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931.
Dynamics of arsenic in salt marsh sediments from Dongtan wetland of the Yangtze River estuary, China
The mobility and transformation of arsenic (As) in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were quantified. The microcosm incubation experiments were conducted during the flooding of the sediments to examine As dynamics that occurred during changing redox conditions. The concentrations of dissolved As in pore water (0.04-0.95 μmol/L) were significantly greater than that in surface water (0.03-0.06 μmol/L). Under anoxic conditions, the reactive As could be initially mobilized by the reductive dissolution of Fe(III) (hydr)oxides. Subsequently, most of the dissolved As was likely to be associated with secondary iron (hydr)oxide phases and remained in solid phases. The seasonal variability of acid volatile sulfide concentrations suggest the anoxic conditions are enhanced during summer by Spartina alterniflora compared to Phragmites australis and Scirpus mariqueter, causing a notable increase in As mobility. Generally, there was a typical variation in redox conditions with season in salt marsh sediments of Dongtan wetland, in which the dynamics of As mobility and transformation possibly were controlled by iron, and all of this could be significantly influenced by the rapid spread of S. alterniflora. 相似文献
932.
933.
以Fe(NO3)3为前驱物,制备了水合氧化铁吸附剂样品,以NaOH为解吸剂,研究了样品对模拟废水中磷酸根的吸附和解吸性能。结果表明,水合氧化铁对磷酸根有较好的吸附效果;随着pH的降低,水合氧化铁对磷酸根的吸附能力增强,在pH为2时吸附达92.5%;吸附前15 min吸附速率较快,约150 min达到平衡,吸附动力学曲线符合二级动力学模型;用水合氧化铁对初始浓度为50~100 mg/L模拟含磷废水吸附,随着初始浓度的增大,磷的去除率下降;水合氧化铁对磷酸根的吸附等温线较符合Langmuir吸附模型;用NaOH对水合氧化铁行解吸,浓度为40 g/L有最好的解吸率,60 min时达到解吸平衡。 相似文献
934.
935.
936.
A sequential zero valent iron and aerobic biodegradation treatment system for nitrobenzene 总被引:27,自引:0,他引:27
The remediation of nitroaromatic contaminated groundwater is sometimes difficult because nitroaromatic compounds are resistant to biodegradation and, when they do transform, the degradation of the products may also be incomplete. A simple nitroaromatic compound, nitrobenzene, was chosen to assess the feasibility of an in situ multi-zone treatment system at the laboratory scale. The proposed treatment system consists of a zero valent granular iron zone to reduce nitrobenzene to aniline, followed by a passive oxygen release zone for the aerobic biodegradation of the aniline daughter product using pristine aquifer material from Canadian Forces Base (CFB) Borden, Ontario, as an initial microbial source. In laboratory batch experiments, nitrobenzene was found to reduce quickly in the presence of granular iron forming aniline, which was not further degraded but remained partially sorbed onto the granular iron surface. Aniline was found to be readily biodegraded with little metabolic lag under aerobic conditions using the pristine aquifer material. A sequential column experiment, containing a granular iron reducing zone and an aerobic biodegradation zone, successively degraded nitrobenzene and then aniline to below detection limits (0.5 microM) without any noticeable reduction in hydraulic conductivity from biofouling, or through the formation of precipitates. 相似文献
937.
Fe0-PRB修复地下水硝酸盐污染数值模拟 总被引:1,自引:0,他引:1
基于地下水对流-弥散作用,采用数值分析方法,构建了GMS地下水渗流和硝酸盐污染物迁移三维耦合模型.在污染物迁移过程中,不考虑吸附降解和考虑吸附降解两种工况下,分析了污染物在地下水中的迁移特征.结果表明:地下水和土壤存在天然净化污染物的能力,但不显著,必须采取有效措施控制污染.以零价铁作为PRB墙体介质,并用GMS软件模拟Fe0-PRB修复地下水中硝酸盐的效果.PRB存在时能显著控制污染物的污染范围并降低污染物浓度.PRB厚度为4m时,污染物经过550d开始透过PRB墙,PRB运行10a后,1、2、3号观测井的浓度分别1.712,0.011,0.018mg/L,PRB下游污染羽拖尾明显;PRB厚度为6m时,污染物经过850d开始透过PRB墙,PRB运行10a后,1、2、3号观测井的浓度分别0.52,0.004,0.005mg/L,与4mPRB相比浓度分别降低69.6%、63.6%和72.2%,PRB下游污染羽拖尾仍存在但不明显.污染物迁移数值模拟是评价PRB修复污染地下水效果及确定PRB参数的重要手段. 相似文献
938.
零价铁处理污水的机理及应用 总被引:76,自引:0,他引:76
介绍了零价铁的性质及其处理污水的机理,概述了零价铁在处理含重金属、染料、多氯化合物、生物难降解有机物等废水的应用状况,评述了零价铁处理废水的特点及应用前景。 相似文献
939.
940.
为了解重庆市南部某历史遗留铁矿区周边耕地土壤重金属污染状况及污染来源,在铁矿渣场周边采集了34个耕地表层土壤样品,分析了重金属Cd、Hg、As、Pb、Cr、Cu、Ni和Zn的含量,采用地累积指数和潜在生态风险指数对铁矿渣场周边耕地土壤污染进行评价,并利用主成分分析(PCA)和绝对主成分得分多元线性回归受体模型(APCS-MLR)识别铁矿区周边耕地土壤重金属的污染来源及贡献率.结果表明,研究区土壤除Cr外,其余重金属含量平均值均超过重庆市土壤背景值,且有20.6%的土壤点位Cd以及2.94%的土壤点位Hg、Cu和Ni超过《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB15618-2018)风险筛选值;地累积污染指数评价结果显示研究区土壤主要受Cd和Hg污染,呈现无污染到中度污染等级,并且Cd与Hg对潜在生态污染指数(RI)贡献率分别达到24.47%和60.33%.相关性分析与主成分/绝对主成分(PCA/APCS)受体模型分析结果表明,Cr、Cu、Ni和Zn主要来源于成土母质,Hg和Pb来源主要为化石燃料燃烧及交通运输,Cd和As主要来源于采矿冶炼、施用化肥等采矿工业活动及农业活动... 相似文献