的区域差异特征及动态演变格局——基于长江三角洲地区的实证分析

基于长江三角洲地区25个城市的土地经济密度数据,利用泰尔指数、空间自相关等方法对1995-2007年长江三角洲地区土地经济密度的区域差异特征及动态演化格局进行了初步探索。研究表明：①该区域的土地经济密度总体呈不断上升趋势,但是城市间差异明显,其高值点主要集中于沪苏锡常地区;②土地经济密度的总体差异和区间差异呈现波动性缩小趋势,江苏省内部差异和区间差异是总体差异的主要组成部分;③土地经济密度总体上趋于空间集聚,但局部的空间集聚中心从环杭州湾城市转移到苏南地区和上海。可见,高投入、低效率的土地利用方式已不适合长江三角洲地区的发展,未来必须统筹区域土地利用,合理配置土地资源,促进区域合理分工和协调发展。     

基于能值-生命力指数的城市生态系统健康集对分析

综合考虑城市的生命体特征及物质能量代谢层面因素,依托城市生命力指数框架,结合能值指标,构建城市能值-生命力指数,以全面反映城市生态系统健康状况.引入集对分析这种不确定理论与方法,比较城市生态系统相对健康状况.采用基于集对分析的城市能值-生命力指数综合评价模型及信息熵权重,比较北京、上海、武汉、广州等16个城市的生态系统相对健康状况,结果表明,厦门、青岛、杭州、上海、北京健康水平相对较高,而乌鲁木齐、成都、哈尔滨健康水平相对较低,其他城市则为中等水平.     

西安市生态文明建设度评价

根据生态文明的内涵和本质特征,提出了一个3层、6个维度(经济潜力、生态环境、民生改善、基础设施、生态文化及廉洁高效)和33个单项评价指标的生态文明建设度评价指标体系。通过对2004-2008年西安市及其区县生态建设度的评价研究,表明西安市生态、环境和社会经济条件都有一定程度的改善,生态文明建设度有所发展,但整体上发展过于缓慢,各部分发展不均衡。     

SPATIAL VARIATIONS OF WATER LOSS DURING DROUGH A CASE STUDY1

ABSTRACT: A regional water conservation system for drought management involves many uncertain factors. Water received from precipitation may stay on the ground surface, evaporate back into the atmosphere, or infiltrate into the ground. Reliable estimates of the amount of evapotranspiration and infiltration are not available for a large basin, especially during periods of drought. By applying a geographic information system, this study develops procedures to investigate spatial variations of unavailable water for given levels of drought severity. Levels of drought severity are defined by truncated values of monthly precipitation and daily streamflow to reflect levels of water availability. The greater the truncation level, the lower the precipitation or streamflow. Truncation levels of monthly precipitation are recorded in depth of water while those of daily streamflow are converted into monthly equivalent water depths. Truncation levels of precipitation and streamflow treated as regionalized variables are spatially interpolated by the unbiased minimum variance estimation. The interpolated results are vector values of precipitation and streamflow at a grid of points covering the studied basin. They are then converted into raster‐based values and expressed graphically. The image subtraction operation is used to subtract the image of streamflow from that of precipitation at their corresponding level of drought severity. It is done on a cell‐by‐cell basis resulting in new attribute values to form the spatial image representing a spatial distribution of potential water loss at a given level of drought severity.     

OREGON WATER QUALITY INDEX A TOOL FOR EVALUATING WATER QUALITY MANAGEMENT EFFECTIVENESS1

ABSTRACT: The Oregon Water Quality Index (OWQI) is a single number that expresses water quality by integrating measurements of eight water quality variables (temperature, dissolved oxygen, biochemical oxygen demand, pH, ammonia+nitrate nitrogen, total phosphorus, total solids, and fecal coliform). Its purpose is to provide a simple and concise method for expressing the ambient water quality of Oregon's streams for general recreational use, including fishing and swimming. The OWQI, originally developed in the 1970s, has been updated based upon improved understanding about water quality behavior. This report describes the historical basis of the OWQI and defines the improved design of the present OWQI. The index allows users to easily interpret data and relate overall water quality variation to variations in specific categories of impairment. This report demonstrates the value of the OWQI in presenting spatial and temporal water quality information. The OWQI improves comprehension of general water quality issues, communicates water quality status, and illustrates the need for and effectiveness of protective practices.     

TOWARDS CHARACTERIZING AND PLANNTNG FOR DROUGHT IN VERMONT‐PART II: POLICY IMPLICATIONS1

ABSTRACT: Vermont is one of approximately half a dozen states for which no official drought mitigation plan exists. Given the recurring nature of this natural hazard, current contingency measures should be expanded upon into a coherent mitigation framework. The types of drought and impacts resulting from the 1998 to 1999 event were the focus of a previous article in this volume. The present article builds on the understanding of drought characteristics specific to the Vermont context and introduces the rationale behind a proposed drought planning framework. Pivotal organizations and institutions that should be involved in this process are also presented.     

A TREE‐RING RECONSTRUCTION OF STREAMFLOW FOR THE COLORADO FRONT RANGE1

ABSTRACT: Water resource planning is based primarily on 20th century instrumental records of climate and streamflow. These records are limited in length to approximately 100 years, in the best cases, and can reflect only a portion of the range of natural variability. The instrumental record neither can be used to gage the unusualness of 20th Century extreme low flow events, nor does it allow the detection of low‐frequency variability that may underlie short‐term variations in flow. In this study, tree rings are used to reconstruct mean annual streamflow for Middle Boulder Creek in the Colorado Front Range, a semi‐arid region of rapid growth and development. The reconstruction is based on a stepwise regression equation that accounts for 70 percent of the variance in the instrumental record, and extends from 1703–1987. The reconstruction suggests that the instrumental record of streamflow for Middle Boulder Creek is not representative of flow in past centuries and that several low flow events in the 19th century were more persistent than any in the 20th century. The 1840s to early 1850s period of low flow is a particularly notable event and may have coincided with a period of low flow in the Upper Colorado River Basin.