硅肥对农田镉轻度污染水稻修复效果的研究

为探讨硅肥对农田土壤Cd污染的修复效果,在田间试验条件下,研究了不同硅肥处理对Cd轻度污染农田水稻的修复效果。结果表明:不同硅肥处理可以降低Cd轻度污染农田中水稻糙米Cd含量,降幅为2.02%~16.00%,提高土壤pH值0.36~0.45,降低土壤有效态Cd含量,降幅为34.88%~45.47%,水稻产量增加3.63%~6.23%,基施与叶面喷施联合施用硅肥对农田土壤Cd污染的修复效果最好。     

Ion adsorption components in liquid/solid systems

Experiments on Zn^2＋ and Cd^2＋ adsorptions on vermiculite in aqueous solutions were conducted to investigate the widely observed adsorbent concentration effect on the traditionally defined adsorption isotherm in the adsorbate range 25--500 mg/L and adsorbent range 10--150 g/L. The results showed that the equilibrium ion adsorption density did not correspond to a unique equilibrium ion concentration in liquid phase. Three adsorbate/adsorbent ratios, the equilibrium adsorption density, the ratio of equilibrium adsorbate concentration in liquid phase to adsorbent concentration, and the ratio of initial adsorbate concentration to adsorbent concentration, were found to be related with unique values in the tested range. Based on the assumption that the equilibrium state of a liquid/solid adsorption system is determined by four mutually related components： adsorbate in liquid phase, adsorbate in solid phase, uncovered adsorption site and covered adsorption site, and that the equilibrium chemical potentials of these components should be equalized, a new model was presented for describing ion adsorption isotherm in liquid/solid systems. The proposed model fit well the experimental data obtained from the examined samples.     

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。     

镇江地区土壤样品中重金属Cd含量与空间分布

通过对镇江地区土壤样品中 Cd 监测结果统计分析表明,全市69个样品中 Cd 质量比范围为0．06 mg/kg ～1．37 mg/kg,均值为0．23 mg/kg,与全国背景值相比,有一定程度富集;样品中 Cd 质量比成偏态分布,相对标准偏差较大。选用单项污染指数法对 Cd污染程度评价表明,镇江地区83％的土壤样品未受到 Cd 污染,14％为轻度污染,3％为中度污染。结合镇江地区的产业结构分析,电镀行业是土壤 Cd 污染的主要来源,道路运输、农药化肥在一定程度上也加重了污染。     

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)。     

施工扬尘环境下短时强降雨屋面径流中砷、汞、铅、镉、锌的污染特征研究

以南京北郊为例,测量分析了屋面径流中砷(As)、汞(Hg)、铅(Pb)、镉(Cd)和锌(Zn)5种元素的浓度、形态特征。结果表明:短时强降雨过程中这5种元素浓度在较大范围内无规则波动,且不同元素间浓度分布存在较大差异;Zn与Pb的平均浓度分别高于《地表水环境质量标准》(GB 3838—2002)的Ⅴ类和Ⅳ类标准限值,污染程度从大到小依次为ZnPbAsHgCd。元素形态分析表明,径流中除Hg外其他4种元素主要以颗粒态形式存在,各元素颗粒态占总形态的平均分数分别为:As,64.5%;Hg,43.7%;Pb,76.5%;Cd,54.6%;Zn,54.3%。     

东北地区污染黑土中重金属与有机质的关联作用

通过对东北地区污染农田黑土剖面的取样调查,对重金属Cd,Pb,Cu,Zn在农田黑土中不同采样点的全量、有效态和有机质结合态的分布特征及其与有机质的关系进行了研究,并分析了土壤有机质对重金属有机质结合态的影响.结果表明,Pb以有机质结合态存在的量较大,能与有机质形成较多的络合物,而Zn的有机质结合态占全量的比例相对较小,Cd和Cu有机质结合态占全量的比例处于Pb和Zn之间.由于外源污染的影响,土壤有机质含量与重金属有机质结合态相关性并不显著.由于土壤样品的不同解离功能团结合重金属的能力不同,采样区的重金属有机质结合态未表现出明显的分布规律.      

无患子皂苷与柠檬酸协同洗脱污染土壤中镉铅

以某废弃铅锌矿区重金属污染土壤为研究对象,采用无患子皂苷与柠檬酸(CA)协同洗脱污染土壤中的Cd和Pb.以无患子果皮投加量为20 g/L所得水浸提液和浓度为0.3 mol/L的CA配制复配淋洗剂.在浸提液中添加CA后,能有效提高对土壤中Pb的去除率.在浸提液和CA的体积比为1:3、淋洗剂pH为5、淋洗时间为12.0 h...     

南广河水体中砷镉铅铬含量分布特征及质量探讨

本文对南广河水体中的砷镉铅铬含量分布特征进行了描述,并探讨了南广河的水质质量。结果表明：南广河从上游到下游水体中污染物含量为增大趋势;在时间上也存在一定的变化,枯水期水体中污染物含量高于平水期和丰水期。目前南广河综合水质质量可满足Ⅱ类水质标准要求。     

Interactive effects of cadmium and hypoxia on metabolic responses and bacterial loads of eastern oysters Crassostrea virginica Gmelin

Pollution by toxic metals including cadmium (Cd) and hypoxia are important stressors in estuaries and coastal waters which may interactively affect sessile benthic organisms, such as oysters. We studied metabolic responses to prolonged hypoxic acclimation (2 weeks at 5% O₂) in control and Cd-exposed (30 d at 50 μg L⁻¹ Cd) oysters Crassostrea virginica, and analyzed the effects of these stressors on abundance of Vibrio spp. in oysters. Hypoxia-acclimated oysters retained normal standard metabolic rates (SMR) at 5% O₂, in contrast to a decline of SMR observed during acute hypoxia. However, oysters spent more time actively ventilating in hypoxia than normoxia resulting in enhanced Cd uptake and 2.7-fold higher tissue Cd burdens in hypoxia. Cd exposure led to a significant decrease in tissue glycogen stores, increase in free glucose levels and elevated activity of glycolytic enzymes (hexokinase and aldolase) indicating a greater dependence on carbohydrate catabolism. A compensatory increase in activities of two key mitochondrial enzymes (citrate synthase and cytochrome c oxidase) was found during prolonged hypoxia in control oysters but suppressed in Cd-exposed ones. Cd exposure also resulted in a significant increase in abundance of Vibrio parahaemolyticus and Vibrio vulnificus levels during normoxia and hypoxia, respectively. Overall, Cd- and hypoxia-induced changes in metabolic profile, Cd accumulation and bacterial flora of oysters indicate that these stressors can synergistically impact energy homeostasis, performance and survival of oysters in polluted estuaries and have significant consequences for transfer of Cd and bacterial pathogens to the higher levels of the food chain.