Arsenic-contaminated Soil Research Articles

Study on Arsenic Contamination in Soil and Water in Five-selected Agro Ecological Zone (AEZ) of Bangladesh

A research was carried out at the five different Agro-Ecological Zones (AEZ) of Bangladesh, viz. Tista Meander Floodplain (FP), High Ganges FP, Low Ganges FP, Active Ganges FP and Gopalganj-Khulna Bills during January 2001 to January 2002. The objectives were to assess the arsenic (As) concentration in the soil and water as well as to test tube well water samples and examines whether these exceed the acceptable limit of As. Water of shallow tube wells (STW) and soil samples were collected from ten sites under five AEZs of Bangladesh. Considerable number of water samples showed high contents of arsenic, which ranged from 0.032 to 203.9 ?g/l. Out of 428 water samples, 155 were found unsafe (>10-<50 ?g/l) and 78 were toxic (>50 ?g/l) for drinking purpose. However, out of 2648 soil samples collected from different Upazilas, only 4 samples collected from Chargat showed toxic level (>20 ?g/kg).

Mechanism for the stabilization/solidification of arsenic-contaminated soils with Portland cement and cement kiln dust

In this study, the mechanism for the stabilization/solidification (S/S) of arsenic (As)-contaminated soils with Portland cement (PC), and cement kiln dust (CKD) using 1 N HCl extraction fluid, X-ray powder diffraction (XRPD), X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy was investigated. The degree of As immobilization after stabilization was assessed using a 1 N HCl extraction on the basis of the Korean Standard Test (KST). After 1 day of curing with 30 wt% PC and 7 days of curing with 50 wt% CKD, the concentration of As leached from the amended soils was less than the Korean countermeasure standard (3 mg L −1). The As concentrations in the leachate treated with PC and CKD were significantly decreased at pH > 3, indicating that pH had a prevailing influence on As mobility. XRPD results indicated that calcium arsenite (Ca–As–O) and sodium calcium arsenate hydrate (NaCaAsO 4·7.5H 2O) were present in the PC- and CKD-treated slurries as the key phases responsible for As(III) and As(V) immobilization, respectively. The XANES spectroscopy confirmed that the As(III) and As(V) oxidation states of the PC and CKD slurry samples were consistent with the speciated forms in the crystals identified by XRPD. EXAFS spectroscopy showed As–Ca bonding in the As(III)-PC and As(III)-CKD slurries. The main mechanism for the immobilization of As-contaminated soils with PC and CKD was strongly associated with the bonding between As(III) or As(V) and Ca.

Speciation analysis to unravel the soil-to-plant transfer in highly arsenic-contaminated areas in Cornwall (UK)

Two areas near derelict calciners in Cornwall (UK) were chosen to study the uptake of arsenic from arsenic-contaminated soil into indigenous plants (heather, Calluna vulgaris; blackberry, Rubus ulmifulmus; gorse, Ulex europaeus). With total arsenic concentrations in soil ranging from 1240 to 2860 mg kg−1 at Site 1 (Tuckingmill), no adverse effects on the growth of the plants studied were observed. Very low soil-to-plant transfer factors (0.01 to 0.03) were found although they were much higher when the extractable soil arsenic concentrations were taken into account (0.1 to 1.1). In the central dump area at Site 2 (Bissoe, 9.78% [w/w] arsenic in soil), the only plant to grow was heather, although it was severely impaired. However, heather was thriving at the edge of the dump where higher soil arsenic concentrations were found (10.32% [w/w]), indicating that arsenic is not a growth-limiting factor in itself. Soil-to-plant transfer factors in the range 2 × 10−5–9 × 10−4 confirm that arsenic is indeed effectively excluded from uptake, even taking into account extractable soil arsenic concentrations (9 × 10−4–1.2 × 10−2). Extraction of bioavailable arsenic from soil using 0.05 mol L−1 ammonium sulphate yielded recoveries from 1.18 to 3.34% of the total arsenic, predominantly in the form of arsenate. Extraction of arsenic and its metabolites from plants was achieved with water or a water/methanol mixture yielding recoveries up to 22.4% of the total arsenic, with arsenite and arsenate the predominant arsenic species and a minor fraction consisting of methylarsonic acid, dimethylarsinic acid and trimethylarsine oxide. The identity of the remainder of the non-extractable arsenic species still has to be revealed. Although the data suggest that higher plants synthesise organoarsenic compounds it cannot be excluded that symbiotic organisms have synthesised these compounds.

