科学家利用植物处理土壤中的砷

美国乔治亚大学的研究人员发明了一种从土壤中去除砷的方法。乔治亚州的科学家们称：砷污染是一个日益严峻的环境问题。科学家们表示：土壤中累积的砷大部分都固定在植物的根系中，这使得对其进行安全处置非常困难。如今，遗传学家Richard Meagher所领导的该研究小组发现了一种将砷从植物根系中转移到叶子中的方法。这对于清理数千个对人类健康构成严重威胁的砷污染场地是个很有效的工具。     

成都地区典型土壤与农作物中砷含量研究

成都地区土壤和农作物中砷污染研究资料不多，本文以成都地区7类典型土壤和该土壤上生长的10余种常见农作物中的砷含量为研究对象，通过对监测数据的整理、分析，应用正态分布、方差分析、线性相关检验等方法对土壤和农作物中砷的分布规律以及两者的关系进行了比较详尽的分析和研究，并对比了国内相关研究结果，说明了成都地区土壤和农作物中砷污染的规律和相关性。     

土壤中痕量砷的调查与研究

通过对6个典型区域和农村主要地区进行调查，共采集具有代表性的土壤样品330个。采用王水体系消解-原子荧光光度法测定土壤样品中砷的含量，结果表明：砷标准样品在10．0-60．0μg·L-1范围内，线性相关系数为0．9995；取0．5g样品消解，方法检出限为0．007mg·kg-1；以20．0μg·L-1的标准溶液连续测量11次，相对标准偏差为0．2％；调查的6个典型区域的180个点位和农村主要土壤耕层的150个土样中，砷含量在1．02-32．87mg·kg-1之间，根据《土壤环境质量标准》（GB15618--1995）三级标准评价，土壤中砷的含量均未超过国家标准。     

环境中砷的分布及其对健康的影响(上)

砷俗称砒,是非金属,但它的毒性及某些性质类似重金属(重金属系比重在5.0以上的金属元素,砷的比重为5.727),所以往往将砷列入重金属范围内加以论述。砷具有两性元素特性,非金属性更强些,故称之为类金属。砷是地壳的组成成分,其含量为2～5ppm,在构成地壳的各种元素中居第20位。在人类环境中砷以5价和3价态遍布于土壤、水、空气、食物中,它通过食物链进入动、植物中,     

农村建设用地拆旧复垦土壤重金属含量分析

文章选取了化州市丽岗镇、林尘镇、新安镇各5个拆旧复垦地块进行土壤重金属镉、汞、砷、铅、铬检测分析，分析结果表明，复垦地块的重金属含量均未超过《土壤环境质量农用地土壤污染风险管制标准（试行）》（GB 15618—2018）中的农用地污染风险管制值；丽岗镇和林尘镇同一乡镇的不同复垦地块的土壤重金属含量基本一致，新安镇差异较大；土壤砷分布具有区域性。     

磁性粉煤灰对磷吸附特性的影响

在含磁性物质（Fe、Co、Ni）的介质中，加入适量的化肥和其它添加物质，经一定磁场强度磁化后制成的具有剩磁和矫顽力的新型肥料，定名为磁化肥料，现已获得国家发明专利。目前提供大量磁性物质的主要载体是火力发电厂排放的粉煤灰。粉煤灰和磁性粉煤灰对主要农作物的增产效果和对土壤的理化性质的影响有不少报道［‘－‘1，但对磷吸附特性的影响则未见报道。因此，我们应用tang－muir等温吸附方程研究了粉煤灰和磁性粉煤灰（并与江汉平原主要土壤黄棕壤、潮土作对照比较）对磷酸盐的吸附特性，探讨了粉煤灰和磷酸根离子之间的相互作用，…     

黄河上游水体中砷的来源及迁移初探

在对黄河上游水体及沿岸表层土壤、底泥中的砷进行监测分析的基础上,对水体中砷的来源、迁移过程进行了初步探索。结果表明:黄河上游沿岸土壤中砷的含量偏高,水体中的砷来源于沿岸的土壤。     

