微生物铁氧化作用对砷迁移转化的影响

采用厌氧培养的方法,从砷污染的水稻上中富集依赖硝酸盐的铁氧化菌群,通过监测培养体系中Fe和A$的形态变化模拟水稻厌氧条件下微生物铁氧化过程对As迁移转化的影响.结果表明,约96%外源添加的Fe(Ⅱ)可在10d内氧化成Fe(Ⅲ),As(Ⅲ)对Fe(Ⅱ)的初期氧化速率具有一定的抑制作用;在微生物铁氧化过程中,As(Ⅲ)被氧...     

共生细菌对盐生小球藻亚砷酸盐代谢的影响

为探讨共生细菌对盐生小球藻（Chlorella salina）亚砷酸盐（As（III））富集和形态转化的影响,从C.salina培养液中分离培养出一株共生细菌,并采用抗生素处理C.salina获得无菌藻,设置0,75,150,300,750 μg/LAs（III）溶液处理带菌和无菌的C.salina,7d后测定C.salina对As（III）的吸收、吸附和富集量,以及培养液和藻细胞内As的形态,计算带菌和无菌C.salina对As（III）的氧化率和去除率;使用不同浓度的As（III）处理共生细菌7d,并以300μg/L的As（III）处理共生细菌不同时间,计算两种情况下共生细菌对培养液中As（III）的氧化率和去除率.结果表明：C.salina的共生细菌为根癌农杆菌（Agrobacterium tumefaciens WB-1）;与无菌C.salina相比,带菌C.salina生长更快、对As（III）的耐性更强.带菌C.salina对As（III）的富集量为103.10~448.12mg/kg、氧化率为78.93%~96.88%、去除率为18.92%~55.21%,显著高于无菌C.salina的富集量（11.68~91.39mg/kg）、氧化率（14.46%~26.39%）和去除率（12.82%~29.15%）,也高于A.tumefaciens WB-1对As（III）的氧化率（4.51%~30.61%）和去除率（1.86%~16.19%）.此外,带菌C.salina胞内还检测到少量的As（III）和甲基砷,而在无菌C.salina胞内没有甲基砷存在.共生细菌促进了盐生小球藻对As（III）的富集和形态转化.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.     

Anaerobic oxidation of arsenite by bioreduced nontronite

The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay minerals are commonly found in soils and sediments, which are an important host for arsenic. However, limited information is known about the redox reactions between arsenic and structural Fe in clay minerals. In this study, the redox reactions between As(III)/As(V) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments. No oxidation of As(III) was observed by the native Fe(III)-NAu-2. Interestingly, anaerobic oxidation of As(III) to As(V) occurred after Fe(III)-NAu-2 was bioreduced. Furthermore, anaerobic oxidization of As(III) by bioreduced NAu-2 was significantly promoted by increasing Fe(III)-NAu-2 reduction extent and initial As(III) concentrations. Bioreduction of Fe(III)-NAu-2 generated reactive Fe(III)-O-Fe(II) moieties at clay mineral edge sites. Anaerobic oxidation of As(III) was attributed to the strong oxidation activity of the structural Fe(III) within the Fe(III)-O-Fe(II) moieties. Our results provide a potential explanation for the presence of As(V) in the anaerobic subsurface environment. Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.     

Arsenic uptake and transport of Pteris vittata L.as influenced by phosphate and inorganic arsenic species under sand culture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator,uptake and transport of arsenate(As(V))and arsenite(As(III))were studied using Pteris vittata L.under sandculture.Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P.vittata.The reduction in As accumulation was greater in old fronds than in young fronds,and relatively weak in root and rhizome.Moderateincreases,from 0.05 to 0.3 mmol/L,in phosphate reduced uptake of As(III)more than As(V),while the reverse was observed at highconcentrations of phosphate(1.0 mmol/L).Phosphate apparently reduced As transport and the proportion of As accumulated in frondsof P.vittata when As was supplied as As(V).It may in part be due to competition between phosphorus and As(V)during transport.Incontrast,phosphate had a much smaller effect on As transport when the As was supplied as As(III).Therefore,the results from presentexperiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P.vittata,especially inthe fronds,when exposed to As(V);but the suppression of phosphate to As transport may be insignificant when P.vittata exposed toAs(III)under sand culture conditions.The finding will help to understand the interaction of P and As during their uptake process in P.vittata.     

