Seasonal changes of arsenic speciation in lake waters in relation to eutrophication

In this study, the influence of eutrophication on arsenic speciation in lake waters was investigated. Surface water samples (n = 1-10) were collected from 18 lakes in Japan during July 2007 and February 2008. The lakes were classified into mesotrophic (7 lakes) and eutrophic (11 lakes) based on the total phosphate (T-P) and chlorophyll-a (Chl-a) concentrations in water column. Inorganic, methylated and ultraviolet-labile fractions of arsenic species were determined by combining hydride generation atomic absorption spectrometry with ultraviolet irradiation. Organoarsenicals (mainly methylated and ultraviolet-labile fractions) comprised 30-60% of the total arsenic in most lakes during summer. On the other hand, inorganic arsenic species (As(III + V)) dominates (about 60-85%) during winter. The occurrence of ultraviolet-labile fractions of arsenic was higher in eutrophic lakes than those in mesotrophic lakes in both seasons. The concentration of dimethyl arsenic (DMAA) was high in eutrophic lakes during winter; and in mesotrophic lakes during summer. The results suggest that the conversion of As(III + V) to more complicated organoarsenicals occurred frequently in eutrophic lakes compared to that in mesotrophic lakes, which is thought to be the influence of biological activity in the water column. The distribution of arsenic species were well correlated with phosphate concentrations than those of Chl-a. This might be due to the competitive uptake of As(V) and phosphate by phytoplankton. The organoarsenicals (OrgAs)/As(V) ratio was higher at low phosphate concentration indicating that conversion of As(V) to OrgAs species was more active in phosphate-exhausted lakes with high phytoplankton density.     

Uptake, transport and transformation of arsenate in radishes (Raphanus sativus)

The localization and identification of arsenic compounds in terrestrial plants are important for the understanding of arsenic uptake, transformation and translocation within these organisms, and contributes to our understanding of arsenic cycling in the environment. High performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS), and X-ray absorption near-edge structure (XANES) analysis identified arsenite, arsenate and arsenic(III)-sulphur compounds in leaf, stem and root sections of Rhaphanus sativus (radish) plants grown in both arsenic contaminated mine waste, and arsenic amended liquid cultures. The total arsenic distribution was similar between the plants grown in mine waste and those grown hydroponically. Arsenate was the predominant form of arsenic available in the growth mediums, and after it was taken up by roots, X-ray absorption spectroscopy (XAS) imaging indicated that some of the arsenate was transported to the shoots via the xylem. Additionally, arsenate was reduced by the plant and arsenic(III)-sulphur compound(s) accounted for the majority of arsenic in the leaf and stem of living plants. In this study the application of synchrotron techniques permitted the identification of arsenic(III)-sulphur species which were "invisible" to conventional HPLC-ICP-MS analysis.     