Behavior of Eucalyptus grandis and E. cloeziana seedlings grown in arsenic-contaminated soil

Arsenic has been considered the most poisonous inorganic soil pollutant to living creatures. For this reason, the interest in phytoremediation species has been increasing in the last years. Particularly for the State of Minas Gerais, where areas of former mining activities are prone to the occurrence of acid drainage, the demand is great for suitable species to be used in the revegetation and "cleaning" of As-polluted areas. This study was carried out to evaluate the potential of seedlings of Eucalyptus grandis (Hill) Maiden and E. cloeziana F. Muell, for phytoremediation of As-polluted soils. Soil samples were incubated for a period of 15 days with different As (Na2HAsO4) doses (0, 50, 100, 200, and 400 mg dm-3). After 30 days of exposure the basal leaves of E. cloeziana plants exhibited purple spots with interveinal chlorosis, followed by necrosis and death of the apical bud at the 400 mg dm-3 dose. Increasing As doses in the soil reduced root and shoot dry matter, plant height and diameter in both species, although the reduction was more pronounced in E. cloeziana plants. In both species, As concentrations were highest in the root system; the highest root concentration was found in E. cloeziana plants (305.7 mg kg-1) resulting from a dose of 400 mg dm-3. The highest As accumulation was observed in E. grandis plants, which was confirmed as a species with potential for As phytoextraction, tending to accumulate As in the root system and stem.

Arsenic affects mineral nutrients in grains of various Indian rice (Oryza sativa L.) genotypes grown on arsenic-contaminated soils of West Bengal

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29-167 mg kg(-1) dw), as well as As transfer factor (4-45%). Grains retained the least level of As (0.7-3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05-0.12 mg kg(-1) dw), whereas that of As was high (0.4-1.68 mg kg(-1) dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas.

Effects of Arbuscular Mycorrhizal Fungi and Earthworm on Nematode Communities and Arsenic Uptake by Maize in Arsenic-Contaminated Soils

The influences of arbuscular mycorrhizal fungi (AMF, Acaulospora spp. and Glomus spp.) and rice straw and earthworms (RE, Eisenia foetida) on nematode communities and arsenic (As) uptake by maize ( Zea mays L.) in As-contaminated soils were examined in a field experiment conducted in Wujiang, Jiangsu Province, China. The experiment was designed as a 2 × 2 factorial with the factors of AMF (inoculated or uninoculated) and RE (added or not added). The results demonstrated that AMF inoculation led to significantly higher root colonization of AMF and root dry weight. Plants inoculated with both AMF and RE had the highest As concentrations in root. The number of total nematodes increased with AMF inoculation when RE was absent, and decreased with RE addition when AMF was inoculated. The improved abundance of nematodes with the AMF treatment implied that the tested AMF acted as food sources for fungivores. The abundances of omnivores-predators and plant parasites were reduced by earthworm activity. Twenty-seven genera of nematodes were identified, with Filenchus dominant in all treatments. Trophic diversity, Shannon-Weaver diversity, Simpson dominance index, and species richness indicated higher species diversity, more proportionate species composition, evenly distributed species, and more food sources in the AMF, RE, and their interaction treatments. Maturity index showed a moderately disturbed environment due to As pollution. Besides enhancing plant uptake of contaminants, AMF and RE amendments could also improve soil health by restoring the structure of soil communities, as reflected by more stable nematode community structure.