基于多采样点的南京市PM2.5中的水溶性砷分析

对南京市的18个采样点进行PM_(2.5)样品采集,并利用电感耦合等离子体质谱仪以及液相电感耦合等离子体质谱联用仪分别对样品中的总砷和4种水溶性砷进行测量,在此基础上研究PM_(2.5)中砷的形态及其时空分布特征.结果表明:南京市PM_(2.5)中的砷以无机砷为主,有机砷为辅.无机砷以三价砷(As(III))为主,五价砷(As(V))为辅,As(III)/As(V)的平均值为0.39±0.03.有机砷以二甲基胂酸(DMAs(V))为主,所有样品均未检出甲基胂酸(MMAs(V)).总砷(As_T)、As(III)、As(V)和DMAs(V)的年平均浓度分别为6.90、0.99、3.20和0.03 ng·m~(-3).PM_(2.5)中的砷浓度具有明显季节变化:总砷和As(V)最大浓度出现在冬季,As(III)最大浓度出现在夏季,DMAs(V)只在夏季出现.T检验表明:As(III)、总砷和DMAs(V)年平均浓度在城区和郊区之间存在显著差异.空间变异系数的计算结果表明DMAs(V)的空间变化最大,其空间变异系数为0.6.总砷和3种水溶性砷年平均浓度由大到小排列为:农村郊区城区.道路采样点和城市背景点的总砷年平均浓度比为0.92,说明城区交通源对PM_(2.5)中砷污染的贡献不明显.As(III)和As(V)的主要排放源可能为燃煤电厂和钢铁冶炼厂,而DMAs(V)可能主要来源于生物挥发产物的二次生成.     

Effect of microbial mediated iron plaque reduction on arsenic mobility in paddy soil

The potential of microbial mediated iron plaque reduction, and associated arsenic (As) mobility were examined by iron reducing bacteria enriched from As contaminated paddy soil. To our knowledge, this is the first time to report the impact of microbial iron plaque reduction on As mobility. Iron reduction occurred during the inoculation of iron reducing enrichment culture in the treatments with iron plaque and ferrihydrite as the electron acceptors, respectively. The Fe(II) concentration with the treatment of anthraquinone-2, 6-disulfonic acid (AQDS) and iron reducing bacteria increased much faster than the control. Arsenic released from iron plaque with the iron reduction, and a significant correlation between Fe(II) and total As in culture was observed. However, compared with control, the increasing rate of As was inhibited by iron reducing bacteria especially in the presence of AQDS. In addition, the concentrations of As(III) and As(V) in abiotic treatments were higher than those in the biotic treatments at day 30. These results indicated that both microbial and chemical reductions of iron plaque caused As release from iron plaque to aqueous phase, however, microbial iron reduction induced the formation of more crystalline iron minerals, leading to As sequestration. In addition, the presence of AQDS in solution can accelerate the iron reduction, the As release from iron plaque and subsequently the As retention in the crystalline iron mineral. Thus, our results suggested that it is possible to remediate As contaminated soils by utilizing iron reducing bacteria and AQDS.     

高锰酸钾强化三氯化铁共沉降法去除亚砷酸盐的效能与机理

研究了不同水质条件下KMnO₄强化FeCl₃共沉降去除亚砷酸盐[As(Ⅲ)]的效能与机理.考察了pH值、天然有机物(NOM)等因素对As去除效能的影响.结果表明,投加KMnO₄显著提高了FeCl₃共沉降除砷(FCP)工艺对As(Ⅲ)的去除效能.随着Fe(Ⅲ)投量由2.0mg/L增大到8.0mg/L,对于FCP工艺,As去除率由41.3%提高到75.4%;而对于KMnO₄-FeCl₃共沉降除砷(POFCP)工艺,As去除率则由61.2%提高至99.3%.FCP及POFCP工艺对As的去除率均随着pH值的升高而升高;与FCP工艺比较,pH值对POFCP工艺除As效果影响较小;NOM降低了FCP工艺对As的去除率,而对POFCP工艺无明显影响.KMnO₄的氧化作用是强化As(Ⅲ)去除效能的主要因素,而KMnO₄的还原产物水合MnO₂(s)对As(Ⅲ)也具有一定的去除能力.POFCP工艺是强化去除水中As(Ⅲ),以保障安全饮用水供给的有效方法.     

