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1.
Batch-type leaching experiments were performed on polluted soil contaminated by pyrite cinders to evaluate the effect of indigenous bacteria on arsenic mobilization. The bacteria, under submerged conditions using citrate as the carbon source, enhanced the solubilization of arsenic, iron and manganese. At the same time, 85 mg kg−1 of copper were abiotically released. Iron reduction significantly (p < 0.05) enhanced the release of arsenic. During 7 days of incubation at high redox potential, the arsenite content increased suggesting aerobic arsenic-resistant bacteria bearing arsC genes as key players for arsenate reduction. Arsenate became prevalent in consequence of arsenic liberation from iron oxides and the lowering of redox potential, driven by citrate, inhibited the growth and activity of arsenate-resistant bacteria. Populations of Bacillus, Pseudomonas, and Geobacter were stimulated by the addition of citrate as evidenced by denaturing gradient gel electrophoresis analysis of 16S rRNA genes. Putative ars genes were retrieved in isolates of Bacillus and Pseudomonas. These isolates were able to reduce 2 mmol l−1 of arsenate in liquid cultures. These results confirm that microorganisms play an important role in As cycling in soils and highlight the complex role of citrate on biotic and abiotic transformations of inorganic contaminants. The environmental dispersion of arsenic can be retarded by resorption or coprecipitation processes occurring during flooding. Nevertheless, periodic flooding can be a crucial factor for the groundwater quality and the soil–water–plant systems. 相似文献
2.
Experiments were conducted to evaluate the arsenic toxicity, its accumulation and phytoremediation potential of bean plants (Phaseolus vulgaris) grown in soils contaminated with different species of arsenic such as arsenite (As(III)), arsenate (As(V)) and dimethylarsinic acid (DMA). Bean plants were grown in soils amended by aqueous solutions of 20 and 50 mg kg?1 of As (III), As(V) or DMA. Arsenic species negatively affected the yield and growth of the plant. The study demonstrated arsenic accumulation in the plant parts. The concentration of arsenic compounds in the shoots decreased in the order arsenate > arsenite > dimethylarsinic acid while in the roots as arsenite > arsenate > dimethylarsinic acid. Most arsenic is accumulated in the roots with limited transfer to shoots. Thus, bean plants can be considered as an arsenic excluder and has the potential for phytostabilization of arsenic contaminated sites. The study also reveals that removal of arsenic by boiling the vegetables with excess of water is not possible. 相似文献
3.
Xi-Xiang Yin L. H. Wang R. Bai H. Huang Guo-Xin Sun 《Water, air, and soil pollution》2012,223(3):1183-1190
Synechocysis sp. PCC6803 is a unicellular blue alga which ubiquitously exists in aquatic system and is considered to play a role in arsenic
cycling. Our results showed that Synechocysis can accumulate arsenic as much as 1.0 and 0.9 g kg−1 DW when exposed to 0.5 mM arsenate and arsenite for 14 days, respectively. In addition, arsenic species in cells were assayed
under different exposure conditions and it was found that inorganic arsenic, including arsenate and arsenite, is the dominant
species. Organic methylated arsenicals can only be detected exposed to higher arsenic concentration range (100–500 μM). Arsenate
is the dominant arsenic species and presents more than 80% of the total arsenic in cells. Efflux of both arsenate and arsenite
was observed. When treated with 2.67 μM arsenite, Synechocysis can rapidly oxidize arsenite to arsenate and accumulate As rapidly. The observed arsenic oxidation in solute is solely caused
by cellular oxidation. Given the robust ability of As accumulation, it can serve as a phytoremediation organism to efficiently
remove arsenic from aquatic environments. 相似文献
4.
结合吸附实验和X光吸收精细结构光谱(XAFS)分析,研究了草酸根和胡敏酸对As(V)在红壤中吸附的影响,分析了As(V)在红壤中的化学形态和微观结构以及草酸根、胡敏酸的影响特征。结果表明,当pH6.0时,红壤主要是通过基团交换反应吸附As(V),草酸根和胡敏酸可以通过竞争吸附位点抑制红壤中As(V)的吸附,其抑制作用随浓度增大而增强。XAFS光谱学数据表明,红壤中吸附的砷以+5价态存在,主要与铁铝矿物形成以约0.317 nm As-Al和0.328 nm As-Fe原子间距为特征的双齿双核结构的内层复合物,复合物结构类型不受砷浓度和草酸根、胡敏酸的影响。 相似文献
5.
