Sediment geochemistry and arsenic mobilization in shallow aquifers of the Datong basin,northern China

Understanding the mechanism of arsenic (As) mobilization from sediments to groundwater is important for water quality management in areas of endemic arsenic poisoning, such as the Datong basin in northern China. The bulk geochemistry analysis of sediment samples from three 50-m boreholes drilled specifically for this study at As-contaminated aquifers, the groundwaters of which have an As concentration up to 1060 μg/l, revealed that the average bulk concentrations of major and trace elements of the samples are similar to those of the average upper continental crust. The average As content of the sediment samples (18.7 mg/kg) is higher than that of modern unconsolidated sediments (5–10 mg/kg). Moreover, the abundance of elements varied with grain size, with higher concentrations in finer fractions of the sediments, such as silt and clay. The concentration of NH₂OH–HCl-extracted iron (Fe) strongly correlated with that of extracted As, suggesting that Fe oxyhydroxides may be the major sink of As in the aquifer. The results of microcosm experiments showed that As mobilization from sediments to groundwater is probably mainly related to changes in the redox conditions, with moderately reducing conditions being favorable for As release from sediments into groundwater.     

海洋沉积物中甾醇类物质的气相色谱/质谱方法分析

应用超声提取技术,结合硅胶-中性氧化铝柱层析净化分离,BSTFA+1%TMCS衍生,及气相色谱-质谱定性定量技术,建立了海洋表层沉积物中8种甾醇类化合物的定量分析方法.实验采用正交实验优化了提取过程中提取剂种类、试剂体积和超声时间,同时对比并优化了柱层析淋洗液的配比、用量以及衍生剂的用量.结果表明,50 mL二氯甲烷/甲醇(V/V,2∶1),超声40 min,超声3次,总甾醇的萃取率可达99.6%;3 g硅胶+2 g中性氧化铝层析,35 mL二氯甲烷/甲醇(V/V,9∶1)淋洗净化回收最佳;8种甾醇在0—848μg.L-1范围内有良好的线性关系;方法检测限为1.2—2.4 ng.g-1.在3种浓度水平0.05、0.1和1.0μg.g-1下,其平均回收率为76.2%—100.9%,相对标准偏差为1.0%—10.3%.应用本方法检测大连湾的3个沉积物样品,8种甾醇的含量在0.079—6.833μg.g-1范围内.本方法的灵敏度高、准确度好,适合用于沉积物样品中甾醇物质的检测要求.     

镇江市老城区不同功能区地表灰尘重金属污染评价

通过采集江苏省镇江市老城区的交通区、大市口广场、江滨公园、商业区、居民区、文教区等不同功能区地表灰尘共54个样品,对其Cu、Pb、Zn、Ni、Cr、Cd、Mn 7种重金属进行分析测定.结果表明,交通区Cu、Ni、Cr、Mn、Cd的平均含量要明显高于其它功能区,Zn的含量在文教区最高,Pb的含量在居民区最高.地累积指数评价表明交通区、文教区两个功能区中Cd达偏重度污染,文教区中Zn也达偏重度污染;潜在生态风险评价结果表明,交通区、大市口广场、文教区3个功能区的潜在生态风险指数均为中等生态危害;江滨公园、商业区、居民区3个功能区的潜在生态风险指数均为轻微生态危害.     

赣江流域中下游底泥中有机氯农药污染特征

为了解赣江流域有机氯农药污染状况,采用索氏提取方法（Soxhlet Extraction,SE）和气相色谱法（GC-ECD）,对所采集的18个底泥样品中10种有机氯农药（OCPs）的残留进行测定,并对其组分分布和来源进行了分析。结果表明,所有样品均检出10种有机氯农药,底泥中∑OCPs质量分数范围为11.813-39.197μg·kg-1,HCHs、DDTs质量分数范围分别为1.636-20.877μg·kg-1和5.590-14.092μg·kg-1,HCHs的质量分数低于DDTs,六氯苯（HCB）和七氯（Heptachlor）的质量分数相对较低,分别为0.229-6.940μg·kg-1和0.507-3.936μg·kg-1。组分分布特征分析表明,它们除了来自环境中的早期残留外,仍然具有大量新的外源HCHs和DDTs的输入,可能是新的林丹输入以及三氯杀螨醇的使用,这可能与近年来沿江农业的发展有关。     

引黄水库沉沙条渠沉积物的表面理化及分形特征研究

研究了引黄水库沉沙条渠泥沙沉积物的表面微观形貌和孔表面分形特征.采集了引黄供水鹊山水库沉沙条渠6个泥沙沉积物样品,对其粒径、形貌、孔隙结构、表面元素分布及分形特征进行分析,目的是考察由不同模型计算的颗粒孔表面分形维数和标度空间存在差异的原因,探讨这些颗粒表面微观形貌对其表面元素分布的影响.结果表明,泥沙沉积物颗粒的平均...     