Review on heterogeneous oxidation and adsorption for arsenic removal from drinking water

The long term exposure of arsenic via drinking water has resulted in wide occurrence of arsenisim globally, and the oxidation of the non-ionic arsenite (As(III)) to negatively-charged arsenate (As(V)) is of crucial importance for the promising removal of arsenic. The chemical oxidants of ozone, chlorine, chlorine dioxide, and potassium permanganate may achieve this goal; however, their application in developing countries is sometimes restricted by the complicate operation and high cost. This review paper focuses on the heterogeneous oxidation of As(III) by solid oxidants such as manganese oxide, and the adsorption of As(V) accordingly. Manganese oxide may be prepared by both chemical and biological methods to achieve good oxidation performance towards As(III). Additionally, manganese oxide may be combined with other metal oxides, e.g., iron oxide, to improve the adsorption capability towards As(V). Furthermore, manganese oxide may be coated onto porous materials of metal organic frameworks to develop novel adsorbents for arsenic removal. To achieve the application in engineering works, the adsorbents granulation may be achieved by drying and calcination, agglomeration, and the active components may also be in situ coated onto the porous materials to maintain the oxidation and adsorption activities as much as possible. The novel adsorbents with heterogeneous oxidation and adsorption capability may be carefully designed for the removal of arsenic in household purifiers, community-level decentralized small systems, and the large-scale drinking water treatment plants (DWTPs). This review provides insight into the fundamental studies on novel adsorbents, the development of innovative technologies, and the demonstration engineering works involved in the heterogeneous oxidation and adsorption, and may be practically valuable for the arsenic pollution control globally.     

Bacterial reduction and release of adsorbed arsenate on Fe(Ⅲ)-, Al- and coprecipitated Fe(Ⅲ)/Al-hydroxides

Mobilization of arsenic under anaerobic conditions is of great concern in arsenic contaminated soils and sediments. Bacterial reduction of As(V) and Fe(Ⅲ) influences the cycling and partitioning of arsenic between solid and aqueous phase. We investigated the impact of bacterially mediated reductions of Fe(Ⅲ)/Al hydroxides-bound arsenic(V) and iron(Ⅲ) oxides on arsenic release. Our results suggested that As(V) reduction occurred prior to Fe(Ⅲ) reduction, and Fe(Ⅲ) reduction did not enhance the release of arsenic. Instead, Fe(Ⅲ) hydroxides retained their dissolved concentrations during the experimental process, even though the new iron mineral-magnetite formed. In contrast, the release of reduced As(Ⅲ) was promoted greatly when aluminum hydroxides was incorporated. Thus, the substitution of aluminum hydroxides may be responsible for the release of arsenic in the contaminated soils and sediments, since aluminum substitution of Fe(Ⅲ) hydroxides universally occurs under natural conditions.     

The potential risk assessment for different arsenic species in the aquatic environment

The different toxicity characteristics of arsenic species result in discrepant ecological risk. The predicted no-effect concentrations (PNECs) 43.65, 250.18, and 2.00 × 10³ μg/L were calculated for As(III), As(V), and dimethylarsinic acid in aqueous phase, respectively. With these PNECs, the ecological risk from arsenic species in Pearl River Delta in China and Kwabrafo stream in Ghana was evaluated. It was found that the risk from As(III) and As(V) in the samples from Pearl River Delta was low, while much high in Kwabrafo stream. This study implies that ecological risk of arsenic should be evaluated basing on its species.     