Colin R. Jackson Sandra L. Dugas Karyn G. Harrison 《Soil biology & biochemistry》2005,37(12):2319-2322
The numbers of arsenate-resistant bacteria present in four different soils were determined. Counts were typically in the order of 106 arsenate-resistant colony forming units g−1 of soil, accounting from 7 to 50% of the total viable count. Arsenate-resistant bacteria obtained from woodland soil and leaf litter were further characterized. 16S rRNA sequence analysis revealed that these bacterial isolates represented six bacterial groups including the Proteobacteria, Bacteroidetes, and Firmicutes. Almost all of these isolates were bacteria that have not previously been shown to tolerate arsenic. Some of these bacteria were capable of growth when exposed to high levels of arsenate (over 250 mM), although arsenite tolerance was much lower. These results support the suggestion that arsenate-resistant bacteria are common in natural environments and may play an important role in arsenic cycling in soils. 相似文献
6.
The arsenic content of soils varies from 0.3–40 p.p.m., but in plants it is rather stationary, being 3 p.p.m.1) However arsenites and arsenates have been used since long ago as insecticides and herbicides respectively, and hence sometimes large amounts of arsenic are detected in soils where arsenicals have been sprayed continuously. The arsenite-arsenate relations in soils are of particular interest because arsenite arsenic is more toxic to plants than arsenate arsenic. 相似文献
7.
《Communications in Soil Science and Plant Analysis》2012,43(7-8):903-919
Abstract Lead arsenate was extensively used to control insects in apple and plum orchards in the 1900s. Continuous use of lead arsenate resulted in elevated soil levels of lead (Pb) and arsenic (As). There are concerns that As and Pb will become solubilized upon a change in land use. In situ chemical stabilization practices, such as the use of phosphate‐phosphorus (P), have been investigated as a possible method for reducing the solubility, mobility, and potential toxicity of Pb and As in these soils. The objective of this study was to determine the effectiveness of calcium carbonate (lime), P, and iron (Fe) amendments in reducing the solubility of As and Pb in lead‐arsenate‐treated soils over time. Under controlled conditions, two orchard soils, Thurmont loam (Hapludults) and Burch loam (Haploxerolls), were amended with reagent‐grade calcium carbonate (CaCO3), iron hydroxide [Fe(OH)3], and potassium phosphate (KH2PO4) and incubated for 16 weeks at 26°C. The experimental results suggested that the inorganic P increased competitive sorption between H2PO4 ? and dihydrogen arsenate (H2AsO4 ?), resulting in greater desorption of As in both Thurmont and Burch soils. Therefore, addition of lime, potassium phosphate, and Fe to lead‐arsenate‐contaminated soils could increase the risk of loss of soluble As and Pb from surface soil and potentially increase these metal species in runoff and movement to groundwater. 相似文献
8.
Ryoji Nakazawa Masayuki Ikawa Kaori Yasuda Hiroshi Takenaga 《Soil Science and Plant Nutrition》2013,59(1):271-275
Simultaneous treatments with Cd and arsenic (arsenite and arsenate) led to the synergistic growth inhibition of tobacco (Nicotiana tabacum cv. BY-2) cells. Cd contents in cells increased by co-treatment with arsenic for 24 h. The amount of total phytochelatins (PCs) per unit of Cd in the cells treated with Cd and arsenate was lower than that in the cells treated with Cd alone. Simultaneous treatments with Cd and arsenic promoted the induction of the biosynthesis of (γ-Glu-Cys)2-Gly and inhibited the induction of the biosynthesis of (γ-GluCys)3-Gly and (γ-Glu-Cys)4-Gly, compared with the treatment with Cd alone. Consequently, since the inhibition of PC biosynthesis led to the increase of the cellular concentration of putative ionic (= toxic) Cd, cell growth was inhibited synergistically by simultaneous treatments with Cd and arsenic. In addition, based on the results showing that buthionine sulfoximine increased the sensitivity to arsenite and arsenate, that PC biosynthesis was induced by treatment with arsenite or arsenate, it is suggested that glutathione and/or its metabolic products such as PCs are involved in arsenic tolerance. 相似文献
9.
