Immobilization of arsenic in soils by stabilized nanoscale zero-valent iron, iron sulfide (FeS), and magnetite (Fe3O4) particles

Arsenic is a widespread contaminant in soils and groundwater. While various iron-based materials have been studied for immobilizing arsenic in contaminated soils, the feasibility of stabilized iron-based nanoparticles has not been reported. This study investigates the effectiveness of using three types of starch-stabilized iron-based nanoparticles, including zero-valent iron (ZVI), iron sulfide (FeS), and magnetite (Fe₃O₄), for immobilization of arsenic in two representative As-contaminated soils (an orchard soil and a fire range soil). To test the effect of the nanoparticles on the arsenic leachability, As-contaminated soils were amended with the nanoparticles at various Fe/As molar ratios (5:1–100:1) and contact time (3 and 7 d). After three days’ treatments of a field-contaminated sandy soil, the PBET-based bioaccessibility of As decreased from an initial (71.3±3.1)% (mean±SD) to (30.9±3.2)% with ZVI, (37.6±1.2)% with FeS, and (29.8± 3.1)% with Fe₃O₄ at an Fe/As molar ratio of 100:1. The TCLP-based leachability of arsenic in a spiked fire range soil decreased from an initial (0.51±0.11)% to (0.24±0.03)%, (0.27±0.04)% and (0.17±0.04)% by ZVI, FeS, and Fe₃O₄ nanoparticles, respectively. The Fe₃O₄ nanoparticles appeared to be more effective (5% or more) than other nanoparticles for immobilizing arsenic. When the two soils were compared, the treatment is more effective on the orchard soil that has a lower iron content and higher initial leachability than on the range soil that already has a high iron content. These results suggest that these innocuous iron-based nanoparticles may serve as effective media for immobilization of As in iron-deficient soils, sediments or solid wastes.     

Variability and reduction of atmospheric pollutants in Beijing and its surrounding area during the Beijing 2008 Olympic Games

The Beijing-Tianjin-Hebei Atmospheric Environment Monitoring Network was established by the Institute of Atmospheric Physics, Chinese Academy of Sciences. The goals of the network were to monitor and provide warnings of the atmospheric quality in Beijing and its surrounding area during the Beijing 2008 Olympic Games. The results showed that the atmospheric complex pollution exhibited high concentrations of ozone and fine particles and oxidation in summer, with a ubiquitous regional source. The regional mean concentrations of SO₂, PM_2.5, NO₂, and O_{3_8h max} (the maximum daily 8 h mean) and O_x were 22±11, 90±40, 25±5, 136±35 and 112±21 μg/m³ in summer, respectively. During the Olympic Games, the mean concentration of SO₂, PM_2.5, NO_{2, O3_8h} max, and O_x were 12.5±4, 56±28, 23±4, 114±29, 95±17 μg/m³ in the region, respectively, and fell by 51.0%, 43.7%, 13%, 20.2%, and 18.9%, respectively, compared to the prophase mean before the Olympic Games. The concentration of atmospheric pollutants declined significantly and achieved the “Green Olympics” control goal of air quality. After the Olympic Games, SO₂, PM_2.5 and NO_x increased significantly as the temporary atmospheric pollution control measures were terminated.     

复合污染重金属在水稻不同部位的积累转运

通过在广东大宝山矿区Fe、Cu、Zn、Pb、As和Cd复合污染土壤中进行大田试验,研究了6种金属元素在杂交稻、常规稻和糯稻3个水稻品系(共21个水稻品种)的稻米、谷壳、稻草、根、铁膜以及根系各部位的积累转运规律。结果表明,6种供试金属元素在水稻体内含量均为地下部(根系)地上部。水稻各部位金属含量指标中,大部分指标品系间含量差异极显著(P0.01)。常规稻和糯稻稻米对Fe、Cu、Zn、Pb和Cd的积累能力均高于杂交稻,但杂交稻稻米对As的积累能力高于其它两个品系。在Fe、Cu、Zn、Pb和Cd污染土壤中较适宜种植杂交稻;在As污染土壤则较适宜种植糯稻。Zn、Pb和As在水稻不同部位的富集系数均为根系稻草谷壳稻米;Fe、Cu和Cd的富集系数均为根系稻草稻米谷壳。除Cu外,其余5种金属元素Fe、Zn、Pb、As和Cd在铁膜的富集系数均高于根部。铁膜对不同金属的富集能力不同,排序为CdAsFeZnPbCu。     

