Ecological condition of US Mid-Atlantic estuaries, 1997-1998     

Kiddon JA  Paul JF  Buffum HW  Strobel CS  Hale SS  Cobb D  Brown BS 《Marine pollution bulletin》2003,46(10):1224-1244

The Mid-Atlantic Integrated Assessment (MAIA-Estuaries) evaluated ecological conditions in US Mid-Atlantic estuaries during the summers of 1997 and 1998. Over 800 probability-based stations were monitored in four main estuarine systems--Chesapeake Bay, the Delaware Estuary, Maryland and Virginian coastal bays, and the Albemarle-Pamlico Estuarine System. Twelve smaller estuaries within the four main systems were also assessed to establish variance at the local scale. A subset of the MAIA-Estuaries data is used here to estimate the extent of eutrophication, sediment contamination, and benthic degradation in mid-Atlantic estuaries. An Environmental Report Card and Index of Environmental Integrity summarize conditions in individual estuaries, the four estuarine systems, and the entire MAIA region. Roughly 20-50% of the region showed signs of eutrophication (high nutrients, excessive production of organic matter, poor water clarity, or depleted dissolved oxygen), 30% had contaminated sediments, and 37% had degraded benthic communities. Compared with the Environmental Monitoring and Assessment Program (EMAP)-Virginian Province study in 1990-1993, larger fractions of Chesapeake Bay (17%) and Delaware River (32%) had increased metals or organics in sediments.  相似文献   

青藏高原冬季积雪时空变化特征EOF分析   总被引：2，自引：0，他引：2  

高文良陈忠明  闵文彬 《四川气象》2004,24(3):7-10

通过对青藏高原冬季积雪的EOF分析．揭示了青藏高原冬季积雪的时间变化和空间分布特征，分析出高原冬季积雪的突变现象．对青藏高原冬季积雪时空变化规律提出了自己的观点。  相似文献   

《公务员法》视野下的气象行政执法队伍建设     

严春银  陈忠 《气象软科学》2006,(3):57-60

气象行政执法队伍整体素质不高的现实状况使得执法人员能力比较欠缺，并导致执法不作为、执法乱作为等现象的产生，加强气象行政执法队伍建设是改善这种现实状况和发展气象事业的需求。《公务员法》创设了行政执法类职位，为把好气象行政执法队伍的进出关、加强约束与管理、强化激励等，提供了很好的依据和启示。  相似文献   

海底天然气水合物分解与甲烷归宿研究进展   总被引：5，自引：1，他引：5  

陈忠  颜文  陈木宏  王淑红  肖尚斌  陆钧  杨华平 《地球科学进展》2006,21(4):394-400

综述了近年来天然气水合物分解与甲烷归宿等方面的研究成果。天然气水合物的汇聚与地质构造或地层圈闭有关，其溶解受物质转换控制，分解则受热转换控制。水合物释放甲烷的运移方式包括分散式、中心式和大规模排放式。缺氧氧化和耗氧氧化是甲烷在海洋环境中的2种主要转化方式。天然气水合物释放甲烷的最终归宿主要为：①重新形成天然气水合物；②形成化能自养生物群落和沉淀出碳酸盐沉积；③与氧发生氧化后转变为CO2；④直接排放进入到大气中。沉积物中的微构造、化能自养生物群落、自生碳酸盐矿物及其碳氧同位素组成是水合物释放事件的指纹记录。  相似文献   

Injection-extraction treatment well pairs: an alternative to permeable reactive barriers   总被引：2，自引：0，他引：2  

Cunningham JA  Reinhard M 《Ground water》2002,40(6):599-607

Two of the biggest drawbacks of using permeable reactive barriers (PRBs) to treat contaminated ground water are the high capital cost of installation, particularly when the contaminated ground water is deep below ground surface, and the uncertainty of whether or not PRBs remain effective for the long time scales (e.g., decades) needed for many contaminant plumes. The use of an injection-extraction treatment well pair (IETWP) for capture and treatment of contaminated ground water can circumvent these difficulties, while still providing many of the same advantages offered by PRBs. In this paper, the hydraulics of IETWPs and PRBs are compared, focusing primarily on the width of the captured plume. It is demonstrated that IETWPs act as hydraulic barriers in a manner similar to PRBs, and that IETWPs provide excellent plume capture. A mathematical expression is presented for the plume capture width of an IETWP oriented perpendicular to the ground water flow direction in a homogeneous aquifer. Also discussed are other practical considerations that might determine whether an IETWP is better suited than a PRB for a particular contaminated site; these considerations include operating and maintenance costs, and the conditions under which an IETWP system can be used for in situ remediation.  相似文献   

Evaluation of two direct immunoassays for rapid detection of petroleum products on marine birds     

Fritcher DL  Mazet JA  Ziccardi MH  Gardner IA 《Marine pollution bulletin》2002,44(5):388-395

To reduce rehabilitation time and improve survival, a practical, objective test is needed to determine if marine birds are contaminated with oil before they enter captivity. The RaPID Assays and EnviroGard immunoassays for detection of polycyclic aromatic hydrocarbons (PAHs) in soil were evaluated for their ability to detect petroleum on feather samples from 30 intermediate fuel oil contaminated and 30 uncontaminated common murres (Uria aalge). Sensitivity, specificity, positive and negative predictive value, precision, and time required to run each assay were determined. The RaPID Assays was 96.7% sensitive and specific, while the EnviroGard assay was 93.3% sensitive, and 90.0% specific. Sensitivity decreased at higher dilutions for both assays. Intra-replicate variation was less than 20%. Our evaluation showed that these immunoassays are rapid and cost-effective methods for detecting oil-contamination on the plumage of seabirds, with the EnviroGard assay being more practical in most oil spill response situations due to ease of use and rapidity of results.  相似文献   

粘土矿物含量分析中的几个问题   总被引：7，自引：1，他引：6  

陈忠  罗蛰潭 《沉积学报》1998,16(1):137-139

储层岩石中粘土矿物种类及含量分析是划分沉积相带和成岩相带的基础,也是油气层钻井、完井、开发改造中储层保护的关键。本文在分析传统粘土矿物抽提分离方法及其缺点的基础上,提出了多级粒度抽提分离方法,为分析储层岩石中的粘土矿物种类和含量提供了首要的保障。  相似文献   

用三维有限差分法求反射走时     

Hole  JA 许健生 《世界地震译丛》1997,(3):71-78

在含有三维几何反射体的复杂三维速度模型，发展了一种计算反射地震波走时方法。为了处理大且急剧的速度反差，对现有的计算初至波走时的有限差分法作了适当修改。修改的计算方法比以前的几种方案更快且更精确，并结合到计算反射走时的程序中。这个反射波走时程序非常适合编入三维反射体结构的反演法中。  相似文献   

线性滞回阻尼与希尔伯特变换     

Inau.  JA 孙建刚 《世界地震工程》1996,(1):73-80

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一种用于编码立体测图仪的AutoCAD制图系统     

Roge.  JA 吴寿虎 《北京测绘》1989,(2):34-36

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