Mobilization of natural arsenic in groundwater: targeting low arsenic aquifers in high arsenic occurrence areas

研究表明饮用水中微小数量的砷会对人类健康产生不利影响.世界上居住在贫穷地区的人数超过了100万,目前他们正直接饮用来自含水层中砷离子含量(>10μg/L)非安全标准的地下水.砷有时称为毒中之王,在水环境中常常以五价氧化物形式出现.自2000年以来,许多国家开始执行更为严格的10μg/L(WHO认可的居民安全饮水标准)饮用水标准,可以确定地说,在世界范围内的饮用水中检测到砷的情况越来越多.亚洲地区砷中毒的人数比世界其他地区总和还多.最受影响的地区位于南亚和东南亚富砷带,环绕恒河一雅鲁藏布江-梅克纳河三角洲及恒河平原上游的冲洪积扇含水层、红河三角洲、湄公河和伊洛瓦底江;在中国境内包括内蒙黄河冲积盆地,山西大同盆地、新疆准噶尔盆地,其中的地下水富含砷和氟化物而引发砷中毒和氟中毒.尽管还未完全掌握其中的水文地质及生物地球化学作用的详细过程,但对大多数沉积介质含水层,在还原条件下砷离子容易从沉积介质转移到地下水中.孟加拉研究实例表明地质时期尺度的冲刷降低了沉积介质中的As和有机物含量从而形成低砷地下水.这一认识为孟加拉国的降砷策略提供了科学指导,是未来水文学,矿物学,地质学和生物地球化学方面很有意义的研究方向,并有利于地砷病区低砷地下水的可持续利用.     

Techniques and methods of arsenic contaminated groundwater exploration in the Hetao plain of Inner Mongolia,China

1990年报道了在中国内蒙古河套平原由于饮用污染的地下水而患砷中毒的病例.估计目前内蒙受到砷中毒影响的居民已超过41万人.从1997年至2004年,在长达8年的时间里,我们进行了水文地质调查、地质调查和医学调查,并装置了管道输送的供水系统.这些调查揭示了河套平原地下水受砷污染的机理:由于被吸收的砷释放进入地下水,蓄水层中不断加强的还原环境造成铁氢氧化物的溶解.为了防止砷中毒病人数量的进一步增加,停止饮用污染过的水和供应安全的饮用水是重要的.我们需要根据当地的地质和水文地质条件来了解砷污染的机理.     

Computing least air pollution exposure routes

Personalized routing counts on traveler’s preferences which are usually based on different criteria, such as shortest, fastest, least traffic, or less expensive (e.g., less fuel cost, toll free). However, people are increasingly becoming concerned about the adverse health effects of exposure to air pollution in chosen routes. Exposures to elevated air pollution concentrations particularly endanger children, pregnant women, elderly people, and people with asthma and other respiratory conditions. Choosing routes with least air pollution exposure (APE) is seen as one approach to minimize the level of pollution exposed, which is a major public health issue. Routing algorithms use weights on segments of road networks to find optimum routes. While existing weights are commonly distance and time, among a few others, there is currently no weight based on APE to compute least APE routes. In this paper, we present a weight function that computes weight based on APE. Two different approaches, geostatistical and non-geostatistical, were used to compute APE weight. Each approach was evaluated, and the results indicate that the APE weight is suitable for computing least APE routes.     

