Occurrence Of Arsenic Research Articles

Distribution of arsenic in groundwater in the area of Chalkidiki, Northern Greece

An integrate study aiming at the occurrence and distribution of arsenic in groundwater in the area of Chalkidiki, Northern Greece has been carried out. Groundwater samples from public water supply wells and private wells were analysed for arsenic and other quality parameters ( T, pH, EC, Ca, Mg, Na, K, Cl, HCO 3, NO 3, SO 4, B, Fe, Mn). Arsenic showed high spatial variation; ranged from 0.001 to 1.840 mg/L. Almost 65% of the examined groundwaters exhibit arsenic concentrations higher than the maximum concentration limit of 0.010 mg/L, proposed for water intended for human consumption. Correlation analysis and principal component analysis were employed to find out possible relationships among the examined parameters and groundwater samples. Arsenic is highly correlated with potassium, boron, bicarbonate, sodium, manganese and iron suggesting common geogenic origin of these elements and conditions that enhance their mobility. Three groups of groundwater with different physicochemical characteristics were found in the study area: (a) groundwater with extremely high arsenic concentrations (1.6–1.9 mg/L) and high temperature (33–42 °C) from geothermal wells, (b) groundwater with relatively high arsenic concentrations (>0.050 mg/L), lower temperatures and relatively high concentrations of major ions, iron and manganese and, (c) groundwater with low arsenic concentrations that fulfil the proposed limits for dinking water.

Uptake and translocation of inorganic and methylated arsenic species by plants

Environmental context. The molecular occurrence of arsenic in soils can vary as a result of soil conditions and/or application of arsenic-containing herbicides or fertiliser. Although large amounts of As-containing herbicides are used for different crops, there is still a lack of understanding as to how the molecular form of As determines the uptake of arsenic into plants and, in particular, the translocation into shoot and grain. Abstract. The uptake and translocation into shoots of arsenate, methylarsonate (MA), and dimethylarsinate (DMA) by 46 different plant species were studied. The plants (n = 3 per As species) were exposed for 24 h to 1 mg of As per litre under identical conditions. Total arsenic was measured in the roots and the shoots by acid digestion and inductively coupled plasma mass spectrometry from which, besides total As values, root absorption factors and shoot-to-root transfer factors were calculated. As uptake into the root for the different plant species ranged from 1.2 to 95 (μg of As per g of dry weight) for AsV, from 0.9 to 44 for MAV and from 0.8 to 13 for DMAV, whereas in shoots the As concentration ranged from 0.10 to 17 for AsV, 0.1 to 13 for MAV, and 0.2 to 17 for DMAV. The mean root absorption factor for AsV (1.2 to 95%) was five times higher than for DMAV (0.8 to 13%) and 2.5 times higher than for MAV (0.9 to 44%). Although the uptake of arsenic in the form of AsV was significantly higher than that of MAV and DMAV, the translocation of the methylated species was more efficient in most plant species studied. Thus, an exposure of plants to DMAV or MAV can result in higher arsenic concentrations in the shoots than when exposed to AsV. Shoot-to-root transfer factors (TFs) for all plants varied with plant and arsenic species. While AsV had a median TF of 0.09, the TF of DMAV was nearly a factor of 10 higher (0.81). The median TF for MAV was in between (0.30). Although the TF for MAV correlates well with the TF for DMAV, the plants can be separated into two groups according to their TF of DMAV in relation to their TF of AsV. One group can immobilise DMAV in the roots, while the other group translocates DMAV very efficiently into the shoot. The reason for this is as yet unknown.

