Effects of calibration on L-THIA GIS runoff and pollutant estimation

Urbanization can result in alteration of a watershed's hydrologic response and water quality. To simulate hydrologic and water quality impacts of land use changes, the Long-Term Hydrologic Impact Assessment (L-THIA) system has been used. The L-THIA system estimates pollutant loading based on direct runoff quantity and land use based pollutant coefficients. The accurate estimation of direct runoff is important in assessing water quality impacts of land use changes. An automated program was developed to calibrate the L-THIA model using the millions of curve number (CN) combinations associated with land uses and hydrologic soil groups. L-THIA calibration for the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana was performed using land use data for 1991 and daily rainfall data for six months of 1991 (January 1-June 30) to minimize errors associated with use of different temporal land use data and rainfall data. For the calibration period, the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The calibrated CN values were used for validation of the model for the same year (July 1-December 31), and the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The Nash-Sutcliffe coefficient was 0.52 for January 1, 1991 to December 31, 1991 using uncalibrated CN values. As shown in this study, the use of better input parameters for the L-THIA model can improve accuracy. The effects on direct runoff and pollutant estimation of the calibrated CN values in the L-THIA model were investigated for the LEC. Following calibration, the estimated average annual direct runoff for the LEC watershed increased by 34%, total nitrogen by 24%, total phosphorus by 22%, and total lead by 43%. This study demonstrates that the L-THIA model should be calibrated and validated prior to application in a particular watershed to more accurately assess the effects of land use changes on hydrology and water quality.     

Synergistic Techniques for Better Understanding and Classifying the Environmental Structure of Landscapes

The desire to capture natural regions in the landscape has been a goal of geographic and environmental classification and ecological land classification (ELC) for decades. Since the increased adoption of data-centric, multivariate, computational methods, the search for natural regions has become the search for the best classification that optimally trades off classification complexity for class homogeneity. In this study, three techniques are investigated for their ability to find the best classification of the physical environments of the Mt. Lofty Ranges in South Australia: AutoClass-C (a Bayesian classifier), a Kohonen Self-Organising Map neural network, and a k-means classifier with homogeneity analysis. AutoClass-C is specifically designed to find the classification that optimally trades off classification complexity for class homogeneity. However, AutoClass analysis was not found to be assumption-free because it was very sensitive to the user-specified level of relative error of input data. The AutoClass results suggest that there may be no way of finding the best classification without making critical assumptions as to the level of class heterogeneity acceptable in the classification when using continuous environmental data. Therefore, rather than relying on adjusting abstract parameters to arrive at a classification of suitable complexity, it is better to quantify and visualize the data structure and the relationship between classification complexity and class homogeneity. Individually and when integrated, the Self-Organizing Map and k-means classification with homogeneity analysis techniques also used in this study facilitate this and provide information upon which the decision of the scale of classification can be made. It is argued that instead of searching for the elusive classification of natural regions in the landscape, it is much better to understand and visualize the environmental structure of the landscape and to use this knowledge to select the best ELC at the required scale of analysis.     

酸雨作用下中亚带森林冠层淋溶规律研究

2001年1月～2002年6月对韶山亚热带常绿阔叶林4个采样区进行了酸雨的监测,以监测数据为依据,分析研究了林内穿透水中主要离子的淋溶规律。结果表明:大气降水经过森林冠层后pH值明显升高,韶山亚热带常绿阔叶林对SO42-、NO3-、Mg2+、NH4+离子具有吸收作用,特别是NH4+和NO3-离子。SO42-、Ca2+和Mg2+离子的冠层淋溶百分率随降雨量的增加有明显减少的趋势。Ca2+、K+和Cl-随着pH的增加,其冠层淋溶百分率呈增加趋势。韶山地区在常年酸沉降作用下,森林冠层对酸性离子SO42-、NO3-的吸收作用最强。根据18个月离子浓度平均值来计算,韶山地区森林冠层离子的淋溶序列为:K+>Ca2+>Cl->Mg2+>SO42->NO3->NH4+>Na+。     

上海市能耗与GDP大气污染的协整关系研究

采用计量经济学中的协整理论考察上海市能源消费量与经济增长、废气排放量、二氧化硫排放量之间的关系。结果显示,上海市能源消费只与经济增长、废气排放量之间存在长期协整关系,并建立了相应的长期均衡方程及误差修正模型。另外,对1978～2003年的能源消费与经济增长之间进行Granger因果关系检验,提出实现上海市经济-能源-环境和谐发展的措施。     

