冶炼厂周边区域夏季大气Cu和Cd沉降特征

为了解贵溪冶炼厂周边农田区域夏季大气重金属沉降状况,于2012年6—8月及2013年6—8月(夏季),设置8个监测点,共收集大气干湿混合样品48个,采用原子吸收分光光度法分析了Cu、Cd。结果发现,冶炼厂周边区域2012年夏季Cu、Cd沉降通量分别为42.5~421、1.01~5.06 mg/m2,平均值149、2.02 mg/m2;2013年夏季Cu、Cd沉降通量分别为40.6~94.3、0.12~0.44 mg/m2,平均值59.4、0.26 mg/m2。同1月份不同监测点Cu、Cd沉降量存在一定差异性,风向为造成该差异性的主要气象因素;不同监测点Cu、Cd月沉降通量与风向频率均具有显著相关性(r均大于0.60)。降雨量影响Cu、Cd月沉降量,Cu、Cd平均月沉降量与降雨量均呈显著相关关系(r=0.91、r=0.87,P0.05)。     

利用自动采样滤膜监测PM_(2.5)中铅和镉的可行性

根据PM2.5中重金属监测国标分析方法,从PM2.5采样方法、采样保存条件、滤膜材质性能等方面说明利用空气自动采样滤膜监测PM2.5中铅和镉是可行的;对手工采样(石英滤膜)和Beta射线法自动采样(自动采样滤膜)2种方法,对PM2.5实际样品中铅和镉的结果进行比较,结果显示:自动采样滤膜的空白检出和检出限均满足铅和镉的监测需求,铅和镉的回收率分别为95.2%~107%和91.8%~105%,与手工采样方法相比测得铅和镉的相对误差分别为3.6%~8.4%和1.3%~10.8%,从实践角度进一步证明了利用自动采样滤膜对PM2.5中铅和镉进行监测是可行的。     

Cadmium removal mechanistic comparison of three Fe-based nanomaterials: Water-chemistry and roles of Fe dissolution

● nZVI, S-nZVI, and nFeS were systematically compared for Cd(II) removal. ● Cd(II) removal by nZVI involved coprecipitation, complexation, and reduction. ● The predominant reaction for Cd(II) removal by S-nZVI and nFeS was replacement. ● A simple pseudo-second-order kinetic can adequately fit Fe(II) dissolution. Cadmium (Cd) is a common toxic heavy metal in the environment. Taking Cd(II) as a target contaminant, we systematically compared the performances of three Fe-based nanomaterials (nano zero valent iron, nZVI; sulfidated nZVI, S-nZVI; and nano FeS, nFeS) for Cd immobilization under anaerobic conditions. Effects of nanomaterials doses, initial pH, co-existing ions, and humic acid (HA) were examined. Under identical conditions, at varied doses or initial pH, Cd(II) removal by three materials followed the order of S-nZVI > nFeS > nZVI. At pH 6, the Cd(II) removal within 24 hours for S-nZVI, nFeS, and nZVI (dose of 20 mg/L) were 93.50%, 89.12% and 4.10%, respectively. The fast initial reaction rate of nZVI did not lead to a high removal capacity. The Cd removal was slightly impacted or even improved with co-existing ions (at 50 mg/L or 200 mg/L) or HA (at 2 mg/L or 20 mg/L). Characterization results revealed that nZVI immobilized Cd through coprecipitation, surface complexation, and reduction, whereas the mechanisms for sulfidated materials involved replacement, coprecipitation, and surface complexation, with replacement as the predominant reaction. A strong linear correlation between Cd(II) removal and Fe(II) dissolution was observed, and we proposed a novel pseudo-second-order kinetic model to simulate Fe(II) dissolution.     

德阳市农用地土壤中镉的分布特征及异常来源分析

通过龙门山区域的德阳市6个县市农用地土壤中镉的采样监测,分析了该区域镉的分布特征及区域分异原因,并对其环境生态风险进行了评价。结果表明,德阳市农用地土壤中镉含量总体水平为0.11~4.68 mg/kg,呈现西北到东南逐渐降低的分布特征;西北部绵竹和什邡市农用地土壤中镉出现超标的范围较广,2个城市约62.5%的监测点土壤中镉出现超标,且绵竹市农用地土壤中镉超标程度和生态风险程度最重,绵竹地区约25%的监测点土壤中镉出现了轻中度超标;监测区域土壤中镉出现较重生态风险点共有4个,均出现在绵竹;但较高含量的镉在该区域并非大范围连片存在;区域农用地土壤中镉异常的来源主要为龙门山中段的地质背景和部分以矿石为原料企业的综合影响。     

再生铅企业土壤-地下水中重金属污染迁移特征

为了解某再生铅企业厂区土壤和浅层地下水重金属污染状况,采集了96个土壤样品和4个地下水样品,定量分析了其Pb,Cd,As的含量及空间分布特征,探讨企业生产对环境造成的影响。结果表明,该区域土壤中Cd、As、Pb超标率分别为67.0%,35.1%,11.7%,在厂区呈现局部富集现象,最大值是土壤背景值的几十倍乃至数千倍;在垂直方向上由于Pb,Cd,As在土壤中迁移率较低,其值随深度增加呈总体下降趋势;该区域地下水中Pb,Cd,As值远低于地下水质量标准值。