Level and distribution of DDT in surface soils from Tianjin, China

One hundred and eighty eight surface soil samples were collected from the Tianjin area to study the contamination of DDT and its metabolites. Measurements were taken for p,p'-DDE, p,p'-DDD, p,p'-DDT, o,p'-DDE, o,p'-DDD and o,p'-DDT for all samples. The results indicated that p,p'-DDT and p,p'-DDE were the predominant contaminant compounds in the surface soil samples, with mean concentrations of 27.5 and 18.8 ng g(-1) respectively. No significant differences in DDT concentrations were found between the soils from wastewater treated irrigated areas and other areas, suggesting that wastewater irrigation is not an important source of DDT in the area. However, the spatial distribution of soil DDTs levels in the area did correlate well with early direct application rates of pesticides. In addition, both pH level and organic carbon content are also known factors affecting the level of DDT and its metabolites. Although it was assumed that the use of these chemicals was banned in the early 1980s, the current concentration levels appear to be too high to be mere residuals after 20 years degradation.     

生物矿化针铁矿吸附铬的机理探讨

针铁矿在自然界中广泛存在,对重金属离子在地表的迁移和转化有重要影响.利用天然生物矿化针铁矿进行了Cr(Ⅲ)吸附研究,并利用扫描电子显微镜(SEM)和X射线光电子能谱(XPS)等对吸附后的样品进行表征,发现样品中铬的含量随着Al2O3含量的增加而增加,说明表面带负电荷的含高岭土等的粘土较针铁矿对Cr(Ⅲ)有更强的吸附能力.样品的XPS研究表明,NO3-也参与了反应,且促进了Cr(Ⅲ)的氧化.研究还发现,Cr(Ⅲ)在针铁矿上的吸附不均匀,与文献报道的情况不同.     

基于分形理论的滑坡空间分布特征研究

以"汶川地震"极端事件为时间分段点,基于ArcGIS网格法定量分析汶川地震重灾区滑坡空间分布的分形分维特征,得出汶川地震重灾区滑坡在震前和震后均具有分形特征。研究表明,汶川地震重灾区滑坡点的空间分布具有统计意义上的自相似结构,无特征尺度。基于分形理论的汶川地震重灾区滑坡空间分布特征分析为进一步研究滑坡的敏感性、危险性及滑坡风险预警奠定了重要的理论基础和前提。     

淮安市典型地区土壤中多环芳烃污染调查

对淮安市5个区域土壤中多环芳烃(PAHs)污染状况进行了调查和分析,结果表明:被调查区域土壤中PAHs的平均质量比为1 641 μg/kg,城市附近区域--淮海南路旁农田、大运河畔城南农田、北京新村土壤中PAHs的质量比最高,分别为3 421 μg/kg、1 730 μg/kg和1 779 μg/kg,其污染特征因子为苊、菲、荧蒽、(艹屈)、茚并[1,2,3-c,d]芘、苯并[g,h,I]苝等;远离城市的区域--洪泽湖畔农田、洪泽湖大墩岛农田土壤中PAHs质量比较低,分别为716.3 μg/kg、560.9 μg/kg,污染特征因子为芴、苊、菲、(艹屈)等.     

本构模型特性对深厚场地非线性地震反应的影响

采用基于Davidenkov和Matasovic骨架曲线构造的不规则加卸荷应力—应变滞回圈,数值模拟了2个剖面的苏州第四纪深厚场地二维非线性地震反应。结果表明:(1)采用Matasovic模型计算的地表峰值加速度稍大于采用Davidenkov模型计算的地表峰值加速度,但前者计算的地表地震动持续时间稍小于后者计算的。随着基岩输入地震动强度的增大,两者给出的地表峰值加速度差异呈现逐渐增大的趋势,并与土体的横向不均匀特性有关;(2)两者给出的地表谱加速度谱形基本相似,其差异随基岩输入地震动强度的增大而增大;远场地震动作用下地表谱加速度的卓越周期也随输入地震动强度的增大而增大;(3)两者给出的峰值加速度随土层深度和横向的空间变化特征基本一致,远场地震动作用下的地表峰值加速度明显大于近场地震动作用下的地表峰值加速度。     