原子荧光测定食品中总砷方法的改进与探讨

针对国标《GB 5009.11—2003食品中总砷及无机砷的测定》中的原子荧光-湿法消解测定总砷的方法中存在的难于控制完全消解样品、测定结果不稳定,试剂用量大的问题,对原方法进行了3点改进。一是利用浓硫酸沸点高,能脱水碳化破坏有机物的特性,通过高温浓缩硫酸对样品进行两次脱水碳化消解,使样品消解的更完全,且节省试剂;二是针对样品中砷形态的多样性,加强温度控制,低温消解、降低易挥发砷化合物的损失,高温加速样品消解,缩短操作时间;三是加盖小漏斗制造回流,减少易挥发砷化合物的损失,使方法易操作、节省试剂。用改进的方法测定菠菜粉(GBW10015)、海带粉(GBW08517)和虾粉(CNAS T0442)中的总砷,不少于6个平行样的测定结果均位于参考值范围的中间部分,且RSD值均小于7%,表明改进的方法准确、稳定。结果还表明,200℃的硫酸、高氯酸的混合酸和高温浓硫酸均能有效消解样品中砷甜菜碱和砷糖类化合物。     

Health risk assessment for typical and abandoned chromium-contaminated sites

Chromium pollution were investigated by sampling the abandoned chromium contaminated sites in Chongqing. Its health risk was assessed following the procedures made by USEPA. The results showed that the most seriously polluted land was found at the former production area （G4） with average Cr（VI） concentration of 3369.2 mg kg-1 on the surface soil. The assessment indicated that there was high risk of non-carcinogens for children. The assessed risk of the first layer of office area （G1） for children, chromium slag transition （G2）, drainage pipeline chromium slag transition （G3） and production area （G4） for both children and adults were not acceptable （〉1.00× 106）. It was strongly suggested that the accessible measures of remediation should be taken for a portion of contaminated sites before the reuse of abandoned lands.     

Arsenic Distribution Pattern in Different Sources of Drinking Water and their Geological Background in Guanzhong Basin,Shaanxi, China

To study arsenic(As) content and distribution patterns as well as the genesis of different kinds of water, especially the different sources of drinking water in Guanzhong Basin, Shaanxi province, China, 139 water samples were collected at 62 sampling points from wells of different depths, from hot springs, and rivers. The As content of these samples was measured by the intermittent flowhydride generation atomic fluorescence spectrometry method(HG-AFS). The As concentrations in the drinking water in Guanzhong Basin vary greatly(0.00–68.08 μg/L), and the As concentration of groundwater in southern Guanzhong Basin is different from that in the northern Guanzhong Basin. Even within the same location in southern Guanzhong Basin, the As concentrations at different depths vary greatly. As concentration of groundwater from the shallow wells(50 m deep, 0.56–3.87 μg/L) is much lower than from deep wells(110–360 m deep, 19.34–62.91 μg/L), whereas As concentration in water of any depth in northern Guanzhong Basin is 10 μg/L. Southern Guanzhong Basin is a newly discovered high-As groundwater area in China. The high-As groundwater is mainly distributed in areas between the Qinling Mountains and Weihe River; it has only been found at depths ranging from 110 to 360 m in confined aquifers, which store water in the Lishi and Wucheng Loess(Lower and Middle Pleistocene) in the southern Guanzhong Basin. As concentration of hot spring water is 6.47–11.94 μg/L; that of geothermal water between 1000 and 1500 m deep is 43.68–68.08 μg/L. The high-As well water at depths from 110 to 360 m in southern Guanzhong Basin has a very low fluorine(F) value, which is generally 0.10 mg/L. Otherwise, the hot springs of Lintong and Tangyu and the geothermal water in southern Guanzhong Basin have very high F values(8.07–14.96 mg/L). The results indicate that highAs groundwater in depths from 110 to 360 m is unlikely to have a direct relationship with the geothermal water in the same area. As concentration of all reservoirs and rivers(both contaminated and uncontaminated) in the Guanzhong Basin is 10 μg/L. This shows that pollution in the surface water is not the source of the high-As in the southern Guanzhong Basin. The partition boundaries of the high- and low-As groundwater area corresponds to the partition boundaries of the tectonic units in the Guanzhong Basin. This probably indicates that the high-As groundwater areas can be correlated to their geological underpinning and structural framework. In southern Guanzhong Basin, the main sources of drinking water for villages and small towns today are wells between 110–360 m deep. All of their As contents exceed the limit of the Chinese National Standard and the International Standard(10 μg/L) and so local residents should use other sources of clean water that are 50 m deep, instead of deep groundwater(110 to 360 m) for their drinking water supply.     

