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851.
852.
将三油酸甘油酯-醋酸纤维素复合膜(TECAM)用作被动采样器,开展水体中一甲基锡(MMT)、二甲基锡(DMT)、一丁基锡(MBT)、二丁基锡(DBT)、三丁基锡(TBT)、二苯基锡(DPhT)和三苯基锡(TPhT)等7种有机锡氯化物的富集实验,膜样品经甲醇/醋酸溶液提取、乙基化衍生和正己烷萃取等前处理后,用气相色谱-质谱法(GC-MS)进行定性和定量检测,得到水体中痕量有机锡污染的相关指纹信息。结果表明,7种目标化合物均可在TECAM膜上富集,48 h后均可达到平衡状态;有机锡富集能力差异较大,其TECAM膜/水分配系数(log KTECAM)与其辛醇-水分配系数(log Kow)呈现显著正相关性(r=0.97, n=7)。甲基锡富集能力较低,但可定性筛查;而苯基锡和丁基锡等5种目标化合物在TECAM膜上的被动采样速率在0.06~0.16 L·g~(-1)·d~(-1)范围变化,经反演所得其在水体中的时间加权平均浓度与传统的主动采样法所得浓度没有显著差异(P0.05)。因此,基于TECAM被动采样技术可以实现水体中极性范围较广的痕量有机锡污染筛查取证。 相似文献
853.
A traditional method of summarizing spatial distribution of species is the observed species-area curve. Often the observed species-area curve is surprisingly close to the expected species-area curve under the hypothesis of random placement of individuals. This has been used as evidence supporting the hypothesis. In this paper, we argue that using the observed species-area curve to test the general random placement hypothesis is highly inefficient. We present a testing method based on the classical 2 test for over-dispersion which is not only more efficient but also applicable to situations where complete abundance information are unavailable. We also discuss three alternatives of the hypothesis. The focus of this paper is on these and other general issues relevant to communities of different types. No applications are included in this paper. 相似文献
854.
M. Turk J. Jakšić M. Vojinović Miloradov J. Klanova 《Environmental Chemistry Letters》2007,5(3):109-113
For the duration of the war accident in former Yugoslavia, several industrial and military targets were burnt and damaged,
resulting in a significant release of persistent organic pollutants. Locations heavily targeted in the attacks were later
defined by UNEP as four “hot spots”: Kragujevac, Novi Sad, Pancevo and Bor. We analyzed concentration levels of pollutants
collected in 2004 and 2005 in air samples from the city of Kragujevac, Serbia, following the war accident of 1999. Pollutants
included polycyclic aromatic hydrocarbons (PAHs), hexachlorocyclohexane (HCH), dichloro-diphenyl-trichloroethane (DDT), dichloro-diphenyl-dichloroethylene
(DDE), dichloro-diphenyl-dichloroethane (DDD) and polychlorinated biphenyls (PCBs). We present results obtained during air
sampling campaign conducted in July 2004 by the active sampling method; and during September 2004–June 2005 by the passive
sampling method. Our findings show the occurrence of residual quantities of DDT, HCH, PCBs and PAHs in air samples. High levels
of PCBs are probably due to the destruction of transformers during the war accident. 相似文献
855.
Environmental Impact of Undular Tidal Bores in Tropical Rivers 总被引:3,自引:1,他引:3
A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment
motion beneath tidal bores. In the absence of detailed systematic field measurements, a quasi-steady flow analogy was applied
to investigate undular tidal bores with inflow Froude numbers between 1.25 and 1.6. Experimental results indicated that rapid
flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave
crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of undular tidal bores. The effects
of periodic loading on river sediments, scour of river bed and flow mixing behind the bore are discussed. A better understanding
of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx and Daly
rivers in tropical Australia. 相似文献
856.
Interest in natural resources and the environment has led to the development of new federal monitoring efforts, the expansion of existing federal inventory programmes, and discussions of inter-agency collaboration for natural resource assessment data collection. As federal programmes evolve, knowledge gained from existing long-term survey programmes can provide valuable contributions to statistical and operational aspects of survey efforts. This paper describes the National Resources Inventory (NRI), which has been conducted by the US Department of Agriculture's Natural Resources Conservation Service in cooperation with the Iowa State University Statistical Laboratory for several decades. The current NRI is a longitudinal survey of soil, water, and related environmental resources designed to assess conditions and trends every five years on non-federal US lands. An historical overview is provided highlighting the development of the survey programme. Sample design, data collection, and estimation procedures used in the 1992 NRI are described, and statistical issues related to long-term monitoring are discussed. 相似文献
857.
天然水体沉积物的表面特征 总被引:13,自引:2,他引:13
本文运用表面络合的模式和原理,研究了江西乐安江下游黄龙庙沉积物的表面特征,通过酸碱滴定实验求定了样吕的零电点pHPZC、表面质子电荷密度σH和表面总吸附位NS;应用图解法和FITEQL程序计算法求定了江西乐安江下游黄龙库沉积物样品的表面固有常数;对恒定容量模式、扩散层模式和三层模式在天然水体沉积物中的应用进行了比较,研究表明,应用表面络合模式研究天然水体沉积物的表面特是可行的,三种模式都能在一定程 相似文献
858.
土壤,沉积物中微量金属形态分配预测初步研究 总被引:9,自引:2,他引:9
本文讨论了土壤、沉积物中微量金属的形态分配预测问题。对已有的一些工作进行了总结,并以我国东部平原为例,建立了土壤微量金属多元回归相分配预测摸型。 相似文献
859.
杞麓湖“十五”期间污染底泥环境疏浚工程效益评估研究 总被引:5,自引:0,他引:5
对疏浚工程前杞麓湖湖泊生态系统存在的问题进行了深入分析,并在对底泥中污染物释放的原理进行简述的基础上,对底泥疏浚工程效益展开详细的评估,认为底泥疏浚有效地带出湖内污染源,疏浚区水质明显改善,扩大了湖容量,并为湖泊水生态系统恢复创造了适宜的光照条件、底质条件和水深条件,有利于水生态系统的自然恢复,促进湖泊生态系统好转。同时,疏浚底泥的吹填改造了湖周围冷浸田,促进了湖周农田基本建设及农业经济的可持续发展。 相似文献
860.
Data were tabulated and compared for cases involving prenatal diagnostic procedures performed in the 8 years between January 1985 and December 1992. Of a total of 2781 pregnancies, 2546 cases (91·5 per cent) were diagnosed by amniocentesis, and 235 (8·5 per cent) by chorionic villus sampling (CVS). These findings reflect the fact that amniocentesis has taken deep root as the prenatal diagnostic procedure widely acknowledged by society, whereas even the existence of CVS has yet to be generally recognized. Analysis of our clinical and laboratory results and complication rates, however, suggests that CVS is a safe and accurate alternative to amniocentesis which should and can be positively presented to all patients who are candidates for prenatal diagnosis. 相似文献