Assessment of the temporal and spatial distribution of atmospheric PCNs and their air–soil exchange using passive air samplers in Shanghai,East China

A total of 47 passive air samples and 25 soil samples were collected to study the temporal trend, distribution, and air–soil exchange of polychlorinated naphthalenes (PCNs) in Shanghai, China. Atmospheric PCNs ranged from 3.44 to 44.1 pg/m³ (average of 21.9 pg/m³) in summer and 13.6 to 153 pg/m³ (average of 40.0 pg/m³) in winter. In the soil samples, PCN concentrations were 54.7–1382 pg/g dry weight (average of 319 pg/g). Tri-CNs and tetra-CNs were two dominant homolog groups in air samples, while di-CNs were also found at comparable proportions to tri-CNs and tetra-CNs in soil samples. Most air and soil samples from the industrial and urban areas showed higher PCN concentrations than those from suburban areas. However, some soil samples in urban centers presented higher PCN concentrations than industrial areas. Analysis of PCN sources indicated that both industrial thermal process and historical usage of commercial PCN mixtures contributed to the PCN burden in most areas. The fugacity fraction results indicated a strong tendency of volatilization for lighter PCNs (tri- to hexa-CNs) in both seasons, and air–soil deposition for octa-CNs. Moreover, air–soil exchange fluxes indicate that soil was an important source of atmospheric PCNs in some areas. The results of this study provide information for use in the evaluation of the potential impact and human health risk of PCNs around the study areas.

     

典型村镇生活垃圾动态淋滤过程中污染物的释放特征研究

选取我国东、中、西部3个地区6个典型村镇的生活垃圾,设计了两种淋滤强度:低强度(10 mm·d~(-1))和高强度(20 mm·d~(-1)),采用室内降雨模拟实验,研究了生活垃圾污染物如CODCr、BOD5、TN和NH3-N等的动态淋滤释放特征.结果显示,两种淋滤强度下,3个地区淋滤液pH值整体随时间的增加呈现小幅的上升,变化范围分别在6.5~8.0(10 mm·d~(-1))和5.5~8.0(20 mm·d~(-1))之间;CODCr呈现显著下降(1~2周)、缓慢下降(2~7周)和相对平稳(7~10周)3个阶段.淋滤液BOD5在前6周降低明显,在第7和第8周基本达到了溶出的平衡点.淋滤液TN分别在第8周(10 mm·d~(-1))和第7周(20 mm·d~(-1))基本达到了溶出平衡,NH3-N分别在第8周(10 mm·d~(-1))和第6周(20 mm·d~(-1))基本达到了溶出平衡.整个淋溶周期内(10周),淋滤液CODCr、BOD5、TN和NH3-N浓度变化规律整体呈现:高强度(20 mm·d~(-1))淋滤条件下浓度降低率高于低强度(10 mm·d~(-1)).     

磷石膏再生利用途径的综合评价

依据层次分析法原理,用经济、环境和资源化3个影响因素建立磷石膏资源化途径优选的递阶层次结构模型。以山东某化工厂生产磷酸产生的磷石膏为研究案例,从磷石膏组成成分与含量分析的角度出发,结合磷石膏各资源化途径的独特要求,探讨磷石膏资源化特性与资源化途径的密切关系,拟合出磷石膏的各种资源化特性,作为结构模型中的资源化因子。然后分别对模型中的3个影响因素进行定性和半定量化处理,最终实现磷石膏资源化途径优选的决策评价,为政府部门和环境管理者提供决策参考。     

废物水泥窑共处置产品中重金属释放模型研究——混凝土路面场景

通过模拟煅烧试验制取水泥熟料,并制得混凝土样品。在混凝土路面场景分析的基础上,参照欧盟固体中无机组分有效量测试方法(EA NEN7371),以pH=3.2的HNO3/H2SO4溶液(质量比为1∶2)为浸取液,在液固比为20 L/kg条件下,对混凝土样品进行模拟浸出实验;参照欧盟块状材料中无机组分的扩散实验方法(EA NEN7375)测定混凝土样品中重金属的有效释放量。模拟浸出实验结果表明,Cr、Ni和Cd在浸出过程中扩散控制是其释放的主要因素。在此基础上建立了重金属在混凝土路面中的释放模型。实验室实测累积释放量(实测值)与模型预测累积释放量(预测值)的拟合检验结果表明,实测值与预测值之间差异不显著,释放模型能较好地预测混凝土路面中重金属的长期累积释放量。     