Arsenic speciation in river and estuarine waters from southwest Spain

An arsenic speciation survey was carried out in water samples from the Tinto and Odiel Rivers (southwest of Spain), as well as their common estuary. Both rivers are affected by acid mine drainage (AMD) and represent an input of heavy metals into the estuary, which also suffers from industrial water discharges. Samples were taken in December 2000 and July 2001. The arsenic species considered were arsenite (As(III)), arsenate (As(V)), monomethylarsonic (MMA) and dimethylarsinic (DMA) ions using coupled high-performance liquid chromatography-hydride generation-inductively coupled plasma-mass spectrometry (HPLC-HG-ICP-MS) for their determination. Parameters such as pH, salinity, redox potential and dissolved O2 were also measured. The results revealed that the acid mine drainage originating mainly during winter along the upper part of the Tinto River course causes high inorganic concentrations of dissolved arsenic, up to 600 microg l(-1) of As(III) and 200 microg l(-1) of As(V). In summer, As(III) levels decreased due to the diminution of the input from acid mine drainage and also because of oxidation, with a corresponding increase of As(V) level. Furthermore, the extreme acidic conditions of this river (pH 2.3-2-6) do not allow biological activity sufficient to produce significant concentrations of methylated arsenic species. The arsenic concentrations in the nearby Odiel River were always 5-10 times lower than in the Tinto River, with arsenic levels usually below 100 microg l(-1), dominated by As(V), indicating that it is less affected by acid mine drainage. The highest inorganic arsenic species concentrations were found where the river crosses a mining site, which corresponds to the highest As(III) values. Significant biological activity in this river produced methylated species that were detected along the water-course, with the highest concentrations at the lower course of the river, accounting for up to 53-61% of the total dissolved arsenic. At the common estuary formed by both rivers, only arsenate was detected in most samples at lower concentrations than in the riverine water samples. The tidal cycle showed a similar pattern of dilution of the arsenate when seawater comes into the estuary. Methylated species were not found either in summer or winter, at least at the 0.1 microg l(-1) level, possibly because of the high turbidity of the waters, producing an inhibition of the phytoplankton activity. In addition to the riverine inputs into the common estuary, industrial activity also represents an important source of arsenic as the discharge from a Cu smelter produced the highest arsenate level of all samples in estuary and also the only sample with significant arsenite concentration. Furthermore, the underlying iron-oxide-rich sediments represent an importance source of arsenic into the water column. In three nearby estuaries not affected by industrial activity or acid mine drainage, arsenic levels remained below detection limits.     

Mobile arsenic species in unpolluted and polluted soils

The fate and behaviour of total arsenic (As) and of As species in soils is of concern for the quality of drinking water. To estimate the relevance of organic As species and the mobility of different As species, we evaluated the vertical distribution of organic and inorganic As species in two uncontaminated and two contaminated upland soils. Dimethylarsinic acid (up to 6 ng As g(-1)), trimethylarsine oxide (up to 1.5 ng As g(-1)), 4 unidentified organic As species (up to 3 ng As g(-1)) and arsenobetaine (up to 15 ng As g(-1)), were detected in the forest soils. Arsenobetaine was the dominant organic As species in both unpolluted and polluted forest soils. No organic As species were detected in the contaminated grassland soil. The organic As species may account for up to 30% of the mobile fraction in the unpolluted forest floor, but never exceed 9% in the unpolluted mineral soil. Highest concentrations of organic As species were found in the forest floors. The concentrations of extractable arsenite were highest in the surface horizons of all soils and may represent up to 36% of total extractable As. The concentrations of extractable arsenate were also highest in the Oa layers in the forest soils and decreased steeply in the mineral soil. In conclusion, the investigated forest soils contain a number of organic As species. The organic As species in forest soils seem to result from throughfall and litterfall and are retained mostly in the forest floor. The relative high concentrations of extractable arsenite, one of the most toxic As species, and arsenate in the forest floor point to the risk of their transfer to surface water by superficial flow under heavy rain events.     

Field and laboratory arsenic speciation methods and their application to natural-water analysis

The toxic and carcinogenic properties of inorganic and organic arsenic species make their determination in natural water vitally important. Determination of individual inorganic and organic arsenic species is critical because the toxicology, mobility, and adsorptivity vary substantially. Several methods for the speciation of arsenic in groundwater, surface-water, and acid mine drainage sample matrices using field and laboratory techniques are presented. The methods provide quantitative determination of arsenite [As(III)], arsenate [As(V)], monomethylarsonate (MMA), dimethylarsinate (DMA), and roxarsone in 2-8 min at detection limits of less than 1 microg arsenic per liter (microg As L(-1)). All the methods use anion exchange chromatography to separate the arsenic species and inductively coupled plasma-mass spectrometry as an arsenic-specific detector. Different methods were needed because some sample matrices did not have all arsenic species present or were incompatible with particular high-performance liquid chromatography (HPLC) mobile phases. The bias and variability of the methods were evaluated using total arsenic, As(III), As(V), DMA, and MMA results from more than 100 surface-water, groundwater, and acid mine drainage samples, and reference materials. Concentrations in test samples were as much as 13,000 microg As L(-1) for As(III) and 3700 microg As L(-1) for As(V). Methylated arsenic species were less than 100 microg As L(-1) and were found only in certain surface-water samples, and roxarsone was not detected in any of the water samples tested. The distribution of inorganic arsenic species in the test samples ranged from 0% to 90% As(III). Laboratory-speciation method variability for As(III), As(V), MMA, and DMA in reagent water at 0.5 microg As L(-1) was 8-13% (n=7). Field-speciation method variability for As(III) and As(V) at 1 microg As L(-1) in reagent water was 3-4% (n=3).     

