RISK ASSESSMENT METHODOLOGY FOR KARST AQUIFERS: (2) SOLUTE-TRANSPORT MODELING

Ground-water flow and solute-transport simulation modeling are major components of most exposure and risk assessments of contaminated aquifers. Model simulations provide information on the spatial and temporal distributions of contaminants in subsurface media but are difficult to apply to karst aquifers in which conduit flow is important. Ground-water flow and solute transport in karst conduits typically display rapid-flow velocities, turbulent-flow regimes, concentrated pollutant-mass discharge, and exhibit open-channel or closed-conduit flow. Conventional ground-water models, dependent on the applicability of Darcy`s law, are inappropriate when applied to karst aquifers because of the (1) nonapplicability of Darcian-flow parameters, (2) typically nonlaminar flow regime, and (3) inability to locate the karst conduits through which most flow and contaminant transport occurs. Surface-water flow and solute-transport models conditioned on a set of parameters determined empirically from quantitative ground-water tracing studies may be effectively used to render fate-and-transport values of contaminants in karst conduits. Hydraulic-flow and geometric parameters developed in a companion paper were used in the surface-water model, TOXI5, to simulate hypothetical slug and continuous-source releases of ethylbenzene in a karst conduit. TOXI5 simulation results showed considerable improvement for predicted ethylbenzene-transport rates and concentrations over qualitative tracing and analytical ground-water model results. Ethylbenzene concentrations predicted by TOXI5 simulations were evaluated in exposure and risk assessment models.     

不同国家基于健康风险的土壤环境基准比较研究与启示

20世纪90年代以来,许多发达国家颁布了基于健康风险的土壤环境标准及基准背景技术文件,为发展中国家启动标准制订和开展基准研究提供了重要的方法学参考.然而,由于各国在环境立法框架、基准推导过程、环境气候特征、土壤类型、人群生活方式与习惯等方面的不同,导致其基准名称、基准功能、保护受体以及基准取值等存在较大的差异.本文在综述基于健康风险的土壤环境基准科学内涵与基本特征的基础上,对不同国家场地土壤环境基准的名称、功能及基准值的差异进行了比较研究,从土地利用类型划分、暴露情景和暴露途径设定、致癌物可接受风险水平选择以及人体暴露参数确定等4个方面,对不同国家制定场地土壤环境基准的关键技术和影响因素进行了总结分析,探讨了借鉴国外经验考虑区域差异制定我国土壤环境基准的对策与方略,并指出了当前我国制定场地土壤环境基准和标准面临的困难和挑战.     

Assessment of potential dermal and inhalation exposure of workers to the insecticide imidacloprid using whole-body dosimetry in China

In China, although improvements to the pesticide registration process have beenmade in last thirty years, no occupational exposure data are required to obtain a commercial license for a pesticide product. Consequently, notably little research has been conducted to establish an exposure assessment procedure in China. The present study monitored the potential dermal operator exposure from knapsack electric sprayer wheat field application of imidacloprid in Liaocheng City, Shandong Province and in Xinxiang City, Henan Province, China, using whole-body dosimetry. The potential inhalation exposure was determined using a personal air pump and XAD-2 sample tubes. The analytical method was developed and validated, including such performance parameters as limits of detection and quantification, linear range, recovery and precision. The total potential dermal and inhalation exposures were 14.20, 16.80, 15.39 and 20.78 mL/hr, respectively, for the four operators in Liaocheng and Xinxiang, corresponding to 0.02% to 0.03% of the applied volume of spray solution. In all trials, the lower part (thigh, lower leg) of the body was the most contaminated, accounting for approximately 76% to 88% of the total exposure. The inhalation exposure was less than 1% of the total exposure. Such factors as the application pattern, crop type, spray equipment, operator experience and climatic conditions have been used to explain the exposure distribution over the different parts of the body. As indicated by the calculated Margin of Exposure, the typical wheat treatment scenarios when a backpack sprayer was used are considered to be safe in terms of imidacloprid exposure.     

SO2和O3动态胁迫烟草致病的暴露试验

ＳＯ_２和Ｏ_３动态胁迫烟草致病的暴露试验陈锦云，兰志斌，苏珍山，曾军，王阳青（福建龙岩地区烟科所龙岩３６４０００）关键词Ｓ）_２和Ｏ_３；烟草；气候斑点病，动态胁迫暴露ＴＨＥＤＹＮＡＭＩＣＳＴＲＥＳＳＥＸＰＯＳＵＲＥＴＥＳＴＯＮＴＯＢＡＣＣＯＢＬＡＤＥ...     

A preliminary examination of the translocation of microencapsulated cyfluthrin following applications to the perimeter of residential dwellings

Abstract

Methods have been developed to monitor the translocation of microencapsulated cyfluthrin following perimeter applications to residential dwellings. A pilot study was implemented to determine both the potential for application spray to drift away from dwellings and the intrusion of residues into homes following perimeter treatments. Residential monitoring included measuring spray drift using cellulose filter paper and the collection of soil samples from within the spray zone. In addition, interior air was monitored using fiberglass filter paper as a sorbent medium and cotton ball swabs were used to collect surface wipes.