A multiwell plate bioassay was developed using genetically modified bacteria (bioreporter cells) to detect inorganic arsenic extracted from rice. The bacterial cells expressed luciferase upon exposure to arsenite, the activity of which was detected by measurement of cellular bioluminescence. The bioreporter cells detected arsenic in all rice varieties tested, with averages of 0.02-0.15 microg of arsenite equivalent per gram of dry weight and a method detection limit of 6 ng of arsenite per gram of dry rice. This amounted to between approximately 20 and 90% of the total As content reported by chemical methods for the same sample and suggested that a major proportion of arsenic in rice is in the inorganic form. Calibrations of the bioassay with pure inorganic and organic arsenic forms showed that the bacterial cells react to arsenite with highest affinity, followed by arsenate (with 25% response relative to an equivalent arsenite concentration) and trimethylarsine oxide (at 10% relative response). A method for biocompatible arsenic extraction was elaborated, which most optimally consisted of (i) grinding rice to powder, (ii) mixing with an aqueous solution containing pancreatic enzymes, (iii) mechanical shearing, (iv) extraction in mild acid conditions and moderate heat, and (v) centrifugation and pH neutralization. Detection of mainly inorganic arsenic by the bacterial cells may have important advantages for toxicity assessment of rice consumption and would form a good complement to total chemical arsenic determination. 相似文献
10.
采用室内土壤培养试验,探讨了外源添加耐砷真菌棘孢木霉（TrichodermaasperellumL．）和零价铁对土壤砷的有效性和形态转化的影响。结果表明：向污染土壤中添加耐砷真菌棘孢木霉后,随着培养时间的延长,土壤中水溶态砷和NaHCO,提取态砷含量均呈稳定增加趋势,耐砷真菌促进了土壤中砷的溶出和释放;培养30d时,耐砷菌处理土壤有效砷含量比同期对照增幅达3．9％-10．7％,水溶态砷以As（V）为主,未检测到As（Ⅲ）、一甲基胂（MMA）、二甲基胂（DMA）等其他形态的砷;随着外源零价铁的加入,土壤中砷的活性大大降低,其有效砷含量降幅为76．5％-90．4％;在耐砷菌与零价铁联合作用下,相比于单纯的零价铁处理,土壤有效砷含量显著增加（p〈0．05）,因耐砷真菌棘孢木霉的加入导致零价铁对土壤砷的固定效率下降7．0％-11．1％。耐砷菌导致土壤砷活化可能主要与残渣态向非专性吸附态砷的转化等过程有关,外源零价铁对土壤砷的固定作用可能与非专性吸附态向无定形及弱晶质氧化物结合态、残渣态砷等转化过程相关;耐砷菌的加入抵消了零价铁对土壤砷的部分固定效果,但短期内（〈30d）不会构成大的影响。 相似文献
11.
Environmental arsenic (As) contamination, considered as the largest mass poisoning of the human population, has become a serious health concern for the people of South East Asia, including those living in the Bengal delta. An As-resistant strain, KUMAs15, was isolated from the As-contaminated fields in Nadia Ddistrict in West Bengal, India and was evaluated for its possible use in environmental As bioremediation. Molecular identification based on 16S rDNA gene sequencing revealed that the strain belonged to the genus Micrococcus. The strain tolerated high levels of As and oxidized arsenite under the culture condition. The strain also accumulated large quantities of As when exposed to a wide range of environmentally relevant concentrations of inorganic As. Analysis of the aoxB, arsB, and arsC gene expression explained the underlying cause of arsenite oxidation and As accumulation by KUMAs15. The As-resistant strain KUMAs15 of Micrococcus sp. was suggested to be a potential environmental As decontaminant. 相似文献
12.
