Sedimentation and seasonal variation of hexachlorocyclohexanes in sediments in a eutrophic lake,China

Hexachlorocyclohexane (HCH) concentrations in sediments and sediment trap fluxes of particulate organic carbon and HCHs were measured bi-weekly from March 31 to October 18, 2006 in an urban eutrophic lake in Tianjin, China, in order to investigate sedimentation and seasonal variation of HCHs in sediments. HCH concentrations (dry weight basis) ranged from 2.2 to 20.2 ng/g (mean 7.7 ng/g) in surface sediments and from 26.6 to 972.7 ng/g (mean 187.0 ng/g) in settling particles, respectively. A clear seasonal variation in HCH sedimentation and HCH concentrations in sediments was observed. The maximal HCH deposition occurred following a spring phytoplankton bloom. The average flux of HCHs to sediment was approximately 21-fold higher in April to mid-June as compared to late June to October. This was attributed to the high vertical fluxes at the end of the spring phytoplankton bloom. The maximum values of HCH concentrations in sediments were observed in mid-June to late July. Concentrations of HCHs in sediments from the eutrophic lake were well-correlated with organic carbon contents in sediments. The annual sediment trap flux of HCHs in the eutrophic lake, which was estimated using data obtained in the eutrophic lake, was 117 μ g/m² yr, about 72% of which was attributed to the sedimentation corresponding to spring bloom phytoplankton deposition in late May to mid-June. The high sediment trap flux of HCHs in the eutrophic lake was related to serious local contamination.     

缺氧环境下无定形FeS对六六六的转化动力学

采用批处理实验方法，在缺氧还原的环境下对无定形FeS转化六六六的动力学进行了研究。结果表明，无定形FeS水溶液体系（pH值8.30)可以将六六六的γ-异构体-林丹转化为低氯化合物三氯苯，二氯苯和氯苯，并且产物的形成有异构体选择性；检测到的中间产物为五氯环己烯，四氯环已烯和二氯环已二烯。并提出相应的转化路径和反应机理。以说明溶液中的动态变化过程，反应动力学遵从准一级速率反应。反应机理推测为去氯化氢反应和双氯消除反应。     

Assessment of Organochlorine Pesticide Residues in Water,Sediment, and Fish of the Songhua River,China

This study examined residual concentrations and associated ecological risks of the organochlorine pesticides (OCPs) hexa- chlorocyclohexane (HCH) and dichloro-diphenyl-trichloroethane (DDT) in water, sediment, and fish of the Songhua River in Zhaoyuan County, China. In June 2012, 10 water, 10 sediment, and 20 fish samples were collected. Residual concentrations of ΣHCH and ΣDDT ranged from 10.0–35.59 ng L^?1 (mean 28.03 ± 11.66 ng L^?1) and 5.12–39.66 ng L^?1 (mean 32.36 ± 11.58 ng L^?1) for water. Residual concentrations of ΣHCH and ΣDDT ranged from 0.52–3.00 ng g^?1 (mean 2.04 ± 0.73 ng g^?1) and 0.34–3.41 ng g^?1 (mean 2.38 ± 0.92 ng g^?1) for sediment. The ratios of α-HCH/γ-HCH were close to 1 at the majority of sampling points, indicating considerable new pollution from the use of lindane. The ratios of p,p′-DDE + p,p′-DDD/ΣDDT were less than 0.5, indicating recent inputs from DDT impurities in dicofol. All HCH and DDT isomers except for p,p′-DDD were detected in fish tissue samples, but the associated ecological risks were estimated to be below levels of concern. The study revealed a historical usage of OCPs in the Zhaoyuan section of the Songhua River and new OCP from the use of lindane and dicofol.     

Volatile organic compounds at swine facilities: A critical review

Volatile organic compounds (VOCs) are regulated aerial pollutants that have environmental and health concerns. Swine operations produce and emit a complex mixture of VOCs with a wide range of molecular weights and a variety of physicochemical properties. Significant progress has been made in this area since the first experiment on VOCs at a swine facility in the early 1960s. A total of 47 research institutions in 15 North American, European, and Asian countries contributed to an increasing number of scientific publications. Nearly half of the research papers were published by U.S. institutions.Investigated major VOC sources included air inside swine barns, in headspaces of manure storages and composts, in open atmosphere above swine wastewater, and surrounding swine farms. They also included liquid swine manure and wastewater, and dusts inside and outside swine barns. Most of the sample analyses have been focusing on identification of VOC compounds and their relationship with odors. More than 500 VOCs have been identified. About 60% and 10% of the studies contributed to the quantification of VOC concentrations and emissions, respectively. The largest numbers of VOC compounds with reported concentrations in a single experimental study were 82 in air, 36 in manure, and 34 in dust samples.The relatively abundant VOC compounds that were quantified in at least two independent studies included acetic acid, butanoic acid (butyric acid), dimethyl disulfide, dimethyl sulfide, iso-valeric, p-cresol, propionic acid, skatole, trimethyl amine, and valeric acid in air. They included acetic acid, p-cresol, iso-butyric acid, butyric acid, indole, phenol, propionic acid, iso-valeric acid, and skatole in manure. In dust samples, they were acetic acid, propionic acid, butyric acid, valeric acid, p-cresol, hexanal, and decanal. Swine facility VOCs were preferentially bound to smaller-size dusts.Identification and quantification of VOCs were restricted by using instruments based on gas Chromatography (GC) and liquid chromatography (LC) with different detectors most of which require time-consuming procedures to obtain results. Various methodologies and technologies in sampling, sample preparation, and sample analysis have been used. Only four publications reported using GC based analyzers and PTR-MS (proton-transfer-reaction mass spectrometry) that allowed continuous VOC measurement. Because of this, the majority of experimental studies were only performed on limited numbers of air, manure, or dust samples. Many aerial VOCs had concentrations that were too low to be identified by the GC peaks.Although VOCs emitted from swine facilities have environmental concerns, only a few studies investigated VOC emission rates, which ranged from 3.0 to 176.5 mg d⁻¹ kg⁻¹ pig at swine finishing barns and from 2.3 to 45.2 g d⁻¹ m⁻² at manure storages. Similar to the other pollutants, spatial and temporal variations of aerial VOC concentrations and emissions existed and were significantly affected by manure management systems, barn structural designs, and ventilation rates.Scientific research in this area has been mainly driven by odor nuisance, instead of environment or health concerns. Compared with other aerial pollutants in animal agriculture, the current scientific knowledge about VOCs at swine facilities is still very limited and far from sufficient to develop reliable emission factors.     