Remediation of Arsenic-Contaminated Soils by Iron Amendments: A Review

Arsenic (As) in soil is a serious environmental issue, and although As occurs naturally in soil, anthropogenic activities have greatly increased As soil contamination. Several technologies can be used to reduce arsenic contamination in soils, among them in situ chemical immobilization by application of inorganic amendments, which are incorporated and mixed with the contaminated soil. The binding of As to the additive reduces its mobility and bioavailability in the soil, with the long-term stability of the new compounds formed being an important issue. The objective of this study was to review the literature concerning remediation of As-contaminated soils with different iron sources and to evaluate their effectiveness.

Rhizosphere characteristics of two arsenic hyperaccumulating Pteris ferns

Better understanding of the processes controlling arsenic bioavailability in the rhizosphere is important to enhance plant arsenic accumulation by hyperaccumulators. This greenhouse experiment was conducted to evaluate the chemical characteristics of the rhizosphere of two arsenic hyperaccumulators Pteris vittata and Pteris biaurita. They were grown for 8 weeks in rhizopots containing arsenic-contaminated soils (153 and 266 mg kg − 1 arsenic). Bulk and rhizosphere soil samples were analyzed for water-soluble As (WS-As) and P (WS-P), pH, and dissolved organic carbon (DOC). Comparing the two plants, P. vittata was more tolerant to arsenic and more efficient in arsenic accumulation than P. biaurita, with the highest frond arsenic being 3222 and 2397 mg kg − 1 . Arsenic-induced root exudates reduced soil pH (by 0.74–0.92 units) and increased DOC concentrations (2–3 times) in the rhizosphere, resulting in higher WS-P (2.6–3.8 times higher) compared to the bulk soil. Where there was no difference in WS-As between the rhizosphere and bulk soil in soil-153 for both plants, WS-As in the rhizosphere was 20–40% higher than those in bulk soil in soil-266, indicating that the rate of As-solubilization was more rapid than that of plant uptake. The ability to solubilize arsenic via root exudation in the rhizosphere and the ability to accumulate more P under arsenic stress may have contributed to the efficiency of hyperaccumulator plants in arsenic accumulation.

Health risks from arsenic-contaminated soil in Flin Flon–Creighton, Canada: Integrating geostatistical simulation and dose–response model

Elevated concentrations of arsenic were detected in surface soils adjacent to a smelting complex in northern Canada. We evaluated the cancer risks caused by exposure to arsenic in two communities through combining geostatistical simulation with demographic data and dose–response models in a framework. Distribution of arsenic was first estimated using geostatistical circulant-embedding simulation method. We then evaluated the exposures from inadvertent ingestion, inhalation and dermal contact. Risks of skin caner and three internal cancers were estimated at both grid scale and census-unit scale using parametric dose–response models. Results indicated that local residents could face non-negligible cancer risks (skin cancer and liver cancer mainly). Uncertainties of risk estimates were discussed from the aspects of arsenic concentrations, exposed population and dose–response model. Reducing uncertainties would require additional soil sampling, epidemic records as well as complementary studies on land use, demographic variation, outdoor activities and bioavailability of arsenic.

Potencial de quatro espécies herbáceas forrageiras para fitorremediação de solo contaminado por arsênio

