Aquatic arsenic: Toxicity,speciation, transformations,and remediation

This paper reviews the current knowledge on the toxicity, speciation and biogeochemistry of arsenic in aquatic environmental systems. The toxicity of arsenic is highly dependent on the chemical speciation. The effects of pH, E_h, adsorbing surfaces, biological mediation, organic matter, and key inorganic substances such as sulfide and phosphate combine in a complex and interwoven dynamic fashion to produce unique assemblages of arsenic species. The number of different arsenic species found in environmental samples and an understanding of the transformations between arsenic species has increased over the past few decades as a result of new and refined analytical methods. Changes in arsenic speciation and in total arsenic content of foods upon processing have suggested possible risks associated with processed and unprocessed food. Arsenic removal from water using adsorbents, chemical oxidation, photolysis and photocatalytic oxidation techniques is also reviewed.     

Variability of the sorption of Cs, Zn, Sr, Co, Cd, Ce, Ru, Tc and I at trace concentrations by a forest soil along a transect

The variability of the sorption properties (characterized by the distribution coefficient K_d) of a forest soil for Cs, Zn, Sr, Co, Cd, Ce, Ru, Tc, and I were determined along a transect of 150 m in regular intervals of 3 m. Radioactive tracers were used to ensure trace concentrations of these elements. For comparison, for each soil sample the loss on ignition, as a measure of the soil organic matter content, and the pH were also determined. On average, the K_d values increase in the sequence Tc < I < Ru ≈ Co ≈ Zn ≈ Sr < Cd < Ce < Cs; the spatial variability in the sequence I < Zn ≈ Sr ≈ Co ≈ Cd ≈ Ru ≈ Tc < Cs, and I ≈ Ce < Tc. Correlation analysis revealed that, when moving along the transect, the K_d values for some elements changed in a similar, and for others in a dissimilar pattern. In a few cases a correlation between the pH or the loss on ignition and the K_d values was also present. The spatial structure of the data was examined by semivariograms. For the elements Co, Cd, Zn, and Sr, the K_d values showed an almost periodic behaviour along the transect, which is probably due to periodic changes of some soil properties in a forest with regularly spaced trees.     

三峡库区香溪河中重金属元素的分布特征

长江三峡水库蓄水后,香溪河水环境条件将发生变化,也导致该流域内重金属环境化学行为的变化,有些金属的危害比现在会更大.为积累蓄水前的基本资料,在1996～ 1997年春、夏、秋、冬四季采集了香溪河原水、沉积物、鱼类和植物样品,并对所采集的鱼进行分类,分析这些样品中的Ca、Mg、As、Pb、Cd、Cr、Cu、Hg和Zn元素的含量.研究结果显示,香溪河局部地区因小金矿开发引起的Hg污染十分严重;洪水期(7月)原水中的Pb、C d、Cr、Cu浓度大于枯水期(1月);沉积物中Pb、Cd浓度在7月最低,10月浓度达到全年最高点;原水中Pb、Cd、Cr、Cu重金属浓度均低于国家Ⅰ类地面水环境质量标准;香溪河水中不同种鱼类的金属富集能力各不相同,鱼类的重金属富集系数顺序为Cd>Zn>Pb>Ca>Cu>Cr>Mg .统计分析表明鱼体中的Pb和Cd浓度分别与沉积物、原水中的某些金属呈显著相关.     

Attributable risk, probability of causation, assigned shares, and uncertainty

Calculations of attributable risks, probabilities of causation, and assigned shares attracted increasing interest recently, particularly since the enactment of the Orphan Drug Act. Although efforts have been limited mostly to radiation as the toxic agent, the concept is general to all toxicants. In this paper, the systematic and random uncertainties in calculations of assigned shares are reviewed globally, and possibilities for their reduction are discussed. In addition, an algebraic study is made of the influence of random uncertainties in the input parameters on the random error of the assigned shares. Three dose-effect functions, appropriate for the low-dose, low-effects regions that are of interest here, are chosen for this investigation, and the algebraic properties of the random errors of the assigned shares are discussed. For shares near 0 and 1, the errors are shown to be small and to depend linearly on the value of the shares; the errors are largest for values of the shares near 50%, that is, in the region of almost equal or equal shares.     

Traceability,quality assurance,and standards

The development of traceability in low-level radioactivity measurements is discussed. The role that the development of large quantities of natural matrix standards can play is also discussed.     

Landslide hazard,vulnerability, and risk assessment (HVRA), Mussoorie township,lesser himalaya,India

Environment, Development and Sustainability - In the present study, landslide hazard, vulnerability and the risk assessment of the Himalayan township Mussoorie, located in the lower part of the...