Major Factors Controlling Arsenic Occurrence in the Groundwater and Sediments of the Chianan Coastal Plain, SW Taiwan

The Chianan coastal plain in southwestern Taiwan has long been well known for the prevalence of black-foot disease during the period 1961 to 1985. This disease resulted from drinking groundwater rich in arsenic and dissolved humic substances. However, the occurrence of arsenic and its controlling factors have not yet been studied in detail. Water samples from a total of 86 newly established monitoring wells and sediment samples from 28 fully cored boreholes were analyzed in this study to investigate major chemical [such as SO4 2- , Cl - , redox potential (Eh), pH, and 14 CDIC ages] and geological (such as depositional environment, grain size and arsenic content of sediments) factors which may control the distribution of arsenic in groundwater of the upper ~300-m thick strata. This study shows that arsenic concentrations of almost all groundwater samples exceed the 0.01 mg L -1 limit of the WHO guidelines, with the highest values up to ~1.2 mg L -1 . Only the deep aquifers (> 50 m) deposited before Holocene transgression contain groundwaters with relatively high arsenic contents (> 0.1 mg L -1 ). All the arsenic-rich groundwaters are under strongly reducing conditions with low Eh (< 110 mV) and low SO4 2- (nearly all < 2 mg L -1 ). The different combination of As, Fe, and SO4 2- concentrations of groundwater reflect various redox potentials. The reductive dissolution of As-rich Fe-(hydr)oxides is believed to be the major source of As in the groundwater, but the contents of SO4 2- , humic substances and residence time of water are also responsible for the variation of dissolved As in the Chianan coastal plain.

The source of naturally occurring arsenic in a coastal sand aquifer of eastern Australia

The discovery of dissolved arsenic in a coastal aquifer used extensively for human consumption has led to widespread concern for its potential occurrence in other sandy coastal environments in eastern Australia. The development of an aquifer specific geomorphic model (herein) suggests that arsenic is regionally derived from erosion of arsenic-rich stibnite (Sb(2)S(3)) mineralisation present in the hinterland. Fluvial processes have transported the eroded material over time to deposit an aquifer lithology elevated in arsenic. Minor arsenic contribution to groundwater is derived from mineralised bedrock below the unconsolidated aquifer. An association with arsenic and pyrite has been observed in the aquifer in small discrete arsenian pyrite clusters rather than actual acid sulfate soil horizons. This association is likely to influence arsenic distribution in the aquifer, but is not the dominant control on arsenic occurrence. Arsenic association with marine clays is considered a function of their increased adsorptive capacity for arsenic and not solely on the influence of sea level inundation of the aquifer sediments during the Quaternary Period. These findings have implications for, but are not limited to, coastal aquifers. Rather, any aquifer containing sediments derived from mineralised provenances may be at risk of natural arsenic contamination. Groundwater resource surveys should thus incorporate a review of the aquifer source provenance when assessing the likely risk of natural arsenic occurrence in an aquifer.

Analytical speciation as a tool to assess arsenic behaviour in soils polluted by mining

A study is performed to evaluate the occurrence of arsenic in polluted soils using acidic extractions and liquid chromatography-hydride generation-atomic fluorescence spectrometry (LC-HG-AFS) for speciation analysis. Seven soil samples were collected in an abandoned area polluted by mining in the Eastern Pyrenees (Spain), and two uncontaminated soils were taken for reference purposes. Moreover, the total arsenic content is evaluated in two different sieved fractions in order to obtain information on the possible particle-size-dependent association of arsenic with soil components. Soil samples were extracted with both phosphoric and ascorbic acids and the stabilities of the extracted species were studied. The arsenic species were determined by LC-HG-AFS. In addition, the ability of soil grinding to effect species change is also assessed. Arsenite and arsenate were found in the polluted soils, but only arsenate was found in the unpolluted soils. The quality of the results was assessed through a mass balance calculation and by analysing two soil Certified Reference Materials. Valuable information regarding arsenic occurrence in the studied soils is obtained from the speciation results. The presence of arsenite in the extracts can be attributed to arsenopyrite residues, whereas the presence of arsenate indicates release from weathered material.

