Stable chlorine intramolecular kinetic isotope effects from the abiotic dehydrochlorination of DDT

INTENTION, GOAL, SCOPE, BACKGROUND: Identifying different sources and following reaction pathways of chlorinated organic contaminants in the environment can be challenging, especially when only their concentrations are available. Compound-specific stable chlorine measurements of some contaminants have recently been shown to provide additional information and an increased understanding of their biogeochemistry. These studies, however, have been generally limited to volatile molecules. OBJECTIVE: Here, the stable chlorine isotope ratios of the semi-volatile pesticide, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) were investigated. Specifically, the intramolecular stable chlorine isotopic compositions of DDT and the kinetic isotope effect (KIE) for the abiotic dehydrochlorination of DDT to 2,2-bis(p-chlorophenyl)-1,1-dichloroethene (DDE) were determined. METHODS: Selective chemical oxidation of DDT to dichlorobenzophenone (DCBP) and analysis of each compound was used to calculate the stable chlorine isotope ratios of the alkyl and aromatic chlorines in DDT. To determine the KIE for dehydrochlorination, DDT was reacted in a basic solution to yield DDE at 52 degrees C, 60 degrees C, and 72 degrees C for 3, 5, and 5 days, respectively. RESULTS AND DISCUSSION: Significant intramolecular stable chlorine isotopic differences were observed in one sample of DDT where the alkyl and aromatic delta 37Cl values were -5.76 +/- 0.45 and -2.21 +/- 0.24%@1000, respectively. Dehydrochlorination of DDT to DDE in basic solutions at 52, 60, and 70 degrees C resulted in a substantial intramolecular KIE where the alkyl chlorines of DDE shifted by approximately 3%@1000 relative to the alkyl chlorines in DDT. However, no temperature dependence was observed. The KIE, calculated by an iterative program, was 1.009. CONCLUSIONS: Intramolecular differences in the stable chlorine isotope ratios were observed in DDT and this is the first such finding. Dehydrochlorination of DDT yields a measurable and distinct intramolecular stable chlorine KIE. RECOMMENDATION AND OUTLOOK: The results of this study demonstrate the existence of significant intramolecular differences in chlorinated organic compounds. Many other chlorinated semi-volatile and volatile organic contaminants are synthesized from multiple sources of chlorine, and we recommend that similar studies be performed on many such molecules in order to attain a clear understanding of their intramolecular chlorine isotopic differences. The existence of a measurable KIE for the dehydrochlorination of DDT to DDE shows the potential strength of using isotopic measurements to investigate the biogeochemistry of these important compounds. For example, the isotopically depleted aqueous chloride produced by dehydrochlorination of DDT to DDE may be a useful tracer of these reactions in freshwater environments.     

POPs污染场地土壤健康风险评价

文章以常州市某化工厂为例,介绍了POPs污染场地的健康风险评价,分别对两种土地利用类型假设下土壤的3条暴露途径进行估算,重点考虑了儿童对污染土壤的敏感性,用年龄修正因子计算居民的致癌风险。结果表明两种假设下氯丹和灭蚁灵的致癌风险都超过了可接受的风险水平,在部分高暴露点甚至超过了目标风险值的100倍,需要对场地进行修复。各暴露途径对健康风险的贡献按从大到小排列依次为:直接摄入土壤﹥皮肤接触﹥呼吸摄入。文章还根据健康风险评价的公式反推出适合本污染场地的土壤初级修复目标分别为:氯丹5.2mg/kg、灭蚁灵7.4×10-1mg/kg(工业用地);氯丹1.6mg/kg、灭蚁灵2.7×10-1mg/kg(居住用地)。     

Accumulation, distribution and transformation of DDT and PCBs by Phragmites australis and Oryza sativa L.: II. Enzyme study