A fitorremediação de solos e substratos contaminados por elementos tóxicos tem despertado crescente interesse entre pesquisadores e técnicos. Particularmente em relação ao As, o obstáculo ao emprego desta técnica é o pequeno número de espécies identificadas capazes de acumular este elemento. O objetivo deste trabalho foi avaliar o potencial de plantas de estilosante (Stylosanthes humilis HBK), amendoim (Arachis pintoi Krapov. & Gregory), aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.) como espécies fitorremediadoras de áreas contaminadas por As. Amostras de Latossolo Vermelho-Amarelo foram incubadas por 15 dias com diferentes doses de As: 0; 50; 100; e 200 mg dm-3. Em seguida, realizaram-se a semeadura das quatro espécies e as respectivas adubações. Aos 65 dias após a semeadura, as plantas foram avaliadas quanto à altura, à matéria seca da parte aérea e raízes. Determinaram-se os teores de As nas folhas jovens, intermediárias e basais, no caule e nas raízes, bem como o conteúdo e o índice de translocação (IT) de As. Por meio de análises de regressão, foram estimados os teores críticos (TC) de As disponíveis no solo, que proporcionaram redução de 50 % da matéria seca. As espécies estudadas apresentaram comportamento diferenciado quanto à tolerância ao As, com destaque para azevém, amendoim e estilosante, que não apresentaram lesões foliares decorrentes de fitotoxidez por esse elemento. Os TC para as plantas de aveia e azevém foram significativamente superiores aos observados para as demais espécies, caracterizando-as como espécies tolerantes ao As. As plantas de amendoim e estilosante apresentaram maior capacidade de absorção e maior IT de As para a parte aérea. As plantas de amendoim apresentaram maiores teores nas folhas basais e raízes, mostrando potencial para serem utilizadas em programas de fitorremediação. As plantas de azevém, amendoim e estilosante podem ser utilizadas na fitoestabilização e, ou, na revegetação de áreas contaminadas por As, uma vez que apresentaram tolerância a esse elemento. Por se tratar de espécies forrageiras, quando utilizadas para esses fins, cuidados especiais são necessários, como o isolamento da área, para evitar a entrada do elemento na cadeia trófica.

Arsenic-resistant bacteria isolated from agricultural soils of Bangladesh and characterization of arsenate-reducing strains

To analyse the arsenic-resistant bacterial communities of two agricultural soils of Bangladesh, to isolate arsenic-resistant bacteria, to study their potential role in arsenic transformation and to investigate the genetic determinants for arsenic resistance among the isolates. Enrichment cultures were performed in a minimal medium in the presence of As(III) and As(V) to isolate resistant bacteria. Twenty-one arsenic-resistant bacteria belonging to different genera of Gram-positive and Gram-negative bacteria were isolated. The isolates, with the exception of Oceanimonas doudoroffii Dhal Rw, reduced 2 mmol l(-1) As(V) completely to As(III) in aerobic conditions. Putative gene fragments for arsenite efflux pumps were amplified in isolates from Dhal soil and a putative arsenate reductase gene fragment was amplified from a Bacillus sp. from Rice soil. Phylogenetically diverse arsenic-resistant bacteria present in agricultural soils of Bangladesh are capable of reducing arsenate to arsenite under aerobic conditions apparently for detoxification purpose. This study provides results on identification, levels of arsenic resistance and reduction of arsenate by the bacterial isolates which could play an important role in arsenic cycling in the two arsenic-contaminated soils in Bangladesh.

Composition, biomass and activity of microflora, and leaf yields and foliar elemental concentrations of lettuce, after in situ stabilization of an arsenic-contaminated soil

Beringite (B) and zerovalent iron grit (Z), singly and in combination (BZ), were added to a loamy sand soil contaminated by trace elements (Reppel, Belgium), mainly by arsenic (As), to reduce As labile fractions and phytoavailability. An uncontaminated sandy soil was studied for comparison. Soils were placed in large lysimeters cultivated with maize and vegetables for 6 years. pH, organic C and total N content increased in amended soils. The Z and BZ treatments reduced the Ca(NO 3) 2 − extractable soil As and As uptake by lettuce. The BZ lettuces had also the lowest foliar Pb, Cd, Zn, and Mn concentrations. All amendments had positive effects on the soil microbial biomass and reduced the qCO 2. Glucose mineralization was increased in Z and BZ amended soils. Acid phosphomonoesterase activity was higher in the untreated soil than in the other soils; the alkaline phosphomonoesterase, phosphodiesterase and protease activities were increased by Z and BZ treatments, whereas B amendment had less positive effects. Genetic fingerprinting using Denaturing Gradient Gel Electrophoresis (DGGE) revealed shifts in the composition of eubacterial and fungal communities of the amended soils. Microbial species richness decreased rather than increased in the treated soils, regardless of reduced trace element availability and increased soil microbial biomass and activity.