A nationwide survey of NDMA in raw and drinking water in Japan

A nationwide survey of N-nitrosodimethylamine (NDMA) in both raw and finished water samples from drinking water treatment plants (DWTPs) in Japan was conducted. NDMA was analyzed by solid-phase extraction (SPE) followed by ultra performance liquid chromatography (UPLC) coupled with tandem mass spectrometry (MS/MS). NDMA was detected in 15 of 31 raw water samples collected in the summer at concentrations up to 2.6 ng/L, and in 9 of 28 raw water samples collected in winter at concentrations up to 4.3 ng/L. The NDMA concentrations were higher in raw water samples collected from treatment plants with catchment areas that have high population densities. The NDMA concentrations were higher in river water samples collected from the east and west of Japan than in those collected from other areas. NDMA was detected in 10 of 31 finished samples collected in summer at reduced concentrations of up to 2.2 ng/L, while 5 of 28 finished samples collected in winter showed NDMA concentrations up to 10 ng/L. The highest NDMA levels were detected in finished water samples collected from the Yodo River basin DWTP, which uses ozonation. Furthermore, evaluation of the process water produced at six advanced water treatment plants was conducted. Influent from the Yodo River indicated that the NDMA concentration increased during ozonation to as high as 20 ng/L, and then decreased with subsequent biological activated carbon treatment. To our knowledge, this is the first nationwide evaluation of NDMA concentrations in water conducted in Japan to date.     

毛竹复合土钉墙工作性状的数值分析研究

以某软土基坑采用毛竹复合土钉墙支护的工程实例为背景,利用有限元软件PLAXIS建立某设计剖面的平面应变有限元模型。为提高数值分析定量计算分析的精度,采用了能反映土体小变形和加卸载变形等特点的小应变刚度模型。通过对土钉墙面层及毛竹排桩的水平位移、坡顶沉降、毛竹土钉的轴力以及毛竹排桩的剪力和弯矩分布规律的分析,对堤坝形毛竹复合土钉墙的工作性状获得了较全面的认识,并探索了其可能的失稳破坏形式。采用该程序自带的强度折减有限元法计算了各开挖工况下支护体系的稳定安全系数,表明毛竹复合土钉墙在施工期间和施工后均具有较高的稳定性,具备可靠的支护能力。     

Arsenic accumulation by plants on mine waste (United Kingdom)

Information is provided concerning the concentrations of arsenic found in plants and soils from various sites in the U.K. that are enriched in arsenic. Ecotypes of various species can accumulate arsenic to extreme levels and these have been related to the total arsenic present in the soils. Clonal material from one such species exhibited tolerance to levels of arsenate that were lethal to normal ecotypes. Inter-element correlations were found for arsenic and iron in the aerial parts of the plants, but no such correlations were found between arsenic and either copper, zinc, lead or phosphate. Although arsenic occurred at high levels throughout the plant, including the seeds, the highest concentrations were recorded in old leaves.     

Influence of microbes on the mobilization, toxicity and biomethylation of arsenic in soil.

