溶解氧对河流底泥中三氮释放的影响

作为内源污染的底泥沉积物中营养物的释放引起了越来越多的关注。通过大型静态土柱模拟实验,研究氮在上覆水和孔隙水中的分布特性和释放特性。在控制氧气条件、底泥有机质含量和粒径大小的条件下,连续观测氨态氮、亚硝态氮和硝态氮的浓度及其垂向分布特性。结果发现：时间分布上,通氧条件明显影响水体底泥中三氮释放与反硝化作用达到平衡的时间;垂向分布上,三期实验的上覆水的无机氮以氨态氮为主,不同的通氧条件下,各柱的孔隙水的三氮浓度比上覆水高,且三氮在沉积物中随深度增加而增加;氨态氮和硝态氮浓度则以孔隙水的为高,随深度增加而增加;低溶解氧水平加快底泥释放氨氮速度和增大释放量。     

产芝水库底泥和其间隙水中氮、磷分布特征

在现场调查和样品采集的基础上,对产芝水库主要采样点底泥及其间隙水中TN、NH+-N、NO3--N和TP浓度进行了测定,并对底泥TN,TP和其间隙水中TN、总溶解性磷(TDP)浓度进行了相关性分析.研究结果表明,产芝水库底泥含水率和有机质含量在表层均较高;而底泥中氮、磷浓度自深度为10 cm处向表层多表现出增加的趋势,间...     

阳宗海沉积物中磷的稳定性

絮凝剂(Fe Cl3)治理阳宗海砷污染的过程中,水体中的磷被大量沉积进入底泥,弄清其是否会在环境条件变化后发生反溶形成二次污染对湖泊富营养化防治具有重要意义。通过模拟实验模拟泥-水界面p H变化、物理扰动和微生物活动的变化,旨在分析这些环境因子变化对沉积物中磷溶出的影响。结果表明,阳宗海水体在目前这种磷浓度下,底泥的磷会随时间的增加而溶出再次造成水体磷污染,当暴露在清洁水条件下时磷的释放率会增加;这种由于絮凝剂吸附沉淀到湖底的磷,在上覆水p H增加0.5时底泥磷解吸附释放速率增加;每年秋季湖泊上下层水的交换活动会造成水体磷浓度的季节性升高,形成不可忽视的磷内源。而夏季水温分层导致湖泊底部厌氧,使厌氧微生物活性增强,这将进一步促进底泥中磷的释放。     

曝气和pH对城市污染河道底泥氮形态的影响

以城市重污染河道表层沉积物为研究对象,采用模拟实验方法,探讨了不同曝气方式(水曝气和泥曝气)、上覆水初始pH(自然状态pH=7和pH=11)对城市污染河道底泥氮形态的影响。结果表明:采用水曝气+pH11方式对城市重污染河道上覆水、间隙水中总氮去除率分别为70.03%和44.66%;泥曝气+pH7方式对上覆水、间隙水、底泥中氨氮去除率分别为94.31%、84.07%和68.29%;底泥pH与上覆水总氮浓度呈正相关(p<0.05);泥曝气+pH11方式使底泥含水率、烧失率明显升高,继而影响各形态氮在泥水系统中的赋存,其中底泥吸附态氨氮含量与底泥含水率呈显著负相关(p<0.01),间隙水可溶态氨氮浓度与底泥烧失率显著正相关(p<0.01)。     

风浪扰动对太湖梅梁湾水体总磷变化的驱动模式研究

风浪扰动下的底泥再悬浮是浅水湖泊水体底泥内源性磷向水体释放的关键驱动因子。水体总磷(TP)受底泥内源磷释放过程影响频繁波动。基于风浪扰动强度与底泥悬浮物(SS)浓度定量关系模型,采用太湖原位未扰动柱状底泥开展水体底泥再悬浮过程模拟研究,分别模拟在小风(搅拌强度100～125 r/min)、大风(搅拌强度200～220 r/min)模式下底泥内源释放过程,探究风浪扰动对太湖梅梁湾水域TP浓度波动的贡献。结果表明,风浪扰动显著增加(P<0.01)了水体SS,小风与大风下水体SS均值分别增加了80.9%与360.8%,但随着扰动周期的延长,风浪扰动的效果会削弱。不同风浪扰动强度下水体TP均呈先上升后下降趋势。小风下水体TP为0.08～0.20 mg/L;大风下水体TP为0.09～0.34 mg/L。与对照组相比,小风组水体TP浓度呈现显著下降的趋势(P<0.05),而大风组水体TP浓度则表现为显著上升的趋势(P<0.01)。此外,大风持续扰动增加了水体TP浓度,但效果不显著(P>0.05)。风浪扰动致使0～3 cm底泥内的TP含量有所提高,底泥表面氧化还原条件的改变是...     