Thermogravimetric and XRD study of the effects of chloride salts on the thermal decomposition of mercury compounds

In this paper, the effects of chloride salt (MgCl₂, CaCl₂ or NaCl) addition on the thermal decomposition of five inorganic mercury compounds (HgCl₂, HgS, Hg(NO₃)₂·H₂O, HgO, and HgSO₄) were investigated by thermogravimetric analysis. Mercury-contaminated soil samples collected from Inner Mongolia were used to verify the results. The desorption temperatures of the mercury compounds increased in the following order: HgCl = HgCl₂ < HgS < Hg(NO₃)₂·H₂O < HgO < HgSO₄. Among the chloride salts, MgCl₂ had the greatest effect on thermal desorption of the mercury compounds, with the greatest reduction in the initial temperature of thermal desorption. After MgCl₂ treatment, the mercury removal rates for the soil were 65.67–81.35 % (sample A), 70.74–84.91 % (sample B), and 69.08 % (sample C). The increase in the mercury removal rate for sample C with addition of MgCl₂ was particularly large (34.96–69.08 %). X-Ray diffraction analysis of white crystals from the thermal desorption with MgCl₂ indicated that MgCl₂ promoted conversion of the mercury compounds in the soil to mercury(II) chloride and dimercury dichloride. This transformation is beneficial for applying thermal desorption to remedy mercury-contaminated soils and treat of mercury containing waste.     

土壤粒径及有机质对多溴二苯醚热脱附的影响

在实验室条件下,研究了土壤粒径与土壤有机质含量对多溴二苯醚(PBDEs)热脱附的影响,以期为PBDEs污染土壤热脱附修复提供理论依据。实验结果表明,300℃停留30 min条件下,粒径为<75、75～125、125～250、250～425和425～850μm的土壤中PBDEs去除率分别为49.53%、73.88%、79.39%、83.56%和87.09%,PBDEs总去除率随粒径的增大而增大,土壤BDE209较BDE206、BDE207和BDE208更易于脱除。此外,温度低于450℃时,H2O2氧化部分去除有机质后土壤中PBDEs的去除率较原土高;表明,土壤有机质可能抑制土壤中PBDEs的热脱附。     

pH值对烧结砖中重金属释放的影响

采用酸消解实验和NEN 7371浸出实验研究了烧结砖中重金属总量和有效释放量,采用pH-dependence实验研究pH对破碎烧结砖样品中重金属(Cr、Ni、As、Cd和Pb)浸出特性的影响,以及烧结砖样品的酸碱缓冲容量。结果表明,烧结砖中重金属的有效释放量低于总量,释放率从大到小依次为CdAsPbNiCr;烧结砖的酸缓冲容量较小,浸出液pH从7.03降到3.64,消耗了29.33 mmol/kg硝酸,碱缓冲容量较大,pH从7.03升到12.40,共消耗256 mmol/kg氢氧化钠溶液,因此在使用烧结砖的过程中要特别注意环境pH;浸提液的酸碱性是影响烧结砖中重金属浸出的重要参数,在实验研究的pH范围内,不同重金属的浸出规律不同。Cr和As的释放受pH影响较小,而Ni和Cd的浸出量随pH的增大而降低,Pb的浸出量在强酸和强碱条件下均较大,当pH在5.59~9.86的范围内浸出量很低。     

有机质对污染土壤中DDTs热脱附行为的影响

采用2种不同性质土壤(黑土和棕壤)作为供试土壤,利用DDT农药自配滴滴涕类(DDTs,包括p,p'-DDT、o,p'-DDT、p,p'-DDD、p,p'-DDE)污染土壤.采用热脱附方法,研究了原土及去有机质后土壤中DDTs在300℃,6个停留时间(5、10、20、30、40和50 min)下的去除率以及脱附后土壤中D...     

废旧电视机CRT玻壳中Pb的浸出及豁免处置

采集黑白和彩色废旧电视机的阴极射线管(CRT)玻璃外壳(玻壳),利用X射线荧光分析了其化学组成,并采用浸出毒性浸出方法对玻壳中Pb的浸出进行了研究.结果表明,不同类型的CRT玻壳铅含量(以PbO计)差别较大,彩色CRT屏玻璃最低(0.07%),黑白CRT屏玻璃、锥玻璃次之(2.83%),而彩色CRT锥玻璃最高(22.6...