Slurry bioreactor modeling using a dissimilatory arsenate-reducing bacterium for remediation of arsenic-contaminated soil

A slurry bioreactor using a dissimilatory arsenate (As(V))-reducing bacterium is proposed for remediation of arsenic-contaminated soils. Bacterial As(V) reduction can cause arsenic extraction from the solid to the liquid phase because arsenite, As(III), is much less adsorptive than As(V). A mathematical model was developed incorporating the reversible sorption process of arsenic as well as bacterial growth and decay via As(V) reduction. A linear isotherm equation expressed the sorption process. The model included Haldane kinetics with high As(V) concentrations and cell inactivation by toxicity due to As(III). Extraction experiments used synthetic contaminated soils (forest soil, Soil SF, 1100 mg kg(-1); paddy soil, Soil SP, 1100 mg kg(-1)) and actual contaminated soils (Soil AH 2200 mg kg(-1) and Soil AL, 220 mg kg(-1)) at 5% w/v slurry concentration. Simulation results matched the observed changes of arsenic concentrations in the liquid phase. The respective extraction efficiencies of arsenic were 63%, 41%, 20%, and 55% for SF, SP, AH, and AL soils. Sensitivity analyses showed that the rate-limiting step was the desorption rate of As(V) from the solid to the liquid phase, rather than the As(V)-reducing rate. The proposed model provides a useful framework for understanding and predicting the extraction of arsenic from soil.

Genes involved in arsenic transformation and resistance associated with different levels of arsenic-contaminated soils

BackgroundArsenic is known as a toxic metalloid, which primarily exists in inorganic form [As(III) and As(V)] and can be transformed by microbial redox processes in the natural environment. As(III) is much more toxic and mobile than As(V), hence microbial arsenic redox transformation has a major impact on arsenic toxicity and mobility which can greatly influence the human health. Our main purpose was to investigate the distribution and diversity of microbial arsenite-resistant species in three different arsenic-contaminated soils, and further study the As(III) resistance levels and related functional genes of these species.ResultsA total of 58 arsenite-resistant bacteria were identified from soils with three different arsenic-contaminated levels. Highly arsenite-resistant bacteria (MIC > 20 mM) were only isolated from the highly arsenic-contaminated site and belonged to Acinetobacter, Agrobacterium, Arthrobacter, Comamonas, Rhodococcus, Stenotrophomonas and Pseudomonas. Five arsenite-oxidizing bacteria that belonged to Achromobacter, Agrobacterium and Pseudomonas were identified and displayed a higher average arsenite resistance level than the non-arsenite oxidizers. 5 aoxB genes encoding arsenite oxidase and 51 arsenite transporter genes [18 arsB, 12 ACR3(1) and 21 ACR3(2)] were successfully amplified from these strains using PCR with degenerate primers. The aoxB genes were specific for the arsenite-oxidizing bacteria. Strains containing both an arsenite oxidase gene (aoxB) and an arsenite transporter gene (ACR3 or arsB) displayed a higher average arsenite resistance level than those possessing an arsenite transporter gene only. Horizontal transfer of ACR3(2) and arsB appeared to have occurred in strains that were primarily isolated from the highly arsenic-contaminated soil.ConclusionSoils with long-term arsenic contamination may result in the evolution of highly diverse arsenite-resistant bacteria and such diversity was probably caused in part by horizontal gene transfer events. Bacteria capable of both arsenite oxidation and arsenite efflux mechanisms had an elevated arsenite resistance level.

Toxicity and accumulation of arsenic in wheat (Triticum aestivum L.) varieties of China

