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21.
Diana Duncan Darryll T. Pederson Timothy R. Shepherd James D. Can 《Ground Water Monitoring & Remediation》1991,11(4):144-150
The city of Lincoln draws water from a well field along the banks of the Platte River in east-central Nebraska. We have been able to follow the infusion of atrazine into this well field under induced recharge. Samples of water from the river, several monitoring wells and a production well were analyzed by GC/MS and solid phase extraction and found to change in concentration over the range 0.1 and 5.0 ppb of atrazine through the spring, summer, and fall 1989. Increases in the concentration of atrazine relating to precipitation events in the Platte River Basin were observable in the well water samples and ultimately in Lincoln municipal tap water. Atrazine from the river was seen to move via induced recharge and into well field ground water and away from the river at an observable rate. The concentration of atrazine in the river is dependent upon time of year and precipitation in the river basin. 相似文献
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在分析了当前测绘仪器管理存在问题的基础上，从仪器在实验室的管理体制、模式方面做了有益探讨和分析，提出了测绘仪器实行动态管理和开放使用的模式。 相似文献
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稳定同位素比值分析已成功用于示踪动物的食物来源研究,近年来已发展了多个同位素混合模型用于计算混合物中多来源物质的组成比例。本文以过去百年来南极菲尔德斯半岛南极毛皮海豹(Arctocephalus gazella)毛发的C、N同位素数据为基础,运用同位素混合模型中的欧几里得距离法、线性模型和贝叶斯模型进行计算、分析和比较,得到毛皮海豹食谱中南极磷虾(Euphausia superb)、南极电灯鱼(Electrona antarctica)和尼氏裸灯鱼(Gymnoscopelus nicholsi)所占比例随时间的变化趋势。各模型计算得出的结果可分为两组,分别是欧几里得距离法公式(1)和(2)的结果,表现为近百年来毛皮海豹食谱中Euphausia superb比例与其毛发稳定N同位素比值呈同步上升的趋势;第二组为欧几里得距离法公式(3)、线性模型和贝叶斯模型的结果,Euphausia superb比例与毛皮海豹毛稳定N同位素比值呈反相关关系。综合对比研究区域气候、海冰环境变化背景和已有的南极磷虾种群密度调查资料分析,第二组模型结果与实际情况较为相符,可用于讨论食物比例的时间变化趋势。近百年来,菲尔德斯半岛毛皮海豹食谱中Euphausia superb的比例显著下降,很可能是由于区域气候快速变暖和海冰的消退造成的。本文的计算结果指示西南极半岛气候变暖已显著影响到区域海洋食物链变化。 相似文献
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In the equatorial western Pacific, iron-manganese oxyhydroxide crusts(Fe-Mn crusts) and nodules form on basaltic seamounts and on the top of drowned carbonate platform guyots that have been swept free of pelagic sediments. To date, the Fe-Mn crusts have been considered to be almost exclusively of abiotic origin. However, it has recently been suggested that these crusts may be a result of biomineralization. Although the Fe-Mn crust textures in the equatorial western Pacific are similar to those constructed by bacteria and algae, and biomarkers also document the existence of bacteria and algae dispersed within the Fe-Mn crusts, the precipitation, accumulation and distribution of elements, such as Fe, Mn, Ni and Co in Fe-Mn crusts are not controlled by microbial activity. Bacteria and algae are only physically incorporated into the crusts when dead plankton settle on the ocean floor and are trapped on the crust surface. Geochemical evidence suggests a hydrogenous origin of Fe-Mn crusts in the equatorial western Pacific, thus verifying a process for Fe-Mn crusts that involves the precipitation of colloidal phases from seawater followed by extensive scavenging of dissolved trace metals into the mineral phase during crust formation. 相似文献
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多时相InSAR技术具有探测大范围毫米级地表形变的能力,已被广泛应用于地面沉降监测.近几年,应用多时相InSAR技术监测以高铁为代表的大尺度人造线状地物形变备受关注.本文将C波段SAR数据用于高铁沿线路基形变监测,应用相位稳定性分析和改进的StaMPS技术来增加相干性点的密度和形变参数解算的稳定性.采用研究区时间跨度为21个月的47景Sentinel-1A数据,对连(云港)盐(城)高铁及其沿线区域进行多时相InSAR分析,并利用同时期连续的北斗导航卫星系统(BeiDou navigation satellite system,BDS)观测数据对线性沉降速率和时序位移分别进行监测分析,进而对比验证二者的沉降监测结果.研究结果表明:利用C波段的Sentinel-1A数据能够获取毫米级的线性形变速率和时序位移序列,InSAR与BDS二者平均时序位移均方根误差为3.8 mm,与BDS监测结果相比取得很好的一致性,且连盐高铁线路整体表现稳定. 相似文献
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By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there. 相似文献
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