Arsenic-Rich Iron Floc Deposits in Seeps Downgradient of Solid Waste Landfills

Iron flocculate or “floc” deposits are commonly observed in groundwater discharge zones downgradient of unlined solid waste landfills. Bright orange in color, and composed predominantly of amorphous iron oxyhydroxides, these deposits generally have been regarded as aesthetically undesirable but environmentally benign. In recent years, there has been increased awareness of the widespread occurrence of elevated arsenic in reducing groundwaters. Research carried out at municipal landfills in New England indicates that naturally occurring arsenic exhibits redox-mediated mobility and is frequently associated with reduced iron as a dissolved constituent in leachate-impacted groundwaters. If iron precipitates in discharge zones where reduced groundwaters are exposed to atmospheric oxygen, it follows that arsenic may co-precipitate with iron in these areas. To assess the prevalence of arsenic as a constituent of iron floc deposits, samples were collected at seven landfills and at one natural mineral spring in the lower Hudson Valley of southeastern New York State. At six of seven landfill sites, arsenic concentrations exceeded 33 mg/kg, which represents the “severe effects level” for aquatic life as identified in New York State regulatory guidance for screening contaminated sediments. These results indicate that arsenic contamination is of potential concern for downgradient of landfills wherever iron-stained leachate discharges are observed. Sampling and analysis of iron flocs associated with such leachates could also provide a means of identifying landfills that may present risks of arsenic contamination to downgradient water supply wells, especially in cases where groundwater monitoring wells are not available for sampling.

Mode of occurrence of arsenic in feed coal and its derivative fly ash, Black Warrior Basin, Alabama

An arsenic-rich (As = 55 ppm) bituminous feed coal from the Black Warrior Basin, Alabama and its derivative fly ash (As = 230 ppm) were selected for detailed investigation of arsenic residence and chemical forms. Analytical techniques included microbeam analysis, selective extraction, and As K-edge X-ray absorption fine-structure (XAFS) spectroscopy. Most As in the coal is contained in a generation of As-bearing pyrite (FeS 2) that formed in response to epigenetic introduction of hydrothermal fluids. XAFS results indicate that approximately 50% of the As in the coal sample occurs as the oxidized As(V) species, possibly the result of incipient oxidation of coal and pyrite prior to our analysis. Combustion of pyrite and host coal produced fly ash in which 95% of As is present as As(V). Selective extraction of the fly ash with a carbonate buffer solution (pH = 10) removed 49% of the As. A different extraction with an HCl–NH 2OH mixture, which targets amorphous and poorly crystalline iron oxides, dissolved 79% of the As. XAFS spectroscopy of this highly acidic (pH = 3.0) fly ash indicated that As is associated with some combination of iron oxide, oxyhydroxide, or sulfate. In contrast, a highly alkaline (pH = 12.7) fly ash from Turkey shows most As associated with a phase similar to calcium orthoarsenate (Ca 3(AsO 4) 2). The combined XAFS results indicate that fly ash acidity, which is determined by coal composition and combustion conditions, may serve to predict arsenic speciation in fly ash.

A comparison of arsenic occurrence and geochemistry in two groundwater environments

A comparison of arsenic occurrence and geochemistry in two groundwater environments

A comparison of arsenic occurrence and geochemistry in two coastal groundwater environments

A comparison of arsenic occurrence and geochemistry in two coastal groundwater environments

Characterization of arsenic occurrence in the water and sediments of the Okavango Delta, NW Botswana

Detailed chemical analyses were performed on surface water, groundwater and sediment samples collected from the Okavango Delta between February and November 2003 in order to examine the distribution and geochemistry of naturally occurring As in the area. Surface water in the Okavango Delta, which is neutral to slightly acidic and has high dissolved organic C (DOC), was found to be slightly enriched in As when compared to a global value for stream water. Of the 20 new borehole analyses from this project, six were found to have values exceeding 10 μg/L, the current World Health Organization provisional guideline value for As. The results from field speciation indicate that As(III) is slightly more predominant than As(V). There is a positive correlation between As and pH and between As and DOC in the groundwater samples. For the sediment samples, there is a positive correlation between As and Co, As and Fe, As and loss on ignition (LOI) and between As and the percent fines in the sample. Reductive dissolution of oxides and hydroxides in the sediments with organic C as an electron acceptor is the likely mechanism for the release of As from the sediments into the groundwater.