磷石膏和废硫酸是有效的土壤改良剂

在硫酸烷化和精制磷酸等化工生产过程中,分别产生大量废硫酸和磷石膏废弃物,造成对环境的污染和危害。试验证明,这两种化工废弃物是盐碱地土壤的有效改良剂。存实验室条件下,磷石膏和废硫酸(2%溶液)对含盐量2。39%(其中对植物有毒害作用的盐分占2.09%)的土壤,分别按20t/ha 和15t/ha的用量都能把土壤淡化到毒性阈以下,即分别使含盐量下降到0.476%和0.287%。在大田条件下,用2%     

砷污染稻作区发展旱稻控制稻米砷暴露风险探讨

农田砷污染是我国中南、西南稻作区面临的重要环境问题之一。水稻淹水种植条件下,土壤砷的溶解度较高,其移动性和生物有效性较大,水稻根系易吸收并向地上部转移砷。而在非淹水富氧条件下,土壤砷的移动性、生物有效性及稻米砷累积量显著降低。本文在综述水分管理影响水稻砷吸收基础上,提出：砷污染稻作区可通过水改旱、发展旱稻种植,显著降低土壤砷的生物有效性;在非淹水种植、降低土壤砷活性基础上,可通过筛选砷低吸收基因型旱稻,进一步控制水稻砷吸收和稻米砷累积,实现砷污染稻作区农产品质量安全保障与水危机缓解的双赢。目前,关于旱稻对砷的胁迫响应及对砷的吸收、转运与代谢研究鲜见报道,无疑,相关工作值得深入开展。     

城市污水污泥资源化利用研究

为确定城市污水的污泥在农用过程中是否存在重金属毒害，文章系统研究了西宁城市污水的污泥中重金属特征。研究表明：①西宁城市污水的污泥中重金属含量较我国其他城市略低；②EDTA（乙二胺四乙酸）提取污泥时，重金属的提取率在18％-55％，这部分重金属有可能被植物吸收。③污泥中所含的有机质、氮、磷、钾微量元素及土壤改良剂（有机腐殖质）等成分可以改善土壤结构，提高土壤的肥力。     

砷污染危害及其治理技术

综合分析了砷的污染途径以及对人类和环境的危害,并对砷污染的治理方法进行了阐述。提出了砷污染治理的一些看法     

活性污泥法处理含砷废水初探

文章概述了含砷废水的产生及其处理方法，重点介绍了国内外研究报道较少的活性污泥法，以引起人们对这一有效除砷方法的重视。通过总结活性污泥法除砷的研究进展，探讨了活性污泥除砷的机理和影响因素，并提出今后要从活性污泥法除砷的机理、除砷工艺、及含砷废渣处理三方面开展研究，以促进该方法的应用。     

Controlling the fate of roxarsone and inorganic arsenic in poultry litter

A growing body of literature reports 3-nitro-4-hydroxyphenylarsonic acid (roxarsone) degradation in poultry litter (PL) to the more toxic inorganic arsenic (As). Aluminum-based drinking-water treatment residuals (WTR) present a low-cost amendment technology to reduce As availability in PL, similar to the use of alum to reduce phosphorus availability. Batch experiments investigated the effectiveness of WTR in removing roxarsone and inorganic As species from PL aqueous suspensions. Incubation experiments with WTR-amended PL evaluated the effects of WTR application rates (2.5-15% by weight) and incubation time (up to 32 d) at two incubation temperatures (23 and 35 degrees C) on As availability in PL. Batch PL aqueous experiments showed the high affinity of As(V), As(III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and roxarsone for the WTR. The 10% WTR amendment rate decreased As availability in PL by half of that of the unamended (no WTR) PL-incubated samples. The reduction in dissolved As concentrations during incubation of WTR-amended PL samples was kinetically limited, being complete within 13 d. Parallel reductions in roxarsone, As(V), and DMA concentrations were observed with liquid chromatography-inductively coupled plasma mass spectrometry, whereas As(III) and MMA concentrations were always <5% of dissolved As. Incubation temperature did not significantly (p > 0.05) influence dissolved As concentrations in the WTR-amended PL. Potential formation of a copper-containing roxarsone metabolite was considered in PL aqueous suspensions with the aid of electrospray mass spectrometry. Further experiments in the field are necessary to ensure that sorbed As is stable in WTR-amended PL.     

