OPTIMIZATION PROCEDURE FOR COST EFFECTIVE BMP PLACEMENT AT A WATERSHED SCALE1

ABSTRACT: A combinatorial optimization procedure for best management practice (BMP) placement at the watershed level facilitates selection of cost effective BMP scenarios to control non point source (NFS) pollution. A genetic algorithm (GA) was selected from among several optimization heuristics. The GA combines an optimization component written in the C++ language with spatially variable NFS pollution prediction and economic analysis components written within the Arc View geographic information system. The procedure is modular in design, allowing for component modifications while maintaining the basic conceptual framework. An objective function was developed to lexicographically optimize pollution reduction followed by cost increase. Scenario cost effectiveness is then calculated for scenario comparisons. The NPS pollutant fitness score allows for evaluation of multiple pollutants, based on prioritization of each pollutant. The economic component considers farm level public and private costs, cost distribution, and land area requirements. Development of a sediment transport function, used with the Universal Soil Loss Equation, allows the optimization procedure to run within a reasonable timeframe. The procedure identifies multiple near optimal solutions, providing an indication of which fields have a more critical impact on overall cost effectiveness and flexibility in the final solution selected for implementation. The procedure was demonstrated for a 1,014‐ha watershed in the Ridge and Valley physiographic region of Virginia.     

Modeling obsolete computer stock under regional data constraints: An Atlanta case study

In this paper, we report on our efforts to develop a research framework that can be used to quantify waste flows for different geographical areas in the face of limited waste data availability. We demonstrate this framework in our case study of obsolete computers in the Atlanta metropolitan area. We develop computer obsolescence rates at the national metropolitan level, and couple this data with economic information at the census tract level to generate product inventory estimates (PIE) of the stock of obsolete computers from both business and household sectors in the Atlanta metropolitan area. We seek to improve the accuracy of waste flow estimates for specific geographic areas over those of previous studies, provide an easily replicable and cost effective methodology, highlight the ensuing spatial implications for collection and recycling systems using GIS, and demonstrate the potential economic benefits from diverting electronic wastes within a region. The modeling framework we have developed is intended to be applicable to other regions and to other medium range durable goods discarded by households, businesses, or obtained from buildings.     

植物CytP450和抗氧化酶对土壤菲、芘暴露的生态毒理响应

以玉米(Zea mays L.)为供试植物,草甸棕壤为供试土壤,以微粒体细胞色素P450含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性为指标,进行了土壤菲、芘暴露的生态毒理响应研究.结果表明,菲、芘暴露均能引起植物代谢解毒和抗氧化防御系统的胁迫响应,不同程度引发植物代谢解毒及抗氧化能力的改变.P450酶活性与低浓度菲、芘单-暴露浓度具有相关性(r=0.834,P<0.01),与菲、芘复合暴露浓度负相关,说明菲、芘复合暴露导致代谢解毒能力下降,对植物的代谢解毒具有协同毒性效应;SOD酶活性与菲、芘单一暴露浓度负相关,CAT酶活性与菲、芘单-暴露浓度正相关,POD酶活性与菲的水溶解度正相关,而与芘的总浓度负相关.SOD、CAT和POD酶活性与菲、芘复合暴露浓度均呈正相关,说明菲、芘复合暴露导致氧化损伤程度减弱,对植物的氧化损伤具有拮抗作用.     

Threats to Riparian Ecosystems in Western North America: An Analysis of Existing Literature1

Poff, Boris, Karen A. Koestner, Daniel G. Neary, and Victoria Henderson, 2011. Threats to Riparian Ecosystems in Western North America: An Analysis of Existing Literature. Journal of the American Water Resources Association (JAWRA) 47(6):1241–1254. DOI: 10.1111/j.1752‐1688.2011.00571.x Abstract: A total of 453 journal articles, reports, books, and book chapters addressing threats to riparian ecosystems in western North America were analyzed to identify, quantify, and qualify the major threats to these ecosystems as represented in the existing literature. Publications were identified either as research, policy, literature review, historical comparison, or management papers. All papers were evaluated based on year of publication, area of interest, and type(s) of threats addressed. Research papers, however, were assessed in more depth. The publications ranged from the 1930s to 2010 and addressed the following threats: dams, pollution (point and nonpoint), grazing, land use change, timber harvesting, water diversion, road construction, recreation, mining, groundwater pumping, invasive species, climate change, salinity, fire, insect and diseases, woody encroachment, watershed degradation, elimination of native vegetation, beavers, fire suppression, and fuel management. While the types of threats vary on spatial and temporal scales, some persist through decades in western North America. This analysis shows that grazing has been perceived as a dominant threat since the 1980s, but has been diminishing in the past decade, while invasive species, dams and, in recent years, climate change are increasingly represented in the literature as threats to riparian ecosystems in western North America.