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861.
The use of chemical dispersants to combat oil spills at sea: A review of practice and research needs in Europe 总被引:1,自引:0,他引:1
In order to better understand the practice of dispersant use, a review has been undertaken of marine oil spills over a 10 year period (1995-2005), looking in particular at variations between different regions and oil-types. This viewpoint presents and analyses the review data and examines a range of dispersant use policies. The paper also discusses the need for a reasoned approach to dispersant use and introduces past cases and studies to highlight lessons learned over the past ten years, focussing on dispersant effectiveness and monitoring; toxicity and environmental effects; the use of dispersants in low salinity waters; response planning and future research needs. 相似文献
862.
Depth-dependent sampling to identify short-circuit pathways to public-supply wells in multiple aquifer settings in the United States 总被引:3,自引:2,他引:1
Matthew K. Landon Bryant C. Jurgens Brian G. Katz Sandra M. Eberts Karen R. Burow Christy A. Crandall 《Hydrogeology Journal》2010,18(3):577-593
Depth-dependent water-quality and borehole flow data were used to determine where and how contamination enters public-supply wells (PSWs) at study sites in different principal aquifers of the United States. At each of three study sites, depth-dependent samples and wellbore flow data were collected from multiple depths in selected PSWs under pumping conditions. The chemistry of these depth-dependent samples, along with samples of the surface discharge from the PSWs, was compared to that of adjacent nested monitoring wells. The results of depth-dependent analyses from sites in Modesto (California), York (Nebraska), and Tampa (Florida) are summarized and compared. Although the exact mechanisms for transport of contaminants to the PSWs varied among these hydrogeologic settings, in all three settings the presence of wells or boreholes or natural preferential flow paths allowed water and contaminants to bypass substantial portions of the aquifer and to reach PSWs or depths in the aquifer more quickly than would have occurred in the absence of these short-circuiting flow paths. The chemistry and flow data from multiple depths was essential to developing an understanding of the dominant flow paths of contaminants to PSW in all three settings. This knowledge contributes to developing effective strategies for monitoring and protection. 相似文献
863.
Hans W. Paerl Karen L. Rossignol S. Nathan Hall Benjamin L. Peierls Michael S. Wetz 《Estuaries and Coasts》2010,33(2):485-497
Estuarine and coastal systems represent a challenge when it comes to determining the causes of ecological change because human
and natural perturbations often interact. Phytoplankton biomass (chlorophyll a) and group-specific photopigment indicators were examined from 1994 to 2007 to assess community responses to nutrient and
climatic perturbations in the Neuse River Estuary, NC. This system experienced nutrient enrichment and hydrologic variability,
including droughts, and an increase in hurricanes. Freshwater input strongly interacted with supplies of the limiting nutrient
nitrogen (N) and temperature to determine the location, magnitude, and composition of phytoplankton biomass. Multi-annual,
seasonal, and episodic hydrologic perturbations, including changes in the frequency and intensity of tropical storms, hurricanes
and droughts, caused significant shifts in phytoplankton community structure. Climatic oscillations can at times overwhelm
anthropogenic nutrient inputs in terms of controlling algal bloom thresholds, duration, and spatial extent. Eutrophication
models should incorporate climatically driven changes to better predict phytoplankton community responses to nutrient inputs
and other anthropogenic perturbations. 相似文献
864.
William R. Hyde Adam A. Garde Nynke Keulen Sebastian N. Malkki Steven J. Jaret Tod Waight Pierre Beck Iain McDonald Nicolaj K. Larsen 《Meteoritics & planetary science》2023,58(6):789-814
Impact melt rocks formed during hypervelocity impact events are ideal for studying impact structures. Here, we describe impact melt rock samples collected proximal to the 31 km wide 58 Ma Hiawatha impact structure, northwest Greenland, which is completely covered by the Greenland Ice Sheet. The melt rocks contain diagnostic shock indicators (e.g., planar deformation features [PDF] in quartz and shocked zircon) and form three groups based on melt textures and chemistry: (i) hypocrystalline, (ii) glassy, and (iii) carbonate-based melt rocks. The exposed foreland directly in front of the structure consists of metasedimentary successions and igneous plutons; however, the carbonate-based impactites indicate a mixed target sequence with a significant carbonate-rich component. Well-preserved organic material in some melt rocks indicates that North Greenland at the time of impact was host to abundant organic material, likely a dense high-latitude temperate forest. Geochemical signatures of platinum-group elements in selected samples indicate an extraterrestrial component and support previous identification of a highly fractionated iron impactor in glaciofluvial sand. Our results illustrate the possibility to study impact structures hidden beneath a thick ice sheet based on transported samples and this opens a new avenue for identifying other potential impact craters in Greenland and Antarctica. 相似文献
865.