Sorghum was inoculated withPseudomonas bacteria, including strains harboring an As-resistance plasmid, pBS3031, to enhance As-extraction by the plants.Pseudomonas strains (P.fluorescens 38a, P.putida 53a, and P.aureofaciens BS1393) were chosen because they are antagonistic to a wide range of phyto-pathogenic fungi and bacteria, and they can stimulate
plant growth. The resistance of natural rhizospheric pseudomonads to sodium arsenite was assessed. Genetically modifiedPseudomonas strains resistant to As(III)/As(V) were obtained via conjugation or transformation. The effects of the strains on the growth
of sorghum on sodium-arsenite-containing soils were assessed. The conclusions from this study are: (1) It is possible to increase
the survivability of sorghum growing in sodium-arsenite-containing soil by using rhizosphere pseudomonads. (2) The presence
of pBS3031 offers the strains a certain selective advantage in arsenite-contaminated soil. (3) The presence of pBS3031 impairs
plant growth, due to the As-resistance mechanism determined by this plasmid: the transformation of the less toxic arsenate
into the more toxic, plant-root-available arsenite by arsenate reductase and the active removal of arsenite from bacterial
cells. (4) Such a mechanism makes it possible to develop a bacteria-assisted phytoremediation technology for the cleanup of
As-contaminated soils and is the only possible way of removing the soil-sorbed arsenates from the environment. 相似文献
13.
Shuzhen Zhang Wei Li Xiao-Quan Shan Anxiang Lu Peijiang Zhou 《Water, air, and soil pollution》2005,167(1-4):111-122
Low-molecular-weight-organic-anions (LMWOAs) are important exudates of plants and may influence the mobility and bioavailability of metals or metalloids. In the present study the effects of selected LMWOAs, citrate, malate and oxalate, on the release of arsenite (As(III)) and arsenate (As(V)) in a contaminated soil were investigated. The organic anions have significant influence upon the release of arsenic from the soil, and a linear relationship exits between the released arsenic and the concentration of LMWOAs in the extractants. pH effects on the arsenite and arsenate adsorption were not significant over the range from 3 to 7. The amounts of arsenite and arsenate released were significantly correlated with the release of Fe, Mn and Al, suggesting that arsenic was mainly released from Fe-, Mn- and Al-oxides or hydroxides in soil. The ratio of released arsenite to arsenate was not influenced by LMWOAs. 相似文献
14.
Possible mechanisms of the effects of silicon (Si) on arsenic (As) uptake were explored using a wild‐type rice and its low‐Si mutant (lsi1). Hydroponic experiments were carried out to investigate the effects of internal and external Si on the As accumulation and uptake by rice in excised roots (28 d–old seedlings) and xylem sap (61 d–old plants). The presence of Si significantly decreased the As concentrations in both shoots and roots of the wild type but not in the mutant with 13.3 μM–arsenite or 10/20 μM–arsenate treatments. The Si‐defective mutant rice (lsi1) also showed a significant reduction in arsenite or arsenate uptake. Moreover, As concentrations in xylem sap of the wild type were reduced by 51% with 1 mM Si– and 15 μM–arsenate treatments, while Si had no effect on As concentrations in the xylem sap of the mutant. Arsenic‐species analysis further indicated that the addition of 1 mM Si significantly decreased As(III) concentrations but had little effect on As(V) concentrations in the xylem sap of the wild type with 15 μM–arsenate treatments. These results indicated that external Si‐mediated reduction in arsenite uptake by rice is due to the direct competition between Si and arsenite during uptake. This is because both share the same influx transporter Lsi1. In addition, internal Si‐mediated reduction in arsenite uptake by rice is due to competition of the Si/arsenite efflux transporter Lsi2 during the As(III)‐transportation process. Silicon also inhibited arsenate uptake by rice. It is proposed that this could actually be due not to the inhibition of arsenate uptake per se but rather the inhibition of arsenite transformed from arsenate, either in the external solution or in rice roots. 相似文献
15.
