石油地质技术进步

石油地质技术进步Ｇ．Ｄ．Ｈｏｂｓｏｎ１．非垂直井和随钻测井最近，尤其是在近海开发油田中，非垂直井钻探数目越来越多。从一个平台钻探一系列这种类型的钻井比从多个平台钻探同样数量井的费用少得多。除了费用降低之外，运输的风险降低，易于生产管理。为了能够钻探井...     

与裂谷有关的极小正断层组分的几何形态和比例关系

与裂谷有关的极小正断层组分的几何形态和比例关系ＲｏｙＷ．Ｓｃｈｌｉｓｃｈ等过去十年中断层组分一直是广泛研究的主题。许多工作集中于确定断层组分的比例关系，包括断层尺寸的分布，位移和长度之间的关系，以及断层作用容纳的应变。许多断层组分表现出断层规模的幂函...     

Effects of land use on ground water quality in the Anoka Sand Plain Aquifer of Minnesota

We began a study, in 1996, to compare ground water quality under irrigated and nonirrigated agriculture, sewered and nonsewered residential developments, industrial, and nondeveloped land uses. Twenty-three monitoring wells were completed in the upper meter of an unconfined sand aquifer. Between 1997 and 2000, sampling occurred quarterly for major ions, trace inorganic chemicals, volatile organic compounds (VOCs), herbicides, and herbicide degradates. On single occasions, we collected samples for polynuclear aromatic hydrocarbons (PAHs), perchlorate, and coliform bacteria. We observed significant differences in water chemistry beneath different land uses. Concentrations of several trace inorganic chemicals were greatest under sewered urban areas. VOC detection frequencies were 100% in commercial areas, 52% in sewered residential areas, and <10% for other land uses. Median nitrate concentrations were greatest under irrigated agriculture (15,350 microg/L) and nonsewered residential areas (6080 microg/L). Herbicides and degradates of acetanilide and triazine herbicides were detected in 86% of samples from irrigated agricultural areas, 68% of samples from nonirrigated areas, and <10% of samples from other land uses. Degradates accounted for 96% of the reported herbicide mass. We did not observe seasonal differences in water chemistry, but observed trends in water chemistry when land use changes occurred. Our results show land use is the dominant factor affecting shallow ground water quality. Trend monitoring programs should focus on areas where land use is changing, while resource managers and planners must consider potential impacts of land use changes on ground water quality.     

Time should be considered in developmental ecotoxicity test

Developmental toxicity tests are often used for the hazard assessment of chemicals and environmental media. One of the most widely used is the oyster embryo larval test (OEL), in which the development of oyster larvae is arrested at a single fixed time (e.g. 24 or 48 h) of toxic exposure, and the proportion of normal larvae measured. However, a major problem with this conventional approach is the lack of information on temporal trends in development. In this study, Pacific oyster Crassostrea gigas embryos were exposed to nominal concentrations of copper (CuSO₄) of <0.001 (control), 0.60, 1.25, 2.5, 5.0, 10.0 and 20.0 μg l⁻¹ (at 20 °C, salinity 35‰ and pH 8.1). Three replicates from each group were arrested and examined every 8 h during 24–72 h of exposure, and the number of viable larvae developed to D-shape was determined. The results revealed that the number of viable D-shape larvae in the control increased rapidly and reached an optimum at 32 h, before declining gradually due to starvation. Analysis of covariance (ANCOVA) showed that larval developmental rates during 0–32 h were significantly inhibited by Cu at all concentrations. This paper demonstrates that arrest and measurement at different time periods are important and should be incorporated into the OEL test. This would maximise the sensitivity of the test in detecting developmental effects in spiked or environmental samples.