Trends in sediment metal concentrations in the River Avoca, South-East Ireland

Variation in sediment metal concentrations in the River Avoca, which is severely polluted by acid mine drainage (AMD) discharged from the abandoned sulphur and copper mines in Avoca, is reported. A survey of surface and subsurface sediments was repeated after seven years during exceptionally low flow conditions in 2001. The present study found that the reference (up-stream) site used in the original 1994 study was itself impacted by AMD, showing sediment metal enrichment by AMD to be greater than originally thought. The new reference site contained elevated Pb (570 µg g^–1) in the subsurface sediment due to abandoned Pb-Zn mines 25 km further upstream. Concentrations of Cu (43 µg g^–1), Zn (349 µg g^–1) and Fe (4.0%) were normal for uncontaminated rivers. All the downstream sites showed sediment metal enrichment arising from the AMD (Cu and Zn p < 0.001; Fe p < 0.01). Subsurface concentrations of metals immediately below the mixing zone were Cu 904 µg g–1 (sd 335), Zn 723 µg g–1 (sd 93), Fe 6.3% (sd 1.5) and Pb 463 µg g^–1 (sd 279). Monthly variation in metal concentrations at sites was not significantly different (p > 0.05). Although surface sediment metal concentrations were more variable, they followed similar trends to subsurface sediment. There were no significant differences in the subsurface sediment concentrations for either Cu or Zn over the period 1994 and 2001 immediately below the mines, although at the lowest site Zn had decreased by 35% over the period (p < 0.01). However there was a significant (p < 0.01) decrease over the period in the Fe concentration at all the impacted sites. This corresponds to a reduction in Fe concentration in the AMD and indicates that some remediation has occurred in the river since 1994.     

Topics of water sciences and technology

In the preceding series of contributions to ESPR typical examples from actual fields of water chemistry were presented on various topics: integrated water quality management, diagnosis of water bodies, therapy of aquatic systems, and fitness for aquatic systems. These contributions clearly showed the need and importance of more intensive research. In the principle committee III 'Basic Research' of the Water Chemical Society, various expert groups work on scientific backgrounds in these fields. Some relevant topics are selected in this outlook, mainly on interactions of solids with water, the role of environmental colloids, the development of modern biochemical methods for diagnosis, the impact of chemical speciation on bioavailability and water technology, and the development of advanced methods in water treatment technology. Innovative approaches to understand the interactions between pollutants, water and solids are crucial for assessment of contaminants with biochemical and analytical methods, for the development of new efficient technologies and for application of treatment methods with little or no waste and by-product formation.     

Metal contamination of riverine sediments below the Avoca mines, south east Ireland

The River Avoca is severely polluted by discharges of acid mine drainage (AMD) from the abandoned sulphur and copper mines at Avoca. The riverine sediments were studied during a low flow period to establish the degree of contamination and to identify the major processes affecting sediment metal concentrations. pH plays a major role in the regulation of zinc adsorption and desorption in sediments, showing a significant correlation (p&0.001). The zinc concentration in the sediment falls below background levels after the input of AMD. However, the metal precipitated when the pH increased downstream of a fertiliser factory (pH8.0), some 7 km below the mine. In contrast Cu and Fe significantly increased (p0.001) both in the sediment (0--30 mm depth) and the surface ochre immediately below the mixing zone. Copper removal appears to be primarily by co-precipitation. Higher sediment enrichment factors for all metals were obtained in the surface sediment layer (ochre) deposited on larger stones and in floc material collected in sediment traps, compared with the subsurface sediment. Cadmium was not recorded in any of the sediment collected at the detection limit used (0.01 g g-1). Metal deposition in the sediments was found to be spacially variable, so sub-sampling is required, although replicates show little variation. Results indicate that short term variation in metal inputs is identified by sampling the surface layer only, whereas sampling of the subsurface layer (<63 m fraction) is more suitable for identifying long-term trends in sediment quality. The implication of sediment analysis in assessing environmental impact is discussed.     

Chromium in intertidal sediments of the Clyde,UK: potential for remobilisation and bioaccumulation

Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter.     

Geochemical Distribution and Bioavailability of Heavy Metals and Oxalate in Street Sediments from Rio de Janeiro, Brazil: A Preliminary Investigation

As urbanisation accelerates within less-economically developed countries, populations in cities such as Rio de Janeiro are subject to numerous health risks relating to “heavy metal”, sewage and vehicle pollution. These risks apply especially to children, through inhalation and dermal contact with pollutant-rich street sediments that reflect contamination from atmospheric deposition and act as effective sinks for heavy metals and oxalates. To assess the nature and extent of these risks street sediments were collected from industrial, commercial, residential and recreational areas with varying traffic densities within Rio de Janeiro. A modified selective extraction procedure was used to study the geochemical partitioning and bioavailability of Fe, Mn, Zn, Cu, Cr, Ni, Pb and C₂O ₄ ⁻ . Oxalate partitioning has not been studied by traditional sequential methods and results from this procedure highlight the potential bioavailability of both oxalates and “heavy metals”, especially Pb and C₂O ₄ ⁻ in industrial and recreational areas.