Occurrence of Arsenic in Groundwater in the Suburbs of Beijing and its Removal Using an Iron-Cerium Bimetal Oxide Adsorbent

Abstract The occurrence of arsenic (As) in groundwater in fourteen villages in Houshayu Town, Shunyi District, Beijing, China, was investigated, and a column experiment for the removal of As was conducted on-site with a pellet type iron-cerium (Fe-Ce) bimetal oxide adsorbent prepared in lab. The As concentration in the groundwater of twelve villages exceeds the maximum contamination level (10 µg/L) of the World Health Organization, and two of them exceed that of China (50 µg/L). A column experiment at a space velocity of 3 h-1 shows that the Fe-Ce adsorbent could remove As(V) (total As, 71 ± 19.7 µg/L) from groundwater with high efficiency. Around 11,500 bed volumes were gained when As(V) in the effluent exceeds 10 µg/L, giving an accumulated adsorption capacity of 6.0 mg As(V)/g adsorbent. Both batch tests and the column test suggest that humic substances might compete with As(V) for the adsorption sites, which disappeared after the column was continuously operated for more than two weeks. The effluent quality including heavy metals, radioactivity, etc., was confirmed to meet the drinking water standards of WHO and China.

Modeling the Probability of Arsenic in Groundwater in New England as a Tool for Exposure Assessment

We developed a process-based model to predict the probability of arsenic exceeding 5 microg/L in drinking water wells in New England bedrock aquifers. The model is being used for exposure assessment in an epidemiologic study of bladder cancer. One important study hypothesis that may explain increased bladder cancer risk is elevated concentrations of inorganic arsenic in drinking water. In eastern New England, 20-30% of private wells exceed the arsenic drinking water standard of 10 micrograms per liter. Our predictive model significantly improves the understanding of factors associated with arsenic contamination in New England. Specific rock types, high arsenic concentrations in stream sediments, geochemical factors related to areas of Pleistocene marine inundation and proximity to intrusive granitic plutons, and hydrologic and landscape variables relating to groundwater residence time increase the probability of arsenic occurrence in groundwater. Previous studies suggest that arsenic in bedrock groundwater may be partly from past arsenical pesticide use. Variables representing historic agricultural inputs do not improve the model, indicating that this source does not significantly contribute to current arsenic concentrations. Due to the complexity of the fractured bedrock aquifers in the region, well depth and related variables also are not significant predictors.

ARSENIC IN THE SHALLOW GROUND WATERS OF CONTERMINOUS UNITED STATES: ASSESSMENT, HEALTH RISKS, AND COSTS FOR MCL COMPLIANCE

: A methodology consisting of ordinal logistic regression (OLR) is used to predict the probability of occurrence of arsenic concentrations in different threshold limits in shallow ground waters of the conterminous United States (CONUS) subject to a set of influencing variables. The analysis considered a number of maximum contaminant level (MCL) options as threshold values to estimate the probabilities of occurrence of arsenic in ranges defined by a given MCL of 3, 5, 10, 20, and 50 μg/l and a detection limit of 1 μg/l. The fit between the observed and predicted probability of occurrence was around 83 percent for all MCL options. The estimated probabilities were used to estimate the median background concentration of arsenic in the CONUS. The shallow ground water of the western United States is more vulnerable than the eastern United States. Arizona, Utah, Nevada, and California in particular are hotspots for arsenic contamination. The risk assessment showed that counties in southern California, Arizona, Florida, and Washington and a few others scattered throughout the CONUS face a high risk from arsenic exposure through untreated ground water consumption. A simple cost effectiveness analysis was performed to understand the household costs for MCL compliance in using arsenic contaminated ground water. The results showed that the current MCL of 10 μg/l is a good compromise based on existing treatment technologies.

Occurrence of arsenic (V) in forearc mantle serpentinites based on X-ray absorption spectroscopy study

We examined As concentration, mineralogical site, and oxidation state in the serpentinites associated with the Tso Morari eclogitic rocks in the Indus suture zone, northwest Himalaya, to examine how highly fluid-soluble elements like As are transferred from slabs to arc magmas in subduction zones. The serpentinite samples represent hydrated peridotites at the base of the mantle wedge beneath Eurasia, and were exhumed from a depth of ∼100 km during subduction of the Indian continental margin. The bulk serpentinite samples contain total As concentrations ranging from 6 to 275 ppm. Arsenic in the samples is most likely present with magnetite and antigorite, since electron probe analysis yielded up to 90 ppm As in these minerals. X-ray absorption near-edge structure spectra indicate that As in serpentinites is mostly As(V) and that the neighboring atoms of As are O, although there are minute grains of sulfides and arsenides. The ratio of As(V) to total As is greater in samples with higher As contents, suggesting that the major source of As was oxidized As(V), introduced to the mantle wedge. Arsenic(V), originally adsorbed on Fe-oxides in slabs and overlying sediments, was most likely liberated during their subduction and incorporated subsequently in the overlying mantle wedge. Our data constrain the introduction of As into the mantle wedge at relatively shallow levels, much shallower than 25 km. Arsenic incorporated in the serpentinites was transported to deeper levels by mantle flow downward along the subduction zone, to be subsequently exhumed together with eclogitic rocks.