Soil arsenic contamination becomes a potential agricultural and environmental hazard worldwide, and has been a serious problem for safe food production. A field experiment on soil contamination was conducted on four wheat varieties ( Jimai, Gaoyou, Weimai and Wennong) in Eastern China, using 50 or 100 mg arsenic/kg soil. Biomass production and yield components were determined and arsenic concentrations were measured in plant tissues. Differential arsenic effects on wheat varieties were determined at maturity. Results showed that addition of arsenic significantly (p stems > leaves and rachises > grains > glumes > awns. In the arsenic treatments, arsenic concentrations in bran were about 2-3 times higher than those in flour. Most of the arsenic contaminated flour exceeded the Chinese tolerance limit. Arsenic contents of grain parts were dependent on variety and treatment level in polluted soils. Weimai and Wennong showed highest amounts of arsenic in flour than the other varieties at 50 or 100 mg/ kg soil treatment, respectively. Weimai possessed significantly lower (p<0.05) amount of arsenic in bran than any other wheat variety. Results showed significant variety differences in arsenic concentration in polluted areas; it is of outstanding importance that wheat with the lowest possible arsenic concentration is used for food or fodder production. The present results provide scientific basis for revising the standards of wastewater discharges.

MODELING ARSENIC DESORPTION FROM HERBICIDE-CONTAMINATED SOILS

The application of arsenical herbicides has created legacy environmental problems by contaminating soil in some agricultural areas and at various industrial sites. Numerous previous studies have suggested that the adsorption of arsenic by common soil components is largely controlled by kinetic factors. Four arsenic-contaminated soil samples collected from industrial sites were characterized and subjected to sequential leaching using a synthetic acid rain solution in order to study the release of arsenic. A dual-site numerical sorption-desorption model was constructed that describes arsenic desorption from these soils in terms of two different release mechanisms: Release from type I (equilibrium) and type II (kinetic) sorption sites. Arsenic held on both type I and II sorption sites is accessible through extensive acid rain leaching. Arsenic desorption from these sites follows a linear Kd model; the manner of approaching the Kd model, however, differs. Arsenic desorption from type I sites reached equilibrium with the aqueous phase under the physical environment provided by the experiment (shaking for 24 h at 25 degrees C), while desorption from type II sites followed a first-order kinetic pattern when approaching equilibrium. During synthetic acid rain sequential leaching of the soils, type I sites released their sorbed arsenic rapidly and subsequent desorption was dominated by the kinetic release of arsenic from type II sites. This shift in desorption mechanism dominance generated data corresponding to two intersecting straight lines in the n-logC dimension for all four soils. The dual-site desorption model was solved analytically and proven to be successful in simulating sorption processes where two different mechanisms are simultaneously controlling the aqueous concentration of a trace element.

A Review on Advanced Treatment Methods for Arsenic Contaminated Soils and Water

Abstract A number of treatment methods have been investigated in the laboratory or full scale to remove arsenic from drinking water and to remediate arsenic-contaminated sites. This paper gives a review on the advanced technologies for the treatment of arsenic-contaminated soils and water. Treatment methods such as oxidation, anion exchange, membrane separation, and adsorption/precipitation have been developed to remove arsenic from drinking water or groundwater. However, further research is needed to find new and more efficient substitute materials for the ion exchange resins, membranes, and adsorbents to improve the treatment and cost efficiencies. A stabilization/solidification method has been demonstrated successfully to contain arsenic in contaminated soils, sediments, and solid wastes. Vitrification is also applicable but may be more expensive due to the high energy requirements. Electrochemical methods based on electrokinetics are emerging. Especially, electrokinetics and electrodialysis are suited for fine-grained soils. Chemical extraction, either in-situ or ex-situ, can be efficient to remove bulk arsenic from contaminated soils and solid wastes. Selection of proper extractants is the key to the success of this method. Bioremediation, phytoremediation, and natural attenuation show great potential for future developments because of their environmental compatibility and cost effectiveness. Generally, it is critical to recognize that no single specific technology may be considered as generally applicable. Combination of existing technologies may provide an efficient and cost-effective treatment alternative. Use of biodegradable and environmentally benign products to enhance the remediation processes should be further investigated.

