Determination of Background Concentrations of Inorganics in Soils and Sediments at Hazardous Waste Sites

Hazardous waste sites may pose a threat to human health and the environment when toxic substances are released. However, the contaminants present at a waste site may have originated on-site (i.e., resulting from releases attributable to site activities) or off-site (i.e., resulting from sources not on-site). Off-site substances may result either from natural sources (e.g., erosion of naturally occurring mineral deposits) or anthropogenic sources (e.g., widespread contamination from automobile exhaust in urban areas). To determine the appropriate action to take at a hazardous waste site, the U.S. Environmental Protection Agency (EPA) must distinguish between substances directly attributable to the hazardous waste site (i.e., site contaminants) and those attributable to natural background concentrations. The most important factor to consider when determining background concentrations is to ensure that the physical, chemical, and biological aspects of the media to be sampled at both the contaminated site and the background site are as similar as possible. Inorganics, in particular metals, are addressed. Radionuclides are not specifically addressed; however, metals with radioactive isotopes that may be encountered at hazardous waste sites are included. There are references and data included in this paper that provide average concentrations and reference values for selected soils and sediments in the United States. Suggested sampling and monitoring design approaches that could be used by scientists and engineers faced with how to determine background concentrations are identified. The issues discussed include the selection of background sampling locations, considerations in the selection of sampling procedures, and statistical analyses for determining whether contaminant levels are significantly different on a potential waste site compared with a background site.     

Biogeochemical reductive release of soil embedded arsenate around a crater area (Guandu) in northern Taiwan using X-ray absorption near-edge spectroscopy

This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure (XANES) and atomic absorption spectrometry.Total arsenic (As) concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite (As(III)) and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.     

影响土壤中钴活性的因素

用大样本统计分析上土壤性质对钴活性的影响及研究改变土壤ｐＨ值，有机质和氧化还原状况对钴活性的影响。结果表明，在其它土壤性质不变情况下，全钴提高，活性钴的数量增加，锰氧化物的作用则相反，在酸性及还原土壤中，土壤ｐＨ值，浸提剂ｐＨ值对钴的提取量有极显的影响；在中性和碱性并处于氧化状态的土壤中，影响不显，增加土壤有机质可以提高活性钴的数量。     

土壤中裂隙与其它类型孔隙结构差异的图像比较

裂隙是孔隙的一类。文章利用土壤切片的数字图像,采用目视分离的方法,比较研究了裂隙与其它类型的孔隙在结构上的差异、选择的土样研究结果表明,目视分离裂隙的方法是可行的,土体中的裂隙直径分布曲线是不规则的,而其它类型的孔隙直径分布曲线则类似对数正态分布;土壤总孔隙中直径较大的部分主要由裂隙构成,直径较小的部分则由其它类型孔隙和裂隙共同构成;土壤表面裂隙与土体内部裂隙在结构上可能具有一定差异。     

Elemental composition of surface waters in the Antarctic Peninsula and interactions with the environment

The fast changes in chemical and biological properties of many coastal and inland waters in the last decades reflect the pressure of man on the environment. The surface waters of the Antarctic Peninsula, located far from industrial or populated areas, could eventually be used as background lines. Surface water samples were taken from five lagoons of King George Island, Antarctic Peninsula, and from the Kitiesh Lake. Sample pH and electrical conductivity were analysed in situ and in the laboratory, respectively. The dissolved fractions were analysed in 1997 and 1998. Total concentrations only for 1998 were determined in another fraction adjusted to pH 2. Aluminium, Ca, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sn, Sb, Ba, Bi, and Pb were quantified in all samples by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total and dissolved elemental concentrations were discussed considering the composition of particulate material suspended in the waters removed by streams or by water runoff, or from atmospheric aerosols. Concentrations of dissolved elements change from one lagoon to another. Total and dissolved elemental concentrations could be related to water movement by windstorms, to chemical mechanisms in water and/or to natural and anthropogenic atmospheric factors.     