Pretreatment Techniques for Arsenic Speciation Analysis in Biosamples

正Introduction Coupled techniques such as HPLC–HG–AAS,HPLC–ICP–MS,HPLC–HG–AFS are widely used for arsenic speciation analysis in biosamples,during which pretreatment method usually plays a significant role.This     

氢化物发生-原子荧光光谱法测定砷等元素分析探讨

本文分析探讨氢化物发生—原子荧光光谱法测定土壤中低质量浓度的砷、锑、铋的方法实验。     

Groundwater geochemistry of the Chihuahua City region in the Rio Conchos Basin (northern Mexico) and implications for water resources management

The Chihuahua City region, located in the semiarid-arid northern highlands of Mexico, has experienced intensive groundwater abstraction during the last 40 years to meet water demands in the region. A geochemical survey was carried out to investigate the evolution from baseline to modern conditions of a 130-km flow path including the El Sauz–Chihuahua–Aldama–San Diego de Alcalá regions. The research approach included the use of major chemical elements, chlorofluorocarbons and environmental isotope (¹⁸O, ²H, ¹³C and ¹⁴C) tracers. Stable isotopes indicate that groundwater evolves from the evaporation of local rainfall and surface water. Groundwater located at the lower end of the flow section is up to 6000 years old and older groundwater in the order of 9000 years BP was found in a deep well located in the upper part of the flow system, implying contribution from a neighbour basin. The background groundwater chemistry upstream of Chihuahua City results from feldspar weathering. Beyond Chihuahua City the chemical conditions are strongly modified owing to disposal of sewage from public and industrial water supplies into the Rio Chuviscar, subsequent allocation of this water to agricultural irrigation areas and direct infiltration under the river bed. As a consequence, anions like chloride and sulphate are mainly related to surface sources. Nitrate is controlled in part by sewage from public supply and industry and in part by agricultural practices. Arsenic and fluoride are related to weathering of rock formations of local mineralized ranges and subsequent enrichment of the basin-fill by magmatic processes. The results of this study have implications for groundwater management in an arid region that depends entirely on groundwater for domestic, industrial and agricultural water consumption. Copyright © 2008 John Wiley & Sons, Ltd.     

Stone run (block stream) formation in the Falkland Islands over several cold stages,deduced from cosmogenic isotope (10Be and 26Al) surface exposure dating

Cosmogenic isotope (¹⁰Be and ²⁶Al) surface exposure dating has been applied to valley‐axis and hillslope stone runs (relict periglacial block streams) and their source outcrops in the Falkland Islands, South Atlantic. The data indicate that stone runs are considerably older landforms than previously envisaged and afford no evidence that they are a product of the Last Glacial Maximum; the samples range in apparent ¹⁰Be age from 42k to 731k yr BP, but some of these are minima. The results indicate that valley‐axis stone runs may be up to 700–800k yr old, have simple exposure histories and are composite landforms that developed over several cold stages. Analyses of some hillslope and outcrop samples also demonstrate simple exposure histories with ¹⁰Be ages from 42k to 658k yr BP. In contrast, isotopic ratios from other hillslope and outcrop samples reveal they have had a complex exposure history involving periods of burial or shielding; the samples range in ¹⁰Be age from 59k to 569k yr BP and these are regarded as minimum age estimates. Larger stone runs may be older than smaller runs and there is a possibility that stone runs older than 800k yr exist in other parts of the Falklands. The assertion that glaciation in the Falklands was restricted to the highest uplands is supported by the data, and the potential for age determination of other boulder‐strewn and bedrock landforms, using cosmogenic isotope analysis, in order to extend the geochronology of Quaternary events and processes is noted. Copyright © 2008 John Wiley & Sons, Ltd.