南宁市朝阳溪岸边地下水持久性有机污染物的污染特征

为了查清南宁市污染内河对岸边地下水持久性有机污染物的污染规律,选择典型污染河道朝阳溪为研究对象,采取野外水文地质调查与钻探工程手段,采集降雨前、后地下水以及地表水、土壤和沉积物样品测试,分析了污染河道岸边地下水持久性有机物多环芳烃荧蒽、芘和六六六(HCHs)的降雨前、后的污染特征。结果表明,降雨前、后地下水荧蒽和芘多环芳烃的平均浓度分别为24.11、7.98ng/L;HCHs的平均浓度分别为19.75、13.24ng/L;朝阳溪地下水有机污染物荧蒽、芘、有机氯农药的检出率和浓度降雨前高于降雨后。有机污染物荧蒽和芘浓度分布随远离朝阳溪的距离增大逐渐升高,而HCHs浓度分布则相反;推测由于物理化学性质的差异,疏水性较强的荧蒽和芘被含水层中悬浮物和河底沉积物强烈吸附,显示近岸未被检出;然而,疏水性较弱的HCHs则有较高浓度,并形成污染源,导致HCHs历史残留源在含水层的"二次释放"。总体上,降雨对地下水中有机污染物有稀释作用,但局部HCHs有扰动释放作用;相关性分析显示地下水中悬浮物浓度与多环芳烃的荧蒽、芘呈中等程度负相关,而与HCHs则呈极强程度正相关,因此含水层中悬浮物对荧蒽、芘的"过滤效应"比HCHs要高。朝阳溪岸边地下水中持久性有机污染物的运移影响因素与地下水包气带、含水层结构以及地下水系统补、径、排条件和污染源所处位置密切相关。     

FeCl_3存在时六六六热解生成PCDD/Fs的研究

在开管体系中,于280℃时研究了六六六无效体在Fe,理体制FeCl_3存在时的热解,以及影响热解产物中PCDD/Fs生成量的因素.PCDD/Fs的生成主要取决于FeCl_3,而Fe的存在并不增加体系中PCDD/Fs的生成量.在封管体系中,研究结果表明PCSS/Fs的生成量随FeCl_3用量、反应时间和反应温度的增加而增加,但温度影响最大.实验还表明,氯苯、氨酚对PCDD/Fs的生成起决定作用.在250─280℃,PCDD/Fs的生成主要在于二者之间的缩合,而单独氯酚间的缩合则居次要地位.氯化对生成PCDD/Fs的种类及量影响很大.250─280℃时,低氯苯、氨酚在FeCl_3作用下氯代成高氯产物,进而缩合成 OCDD/F;但在 350℃以上时,氯酚反应活性增加,故低氯PCDD/Fs生成量增加,OCDD/F生成量相对降低.     

长江口南岸水体SPM和表层沉积物中OCPs的赋存

利用GC-ECD对长江口南岸14个采样点水体悬浮颗粒物(SPM)及表层沉积物进行了有机氯农药(OCPs)的测定,分析了其中HCHs和DDTs的赋存水平和形态分布.研究表明,OCPs的含量水平有DDTs>HCHs的趋势;悬浮物中污染物浓度高于表层沉积物.悬浮物中HCHs污染水平分布在6.24～14.75ng/g,平均值为12.27ng/g;DDTs的污染水平为3.36～25.66ng/g,平均值为16.37ng/g.而表层沉积物中HCHs含量为1.19～8.22ng/g,平均值5.92ng/g;DDTs的含量水平为4.96～14.94ng/g,平均值为8.92ng/g.研究区内OCPs的含量低于ER-M值,对环境生物具有潜在的危害性.     

广州市农业土壤中六六六(HCH)的残留特征

用GC-ECD内标法分析了广州市郊区农业土壤表层土中α-HCH、β-HCH、γ-HCH、δ-HCH四种有机氯农药的残留情况,并对该地区六六六(HCH)的残留特征进行了分析评价。结果表明,在该地区农业土壤中HCH四种异构体均有不同程度的检出,∑HCH残留量介于5.28～174.94ng/g,平均值为62.07ng/g,其中β-HCH残留量的最大值达到了111.18ng/g;∑HCH残留量在不同农业土壤中有明显差异,菜地土壤为54.93ng/g,作物土壤为113.84ng/g,林地土壤为17.42ng/g;HCH各异构体在不同农业土壤中的累积分布比例β-HCH均为最高,分别为菜地土壤73.1%,林地土壤63%,作物土壤53.1%;广州市各类农业土壤中α-/γ-HCH比值均接近于1,指示该地区土壤环境已经发生变化,可能有新的污染源存在。