Soil arsenic (As) pollution from mining and industrial sources is a serious issue in China. Earthworms are considered ecosystem engineers and contribute to soil fertility development and maintenance of soil physico-chemical properties. In this study, earthworms were exposed to soils with different sodium arsenite concentrations (0, 5, 20, and 80 mg As kg-1) for 60 d to investigate the changes in soil properties and the responses of the earthworms (e.g., burrowing activity and respiration). Earthworm burrowing activity decreased with increasing arsenite concentrations, and earthworm respiration was significantly lower in soils with 20 and 80 mg As kg-1 compared to 0 mg As kg-1. Changes in soil properties were also observed after incubation of As-amended soil with earthworms. Specifically, soil pH decreased, while soil electrical conductivity and contents of soil NH3--N, Olsen-P, and available K increased. Our results suggest that arsenite negatively impacts the metabolic activity of earthworms, leading to reduced burrowing activity, which in turn modifies the effects of earthworms on soil fertility and remediation. 相似文献
16.
Fuyong Wu Feifei Xu Xiaona Ma Wanqing Luo Laiqing Lou Ming Hung Wong 《Journal of Soils and Sediments》2018,18(11):3177-3185
Purpose
Although arsenic (As) hyperaccumulation is a constitutive property for Pteris vittata, there is intraspecific variation in As accumulation among metallicolous (from As-contaminated soils) and nonmetallicolous populations (from uncontaminated soils) and the related mechanisms is still not clear.Materials and methods
Pot trials, hydroponic culture, and manual simulation were conducted to investigate the roles of arsenate reductase and root exudates in accumulating As in P. vittata, which were collected from two uncontaminated sites including Sun Yat-sen University campus, Guangdong Province (ZD), and a botanical garden in Guangxi Academy of Forestry Sciences, Nanning City, Guangxi Province (NN), and two As and Pb/Zn mining and/or smelting sites located in Shaoguan of Guangdong Province (SG) and Guiyang of Hunan Province (GY).Results and discussion
The nonmetallicolous populations (ZD and NN) possessed more efficient uptake of arsenate and arsenite than the metallicolous populations (SG and GY). There were significant (p?<?0.05) difference in arsenate reductase activities in roots among the four populations of P. vittata and that the higher arsenate reductase activities were recorded in the nonmetallicolous populations (110 nkat mg?1 protein for ZD, 160 nkat mg?1 protein for NN) compared with the metallicolous populations (62.9 nkat mg?1 protein for SG, 78.1 nkat mg?1 protein for GY). Root exudates from the nonmetallicolous population (NN) and the metallicolous population (GY) of P. vittata contained similar compositions of organic acids including oxalic, malic, and succinic acids, of which oxalate were dominant (>?67%). The NN population exuded 4.23 times more oxalate than the SG population. Root exudates from the NN population mobilized significantly (p?<?0.05) more As from As-contaminated soils than those from the SG population, of which oxalate had the most effective in As mobilization.Conclusions
The present study suggests that higher arsenate reductase activities and oxalate exudation in the nonmetallicolous populations may play an important role in increasing their efficiency in phytoremediation of As-contaminated soils.17.
Purpose
Arsenite and arsenate leaching from iron (hydr)oxides is one major parameter affecting the mobility of arsenic in the natural environment. In the process of arsenic transfer to groundwater, the retention capacity of arsenic by different iron (hydr)oxides needs to be investigated. The aim of this study is to determine the retention capacity of arsenite or arsenate from the ferrihydrite, lepidocrocite, or magnetite-coated sand column in the leaching process as well as the influence factors on leaching.Materials and methods
The leaching of arsenite and arsenate from columns loaded with ferrihydrite, magnetite, or lepidocrocite-coated quartz sand was examined, and the influence factors such as pH, phosphate, and humic acid (HA) contents on leaching and retention were also investigated.Results and discussion
The retention performance of As(III) and As(V) depended on the type of iron (hydr)oxides: ferrihydrite?>?magnetite?>?lepidocrocite. The retention capacities of As(III) and As(V) by amorphous ferrihydrite versus magnetite and lepidocrocite are 3.25, 5.63 (As(III)) and 1.75, 3.65 (As(V)) times higher. The retention capacity of arsenic is largely affected by the pH of leaching solutions. The retention of As(III) by ferrihydrite is efficient in near-neutral or slightly acidic environments. The addition of phosphate or HA significantly affected the leaching and retention. The addition of phosphate severely inhibited the leaching and retention of As(III) and As(V) by ferrihydrite, and the inhibitory effect was more obvious along with the increase of phosphate concentration. The retention of As(III) and As(V) by ferrihydrite was significantly enhanced by the addition of low-dose HA but was inhibited by the addition of excessive HA.Conclusions
Retention performance of As(III) and As(V) from a ferrihydrite-coated sand column is greater than a magnetite- or a lepidocrocite-coated sand column, and the influence factors such as pH, phosphate, and HA affect the leaching and retention of As(III) and As(V). The results theoretically underlie the application of iron (hydr)oxide in arsenic pollution control.18.