Fortification of matrixes resulted in recoveries of >90%. Spray drift was highest at the point of application and declined to low but measurable levels 9.1m from the foundations of dwellings. Soil residues declined to low, but measurable levels by 45 days post‐application. No cyfluthrin was measured from indoor air; however, some interior surfaces had detectable levels of cyfluthrin until three days post‐application.

Findings indicate that spray drift resulting from perimeter applications might contaminate non‐target surfaces outside the spray zone. Soil borne residues may serve as persistent sources for human exposure and potentially intrude into dwellings through the activities of occupants and pets. Residues do not appreciably translocate through air and consequently inhalation is not a likely route for human exposure. Surface residues detected indoors suggest that the physical movement of residues from the exterior to the interior might be a viable route of movement of residues following this type of application.     

Polybrominated diphenyl ethers and organochlorine compound levels in brown trout (Salmo trutta) from Andean Patagonia, Argentina

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), DDTs and endosulfan residues were analyzed in muscle, liver, gonads, gills and stomach content of brown trout (Salmo trutta) from the Andean Patagonia. PBDEs, PCBs and DDTs levels were positively correlated with lipid content, while less hydrophobic endosulfans showed a poor correlation. Endosulfan levels were about 99.9% of total contaminant (highest levels in liver 500 × 10³ ng g⁻¹ lipid weight), with α-/β-isomers ratio >1 in all organs. These results are in agreement to the current-use of the technical endosulfan and also suggest acute exposure to this insecticide. Conversely, DDT/DDE ratio reflects fish exposure to old DDT sources, showing a DDE predominance. Gills had the highest levels of DDTs, PCBs and PBDEs, indicating they represent the main uptake pathway for such hydrophobic compounds from water column. PCBs showed the lowest levels in all organs and the PBDEs/PCBs ratios >1 agree with worldwide trends. PBDEs levels in gonads, gills, liver and muscle exceeded 80 ng g⁻¹ (lipid weight) and were higher than other values reported in the Southern Hemisphere. BDE-47 was the predominant congener, suggesting higher bioaccumulation potential and possible brown trout metabolism of higher congeners. Since there is no point source of PBDEs in the region and residues were dominated by lower brominated congeners, atmospheric transport could be the main source of these compounds. This first report of PBDEs levels in fish from Argentina contributes to the knowledge about environmental trends of these persistent organic pollutants (POPs) in remote areas such as the Andean Patagonia.     

API Standard 521 new alternative method to evaluate fire relief for pressure relief device sizing and depressuring system design

Since the 1950's, API Standards have provided guidance on determining relief loads for equipment exposed to pool fires. The API method is empirical based on tests performed in the 1940's. There is increasingly widespread interest in analytical methods based on heat transfer principles to model fire heat input. The API committee agreed to include an analytical method in the 6th edition of API Standard 521 to establish relief loads for pressure relief devices and to design depressuring systems for the fire scenario. The analytical method provides more flexibility than the empirical method but has limitations (e.g., too many permutations are possible leading to potential under-sizing of the pressure relief device).This paper discusses the basis for the empirical method in API Standard 521 and provides comparisons of the empirical and analytical method with two more recent large-scale pool fire tests. This pool fire test data indicates that the empirical method will provide a conservative estimate of pool fire heat input for most applications and is still the method of choice when designing pressure relief systems. However, these recent tests indicate the empirical method needs to be modified when a vessel or equipment is partially confined by adjacent embankments or walls equal or greater than the vessel height. In such cases, the wetted area exponent should be 1.0 instead of 0.82.The analytical method is useful in determining time-versus-temperature profiles for heating unwetted vessels of varying wall thicknesses and materials of construction. These profiles, which depend upon the type of fire (e.g., unconfined pool fire, jet fire, etc.), can be combined with tensile strength and stress-rupture data to specify a depressuring system's pressure-versus-time profile. This will minimize failure and/or mitigate the effects of failure due to overheating from fire exposure.     

装甲钢自然环境试验与人工加速试验的相关性

对某型装甲钢在酸雨大气环境下自然暴露与人工模拟加速试验的相关性进行了研究。利用腐蚀机理对比、Spearman秩相关系数、灰色关联度、加速转换因子等方法进行了相关性的定性定量评价。评价结果表明模拟加速试验与自然环境暴露试验有较好相关性。     

某市区重点行业职业病危害因素现状调查研究

对某市区重点行业15家企业职业病危害因素进行检测与评价,对普查结果进行综合分析。结果表明:15家企业工作场所化学有害因素职业卫生现状情况良好,但噪声危害程度较大;在6个重点行业中,电子制造行业有害因素合格率最低,为84%,其次是纺织行业,有害因素合格率为85%,其他化学原料及化学制品、化工、木制家具、石材加工四个行业合格率均较高;市直以上企业职业卫生现状情况优于区属企业,300-2000人之间较大规模的企业职业卫生现状情况优于300人以下的企业。同时,对企业提出了职业危害现状的改进措施与建议。