黄海近岸表层沉积物中DDTs、PCBs与酞酸酯的地理分布

依据第二次全国海洋污染基线调查数据,考察黄海近岸表层沉积物中PAEs、DDTs和PCBs污染物的地理分布、组成特征,并基于相应的沉积物质量警戒水平,进行初步的生态风险评价.结果表明,黄海近岸海区PAEs的高值站点集中在大连湾(1389.8 ng/g)和旅顺(1928.0 ng/g)周边海域,已超出相应的警戒水平,各海区主要组分为二丁基和2-乙基己基酞酸酯.黄海近岸海区只有大连湾出口海域沉积物中PCBs浓度(24.2 ng/g)稍高于ERL警戒水平(22.7ng/g);而超过ERL警戒水平(1.58ng/g)的DDTs较高浓度站点则主要位于大连湾(6.3～7.6 ng/g)、烟台-威海近岸(4.5～10.3 ng/g)、胶州湾(5.5～21.2 ng/g)和海州湾(27.4～62.9 ng/g)近海区域,其中海州湾一站点沉积物浓度甚至超过ERM警戒水平(46.1 ng/g).DDTs组成分析显示,p,p′-DDT的代谢产物主要是p,p′-DDD;在大连湾、威海、胶州湾和海州湾近岸海区以及山东半岛东部外海仍存在有DDT的输入,其来源可能是工业三氯杀螨醇和/或工业DDT产品.这些海区表层沉积物存在一定的生态风险,尤其是海州湾的个别站点,潜在生态风险更高.     

Hierarchical modeling of the dilute transport of suspended sediment in open channels

We propose, discuss and validate a theoretical and numerical framework for sediment-laden, open-channel flows which is based on the two-fluid-model (TFM) equations of motion. The framework models involve mass and momentum equations for both phases (sediment and water) including the interactive forces of drag, lift, virtual mass and turbulent dispersion. The developed framework is composed by the complete two-fluid model (CTFM), a partial two-fluid model (PTFM), and a standard sediment-transport model (SSTM). Within the umbrella of the Reynolds-Averaged Navier-Stokes (RANS) equations, we apply K–ε type closures (standard and extended) to account for the turbulence in the carrier phase (water). We present the results of numerical computations undertaken by integrating the differential equations over control volumes. We address several issues of the theoretical models, especially those related to coupling between the two phases, interaction forces, turbulence closure and turbulent diffusivities. We compare simulation results with various recent experimental datasets for mean flow variables of the carrier as well as, for the first time, mean flow of the disperse phase and turbulence statistics. We show that most models analyzed in this paper predict the velocity of the carrier phase and that of the disperse phase within 10% of error. We also show that the PTFM provides better predictions of the distribution of sediment in the wall-normal direction as opposed to the standard Rousean profile, and that the CTFM is by no means superior to the PTFM for dilute mixtures. We additionally report and discuss the values of the Schmidt number found to improve the agreement between predictions of the distribution of suspended sediment and the experimental data.     

曼谷湾沉积物重金属元素的富集效应与生物有效性

2010年在曼谷湾(泰国湾北部)及其北部主要河口(湄干河、拉塞河、湄南河和邦巴功河)采集了46个表层沉积物样品,分析了样品中重金属元素(Cd、Co、Cu、Pb、Zn)的含量水平,并用Al均一化数据,获得消除了粒度效应的重金属地球化学特征.利用1mol/L的HCl对该区沉积物进行了处理,通过分析沉积物重金属在酸溶相和残渣相的分布,揭示其生物有效性.结果表明,曼谷湾周边河流沉积物中重金属元素含量明显高于曼谷湾;曼谷湾沉积物中重金属(Co、Cu、Pb、Zn)从北向南随着离岸距离的增加而增加,Cd没有明显分布规律;地累积指数显示Cd和Pb存在显著的地球化学富集特征.Cd和Pb在酸溶相中的比例相对较高,表明其生物有效性较高,易引发二次污染.     

Anthropogenic metal pollution in surface sediments of the Tambaraparni River Estuary

Estuarine sediments in the<63 μm size fraction were collected from 15 stations within the Tambaraparni River Estuary, located on the east coast of India. The distribution of the heavy metals Cd, Co, Cr, Cu, Ni, Pb and Zn was recorded. Our analysis distinguished two groups of elements. First, Cd, Pb and Zn, which occurred in higher than expected concentrations indicative of pollution, and second, Co, Cr, Cu and Ni, which occurred at background levels. The highest metal concentration found in the study area was for Zn (1200 μ g·g^?1), and the lowest was for Cd (0.42 μ g·g^?1). It is presumed that river run-off, industrial waters and untreated domestic waters are major contributors to heavy metal pollution in the Tambaraparni River Estuary. The concentrations of heavy metal species in surface sediments (<2 m water depth) of the Tambaraparni Estuary were studied to determine the extent of anthropogenic inputs from catchment areas and to understand anthropogenic effects on geochemical process in this tropical estuarine system.     