Lead content of plants and soils from three abandoned smelter areas in and near Socorro,New Mexico

Two primary lead smelters and one secondary lead smelter have been active in the Socorro, New Mexico (USA) area in the last 110 years: the Billing smelter from 1883 to 1894, the Cuba Road smelter from 1881 to 1900, and Cal West from 1979 to 1984. Samples of plants and surface soil under each plant from all three sites were analysed for lead. The plants consisted of sparse grasses, cacti, creosote bush, snakeweed, mesquite and fourwing saltbush. Lead levels in the plants increased (2-440 g g^–1) as the lead in the alkaline soils (25-10000 ng g^–1) increased. However, the BAC (biological absorption coefficient), which is the ratio of lead content in the plant to the lead content in the soil, a measure of relative accumulation, decreased by one to two orders of magnitude, except for grasses and snakeweed. At background lead levels, there was little difference between lead in rootsversus foliage. At high lead levels, there was higher lead in roots versus foliage at the Billing and Cuba Road sites. The reverse was noted at Cal West. Because this is a recent operation, the higher lead in foliage may be due to foliar uptake. Plant growth at all sites appeared healthy.     

东南极海硒的形态和分布

采用新的现场分离了东海极海１２个表层海水样及３２个剖面样中硒及各主要溶存形态的含量，发现总硒含量高于其它各大洋，这可能与特殊的极地生态环境对其形态的影响有关〉Ｓｅ（Ⅵ）拟可作为水团指示剂     

Elevated Levels of Cadmium and Zinc in Paddy Soils and Elevated Levels of Cadmium in Rice Grain Downstream of a Zinc Mineralized Area in Thailand: Implications for Public Health

Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken. Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg⁻¹ and 100 to 8036 mg kg⁻¹, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged from 0.05 to 7.7 mg kg⁻¹. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg⁻¹. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body. This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’ areas.     

Evaluating the Applicability of Regulatory Leaching Tests for Assessing Lead Leachability in Contaminated Shooting Range Soils

The toxicity characteristic leaching procedure (TCLP) is the current US-EPA standard protocol to evaluate metal leachability in wastes and contaminated soils. However, application of TCLP to assess lead (Pb) leachability from contaminated shooting range soils may be questionable. This study determined Pb leachability in the range soils using TCLP and another US-EPA regulatory leaching method, synthetic precipitation leaching procedure (SPLP). Possible mechanisms that are responsible for Pb leaching in each leaching protocol were elucidated via X-ray diffraction (XRD). Soil samples were collected from the backstop berms at four shooting ranges, with Pb concentrations ranging from 5,000 to 60,600 mg kg⁻¹ soil. Lead concentrations in the TCLP leachates were from 3 to 350 mg l⁻¹, with all but one soil exceeding the USEPA non-hazardous waste disposal limit of 5 mg l⁻¹. However, continued dissolution of metallic Pb particles from spent Pb bullets and its re-precipitation as cerussite (PbCO₃) prevented the TCLP extraction from reaching equilibrium at the end of the standard leaching period (18 h). Thus, the standard one-point TCLP test would either over- or under-estimate Pb leachability in shooting range soils. Lead concentration in the SPLP leachates ranged from 0.021 to 2.6 mg l⁻¹, with all soils above the USEPA regulatory limit of 0.015 mg l⁻¹. In contrast to TCLP, SPLP leaching had reached equilibrium, with regard to both pH and Pb concentrations, within the standard 18 h leaching period, and the analytical SPLP results were in good agreement with those derived from modeling. Thus, we concluded that SPLP is a more appropriate alternative than TCLP for assessing lead leachability in range soils.     

不同土壤类型中外源汞对白符跳(Folsomia candida)的毒性

参考国际标准化组织(ISO)颁布的跳虫毒性测试方法 ISO11267,分析了汞(Hg)在我国9种典型土壤中对白符跳(Folsomia candida)的急性毒性及繁殖毒性。发现Hg在不同类型土壤中对白符跳的半数致死浓度(LC50)变化为(0.92~1.94)mg·kg-1,而对白符跳繁殖产生影响的半数效应浓度(EC50)变化范围为(0.98~2.43)mg·kg-1,产生10%影响的浓度(EC10)变化范围为(0.29~1.40)mg·kg-1。将土壤的主要理化性质(p H、OM、CEC)与Hg对白符跳的EC50进行相关性回归分析,发现土壤CEC与EC50呈显著正相关关系(r=0.8624,p0.01),随着土壤CEC的增大,Hg的EC50值也趋于升高。因此,土壤CEC可能是导致不同类型土壤中汞对白符跳毒性差异的主要因素。本研究结果可为制定基于我国土壤类型的生态筛选值提供基础参考数据。