Comment on and addenda to “Arsenic in coal: A review” by Yudovich and Ketris

Abstract In their review of arsenic in coal, Yudovich and Ketris (2005) [Yudovich, Ya.E., Ketris, M.P., 2005. Arsenic in coal: a review. Int. J. Coal Geol. 61, 141–196.] largely overlooked the role that arsenic X-ray absorption fine structure (XAFS) spectroscopy can play in determining the mode of occurrence of arsenic in coal. Further, XAFS spectroscopy, being a direct method for determining arsenic speciation coals, can also be used to assess the critical assumptions and inferences present in less direct methods of arsenic speciation based on sequential leaching and other fractionation methods. This communication is designed to redress the oversight given arsenic XAFS spectroscopy in the review by Yudovich and Ketris.

The occurrence and speciation of arsenic, antimony, and selenium in ground water of Poznań city (Poland)

This paper presents results of determination of total arsenic, antimony, and selenium contents as well as their species in ground water from the region of Poznań. Determinations were carried by means of atomic absorption spectrometry hyphenated with generation of hydrides and in situ preconcentration in a graphite tube (HG-GFAAS). In order to obtain the best efficiency of an analyte concentration process on the walls of the tube, palladium was used as a modifying agent. The concentration of total arsenic was up to 2.04 ng ml−1, that of antimony up to 0.71 ng ml−1, and that of selenium up to 0.44 ng ml−1. The lowest concentrations of the investigated elements in ground water and the predominance of As(III), Sb(III), and Se(IV) speciation forms over As(V), Sb(V), and Se(VI) forms were found in the region, where the thickest aquitards (glacial tills of the Vistulian Glaciation) overlay an aquifer. Moreover, the geological and hydrogeological conditions of the study area are presented.

Arsenic Occurrence and Species in Near-Shore Macroalgae-Feeding Marine Animals

This study was undertaken to improve the understanding of arsenic species and their pathways of formation in marine animals: fish (Odax cyanomelas), abalone (Haliotis rubra), and sea urchins (Heliocidaris erythrogramma and Centrostephanus rodgersii) that are directly exposed through their diets to dimethyl arsenoriboses in macroalgae (Phyllospora comosa and Halopteris platycena). The identification of dimethyl arsenoriboses (phosphate, sulfonate, and glycerol) in both dominant macroalgae species, and especially digestive tissues of marine animals that consume them, suggests these arsenic species, are to some degree accumulated directly from their diets without degradation or conversion. An unknown arsenic species in H. rubra intestinal tissue was identified using tandem mass spectrometry as 2',3'-dihydroxypropyl 5-deoxy-5-trimethyl arsonioriboside (trimethyl glycerol arsenoribose). The concentration of trimethyl glycerol arsenoribose in H. rubra intestinal tissue was estimated to account for 28% (5.0 microg g(-1) dry mass) of the methanol-water-soluble arsenic fraction. The presence of a trimethyl glycerol arsenoribose in marine animal tissues may be due to microbial-mediated processes that promote the reduction and methylation of dimethyl arsenoriboses released during the breakdown of macroalgae in their diets. Arsenobetaine formation may then occur in the lumen of the digestive tract (i.e., mediated by microorganisms) or in the liver catalyzed by enzymes. The identification of a large amount of trimethyl glycerol arsenoribose in H. rubra intestinal tissue suggests this species is a main constituent in the pathway for arsenic in this marine animal.