磷的沉积物-水界面反应

本文对磷在水中和沉积物中的赋存状态进行了简单介绍;对磷在沉积物-水界面的反应机制作了详细的介绍;且认为有必要对磷进行更深入地研究.     

Biological filtration for removal of arsenic from drinking water

The main objective of the study was to find a suitable iron to arsenic ratio in water to reduce arsenic to 5 μg/L or lower through sand filtration. Experiments were conducted by varying the quantity of iron(II) while keeping the arsenic concentration at 100 μg/L. A mixture of iron (II) and arsenic at different ratios (10:1, 20:1, 30:1 and 40:1) was pumped to the sand filters in a down flow mode and effluent arsenic and iron were analyzed. It was found that a ratio of iron to arsenic of 40:1 was necessary to ensure an effluent arsenic concentration of 5 μg/L or lower. Iron in the filtrate was found to be below 0.1 mg/L at all times.     

Arsenic and chromium removal by mixed magnetite–maghemite nanoparticles and the effect of phosphate on removal

Adsorption of arsenic and chromium by mixed magnetite and maghemite nanoparticles from aqueous solution is a promising technology. In the present batch experimental study, a commercially grade nano-size ‘magnetite’, later identified in laboratory characterization to be mixed magnetite–maghemite nanoparticles, was used in the uptake of arsenic and chromium from different water samples. The intent was to identify or develop a practical method for future groundwater remediation. The results of the study showed 96–99% arsenic and chromium uptake under controlled pH conditions. The maximum arsenic adsorption occurred at pH 2 with values of 3.69 mg/g for arsenic(III) and 3.71 mg/g for arsenic(V) when the initial concentration was kept at 1.5 mg/L for both arsenic species, while chromium(VI) concentration was 2.4 mg/g at pH 2 with an initial chromium(VI) concentration of 1 mg/L. Thus magnetite–maghemite nanoparticles can readily adsorb arsenic and chromium in an acidic pH range. Redox potential and pH data helped to infer possible dominating species and oxidation states of arsenic and chromium in solution. The results also showed the limitation of arsenic and chromium uptake by the nano-size magnetite–maghemite mixture in the presence of a competing anion such as phosphate. At a fixed adsorbent concentration of 0.4 g/L, arsenic and chromium uptake decreased with increasing phosphate concentration. Nano-size magnetite–maghemite mixed particles adsorbed less than 50% arsenic from synthetic water containing more than 3 mg/L phosphate and 1.2 mg/L of initial arsenic concentration, and less than 50% chromium from synthetic water containing more than 5 mg/L phosphate and 1.0 mg/L of chromium(VI). In natural groundwater containing more than 5 mg/L phosphate and 1.13 mg/L of arsenic, less than 60% arsenic uptake was achieved. In this case, it is anticipated that an optimum design with magnetite–maghemite nanoparticles may achieve high arsenic uptake in field applications.     

The opportunity cost of regulating phosphorus from broiler production in the Illinois River Basin

The Illinois River Basin in eastern Oklahoma and northwest Arkansas is an example of a region where significant growth in poultry production has been accompanied by water quality problems. The primary concern in the basin is the problem of phosphorus in runoff that is associated with application of litter to crops. Existing data suggest that there has been a continuing decline in the quality of water in the Illinois River, and discussions have focused on developing and implementing a phosphorus standard. The specific objectives of this study are to estimate the reduction in poultry production necessary to achieve the reduction in phosphorus runoff under a set of phosphorus constraints, including soil test phosphorus, and to estimate the opportunity costs of reducing poultry production in the basin under each phosphorus constraint on the economic activity in the watershed. A mathematical programming model that incorporates poultry production and cropping decisions is developed. The parameters for the model are identified and then it is solved to provide a base solution. Model solutions are then developed for the different policy target levels of phosphorus. The model structure is modified to account for the presence of soil test phosphorus levels and the corresponding limits on soil test phosphorus throughout the basin. This formulation includes current soil test phosphorus throughout the basin. All of the applications assume that the only disposal option for poultry litter is land application within the basin. An economic impact assessment of the effects of phosphorus limitations in the basin is also conducted for Arkansas counties only, Oklahoma counties only, and all five affected counties combined.     