Two wetland plant species, Phragmites australis and Oryza sativa, were grown in a glasshouse under hydroponics conditions. Enzyme extracts from different parts of the plants were used to determine the transformation rate of o,p′-DDT, p,p′-DDT and PCBs. The organic pollutants were directly spiked into the enzyme extracts, and samples were collected every 30 min and analyzed with a GC-ECD. Root extracts of P. australis readily degraded and transformed DDT and some PCB congeners with a low degree of chlorination. In contrast, crude extracts of O. sativa showed no appreciable degradation or transformation of DDT or PCBs. Inhibition studies indicated that the degradation and transformation of both DDT and PCBs by P. australis enzymes were partly mediated by peroxidase and the plant P-450 system. PCBs with a high degree of chlorination were highly resistant to transformation or degradation by plant enzymes. Both wetland plant species accumulated substantial quantities of the persistent organic chemicals but had different degradation capacities. The enzyme systems in P. australis were much more effective that those in rice in the degradation and transformation of the organic pollutants.     

Biotransfer of persistent organic pollutants from a large site in China used for the disassembly of electronic and electrical waste

Samples of groundwater, river water, river sediment, paddy soil, rice seeds, hen eggs, fish, umbilical cord blood, and newborn meconium were collected from October 2002 to October 2003 near a large site in China used for the disassembly of obsolete transformers and other electronic or electrical waste. Six indicator PCB congeners, three non-ortho dioxin-like PCB congeners, and six organochlorine pesticides were determined in the samples by GC with electron capture detector. The results demonstrated that the local environment and edible foods had been seriously polluted by toxic PCBs and organochlorine pesticides. The actual daily intakes (ADIs) of these pollutants were estimated for local residents living in the area. The intake data showed that the contents of PCBs in these local residents were substantial, as the ADI estimates greatly exceed the reference doses set by the World Health Organization and the United States Agency for Toxic Substances and Disease Registry. The presence of the indicator PCB congeners in the cord blood and the meconium samples, as well as significant correlations (r ² > 0.80, p < 0.05) between these levels, suggests a potential biotransfer of these indicators from mothers to their newborns. This preliminary study showed that obsolete transformers and other electronic or electrical waste can be an important source for the emission of persistent organic pollutants into the local environment, such as through leakage, evaporation, runoff, and leaching. Contamination from this source appears to have reached the level considered to be a serious threat to environmental and human health around the disassembly site.     

Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai

The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe （visibility 〈 2 km） and moderate （2 km 〈 visibility 〈 3 km） haze, mainly distributed in winter and spring. The mean particle number concentration was about 17,000/cm3 in haze, more than 2 times that in clean days. The greatest increase of particle number concentration was in 0.5-1μm and 1-10 μm size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100 nm and 100-200 nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15 μm3/cm3 and 949, 649, 206 μm2/cm3, respectively. As haze events got more severe, the number concentration of particles smaller than 50 nm decreased, but the particles of 50-200 nm and 0.5-1μm increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4, SO24- and NO3 increased great/y, followed by Na＋, IC, Ca2＋ and CI-. These ions were very different in size-resolved particles during haze and photochemical smog episodes.     