凹形基底自然湿地中理化指标的分布特征

对凹形基底自然湿地中的底泥和不同水深的水体进行采样,研究了自然湿地中理化指标的分布特征,并初步分析其形成机制。结果表明:水体中总氮(TN)、总磷(TP)的分层现象明显,且TN、TP浓度随水深增加呈现先下降后上升的趋势;在水深为30~50cm处,TN、TP浓度最低;底泥中TN、TP浓度随水深增加而上升;在水深为30~50cm处,底泥中微生物数量最高。对降雨径流进入湿地及水流在湿地中的速度分布进行模拟分析,得出水流形态是导致湿地水体和底泥中TN、TP分布变化的重要因素,而水流形态又受基底形态的影响。     

徐州市北郊工业区河流底泥重金属污染特征

对徐州市北郊工业区主要纳污河流,京杭大运河徐州段及其支流荆马河底泥中的多种重金属含量(mg/kg)进行测定的结果表明底泥中重金属含量沿顺流方向增加;主要重金属含量的最大值分别为Cu,398.5;Pb,586.9;Zn,6 139.0;Mn,1608.0;Co,28.74;总Cr,28259.0;Ni,50.33;V,123.1.运用地积累指数法评价了底泥的重金属污染程度,徐州市北郊工业区河流底泥已受到了重金属的污染,尤其是Zn污染最为严重.荆马河底泥中的重金属不仅是其水体本身的内源污染,也是京杭大运河铜山段底泥重金属污染的主要来源.     

太湖内源释放及营养盐输运研究

从对流-扩散方程出发,通过公式推导,建立了包含底泥污染的水流-水质模型,对模型进行了率定和验证后,应用于太湖.该模型将湖泊水相和内源悬移相污染作为一个整体,结合污染物在悬移泥沙上的各种迁移过程,研究了太湖总氮、总磷内源释放的分布和数量,过程中考虑了悬移泥沙的各种影响因素,得到了较理想的模拟结果,当风速≤3.5 m/s时,冲刷和悬移造成的内源污染物释放量较小,内源污染物释放主要通过泥-水界面的静态释放;当风速>3.5 m/s时,冲刷和悬移造成的内源污染物释放量随风速增加迅速增大.通过计算得出2001年太湖内源释放的总氮为3.0万t,总磷为0.8万t.     

投加硝酸钙对城市黑臭河道底泥氮迁移转化的影响

投加硝酸钙是目前河道黑臭底泥原位治理常用的方法,然而,投加硝酸钙会造成底泥硝态氮和氨氮的过量释放,而其影响机制尚未明确。因此有必要对投加硝酸钙后硝态氮在底泥中的迁移转化规律及其促进氨氮释放的机理进行研究。结果发现,硝酸盐在间隙水的迁移距离取决于硝态氮反硝化速率,而在黑臭底泥中硫化物氧化是影响反硝化速率的关键因素。当硝酸钙投加量为20 g/kg时,硝态氮的迁移距离小于6 cm,且在14 d后消耗光;可见,通过控制硝酸钙在底泥中的投加位置可避免硝态氮的二次释放。另一方面,投加硝酸钙会促进底泥氨态氮向间隙水释放,投加当天释放率可高达101%,且会在间隙水中发生累积迁移。其中,氨氮的增加量和底泥氨态氮解吸量呈一级线性关系(r=0.986)、和硝酸钙投加量关系符合cubic曲线;据此可推测,氨氮的急剧释放与钙离子对底泥铵态氮的化学浸提有关。     

水源水库沉积物磷的赋存形态及其与间隙水磷的关系

为了探明水源水库沉积物磷的赋存形态及其对水体磷的影响,采用连续提取方法,研究了周村水库沉积物中磷的赋存形态分布特征,并探讨了沉积物各形态磷与总磷、烧失量及间隙水中磷的相关性。结果表明,周村水库内源磷负荷较高,沉积物中TP表现出表层富集的现象,表层沉积物中TP空间分布存在较大差异,上游浅水区为554~563 mg·kg~(-1),库心附近为424~1 161 mg·kg~(-1),而坝前深水区高达812~2 969 mg·kg~(-1)。无机磷(IP)是总磷(TP)的主要成分,占TP的79.26%~89.12%,IP主要由铝/铁磷(Al/Fe-P)构成。沉积物中的Al/Fe-P含量很高,具有很大的磷释放潜能。沉积物中各形态磷的浓度垂向分布随深度增加而逐渐降低,其中B、C两点变化最为明显。相关性分析结果表明,间隙水PO3-4-P与Fe-P存在较好的相关性,说明Fe-P对周村水库沉积物间隙水中PO3-4-P浓度分布有着重要的影响,周村水库水体季节性分层导致恒温层厌氧情况的发生,Fe-P在厌氧还原条件下释放进入间隙水并向上覆水扩散,进而可能对水体水质产生影响。     