To understand the effects of microbial activity on the mobilization and speciation of arsenic in soil, the cycling of arsenic was studied in microcosm experiments under laboratory conditions. Particular attention was paid to the biomethylation of arsenic and to the toxicity of inorganic and organic arsenic species for microbes. Microbes enhanced mobilization of arsenic from soil by 19-24% compared to formaldehyde inhibited controls. Formation of dissolved methylated arsenic species by microbes was low (< 0.1%) during the 5-day incubation. Even though methylation may function as a detoxification method, it was of minor importance in the soil tested.     

Partitioning and speciation of chromium, copper, and arsenic in CCA-contaminated soils: influence of soil composition

This study focused on the influence of soil composition and physicochemical characteristics on the retention and partitioning of Cu, Cr and As in nine chromated copper arsenate (CCA) artificially contaminated soils. A statistical mixture design was used to set up the number of soils and their respective composition. Sequential extraction and modified solvent extraction were used to assess Cu and Cr partitioning and As speciation [As(III) or As(V)]. It was found that peat had a strong influence on CEC (232 meq/100 g), on buffer capacity and on Cu and Cr retention, whereas kaolinite's contribution to the CEC was minor (38 meq/100 g). Average metal retention in mineral soils was low (58% for Cu and 23% for Cr) but increased dramatically in highly organic soils (96% for Cu and 78% for Cr). However, both organic and mineral soils demonstrated a very high sorption of added As (71-81%). Levels of Cu and Cr in a soluble or exchangeable form (F1) in highly organic soils were very low, whereas the levels strongly bound to organic matter were much higher. Conversely, in mineral soils, 47% of Cu and 18% of Cr were found in F1. As a result, Cr and Cu in moderately and highly organic contaminated soils were present in less mobile and less bioavailable forms, whereas in mineral soils, the labile fraction was higher. The modified method used for selective determination of mineral As species in CCA-contaminated soils was found to be quantitative and reliable. Results revealed that arsenic was principally in the pentavalent state. Nevertheless, in organic soils, arsenite was found in significant proportions (average value of 29% in highly organic soils). This indicates that some reduction of arsenate to arsenite occurred since the original species in CCA is As(V).     

Uptake of methylated arsenic by a polymeric adsorbent: process performance and adsorption chemistry

Methylated arsenic in groundwater has caused a series of health problems to human beings. A N-methylglucamine modified chitosan polymeric adsorbent was successfully developed for efficient adsorption of methylated arsenic from water solution. Adsorption behaviors of two common methylated arsenic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), onto the adsorbent were investigated in this paper. The surface modification increased the adsorption capabilities for the arsenic. The uptake of MMA was higher than that of DMA throughout all pH values. The maximum adsorption capacities were 15.4 mg/g for MMA and 7.1 mg/g for DMA, exhibiting competitive advantages with other reported materials. The affinity of these arsenic species for the adsorbent followed a pattern of MMA > DMA. The adsorption equilibrium was achieved within 20 h. The uptake of MMA and DMA was dependent upon the concentration of background electrolytes, indicating the formation of outer-sphere complexes of both organoarsenic species with the adsorbent during the adsorption. The existence of natural organic matter and competitive anions cause decrease in the uptake of both arsenic species. Furthermore, the simultaneous uptake of organic contaminants such as humic acid was observed. The spectroscopic analysis demonstrated the strong attachment of both organic arsenic species onto the amine functional group of the adsorbent.     

Arsenic speciation and mobilization in CCA-contaminated soils: influence of organic matter content