Phylogenetic analysis and arsenate reduction e ect of the arsenic-reducing bacteria enriched from contaminated soils at an abandoned smelter site

Microbial reduction of As(V) (i.e., arsenate) plays an important role in arsenic (As) mobilization in aqueous environment. In this study, we investigated As(Ⅴ) reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site. It was found that As(Ⅴ) was completely reduced to As(Ⅲ) (i.e., arsenite) in 21 h. After 3-d incubation, a yellow solid was precipitated and the concentration of As(Ⅲ) decreased sharply. After 150 h incubation, ca. 65% of soluble arsenic was removed from the solution. The analysis of the precipitate by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) revealed that the main component was crystalline arsenic sulfide (ASS). Microbial mediated reduction and mobilization of adsorbed As(Ⅴ) on ferric hydroxide was also examined. In the microcosm slurry experiment, ca. 53% of the adsorbed As(V) was reduced to As(Ⅲ) by the bacteria, which resulted in an appreciable release of arsenic into aqueous phase. The released arsenic was present predominantly as As(Ⅲ). The microbial diversity was analyzed by 16S rDNA-dependent molecular phylogeny. A near-full-length 16S rDNA gene clone library was constructed. The 197 clones were analyzed using RFLP (restriction fragment length polymorphism) and 72 OTUs were obtained, which contributed 51% of the content for total clone number in six OTUs. Six bacterial clones in these six OTUs were selected for sequencing and the sequenced clones were found to belong to the group Caloramator, Clostridium, and Bacillus.     

Shewanella oneidensis MR-1对不同价态砷的生物转化与甲基化

在实验室纯培养条件下,通过分别向培养基中投加As(Ⅲ)和As(Ⅴ),探讨Shewanella oneidensis MR-1对不同价态砷的生物转化与甲基化作用.结果表明,S.oneidensis MR-1介导下不同价态砷的生物转化与微生物对砷的耐受和代谢特性有着密切联系,在投加As(Ⅲ)时,由于细胞自身的解毒作用会产生少量的As(Ⅴ),同时在酶的作用下As(Ⅲ)与甲基供体结合生成甲基砷;而在投加As(Ⅴ)时,遵循Challenge机制,先产生一甲基砷后生成二甲基砷.此外,弱酸性环境比碱性更有利于甲基砷的产生;温度30℃时甲基砷的产生量较高,过低或过高的培养温度砷甲基化率下降.     

包埋氨氧化细菌短程硝化的高效稳定运行

为了提高包埋氨氧化细菌短程硝化的效率,富集培养氨氧化细菌(AOB)并固定化.富集培养阶段采用连续式运行方式,以游离氨(FA)为抑制亚硝酸盐氧化菌(NOB)生长的手段,并通过定时排泥方法使NOB逐渐从系统中淘洗出去.富集培养结束后以聚乙烯醇(PVA)为包埋材料,对筛选培养的氨氧化细菌进行固定化,反应器包埋填充率为8%.采用连续式运行方式,通过逐步增加氨氮负荷的方法提高氨氧化速率.最终在富集培养系统中实现了污泥比氨氧化速率(以NH_4~+-N/VSS计)2.028 g·(g·d)~(-1)的高表达和亚硝酸盐氮90%以上的高积累.通过对污泥富集培养前后细菌群落组成的高通量测序分析,结果表明,培养前原污泥多样性较大,具有硝化作用的Nitrosomonas仅有0.24%,Nitrospira有2.7%.富集培养后的活性污泥多样性明显变小,优势菌种为Nitrosomonas(18%),而Nitrospira仅剩0.02%;包埋固定化后,系统迅速实现了短程硝化,最终短程硝化的速率达到了50 mg·(L·h)~(-1),亚硝酸盐氮积累率稳定在90%以上.     

多功能高铁酸盐去除饮用水中砷的研究

利用高铁酸盐的氧化絮凝双重水处理功能,取代氧化铁盐法,对其氧化除砷效果进行了评价.考察了高铁酸盐除砷的适宜pH值范围、氧化时间和絮凝时间,定性和定量分析了盐度、硬度等因素对高铁酸盐除砷效果的影响.结果表明,高铁酸盐与砷浓度比为15∶1,最佳pH为5.5～7.5,适宜的氧化时间为10min,絮凝时间为30min,处理后的水样中砷残留量可达到国家饮用水标准;盐度和硬度不干扰除砷过程.与传统的铁盐法和氧化铁盐法对比,此方法简便,高效,无二次污染,更有利于饮用水的清洁化除砷.     