The increasing mobility of arsenate will increase its leachingpotential to groundwater and uptake by plants. The mobility ofarsenate in soils is related to the competitive adsorption with other substances. The effect of organic substances on the adsorption of arsenate by soils was evaluated using the water extract of compost (WEC) as a complex anion source in a batch experiment. Two calcareous slate alluvial soils, Chiwulan andShuipientou, with higher arsenic contents of 23.7 and 12.9 mg kg-1, respectively, were used. The Langmuir equation has been used to describe successfully the As adsorption isotherm for the two soils. The maximum adsorption of As was 6.098 and 4.785 μmol g-1 for Chiwulan and Shuipientou soils, respectively. There was competitive adsorption for binding siteson the soils between arsenate oxyanions and organic anions derived from the dissolved organic carbon (DOC) of WEC. Differentcritical pH values were for arsenate addition related to arsenateadsorption on both soils in the absence of DOC of WEC but not inthe presence of DOC of WEC. The soil properties related to arsenate adsorption by the two soils may govern the critical pH values. 相似文献
19.
Marcio R. Lambais Xosé Luis Otero Juliano C. Cury 《Soil biology & biochemistry》2008,40(11):2854-2864
Microbial community structure in saltmarsh soils is stratified by depth and availability of electron acceptors for respiration. However, the majority of the microbial species that are involved in the biogeochemical transformations of iron (Fe) and sulfur (S) in such environments are not known. Here we examined the structure of bacterial communities in a high saltmarsh soil profile and discuss their potential relationship with the geochemistry of Fe and S. Our data showed that the soil horizons Ag (oxic–suboxic), Bg (suboxic), Cr1 (anoxic with low concentration of pyrite Fe) and Cr2 (anoxic with high concentrations of pyrite Fe) have distinct geochemical and microbiological characteristics. In general, total S concentration increased with depth and was correlated with the presence of pyrite Fe. Soluble + exchangable-Fe, pyrite Fe and acid volatile sulfide Fe concentrations also increased with depth, whereas ascorbate extractable-Fe concentrations decreased. The occurrence of reduced forms of Fe in the horizon Ag and oxidized Fe in horizon Cr2 suggests that the typical redox zonation, common to several marine sediments, does not occur in the saltmarsh soil profile studied. Overall, the bacterial community structure in the horizon Ag and Cr2 shared low levels of similarity, as compared to their adjacent horizons, Bg and Cr1, respectively. The phylogenetic analyses of bacterial 16S rRNA gene sequences from clone libraries showed that the predominant phylotypes in horizon Ag were related to Alphaproteobacteria and Bacteroidetes. In contrast, the most abundant phylotypes in horizon Cr2 were related to Deltaproteobacteria, Chloroflexi, Deferribacteres and Nitrospira. The high frequency of sequences with low levels of similarity to known bacterial species in horizons Ag and Cr2 indicates that the bacterial communities in both horizons are dominated by novel bacterial species. 相似文献
20.
Concerns have been raised of possible human food chain transfer of lead and arsenic from crops grown on orchard soils with histories of lead arsenate use. The objective of this study was to determine arsenic and lead uptake by three cultivars of carrots grown on four orchard soils with histories of lead arsenate use. Total concentrations of arsenic and lead in these soils ranged from 93 to 291 and from 350 to 961 mg kg?1 for arsenic and lead, respectively. Arsenic in peeled carrot ranged from 0.38 to 1.64 mg kg?1, while lead ranged from 2.67 to 7.3 mg kg?1 dry weight. This study demonstrated that carrots will accumulate arsenic and lead in the root, which may become a human health risk when consumed. However, further studies are needed to determine what fraction of arsenic and lead in these carrots are bioavailable to humans when consumed. 相似文献