Concentrations of additive arsenic in Beijing pig feeds and the residues in pig manure

The swine industry in China has grown rapidly over last two decades. Great amount of pig manure is generated in China, which can be used as organic fertilizers on agricultural lands. Meanwhile, the organic arsenic compounds have been used as feed additives for swine disease control and weight improvement. Once the excessive additives are released in the environment, arsenic may compromise food safety and environmental quality. There is a growing public concern about the arsenic residues accumulation in pig manure, however, little work has been done to investigate the exact arsenic content in pig feed and the residues in manure in China This study investigates the concentrations of arsenic in 29 pig feed samples and 29 manure samples collected from eight pig farms in the Chaoyang district, Beijing city. The detected rate of arsenic in 29 couples of samples was 100%. The concentrations of arsenic in pig feeds and manures ranged from 0.15 to 37.8 mg/kg and 0.42 to 119.0 mg/kg, respectively. The result showed that arsenic concentration in pig manure will be greatly elevated when the arsenic in pig feed was largely increased. The loading rates of pig manure in fourteen Beijing counties and districts were in the range of 2.7–57.2 t/ha yr. Accordingly, the potential soil arsenic increase rates resulting from land application of pig manure might range between 11.8 and 78.9 μg/kg yr. Despite these findings, it is too early to draw the conclusion that arsenic pollution from pig manure is serious in Beijing farmland; therefore, longitudinal studies about the chemical form transformation and the environmental behaviors of pig manure arsenic are required in order to come up with more definitive conclusions.     

Sorption of arsenic from soil-washing leachate by surfactant-modified zeolite

Post-treatment of leachate from soil-washing remedial actions may be necessary depending on the amounts of dissolved contaminants present. Uptake of arsenic species by surfactant-modified zeolite (SMZ) from a synthetic soil leachate (pH of approximately 12 [NaOH]) was measured as a test of SMZ as a post-treatment sorbent. Batch sorption isotherms were prepared using leachate to SMZ ratios from 40:1 to 4:1, and temperatures of 25 and 15 degrees C. Equilibrium levels of dissolved and total solution arsenic were similar. At each temperature, sorption appeared to reach a plateau or maximum, then decreased at the highest solution concentration, corresponding to the lowest amount of zeolite added (2.5 g). A maximum sorption value of 72.0 mmol of arsenic per kg of SMZ (5400 mg/kg) was observed at 25 degrees C, and 42.1 mmol/kg (3150 mg/kg) at 15 degrees C. Total arsenic recoveries varied from 74 to 125%. Surfactant-modified zeolite removed up to 97% of dissolved organic carbon and decolorized the leachate solutions. Excluding the points for the highest arsenic to SMZ ratio, the sorption isotherms were well described by the linearized form of the Langmuir equation, with coefficients of determination greater than 0.90 at both temperatures. Sorption of arsenic by SMZ is attributed to anion exchange with counterions on the surfactant head groups, and/or partitioning of organic carbon-complexed arsenic into the surfactant bilayer.     

Iron and aluminium based adsorption strategies for removing arsenic from water

Arsenic is a commonly occurring toxic metal in natural systems and is the root cause of many diseases and disorders. Occurrence of arsenic contaminated water is reported from several countries all over the world. A great deal of research over recent decades has been motivated by the requirement to lower the concentration of arsenic in drinking water and the need to develop low cost techniques which can be widely applied for arsenic removal from contaminated water. This review briefly presents iron and aluminium based adsorbents for arsenic removal. Studies carried out on oxidation of arsenic(III) to arsenic(V) employing various oxidising agents to facilitate arsenic removal are briefly mentioned. Effects of competing ions, As:Fe ratios, arsenic(V) vs. arsenic(III) removal using ferrihydrite as the adsorbent have been discussed. Recent efforts made for investigating arsenic adsorption on iron hydroxides/oxyhydroxides/oxides such as granular ferric hydroxide, goethite, akaganeite, magnetite and haematite have been reviewed. The adsorption behaviours of activated alumina, gibbsite, bauxite, activated bauxite, layered double hydroxides are discussed. Point-of-use adsorptive remediation methods indicate that Sono Arsenic filter and Kanchan™ Arsenic filter are in operation at various locations of Bangladesh and Nepal. The relative merits and demerits of such filters have been discussed. Evaluation of kits used for at-site arsenic estimation by various researchers also forms a part of this review.