辽东湾滨海地区海水入侵分布及地下水化学特征分析

本文通过对辽东湾北部和东、西两侧滨海地区108个地下水井的监测数据进行分析,得出:(1)辽东湾海水入侵严重地区主要分布在辽东湾北部淤泥质海岸,其分布特点是严重海水入侵区、轻度海水入侵区由岸向陆呈带状分布;东西两侧以砂砾质海岸为主,局部地区海水入侵较重,大部分地区海水入侵较轻;(2)辽东湾地下水化学类型可分为五种类型,其分布特点是由岸向陆呈带状分布,规律明显,反映了海水入侵分布特征。氯化物型一般分布在微咸水至咸水区,重碳酸盐氯化物型或氯化物重碳酸盐型、重碳酸盐氯化物硫酸盐型或氯化物重碳酸盐硫酸盐型分布在微咸水向淡水过渡区,硫酸盐重碳酸盐型或重碳酸盐硫酸盐型、重碳酸盐型主要分布在淡水区。     

Mechanism and kinetics study on the ozonolysis reaction of 2,3,7,8-TCDD in the atmosphere

The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin(2,3,7,8-TCDD) is an efcient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2 O are introduced in detail at the method of MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. In ozonolysis, H2O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus(RRKM) theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and O3 is 4.80 × 10 20cm3/(mole·sec) at 298 K and 760 Torr. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin.     

中国生态风险评价研究现状

20世纪90年代后,作为风险评价的一个重要分支,生态风险评价逐渐成为新的研究热点。国际上相关研究已空前活跃,但在中国,生态风险评价还处于起步阶段,目前仅对水环境生态风险评价和区域生态风险评价等领域的基础理论和技术方法进行了相关研究。以此为基础,阐述了生态风险评价和风险管理之间的关系,风险评价首先考虑环境管理的目标,因此生态风险评价的计划有助于评价的结果用于风险的管理和环境决策的制定,而风险管理的结果也可以有效地控制风险。     

基于新型有机多孔复合基质的生物系统去除污染水体中的氮磷

针对太湖入湖河道污染水体中的氮磷超标问题,以海绵铁、沸石、砾石和土壤为基质,采用动态吸附+生物法,对氮磷开展基于新型有机多孔复合填料的去除效果研究,结果表明,生物系统中的新型有机多孔复合基质在空间上形成了好氧-缺氧微环境,获得了较好的同步硝化-反硝化效果;通过正交实验确定流量0.00075 L/s,曝气时间24 h,pH值7,曝气量20 L/min为去除氮磷的最优条件;相对一级动力学方程、双常数方程而言,Elovich方程对3种填料的吸附动力学特征拟合最好,决定系数R2在0.81～0.92之间。通过平均去除效果较优分析,好氧条件下,NH3-N平均去除70.6%,TP平均去除81.2%;厌氧条件下,TN平均去除62.4%,COD平均去除42.6%;NH3-N、TP、TN和COD的最低浓度分别为0.75、0.095、1.1和18.3 mg/L,综合考虑主要污染物的去除效果和经济效益,本项新型有机多孔复合填料结合生物系统适宜去除河原平网地区污染水体中的氮磷。     

Health risk assessment of odors emitted from urban wastewater pump stations in Tianjin,China

In order to evaluate the potential adverse health effects of odor emissions from wastewater pump stations (WWPSs) to human, a health risk assessment was performed to study the odors emitted from an urban WWPS in a residential area, Tianjin (in North China). First, 15 types of volatile organic compounds in the WWPS were collected and analyzed using gas chromatography-mass spectrometry. Next, Monte Carlo probabilistic modeling was applied to evaluate the potential health effects of four odors (chlorobenzene, dichloromethane, hydrogen sulfide, and carbon disulfide), which had higher concentrations. The results revealed that the 95th percentile of the total non-carcinogenic risk was approximately 1.73, which poses a threat to human health. In addition, hydrogen sulfide had the highest non-carcinogenic risk value of the four; the hazard quotient of hydrogen sulfide was estimated to be 1.60 at the 95th percentile, higher than the upper confidence limit (1.0). The 95th percentile of the carcinogenic risk was approximately 5.47E-08, much lower than the maximum acceptable level (1.0E-06). Finally, the influence of the input variables on the output was evaluated using sensitivity analysis, and contaminant concentration, reference concentration, and inhalation unit risk were the most influential variables.