A laboratory incubation experiment was conducted to investigate the influence of organic matter content on arsenic speciation and mobilization in chromated copper arsenate (CCA)-contaminated soils. The study was performed with four synthetic CCA-contaminated soils, with a range of organic matter content (mixture of peat moss and poultry manure) varying between 0.5% and 15% (w/w), under unsaturated and aerobic conditions for 40 days. Changes in water-soluble arsenic speciation (As(V), As(III), MMAA, DMAA) were monitored over time in soil extracts by HPLC-ICP-MS and in the soil solid phase (As(III), As(V)) by a solvent extraction method. Irrespective of organic matter content, As(V) was the predominant soil bound and aqueous phase arsenic species. However, over 40 days, a high soil organic matter content (7.5% and 15%) was able to entail formation of soil bound As(III). Moreover, total water-soluble arsenic was positively correlated with dissolved organic carbon (r(2)=0.88). However, the organic matter content did not influence arsenic speciation in the soluble fraction; neither As(V) reduction nor arsenic biomethylation occurred within 40 days. An increase in dissolved organic carbon content promoted both As(V) and As(III) solubilization in soils. Also, over time, organic matter contents of 7.5% and 15% entailed the persistence of soluble As(V), likely due to the high content of dissolved organic compounds which prevented its sorption onto soil. Based on this data, the environmental risk of aerobic CCA-contaminated soils rich in organic matter may be due to an enhanced availability of soluble As(V) over time, rather than to the formation of the more toxic and more mobile As(III).     

Mobilization of arsenic by dissolved organic matter from iron oxides, soils and sediments

The arsenic contamination of aquifers has been linked to the input of dissolved organic matter (DOM). In light of this suggestion, the aim of this study was to quantify chemical effects of DOM on desorption and redox transformations of arsenic bound to synthetic iron oxide and natural samples from different geochemical environments (soils, shallow aquifer, lake sediment). In batch experiments, solutions containing 25-50 mg/L of two different types of DOM (purified peat humic acid and DOM from a peat drainage) were used as extractants in comparison to inorganic solutions. DOM solution was able to mobilize arsenic from all solid phases. Mobilization from iron oxides (maximum: 53.3%) was larger than from natural samples (maximum: 2.9%). The mobilization effect of extractants decreased in the order HCl>NaH2PO4>DOM>NaNO3. DOM solutions, therefore, mainly targeted weakly sorbed arsenic. Mobilization was complete within 24-36 h and DOM was sorbed during incubation indicating competition for sorption sites. The same patterns were observed for different DOM types and concentrations. Addition of DOM lead to (a) enhanced reduction (maximum 7.8%) and oxidation (6.4%) of arsenic in aqueous solution and (b) the appearance of arsenite in aqueous phase of soil samples (5.5%). As the primary mechanism for the arsenic release from solid phases we identified the competition between arsenic and organic anions for sorption sites, whereas redox reactions were probably of minor importance. The results of this study demonstrate that sorption of DOM has a strong potential to mobilize arsenic from soils and sediments.     

Trace element and Sigma DDT concentrations in horticultural soils from the Tasman, Waikato and Auckland regions of New Zealand

The long-term routine use of agrichemicals can result in elevated levels of trace elements and persistent organic pollutants in soils. Trace element concentrations and SigmaDDT levels were measured in soil (0-7.5 cm) samples collected from horticultural and grazing properties in 3 regions of New Zealand (Auckland, Tasman and Waikato). Elevated levels of arsenic (<2 to 58 mg kg(-1)), cadmium (<0.1 to 1.5 mg kg(-1)), copper (5 to 523 mg kg(-1)), lead (5 to 243 mg kg(-1)) and SigmaDDT (<0.03 to 34.5 mg kg(-1)) were detected in soils from all 3 regions. With the exception of cadmium and zinc, significantly higher levels of contaminants were generally detected in horticultural soils than in grazing soils. Our results have implications for the on-going use of agrichemicals as concentrations of cadmium, copper, tin and zinc in some samples exceeded ecotoxicity based soil criteria. The p,p'-DDE:DDT ratios indicate that the degradation of DDT in NZ horticultural soils may be inhibited by the co-contamination with trace elements.     

