甘ECK989

来源：蜘蛛抓取(WebSpider) 时间：2018-06-26 00:26 标签： 甘之
非法访问，您的行为已被WAF系统记录！Geochemistry of major elements and trace metals in suspended matter of the Scheldt estuary, southwest Netherlands - ScienceDirect
ExportJavaScript is disabled on your browser. Please enable JavaScript to use all the features on this page., July 1999, Pages 91-111Author links open overlay panelShow moreAbstractThe geochemistry of suspended matter from the Scheldt estuary has been studied in eight surveys in . Samples were analyzed for major elements (Al, Ca, Fe, K, Mg, Na, Si, Ti, POC, N, P, S) and trace metals (Ag, Ba, Be, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, Sn, Sr, V, Zn). Physical mixing of fluvial and marine particulates leads to a continuous decrease in the trace metal content of the suspended matter with increasing salinity. Principal component analysis shows that the effect of desorption processes (e.g., of Cd, Cu, and Zn) on the suspended matter composition is relatively minor as compared to that of particle mixing. A particulate S maximum is present in the upper estuary, reflecting resuspension of reduced sediments. Pore water infusion into the (suboxic) upper estuary is a major source of Fe and Mn to the suspended matter. Due to differences in oxidation kinetics, precipitation of dissolved Mn occurs later (in the lower estuary) than that of Fe (in the upper estuary). Coprecipitation with Mn (hydr)oxides is observed for Ni and Co, but not for the other metals studied. Phytoplankton activity leads to a seasonal shift in the suspended matter composition in the lower estuary. During the spring bloom, the contents of trace metals and lithogenic elements are decreased, in favour of biogenic elements (POC, N, P). This observation is attributed to dilution of mineral particles by phytoplankton which, apparently, has lower trace metal levels. However, the Ba content of the suspended matter is increased during the bloom, which is ascribed to biological formation of barite. Another effect of the spring bloom is depletion of dissolved Cd and Zn (but not of Cu), leading to an increase in their distribution coefficients in the lower estuary. Phytoplankton may both directly (through biological uptake) and indirectly (by increasing the pH) be involved in the seasonal shift of Cd and Zn from the dissolved to the particulate phase. Comparison of recent data on suspended matter composition with historical data shows that the trace metal burden of the Scheldt river has decreased considerably between 1980 and 1995. The decrease in trace metal levels of the fluvial suspended matter amounts to 88% for Cd, 85% for Hg, 74% for As, 59% for Cu, and 50–54% for Cr, Ni, Pb and Zn over the time span considered. However, the Mn content of the fluvial suspended matter has doubled from the early 1970s until the mid 1990s, reflecting the gradual increase in the dissolved oxygen concentration of the river water over the last 20 years.Keywordssuspended mattertrace metalsgeochemistryseasonal variabilityScheldt estuaryChoose an option to locate/access this article:Check if you have access through your login credentials or your institution.ororRecommended articlesCiting articles (0)Needs assessment for IMCI management components, Guatemala, March 9-20, 1998. | POPLINE.orgBrowser Not Supported
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is available for basic searches with links to full-text.戴尔989在网上说的那么差，真的有那么差么？_百度知道
戴尔989在网上说的那么差，真的有那么差么？
我有更好的答案
硬盘很垃圾！！！其他的都还可以。。。
硬盘不是一般化么，很多笔记本都用5400转
采纳率：15%
您好请您不要相信一些别有用心的谣言和诋毁，戴尔作为知名品牌是不会这样的。客服人员会为您进行一对一解答，这样比较保险和稳妥。戴尔是国际名牌产品，用户至上是一贯的宗旨。戴尔厂家直接销售地址：
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