磁性吸附材料CuFe2O4吸附砷的性能

根据Cu(Ⅱ)和Fe(Ⅲ)都对砷有较强的亲和性,制备了同时含有Cu(Ⅱ)和Fe(Ⅲ)的、可用磁分离方法进行分离回收的磁性吸附材料CuFe₂O₄,并对其进行了表征及吸附砷的性能研究.结果表明,该吸附剂对砷的吸附能力与溶液pH有关,在弱酸性及中性条件下,吸附砷的能力最强,而对As(V)的吸附能力比对As(Ⅲ)更强些,在平衡浓度为10μg/L时,其吸附容量可达10mg/g左右,可以很容易地将水中浓度为1～20mg/L的As(V)降到10μg/L以下.实验考察了几种无机阴离子对吸附砷的影响,表明较高浓度(砷浓度的20倍)的硫酸盐对As(Ⅲ)和As(V)的吸附均有一定影响,盐酸盐及磷酸盐则影响不明显;负载的As(V)可较容易地用0.1mol/L NaOH洗脱下来,使吸附剂再生,而As(Ⅲ)则难以洗脱,这与2种价态砷的吸附机理不同有关.     

天然菱铁矿改性及强化除砷研究

我国高砷地下水分布广泛,经济、高效地饮用水除砷技术受到广泛关注.静态批实验采用资源丰富、价格便宜的天然菱铁矿为主要原材料,考虑灼烧温度、时间及添加黏合剂等因素确定最优改性条件使除砷效果达到最佳.结果表明,在加铝量为10 mg.g-1、350℃下恒温灼烧90 min后造粒达到强度要求并除砷效果较优.25℃、固液比为0.5 g∶50 mL、As(Ⅲ)和As(Ⅴ)初始浓度为5 mg.L-1时,吸附后溶液中残留As浓度均<10μg.L-1.静态吸附批实验结果表明,25℃时,接触反应时间为12 h可达到吸附平衡,吸附过程较好地符合Lagergren假二级吸附速率方程;最优改性天然菱铁矿对砷的吸附规律可用Langmuir和Freundlich等温吸附模型很好地描述,As(Ⅲ)、As(Ⅴ)饱和吸附容量分别可以达到1 039、1 026μg.g-1.结合XRD、SEM等研究方法和比表面及孔结构分析初步探讨天然菱铁矿改性以及除砷的主要机制.分析表明,改性后天然菱铁矿比表面积大幅度增大,孔径减小,且在表面活化生成一层圆球状的含Fe(Ⅱ)和Fe(Ⅲ)的化合物.改性天然菱铁矿是一种值得进一步研究并实际应用的除砷材料.     

城市污水厌氧氨氧化脱氮面临的挑战与应对策略

基于厌氧氨氧化(Anammox)的高效自养脱氮技术用于城市污水处理为污水处理厂的能量自给运行提供了可能。首先,简述了污水Anammox自养脱氮的反应过程和技术优势,然后重点从亚硝酸盐氧化细菌(NOB)抑制、厌氧氨氧化细菌(AnAOB)富集截留以及AnAOB与好氧氨氧化细菌(AOB)等之间平衡调控3个方面总结分析了Anammox自养脱氮技术用于城市污水处理面临的挑战及其应对策略。最后展望了城市污水Anammox自养脱氮技术的未来研究方向。     

Removal of arsenate and arsenite from aqueous solution by waste cast iron

The removal of As(III) and As(V) from aqueous solution was investigated using waste cast iron, which is a byproduct of the iron casting process in foundries. Two types of waste cast iron were used in the experiment: grind precipitate dust (GPD) and cast iron shot (CIS). The X-ray diffraction analysis indicated the presence of Fe0 on GPD and CIS. Batch experiments were performed under different concentrations of As(III) and As(V) and at various initial pH levels. Results showed that waste cast iron was effective in the removal of arsenic. The adsorption isotherm study indicated that the Langmuir isotherm was better than the Freundlich isotherm at describing the experimental result. In the adsorption of both As(III) and As(V), the adsorption capacity of GPD was greater than CIS, mainly due to the fact that GPD had higher surface area and weight percent of Fe than CIS. Results also indicated the removal of As(III) and As(V) by GPD and CIS was influenced by the initial solution pH, generally decreasing with increasing pH from 3.0 to 10.5. In addition, both GPD and CIS were more effective at the removal of As(III) than As(V) under given experimental conditions. This study demonstrates that waste cast iron has potential as a reactive material to treat wastewater and groundwater containing arsenic.