The characteristics of rhizosphere microbes associated with plants in arsenic-contaminated soils from cattle dip sites

Soil microorganisms and plants were studied in samples of arsenic-contaminated soil from two cattle dip sites. The aim was to delineate the parameters that will determine the feasibility of future remediation by growing arsenic-accumulating plants, including the identity and characteristics of some rhizosphere soil microbes. The soil samples contained high total, but low soluble arsenic concentrations which, together with other properties, resembled the previously reported characteristics of dip-site soils from this region of rural Australia. A glasshouse trial demonstrated that dip-site rhizosphere microbes promoted arsenic accumulation by the grass Agrostis tenuis on contaminated dip-site soil without inhibition of growth. The arsenic content of the shoots was increased by 45%. We studied the colonization of roots of dip-site plants by mycorrhizal fungi and tentatively identified six genera of other fungi present in the soil samples. Two plant species growing at the sites, Kikuyu grass (the most abundant plant) and Rainbow fern, exhibited mixed infections of their roots by endomycorrhizal fungi (tentatively identified as Acaulospora and Gigaspora) and by soil-born pathogens. Five rhizosphere bacteria were identified to genus level and we determined the effect of arsenic on their growth. The two most prevalent strains differed greatly in their growth sensitivity to arsenate; Arthrobacter sp. being the most sensitive while Ochrobactrum sp. exhibited exceptional resistance to arsenate. Of the other, less prevalent strains, two were Bacillus spp. and the last, Serratia sp., was the most resistant to arsenite. These findings show the importance of understanding plant-soil microbe interactions for developing future strategies aimed at a phytoremediation-based approach to removing arsenic from soil at dip sites.     

Distribution of arsenic compounds in Mytilus galloprovincialis of the Venice lagoon (Italy)

Samples of Mytilus galloprovincialis collected in different sites of the Venice lagoon (Italy) were investigated for total arsenic concentrations by ICP-AES and for single arsenic species by HPLC-ICP-MS. For this purpose, an analytical procedure for the sensitive and efficient speciation of the arsenic species As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC), and four arsenosugars was optimised. The total arsenic and the single arsenic species were determined in both the hepatopancreas (digestive gland) and the remaining soft tissues in order to verify the different arsenic accumulation in the body parts of mussels. Arsenic compounds were extracted from the mussels with a methanol/water mixture; the extracts were evaporated to dryness, redissolved in water, and chromatographed in an anion-exchange column, a Hamilton PRP-X100. Only small quantities or traces of inorganic arsenic were detected in the mussels. The majority of arsenic compounds detected in the extracts were organic species, with a predominance of arsenobetaine and of an arsenosugar. In addition, a greater arsenic accumulation in the digestive glands of mussels was observed.     

Binding and mobility of mercury in soils contaminated by emissions from chlor-alkali plants

Chlor-alkali plants are known to be an important source of Hg emissions to the atmosphere and related contamination of soils in their vicinity. In the present study, the results of Hg speciation and mobility of Hg in soils affected by Hg emissions from three chlor-alkali plants are compared. Solid phase mercury speciation analyses was carried out using a mercury-thermo-desorption technique with the aim of distinguishing elemental Hg [Hg(0)] from Hg(II)-binding forms. Mercury species in soil leachates were distinguished using an operationally defined method, which is based on the reactivity of soluble Hg compounds. Results show that the Hg(0) emitted from the plants could not be detected in any of the investigated soils. This indicates quantitative re-emission or oxidation of this Hg species in the atmosphere or soils. In most soils Hg was predominately bound to organic matter. Only in sandy soils deficient in organic matter was Hg, to a larger extent, sorbed onto mineral soil components. Leachable Hg in most soils occurred as non-reactive, soluble organic Hg complexes such as fulvic acid-bound Hg, and reach their highest values (90 microg kg(-1)) in soils rich in organic matter. Concentrations of reactive, soluble Hg compounds were highest in sandy soils where the content of organic matter was low. Leachability of Hg was found to be inhibited in soils with a high content of clayey soil components. The distribution of Hg in soil profiles suggests that migration of Hg to deeper soil layers (approx. 20 cm) is most effective if Hg is bound to soluble organic complexes, whereas reactive Hg or weak Hg complexes are effectively retained in the uppermost soil layer (5 cm) through sorption on mineral surfaces.     