Isolation and characterization of arsenite-oxidizing bacteria from arsenic-contaminated soils in Thailand

Two hundred and eighty-eight arsenic-resistant bacteria were isolated by an enrichment culture method from a total of 69 arsenic-contaminated soil-samples collected from Dantchaeng district in Suphanburi province (47 samples), and from Ron Phiboon district in Nakhon Sri Thammarat province (22 samples), in Central and Southern Thailand, respectively. Twenty-four of the 288 isolated arsenic-resistant bacteria were found to be arsenite-oxidizing bacteria. On the basis of their morphological, cultural, physiological, biochemical and chemotaxonomic characteristics, and supported by phylogenetic analysis based upon their 16S rRNA gene sequences, they were divided into five groups, within the genera Acinetobacter, Flavobacterium, Pseudomonas, Sinorhizobium and Sphingomonas, respectively. Within genera, phylogenetic analysis using the 16S rRNA gene sequences suggested that they were comprised of at least ten species, five isolates being closely related to known bacteria (Acinetobacter calcoaceticus NCCB 22016T, Pseudomonas plecoglossicida FPC951T, Ps. knackmussii B13T, Sinorhizobium morelense Lc04T, and Sphingomonas subterranea IFO16086T). The other five proposed species are likely to be new species closely related to Flavobacterium johnsoniae, Sinorhizobium morelense, Acinetobacter calcoaceticus and Pseudomonas plecoglossicida, but this awaits further characterization for confirmation of the taxonomic status. No overlap in isolated species or strains was observed between the two sites. The strain distribution and characterization are described.

Growth Response and Arsenic Uptake of White Clover (Trifolium repens) and Evening Primrose(Oenothera odorata) Colonized with Arbuscular Mycorrhizal Fungi in Arsenic-Contaminated Soil

A greenhouse experiment was conducted to investigate the role of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae (BEG 107) in enhancing growth and arsenic (As) and phosphorus (P) uptake of white clover (Trifolium repens) and evening primrose (Oenothera odorata) in soil collected from a gold mine having concentrations of 381.6 mg total As kg -1 and 20.5 mg available As kg -1 . Trifolium repens and O. odorata are widely distributed on abandoned metalliferous mines in Korea. The percent root colonization by the AM fungus was 55.9 % and 62.3 % in T. repens and O. odorata, respectively, whereas no root colonization was detected in control plants grown in a sterile medium. The shoot dry weight of T. repens and O. odorata was increased by 323 and 117 % in the AM plants compared to non-mycorrhizal (NAM) plants, respectively. The root dry weight increased up to 24 % in T. repens and 70% in O. odorata following AM colonization compared to control plants. Mycorrhizal colonization increased the accumulation of As in the root tissues of T. repens and O. odorata by 99.7 and 91.7 % compared to the NAM plants, respectively. The total uptake of P following AM colonization increased by 50% in T. repens and 70 % in O. odorata, whereas the P concentration was higher in NAM plants than in the AM plants. Colonization with AM fungi increased the As resistance of the host plants to As toxicity by augmenting the yield of dry matter and increasing the total P uptake. Hence, the application of an AM fungus can effectively improve the phytoremediation capability of T. repens and O. odorata in As-contaminated soil.

달천광산 주변 토양 내 비소의 존재형태 및 토양세척법에 의한 제거

This study has been carried out to examine the feasibility of soil washing process for reducing arsenic contamination level of soil around Mine. The results of physicochemical tests of the target soil showed that pH was weak alkalic (), soil texture was coarse sand, and organic contents (5.7%) and CEC (Cation exchange capacity; 21.5 meq/100 g) were similar with those of soils generally found in Korea. Contamination levels of arsenic were found to over 201 mg/kg which exceed the Korea standard levels of countermeasure and concern. To investigate chemical partitioning of heavy metals, sequential extraction procedures were adopted and it was found that arsenic was predominantly associated with the residual fraction among five fractional forms as much as over 85%, which is demonstrating that only less than 15% of all might be vulnerable to a selected washing agents. Among 6 kinds of washing agents applied on the screening for arsenic-contaminated soil, HCl and solution were selected as promising washing agents. In comparison with HCl and solutions for arsenic washing by kinetic experiment in the change of pH, soil-solution ratio, temperature, and washing solution concentration, solution was determined to best one of agents tested, which showed faster washing rate than HCl to accomplish regulatory goal.