氯自由基介导的BDD电极选择性氧化脱氮

为实现氨氮的高效选择性转化,设计了一个氯自由基介导的电化学体系。该电化学体系以稳定性好、氧化能力强的掺硼金刚石(BDD)电极为阳极,以Pd-Cu修饰的泡沫镍材料(Pd-Cu/NF)为阴极,以氯化钠为电解质,对BDD电极选择性电催化氧化性能与机理进行了研究。结果表明:在4.0 V电压下,体系中的Cl~-原位可转NO_3~-,副产物N_2;分别探究了阴极材料、电场强度、电极间距、溶液pH和电解质种类对氨氮转化性能的影响。通过电子顺磁共振和自由基捕获实验,证实了Cl·在氨氮转化过程中发挥了重要作用。在最优条件下,可实现40 min内100%的氨氮转化率和25 mg·L~(-1)的N_2生成量,以上研究结果可为解决水体中氨氮的污染问题提供参考。     

县级环境监测站垂直管理后工作思考

简要分析了县级环境监测站在监测监察执法垂直管理制度改革后面临的问题,并针对问题提出建议。     

以科技创新 保障高风险环境生产安全

正由中铁电气化局集团负责实施的重庆轨道交通十号线一期设备系统总承包工程,线路全长33.42 km,工程范围包括110 k V主变电所及外线路、供电设备、供电线路、通信、信号、综合监控、站台门、自动售检票、人防门、电扶梯、车场设备、工程车辆、综合接地等主要专业系统集成、安装、综合调试及相关配合、接口工作。该工程基本包含了站后所有电气专业设备,由于前期工程滞后,     

农业劳动生产率区域差异与农业用能强度收敛性

农业能源的消耗及其增长长期没有引起足够的重视,作为农业大国,在推进现代农业发展的同时,全面考察农业能源的利用效率,对于农业以及整体经济的可持续发展具有重要的现实意义。本文通过对β收敛模型的适当改进,构建了具有时滞因子的调整模型,分别考察了区域农业劳动生产率的收敛性和区域农业用能强度的收敛性,在此基础上进一步分析了农业用能强度随农业劳动生产率变化的收敛或发散情况。结果表明:第一,总体上我国农业劳动生产率是收敛的,即我国农业劳动生产率呈现不断提高的趋势。其中,中部地区农业劳动生产率的收敛速度最快,半生命周期最短,其次为东部地区,西部地区农业劳动生产率的收敛速度在三者中最慢;第二,我国区域农业用能强度也具有收敛性,即我国农业用能效率也呈现不断提高的趋势。具体到不同类别,尽管煤、油、电使用效率都呈现出收敛性,但是电的使用效率最高,而油的使用效率最低,同时,我国农业用能效率主要体现在农业用电上;第三,我国区域农业用能效率的差距在一定程度上也是区域农业劳动生产率差距的结果,并显示出个体属性差异、区域差异和结构特征。就政策建议而言,推动农业生产技术进步,增强农业用能的替代弹性,优化农业用能结构以及通过资本驱动农业发展和培育农业人力资本等途径是提高农业能源使用效率的适宜选择。     

玛纳斯河流域生态问题的潜在风险性评估

玛纳斯河流域是中国干旱区最具代表性的山地-绿洲-荒漠生态系统,三大生态系统表现出的区域生态、经济要素的空间状况有所分异,所存在的生态安全问题的表现形式也各不相同。根据流域土地利用和水资源数据库,在生态经济功能分区的基础上,针对流域不同分区存在的生态安全问题,选取相应的17个生态风险评估指标,建立了生态-经济风险性评价模型,对流域各个生态经济功能亚区的生态问题潜在的风险性进行了生态风险评估。结果表明:Ⅰ1,Ⅱ1,Ⅱ2,Ⅱ3,Ⅲ1,Ⅲ2和Ⅲ3亚区的生态问题潜在的风险性在增大,说明生态问题日益突出,而Ⅰ1和Ⅱ4亚区生态问题潜在的风险性指数存在波动;Ⅰ,Ⅱ和Ⅲ三个大区中生态问题潜在的风险性指数最高的分别是Ⅰ1,Ⅱ1和Ⅲ1亚区。评价结果能够较为客观地反映了当地的实际情况,因而对流域可能出现的灾害性的环境问题及由此引起的巨大的经济损失提出了警示。     

基于区域管理的滑坡灾害信息系统研制

在长期的滑坡灾害防治工作中,三峡库区已积累了大量的工程资料,但这些资料主要储存在单项工程报告中而没有被充分利用。为了有效地利用现有的滑坡工程数据,提高资料的管理水平,提出并实现了基于区域管理的滑坡灾害信息系统,该系统可对指定区域多个滑坡工程的数据进行综合管理和处理,为工程建设决策、规划提供了直观的依据;并可利用拟评价工程场地附近的历史资料生成相应的信息,对待评价地区进行预测和预评估评价,这样既可优化评价手段又能节省评估费用。