Mobility of metals and metalloids in a multi-element contaminated soil 20 years after cessation of the pollution source activity

Knowledge of trace element concentrations and mobility is important in the ecotoxicological assessment of contaminated soils. We analysed soil pore water under field conditions to provide new insights into the mobility of residual contaminants in the surface 50cm of a highly contaminated woodland soil. Cadmium and Zn were highly mobile in the acidic soil, concentrations increasing with depth in soil pore water, showing considerable downward mobility. High levels of surface organic matter restricted the solubility of Cu, Pb and Sb, with highest concentrations being found close to the surface. Dissolved organic carbon in pore water had a strong influence on mobility of Cu, Zn, Pb and Sb. Elevated As had moved from the organic surface horizons but was largely immobilised in deeper layers and associated with Fe and Al oxides. The measured differential mobility of pollutants in the present study is highly relevant to protection of groundwater and other receptors.     

A laboratory study of sediment and contaminant release during gas ebullition

Significant quantities of gas are generated from labile organic matter in contaminated sediments. The implications for the gas generation and subsequent release of contaminants from sediments are unknown but may include enhanced direct transport such as pore water advection and diffusion. The behavior of gas in sediments and the resulting migration of a polyaromatic hydrocarbon, viz phenanthrene, were investigated in an experimental system with methane injection at the base of a sediment column. Hexane above the overlying water layer was used to trap any phenanthrene migrating out of the sediment layer. The rate of suspension of solid particulate matter from the sediment bed into the overlying water layer was also monitored. The experiments indicated that significant amounts of both solid particulate matter and contaminant can be released from a sediment bed by gas movement with the amount of release related to the volume of gas released. The effective mass transfer coefficient of gas bubble-facilitated contaminant release was estimated under field conditions, being around three orders of magnitude smaller than that of bioturbation. A thin sand-capping layer (2 cm) was found to dramatically reduce the amount of contaminant or particles released with the gas because it could prevent or at least reduce sediment suspension. Based on the experimental observations, gas bubble-facilitated contaminant transport pathways for both uncapped and capped systems were proposed. Sediment cores were sliced to obtain phenanthrene concentration. X-ray computed tomography (CT) was used to investigate the void space distribution in the sediment penetrated by gas bubbles. The results showed that gas bubble migration could redistribute the sediment void spaces and may facilitate pore water circulation in the sediment.     

The role of aqueous iron(II) and manganese(II) in sub-aqueous active barrier systems containing natural clinoptilolite

Increasing attention is being placed on capping as a relatively new option in managing both contaminated sediments and dredged materials, due to its economic and environmental benefits. Capping denotes the placement of a cover onto potentially hazardous sediments or dredged material dumps to inhibit the transfer of contaminants into the water column. Retention of divalent iron and manganese cations using sandy capping layers containing natural zeolites as a reactive additive (active barrier systems, ABS) is evaluated in this study. Three different natural zeolite (clinoptilolite) rocks, two from deposits in Australia and one from a North-American deposit, were investigated and compared with respect to their mineralogical, physical and chemical properties. In particular, results from batch and column experiments show that ABS based on these materials can efficiently demobilise iron and manganese from percolating, anoxic pore water by cation exchange under favourable conditions. The retention, however, may be reduced strongly where competitive exchange with divalent cations such as calcium prevails or where mobile colloidal pore water constituents such as clay minerals or humic substances bind fractions of the dissolved iron or manganese. Therefore, the potential of ABS as a means for in situ remediation has to be evaluated diligently with particular regard to the pore water composition of the sediment to be capped.     

Seasonal variation of sediment toxicity in the Rivers Dommel and Elbe

Contaminated sediment in the river basin has become a source of pollution with increasing importance to the aquatic ecosystem downstream. To monitor the temporal changes of the sediment bound contaminants in the River Elbe and the River Dommel monthly toxicity tests were applied to layered sediment and river water samples over the course of 10 months. There is an indication that contaminated sediments upstream adversely affected sediments downstream, but this process did not cause a continuous increase of sediment toxicity. A clear decrease of toxic effects in water and upper layer sediment was observed at the River Elbe station in spring related to high water discharge and algal blooms. The less obvious variation of sediment toxicity in the River Dommel could be explained by stable hydrological conditions. Future monitoring programmes should promote a more frequent and intensive sampling regime during these particular events for ecotoxicological evaluation.     