Fuzzy comprehensive assessment of metal contamination of water and sediments in Ondo Estuary,Nigeria

A more reliable methodology for evaluating metal contamination of coastal water and sediments using fuzzy comprehensive assessment (FCA) is presented by this study. Ten metals (As, Cd, Cu, Cr, Fe, Mn, Ni, Pb, V and Zn) were investigated in water and sediments from ten sampling sites and formulated into fuzzy matrix based on three contamination classifications of pristine, moderately enriched and extremely impacted categories using regulatory limits as criteria. The products of the matrices from membership function of the observed data and the weight matrices generate indices that classify the degree of metal impact on the sites. The results of the FCA show that the estuary is negatively impacted by metals in a range of 45.5–75.1% membership in the extremely impacted category with potential adverse effects on the ecosystem of the neighbouring Atlantic Ocean. The crude oil exploration activity at site 1 is the major source input of the metals beside Fe and Mn which are natural to the geological structure of the area while domestic waste discharges contribute notably to metal contamination in some sites.     

Metal concentrations in sediment and Nereis diversicolor in two Moroccan lagoons: Khnifiss and Oualidia

Metal concentrations were measured monthly during an annual cycle (December 2004 to January 2006) in the tissues of Nereis diversicolor ragworms and sediment from two Moroccan Atlantic coastal lagoons: Oualidia in the north, situated in a highly industrialised urban area and Khnifiss in the south, far from anthropogenic influences. Relatively high levels of Zn, Ag and Cd were found in the sediment of Oualidia lagoon, while Ni concentrations were shown to be high at Khnifiss. The significant metal levels at Oualidia are a result of industrial and urban discharges, coupled with discharges from adjacent phosphate ore processing plants. Trace metal concentrations in worms vary according to season; they are usually high in winter and spring, in relation to the animal's reproductive cycle. Comparing the two lagoons, trace metal levels appear to be higher in worms from Khnifiss lagoon, suggesting a higher bioavailability of these elements in a relatively pristine area.     

Assessment of Trace Metals in the Sediments From the Coastal Zone of Alexandria,Egypt

Freshly deposited surface sediments from the Alexandria coastal zone were collected and analysed in 1995 for their trace metal concentrations. Metal concentrations in the sediments vary between sites within a wide range for copper, zinc, iron, lead, chromium and cadmium. the statistical analysis between the metal concentrations and the different constituents (organic carbon, total nitrogen, silt, clay and total iron) showed significant correlations. the enrichment factors for the sediments ranged between 3 and 4-fold for copper, chromium and zinc and reached up to 9-fold for lead and 113-fold for cadmium. the highest index for cadmium and lead may be attributed to the anthropogenic inputs from the surrounding area, where they are highest in lower discharge areas.     

Correlation between levels of some heavy metals in plants and sediments from a segment of Calabar River and associated creeks in Cross River state of Nigeria

Plants and sediments were collected at three sites along Calabar River (CR), Upper Town Creek (UCC) and Lower Town Creek (LCC). The CR is a major tributary of Cross River, Nigeria. The concentrations of 10 heavy metals were determined and results for Fe, Mn and Zn at almost all the sites showed that the levels of these metals exceeded the amounts present in non-polluted areas. Fe was found in the highest concentration at all three sites in both plants and sediments. Correlation analysis between levels of heavy metals in plants and sediments were also determined. The occurrence of higher concentrations of heavy metals in plants and coastal sediments at CR, UCC and LCC is an indication of anthropogenically induced pollution rather than contributions from natural sources.     

Inorganic and organic contaminants in sediments from an urban playa and associated toxicity among Hyalella azteca

Playa wetlands are important components of the Southern High Plains (USA) landscape as they are the major aquatic surface feature. Chemical contaminants associated with playas have been documented, particularly for grassland and agricultural watersheds, but not for playas in urban settings. The objectives of this study were to determine concentrations of inorganic and organic contaminants in sediments from an urban playa within the I-20 Wildlife Preserve and Jenna Welch Nature Study Center in Midland, TX, and evaluate toxicity of these sediments to Hyalella azteca. Concentrations of most trace elements were below sediment quality guidelines with exceptions of lead, cadmium, and arsenic. Concentrations of organic contaminants, particularly PAHs, DDT, DDE, and malathion, were above sediment quality guidelines at various locations within the playa. Decreased survival was observed among H. azteca exposed to sediment from a single location when compared those exposed to reference sediments. This location also produced maximum observed concentrations for five of seven trace elements, potentially due to its location at the lowest elevation within the playa. This study documented concentrations of contaminants in sediments of an urban playa associated with past and present land uses in its urban setting, including those from automotive emissions and historical pesticide use.