Biochemical properties of vineyard soils in Galicia, Spain

In the present study we investigated changes in soil biochemical activity in vineyard soils. With this aim, soil samples (0-10 cm) from 15 vineyard soils developed on diverse parent materials were collected during winter. All soil samples were analysed for a large number of both general and specific biochemical properties. The values of all of the biochemical parameters analysed were extremely low, between 3 and 39% of the usual values obtained for native Galician soils under climax vegetation. To estimate the level of biochemical quality of vineyard soils, while avoiding the problem of comparing soils with totally different organic matter contents, a biochemical equilibrium equation was used. The results showed that vineyard soils are highly degraded soils, for which in the most extreme cases, the value of the biochemical equilibrium index was 13%, i.e. almost 8 times lower that in high quality soils such as climax soils.     

Risk assessment of a former military base contaminated with organoarsenic-based warfare agents: uptake of arsenic by terrestrial plants

Organoarsenic-based chemical warfare agents (CWAs) such as the sternutators diphenylchloroarsine (CLARK I), diphenylcyanoarsine (CLARK II) or phenyldichloroarsine (PFIFFIKUS) still pose a notable risk in countries where former military bases that have stored these weapons have not yet been reclaimed. In fact, this is the case for many countries of Eastern Europe and the CIS. One of the most important military bases of the former Third Reich, the Heeresmunitionsanstalt I and II, is situated close to the German-Polish border at Loecknitz (Fig. 1). The German army stored and decanted different compounds of CWAs at this military base until 1945. When the Soviet Army destroyed the base in 1946, large amounts of CWAs and other organoarsenic compounds polluted the soil. Today up to 250 g (!) of arsenic may be found in 1 kg of soil at some places in this area. Since 1991, a Government Working Group has been working on the risk assessment in order to define the scope of reclamation measures. This study investigates the contamination and the uptake of arsenic by plants because little is known about the bioavailability and metabolism of sternutators and their constituents. The total arsenic concentration of nine different species of terrestrial plants with at least six samples per species is presented. In spite of the considerable arsenic contamination of the soil (mean value 923 mg arsenic/kg soil) the plant contamination remained comparably low. The median value of arsenic contamination of the above-ground organs of velvet grass, Holcus lanatus, was 0.7 mg/kg dry wt. and the mean value was 4.3 mg/kg dry wt. due to some highly contaminated samples. The highest arsenic concentration registered was 26 mg/kg dry wt. in a sample of H. lanatus, which was most probably caused by soil particles adhering to the plant. The chemical structure of the arsenic compounds carried by the above-ground plant organs has been determined by gas chromatographic investigations and showed an uptake of triphenyl arsine by the plants.     

Bioaccumulation of arsenic in aquatic plants and animals near a municipal landfill

This study was conducted to assess the water quality and arsenic (As) concentrations in water, sediment, aquatic plants and animals near a municipal landfill. The As concentration in the samples was analysed using inductively coupled plasma optical emission spectrometry. Thirty-six aquatic plants of four species were collected. The highest As concentration was found in Limnocharis flava (0.78 ± 0.31 mg/kg). The aquatic animals included 31 fish of four species and 27 freshwater snails of three species. The highest As concentrations in the fish and freshwater snails were found in Oreochromis niloticus (0.16 ± 0.16 mg/kg) and Filopaludina sumatrensis (0.18 ± 0.06 mg/kg), respectively. The highest bioaccumulation factor of As in the aquatic plants, fish and freshwater snails were found in L. flava (131.30 ± 15.35), O. niloticus (228.21 ± 26.99) and F. sumatrensis (33.04 ± 10.58), respectively. Since the accumulation of As was higher in the sediment than in the water, aquatic plants and animals took up As directly from the environment, resulting in As accumulation in the aquatic food web.