Accumulation and persistence of chlorobiphenyls, organochlorine pesticides and faecal sterols at the Garroch Head sewage sludge disposal site, Firth of Clyde

The sediment concentrations of organic carbon, faecal sterols, individual chlorobiphenyl congeners and organochlorine pesticides have been measured in seabed cores from the sewage sludge disposal area at Garroch Head in the Firth of Clyde. The measurements confirm the accumulative nature of the site with high levels of sedimentary faecal sterols (152 mg kg(-1) coprostanol). Levels of chlorobiphenyls, DDT compounds and dieldrin in surface sediment were elevated by factors of 12, 40 and 120, respectively, over those observed at a site remote from the effects of dumping. Total chlorobiphenyl levels of 515 microg kg(-1) Arochlor 1254 in surface sediment were comparable to levels found in other areas heavily contaminated with sewage sludge. The 20-cm depth of heavily sludge-contaminated sediment overlays a mixed sludge/basal sediment layer some 10 cm in depth. Levels of organochlorine contaminants were elevated to depths of 90 cm in the sediment, suggesting that the surface layer is a source of contaminants to the deeper sediment. Within the upper 15-20 cm sediment in the disposal area, chlorobiphenyls are conservative, the variation in their concentration with respect to depth being related to historical input. Lindane and possibly dieldrin, and hexachlorobenzene are not conservative. Faecal sterols are removed in sub-surface sediment, in contrast to conservative behaviour previously found at other sewage polluted sites.     

Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices

Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri-Columbia, USA; Williamson et al., Chemosphere (This issue--PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment.     

Application of the comet assay and detection of DNA damage in haemocytes of medicinal leech affected by aluminium pollution: A case study

This report describes an investigation of genotoxic effects in medicinal leech (Hirudo verbana) exposed to water and sediment of Lake Njivice (Krk Island, Croatia) contaminated by aluminium compounds. The levels of primary DNA damage in leech haemocytes and loss of DNA integrity caused by acute and chronic exposure to contaminated water and sediment were investigated using the alkaline comet assay. Genotoxic effects induced by acute exposure to contaminants were evaluated on leech haemocytes and blood cells of fish and mouse treated ex vivo. The effects of chronic exposure were assessed on haemocytes sampled from an animal kept under laboratory conditions on contaminated water and sediment for 180 days. The results indicate the DNA damaging potential of aluminium compounds present in an excess amount in tested samples.     

Simulation of resuspended sediments resulting from dredging operations by a numerical flocculent transport model

Environmental remediations such as dredging operations cause contaminated sediments from the bottom of water bodies to become suspended into the water column. These resuspended particles are significant water quality concerns and cause adverse effects to aquatic organisms. In this paper, we present a vertically integrated two-dimensional flocculent sediment transport model to better model concentration changes of resuspended bottom sediments. The flocculent transport model has been applied to the Savannah River cutterhead dredge field study involving the resuspension of bottom sediments. The results showed that the model predictions correlate reasonably well with field data. These comparisons suggest that the flocculent sediment transport model can be used to predict the concentration profiles of a plume of toxic compounds resulting from cutterhead dredge operation.     

Bioavailability in soil or sediment: exposure of different organisms and approaches to study it

Soil and benthic organisms may be exposed to contaminants via different routes: (pore) water, soil or sediment, and food. Depuration of the contaminant from the organisms may take place via the same routes and, additionally, via biotransformation, reproduction, etc. Whereas uptake from and depuration to water can be predicted well, predictions for soil or sediment are less accurate. One of the reasons may be the reduced bioavailability of the contaminant in the soil or sediment. In biomimetic approaches, such as solid phase micro-extraction (SPME) or measurements with C18-discs, the freely dissolved concentration in the (pore) water is determined. The SPME-fiber or C18-disc may serve as a surrogate organism, but sometimes underestimates, and sometimes overestimates bioavailability. The soil (or sediment) availability ratio (SARA) method, that uses organisms to study the uptake of freshly added and 'aged' chemicals, is proposed to study the magnitude of the reduction in bioavailability. SARA also includes the organism-specific exposure and depuration routes.     

水体沉积物毒性鉴别与评价研究进展

综述了水体沉积物毒性鉴别与评价的主流方法以及研究进展,指出毒性测试和致毒因子鉴别方法是限制水体沉积物污染生态风险评价的关键因素,认为发展和应用以生物标记物和生物效应为导向,尤其是各种具有污染专一性指示作用的生物效应标志测试方法的建立和应用,并结合具有选择性的样品分级技术和先进的仪器进行定性定量分析,将是以生物效应为导向、以化学分析为基础的复杂水体沉积物毒性鉴别与评价的重要发展方向.