芹菜根对模拟复合污染湿地中芘的降解作用

以吴淞口复合污染湿地土壤为研究背景, 在含有芘、柴油、Pb 的模拟复合污染湿地土壤环境中, 选取对芘具有高效降解作用的芹菜根, 研究芹菜根对复合污染湿地土壤进行生态修复的作用效果及特征. 检测分析了单一与复合污染土壤中多酚氧化酶(polyphenol oxidase, PPO)、过氧化氢酶(catalase, CAT)、脲酶(urease, URE)及不同实验组中芘的降解效果随时间的变化规律. 研究表明, 在芘、Pb、柴油复合污染胁迫下, 芹菜根可以通过根系分泌酶等一些化学物质或者通过刺激其根际微生物细胞分泌各种酶类物质, 来提高其根际微生物的活性, 促进芹菜根与其根际微生物的协同作用, 增强对复合污染土壤中芘的降解效果.     

集群污染源颗粒物允许排放量调控

 以包钢工业园区采暖期颗粒物排放清单为基础,利用CALPUFF大气扩散模型进行集群污染源允许排放量动态调控,其模拟调控结果可为污染物排放控制对策、措施的制定提供一定的理论指导,有助于实现包钢工业园区大气环境稳定达标.模拟结果表明,集群污染源单位排污量对控制点浓度贡献随着污染源高度的增加而降低,低矮点源和面源应作为控制重点.在采暖期气象条件不利于污染物扩散的条件下,集群污染源最大允许排放量减少到现有排放量的8.82%,而在气象条件有利于污染物扩散的条件下,其最大允许排放量减少到现有排放量的12.03%,可以实现控制区大气环境质量达标.     

城市二氧化硫污染传播模型和绿化的效益分析

随着社会经济的高速发展,城市空气质量问题也日益凸显,如何平衡城市建设与保护环境已成为城市规划中必须考虑的重要问题.该文探讨了二氧化硫污染与城市绿化建设的定量关系.首先对空气中二氧化硫的排放、浓度以及传播方式进行了相对准确的描述,建立了两城市之间空气二氧化硫污染相互影响的模型,分析了城市绿化的效益,提出了城市绿化设计的优化算法,最后给出了二氧化硫污染模型的应用及绿化建议.该模型同样适合对其他空气污染物的描述.     

三氯乙烯和四氯乙烯在土壤和地下水中的污染及修复技术

 三氯乙烯和四氯乙烯在工农业生产中被广泛使用,由于其不合理的处置和相对持久性特征,使其成为地下水和土壤中分布最为广泛的污染物之一。因其具有挥发性、毒性和致癌性,受到了国内外的广泛关注。通过查阅国内外资料,本文较为系统地总结了三氯乙烯和四氯乙烯污染的来源、危害和污染现状,述评了修复三氯乙烯和四氯乙烯污染的物理方法、化学方法和生物方法,其中物理方法包括曝气法和活性炭吸附法等,化学方法包括化学氧化法和化学还原法等,生物方法包括微生物修复技术和植物修复技术。同时对三氯乙烯和四氯乙烯的污染修复技术的发展趋势进行了展望,认为微生物修复技术、纳米双金属颗粒技术和光催化氧化技术具有很好的应用前景,建议加强这三项技术的研究和应用。     

我国土壤重金属污染状况及其防治对策

针对如何有效防治土壤重金属污染问题,通过文献资料法,在综述污染现状、来源、挑战的基础上,根据我国实际,提出四点对策.一是加快立法,完善制度,依法治理;二是弄清底数,强化预防,分类管控;三是协同管理,科学治理,强化责任;四是加强监督,公众参与,社会共治.     

重金属镉、铅胁迫下湿地植物丁香蓼的生理生化特征研究

为了研究乡土湿地植物对重金属污染的生理响应特征,并以此作为乡土植物修复湿地土壤重金属污染的可行性依据,以分布于乐安河上游重金属污染区域的优势湿地植物丁香蓼(Ludwigia prostrata)为研究对象,采用土培实验,设置不同浓度重金属镉、铅及其复合污染胁迫处理各盆栽中的土壤,经历2个不同培养周期后,分别测定不同重金属污染胁迫下丁香蓼的生长状况、叶绿素含量、抗氧化酶活性等指标.研究结果表明:Cd、Pb单因素污染或其复合污染均能抑制丁香蓼的生长,且抑制作用随着各污染物浓度的增加而增强; 无论是Cd、Pb单因素或其双因素污染物对丁香蓼的胁迫均呈显著负相关; 丁香蓼叶片的叶绿素a、b及叶绿素a+b的含量则随着重金属污染物胁迫浓度的增加而呈下降趋势; 重金属Cd、Pb的单因素污染或其复合污染对丁香蓼叶片的超氧化物歧化酶(Superoxide Dismutase,SOD)活性的影响表现出不同的趋势.