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451.
Light nonaqueous-phase liquids (LNAPLs) such as gasoline and diesel fuel are among the most common causes of soil and groundwater contamination. Dissolution and subsequent advective transport of LNAPL components can negatively impact water supplies, while biodegradation is thought to be an important sink for this class of contaminants. We present a laboratory investigation of the effect of a water-table fluctuation on dissolution and biodegradation of a multi-component LNAPL (85% hexadecane, 5% toluene, 5% ethylbenzene, and 5% 2-methylnapthalene on a molar basis) in a pair of similar model aquifers (80 cm x 50 cm x 3 cm), one of which was subjected to a water-table fluctuation. Water-table fluctuation resulted in LNAPL and air entrapment below the water table, an increase in the vertical extent of the LNAPL source zone (by factor 6.7), and an increase in the volume of water passing through the source zone (by factor ~18). Effluent concentrations of dissolved LNAPL components were substantially higher and those of dissolved nitrate lower in the model aquifer where a fluctuation had been induced. Thus, water-table fluctuation led to enhanced biodegradation activity (28.3 mmol of nitrate consumed compared to 16.3 mmol in the model without fluctuation) as well as enhanced dissolution of LNAPL components. Despite the increased biodegradation, fluctuation led to increased elution of dissolved LNAPL components from the system (by factors 10-20). Hence, water-table fluctuations in LNAPL-contaminated aquifers might be expected to result in increased exposure of downgradient receptors to LNAPL components. Accordingly, water-table fluctuations in contaminated aquifers are probably undesirable unless the LNAPL is of minimal solubility or the dissolved-phase plume is not expected to reach a receptor due to distance or the presence of some form of containment. 相似文献
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Ester Heath Nives Ogrinc Jadran Faganeli Stefano Covelli 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):605-614
To reconstruct a history of polycyclic aromatic hydrocarbon (PAH) pollution in the Gulf of Trieste, one of the largest urbanized
areas in the Adriatic Sea, we analyzed three long sediment cores collected between 1996 and 1997. Concentrations of total
PAHs, the sum of 16 PAH compounds and six of their methylated analogues, in all three cores show a decrease from 600–800 ng
g−1, at the surface, to levels below 250 ng g−1 in deepest layers (down to 3 m). The same trend was shown with separate representative pyrogenic PAHs (pyrene, benzofluoranthene
and phenanthrene). Using Hg as a recent geochronological tracer, we observe an increasing input of PAHs since the beginning
of the 20th Century and, especially, after the Second World War coinciding with increasing industrialization and urbanization
of the region. This correlation is supported by PAH ratios that are indication of combustion processes and represent a marker
for anthropogenic inputs. No correlation exists between PAHs and black carbon within the core profiles, indicating two different
fractions of the ‘black carbon continuum’. 相似文献
456.
J.??áslavskyEmail author P.?Kotla?íková K.?Bene?ová 《Environmental Chemistry Letters》2004,2(2):89-92
Semipermeable membrane devices (SPMDs) are nowadays used as passive samplers of organic pollutants. The knowledge of the sampling rate values (RS) of each substance trapped on membranes is necessary to calculate their average concentration. Here we calculate RS values for 16 polycyclic aromatic hydrocarbons using the comparison of active sampling method results and the amounts sequestered by SPMDs at varying exposure times.Selected article from the Regional Symposium on Chemistry and Environment, Krusevac, Serbia, June 2003, organized by Dr. Branimir Jovancicevic. 相似文献
457.
Fernández Pilar Rose Neil L. Vilanova Rosa M. Grimalt Joan O. 《Water, Air, & Soil Pollution: Focus》2002,2(2):261-274
Spheroidal carbonaceous particles (SCP) and polycyclicaromatic hydrocarbons (PAH) have been measured in the dated sediment cores of 10 remote lakes distributed across Europe. The geographic trends were evaluated by examination of the superficial sediment fluxes and total sediment inventories. The highest levels of both markers were observed in the Eastern European lakes whereas the minimal values corresponded to the lake located in the Arctic. However, this SCP-PAH correlation was not observed after exclusion of the end member lakes from the series. The temporal trends of both pollutant markers are consistent with the history of pyrolytic emissions over Europe. However, the downcore SCP distributions are shorter than the PAH profiles in nearly all lakes. The differences are probably related to the different size particle fractions involved in the measurement of each marker, >5 and >1 m for SCP and PAH, respectively. Thus, the two proxies probably reflect pollution inputs from closer (SCP) and more distant sites (PAH). 相似文献
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对杭州湾潮滩表层沉积物样品中的多环芳烃(PAHs)进行了定量分析.结果表明,沉积物中PAHs总含量范围为45.78~849.93ng/g.PAHs的空间分布总体呈现钱塘江杭州河段>杭州湾南岸>杭州湾北岸.PAHs含量分布与有机碳(TOC)含量存在良好的线性关系,受人类活动和水动力条件的影响较大.样品中PAHs的燃烧来源所占的比重较大,呈现出油料燃烧与木材、煤燃烧的混合污染来源特征.该地区表层沉积物样品中的PAHs尚未对生物造成显著的负面影响. 相似文献
460.
生态毒理学研究中分子构效相关的应用 总被引:3,自引:1,他引:2
分子定量构效相关(QSAR)理论方法是当前生态毒理学研究领域发展的重要方向和前沿,QSAR法运用多种数学模式和化合物特征表示参数,系统地探究化合物的生态毒理学机制,进行分子水平的综合研究。笔者系统阐述并应用目前生态毒理学研究中采用的分子构效新方法,对取代芳烃类等典型有机物的生态毒理学效应进行了举证性预测研究。 相似文献