白洋淀典型持久性有机污染物污染特征与风险评估

对白洋淀表层水体和表层沉积物中多环芳烃（PAHs）、有机氯农药（OCPs）和多溴联苯醚（PBDEs）三类典型持久性有机污染物（POPs）的污染特征进行综合调查和分析.结果表明：①白洋淀水体中PAHs、OCPs和PBDEs浓度范围分别是71.32~228.27、2.62~6.13和0~6.5 ng·L^-1;沉积物中PAHs、OCPs和PBDEs含量范围分别是163.20~861.43 ng·g^-1、2.25~6.07 ng·g^-1和230.96~1224.13 pg·g^-1.与历史数据相比,白洋淀沉积物PAHs和OCPs含量均有明显下降;与国内外湖泊相比,白洋淀沉积物中PBDEs含量处于较低水平.②水体和沉积物PAHs污染来自于油类排放和木材、煤炭燃烧的共同作用;白洋淀水体和沉积物中OCPs组成均以HCHs为主（93.76%和63.10%）,水体中HCHs主要来源于工业HCHs的降解,部分地区来源于大气的远距离传输和林丹的使用,DDTs则主要来源于历史残留.沉积物中HCHs主要来源于新的林丹使用,也有少量工业HCHs的输入,DDTs则以历史残留为主,可能部分地区存在新的DDTs输入;白洋淀水体中PBDEs组成以BDE-2为主（65.80%）,可能主要来源于大气远距离传输和高溴代联苯醚的降解,沉积物中PBDEs组成以BDE-209为主（63.82%）,主要来源为商用的十溴联苯醚.③生态风险评价结果表明,白洋淀尚无明显生态风险,但部分采样点存在生态风险的可能性,应加强监控.     

我国持久性有机污染物人体负荷研究进展

持久性有机污染物所造成的污染已经成为全球性的环境问题.关于由其污染导致的环境和健康损害的研究是当前环境科学的热点之一.我国正处在经济快速发展时期,环境污染对居民健康的潜在危害尤其值得关注.本文对近年来有关我国居民持久性有机污染物的人体负荷的研究进展进行综述,为我国进一步开展相关研究提供参考.     

北京灰霾天气PM10中微量元素的分布特征

采用电感耦合等离子体质谱法(ICP-MS)对北京市2008年4月和5月不同采样点采集的灰霾天PM₁₀样品中的15种微量元素进行了分析,得出了Ti、Fe、Zn、Sn、Pb为全样样品中相对含量较高元素;Ti、Mn、Ni、Cu、Zn、Pb是水溶样样品中相对含量较高元素。与晴天相比,灰霾天样品中微量元素可溶性增强,对人体危害更严重。与2002年分析数据进行对比,因2002年缺少Cr、Cd元素的测试值,全样样品中除了Co、Ni、Cu、Mo元素外,其余测试元素的浓度均有不同程度的升高,Fe和Sn元素的增幅最大。水溶样品中,参与对比元素的含量均下降。文中对含量相对较高的Cr、Mn、Fe、Cu、Zn、Cd、Sn和Pb元素进行了源解析,分析得出采样点附近的交通源及地面扬尘是这些元素的主要来源。     

电子废物排放持久性有毒污染物的控制政策分析

近年来持久性有毒污染物(PTS)的环境污染和风险问题引起国内外广泛关注,电子废物是其重要的排放源.本研究针对电子废物的排放路径,基于生命周期管理,把电子废物管理分为源头削减、过程控制、末端管理和应急管理四大环节,分析我国电子废物PTS控制相关的法规政策.从管理目标、法规可得性、详细规定、法规协调性和法规政策执行效果五大方面构建法规政策评估体系,采用专家意见法对每个环节涉及的法规政策进行全面评估.源头削减环节的PTS法规政策管理较为完善,有明确的管理目标和较好的法规可得性,而应急管理环节的PTS法规政策管理最不完善,缺乏明确的管理目标和详细规定,法规协调性和执行效果差.根据评估结果针对不同环节提出相应的控制政策建议.     

对广州灰霾天气中单个气溶胶颗粒物的研究

利用电子显微镜，采用形态分析法和X射线能谱分析法相结合的方法对2003年广州灰霾天气中单个气溶胶颗粒物的大小、形态结构和元素组成进行了研究。在灰霾天气中，颗粒物的半径在1．0μm以下，属于细颗粒物；X射线能谱分析的结果显示，它们有比较复杂的组成，大都是混合物。在灰霾天气，常可以观察到一些特殊的颗粒物，它们带有卫星滴结构。比较灰霾天气形成前后一些气溶胶颗粒物的形态结构和元素组成，它们有着较明显的差异。这些观察提供了证据：在灰霾天气过程中，部分粒子的组成有可能发生了变化。