Grain size constraints on arsenic concentration in shallow wells of Nawalparasi, Nepal

Occurrence of arsenic in shallow aquifers was studied from the Nawalparasi district in west Nepal. A higher concentration of arsenic was found in the wells from the north as compared to those from the south. The arsenic level in the north reaches a maximum of 694ppb as compared to a value of 27 ppb in the south near the Nepal-India border. The arsenic concentration analyses carried out in selected sites from March to September 2003 indicate a large variation (exceeding 200%) in the north as compared to the central and southern regions. A general increase in grain size from north to south was observed in the well logs. Generally, fine sediments like clay and silt constitute more than 80% of the drilled depth in the north (i.e., at Panchnagar), while the fines are about 32% in the south (i.e., at Bhujawa). This type of grain size distribution is in contrast to the generally observed fining-southwards pattern in the Terai.

Characterization of Arsenic Emissions from a Coal-Fired Power Plant

An emissions study for arsenic was conducted at a 300-MW coal-fired plant that was equipped with an electrostatic precipitator (ESP). The input and output streams, such as coal, slag, ESP ash, and flue gas that contained the post-ESP particulates, were collected. Gaseous arsenic was sampled using United States Environmental Protection Agency (USEPA) Method 29, and the arsenic concentrations in the samples were measured using inductively coupled plasma−atomic emission spectrometry. The mass balance recovery of arsenic estimated in this study was 87.2%. The arsenic concentration in the stack gas was 2.5 μg/Nm3. Approximately 0.53% of the coal-derived arsenic was incorporated into slag, 84.6% of the arsenic was found on the fly ash that was collected by the ESPs, and 2.16% was found in the vapor phase. The relationship between arsenic concentration and ash particle size was also assessed, and arsenic was significantly concentrated in the small-sized particles. The modes of occurrence of arsenic in ash samples were studied using a modified sequential chemical extraction method. The extractable fraction was 13.78%−25.27% of the total arsenic in the fly ash particles, from the four ESP hopper samples. The arsenic concentrations found in the different extraction fractions were as follows: 74.73%−86.22% in the residue; 11%−19% in carbonate-bound, surface oxide-bound ions; 2.7%−6.0% in readily extractable ions; and 0.076−0.27% in water-extractable form. There were no appreciable differences in the arsenic solubility fractions between the different particle sizes of fly ash.

Arsenic Occurrence, Mobility, and Retardation in Sandstone and Dolomite Formations of the Fox River Valley, Eastern Wisconsin

Elevated levels of groundwater arsenic (approximately 100 microg L(-1) = 1.3 x 10(-6) M) are found in the Fox River Valley, eastern Wisconsin. The goals of this study were to identifythe sources of As contamination and to determine the reactions responsible for As mobilization and retardation in areas lacking a discrete zone of As-enriched sulfides, shown previouslyto cause elevated arsenic in groundwater. Detailed mineralogical and chemical analyses were conducted on samples from the Sinnipee Group dolomite and St. Peter sandstone in eastern Wisconsin. Solution chemistry was monitored in batch reactions of dolomite, quartz, and sulfide mineral fractions with a 0.01 M CsCl solution at pH 7 for 3 weeks in air. Results indicate that arsenic is present in isomorphous substitution with pyrite/marcasite (FeS2), which occurs as disseminated veins, grains, and nodules in the dolomite and sandstone. The released As subsequently sorbs on the ferric oxyhydroxides formed or coprecipitates in a scorodite-like phase. Significantly, oxidative dissolution of the disseminated As-rich FeS2 grains and nodules is sufficient to explain the elevated As levels observed in eastern Wisconsin groundwater. Although complete uptake of As is observed in the batch experiments, persistent elevated As levels with spatial and temporal variations in regional groundwaters are attributed to differences in the type of sulfide occurrence (discrete horizon vs dispersed grains, veins, and nodules), variations in the dissolved oxygen content of the groundwater, and variable (limited) buildup of reacted surface layers on sulfide grains in the natural flow-through system. Discrete nanoparticulate As phases, As surface precipitates on sulfides, and sorbed As on dolomite and quartz are eliminated as major sources, and sorption of arsenic on dolomite and quartz is deemed less important than association with ferric oxyhydroxides for retardation in the regional system.