Arsenic Transport Research Articles

Arsenic Transport in Contaminated Mine Tailings following Liming

AbstractThe practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize arsenic (As), due to the pH dependence of As sorption reactions on oxide minerals and layer silicates. The objectives of this study were to determine the effects of liming on As mobility in mine tailings and identify possible mechanisms controlling As mobilization with increased pH. Six mine tailing samples obtained from an abandoned copper smelter near Anaconda, Montana were analyzed for total As and soluble constituents using saturated paste extractions. Concentrations of soluble As among the six samples did not correlate with total As, but were more closely related to pH. Saturation indices with respect to known metal arsenate solid phases suggested that metal arsenate solid phases were not controlling soluble As in these samples. Two low pH samples (pond tailings and reprocessed tailings) were chosen for more detailed chemical characterization and unsaturated column transport experiments before and after liming. Soluble As concentrations measured in column effluent increased by factors of 10 (reprocessed tailings, RT) to 400 (pond tailings, PT) following liming. Sequential extractions of these tailing samples showed that the PT contained significantly higher “labile” As relative to the RT, consistent with amounts of As mobilized after liming. Further characterization of these samples using scanning electron microscopy (SEM) and energy dispersive analysis of x‐rays (EDAX) suggested that these samples do not contain discrete metal arsenate solid phases. Based on this suite of experimental data, increased mobility of As with liming appears to be consistent with the pH dependence of sorption reactions of As on Fe oxide minerals rather than dissolution‐precipitation reactions involving As.

Arsenic transport in a watershed receiving gold mine effluent near Yellowknife, Northwest Territories, Canada

The presence of abnormally high concentrations of arsenic in sediment and water samples collected from a chain of small lakes afforded a unique opportunity to investigate the environmental partitioning and speciation of inorganic arsenic in fresh water. The distribution of arsenic in water, surface sediment (0–5 cm depth) and associated pore water downstream of the discharge differed from that expected due to conservative dilution and/or sediment adsorption from a point-source. Inorganic arsenic in the water column, sediment particulates and pore water exhibited a maximum concentration ∼ 4–6 km downstream of the gold-mine input. Arsenite (As(III)) was the predominant arsenical in the sediment pore water throughout the watershed, whereas arsenate (As(V)) comprised the vast majority of dissolved arsenic in water column samples. Arsenite was not detected in the mine effluent, but was found in increasing concentrations in the water column with increasing downstream distance from the discharge pipe. There are two possible mechanisms for the downstream redistribution of historical arsenic inputs in this system: (1) bulk movement via sediment/particulate transport; and (2) redissolution from sediments during early diagenesis, followed by upward diffusion and transport to downstream areas. Sediment distributions of other substances which are ‘tracers’ of the gold-mine effluent (e.g. antimony, copper, gold, nickel, zinc, sulphate and chloride ion) were examined in order to distinguish between these mechanisms. Collectively, the data indicate that the arsenic distribution in surficial sediments of the study area is controlled partially by the bulk movement of sediments, followed by burial with less contaminated sediments in the upper reaches of the watershed. Particulate concentrations of arsenic contributed significantly to the total arsenic concentrations in the water column downstream of the gold-mine discharge (up to 70% of total As concentration). The extremely high concentrations of arsenicals in sediment pore water (up to 68.9 μM) and the overlying water column (up to 7.3 μM in dissolved form) in areas further removed from the input, however, are attributable to remobilization from sediments through redox-related dissolution. This release of dissolved arsenic during sediment diagenesis may be enhanced by anthropogenically-enhanced sulfate deposition, also associated with gold-mining activity.

Increased biliary excretion of glutathione is generated by the glutathione-dependent hepatobiliary transport of antimony and bismuth

We have recently demonstrated that the hepatobiliary transport of arsenic is glutathione-dependent and is associated with a profound increase in biliary excretion of glutathione (GSH), hepatic GSH depletion and diminished GSH conjugation (Gyurasics Á, Varga F and Gregus Z, Biochem Pharmacol 41: 937–944 and Gyurasics Á, Varga F and Gregus Z, Biochem Pharmacol 42: 465–468, 1991). The present studies in rats aimed to determine whether antimony and bismuth, other metalloids in group Va of the periodic table, also possess similar properties. Antimony potassium tartrate (25–100 μmol/kg, i.v.) and bismuth ammonium citrate (50–200 μmol/kg, i.v.) increased up to 50- and 4-fold, respectively, the biliary excretion of non-protein thiols (NPSH). This resulted mainly from increased hepatobiliary transport of GSH as suggested by a close parallelism in the biliary excretion of NPSH and GSH after antimony or bismuth administration. Within 2 hr, rats excreted into bile 55 and 3% of the dose of antimony (50 μmol/kg, i.v.) and bismuth (150 μmol/kg, i.v.), respectively. The time courses of the biliary excretion of these metalloids and NPSH or GSH were strikingly similar suggesting co-ordinate hepatobiliary transport of the metalloids and GSH. However, at the peak of their excretion, each molecule of antimony or bismuth resulted in a co-transport of approximately three molecules of GSH. Diethyl maleate, indocyanine green and sulfobromophthalein (BSP), which decreased biliary excretion of GSH, significantly diminished excretion of antimony and bismuth into bile indicating that hepatobiliary transport of these metalloids is GSH-dependent. Administration of antimony, but not bismuth, decreased hepatic GSH level by 30% and reduced the GSH conjugation and biliary excretion of BSP. These studies demonstrate that the hepatobiliary transport of trivalent antimony and bismuth is GSH-dependent similarly to the hepatobiliary transport of trivalent arsenic. Proportionally to their biliary excretion rates, these metalloids generate increased biliary excretion of GSH probably because they are transported from liver to bile as unstable GSH complexes. The significant loss of hepatic GSH into bile as induced by arsenic or antimony may compromise conjugation of xenobiotics with GSH.

Arsenic transport between water and sediments

Arsenic transport between water and sediments

Glutathione-dependent biliary excretion of arsenic

This study aimed to clarify whether glutathione (GSH) plays a role in the hepatobiliary transport of arsenic. For this purpose, the biliary excretion of 74As was measured in urethaneanaesthetized rats for 2hr after the administration of labelled sodium arsenite (50 μmol/kg, i. v.) or arsenate (150 μmol/kg, i.v.) and under the influence of sulfobromophthalein (BSP), indocyanine green (ICG) or diethyl maleate (DEM) which are known to diminish hepatobiliary transport of GSH. Although the biliary excretion of arsenic was different after arsenite and arsenate administration in terms of quantity (19% vs 6% of dose in 2 hr, respectively) and time course, arsenic excretion responded similarly to BSP (50 μmol/kg, i.v.), ICG (25 μmol/kg, i.v.) or DEM (4 mmol/kg, i.p.) irrespective of the injected arsenical. Initially the biliary excretion of arsenic in rats injected with either arsenite or arsenate was significantly reduced, but then moderately increased by BSP and, more lastingly, depressed by ICG, whereas it was virtually abolished by DEM. The responses of arsenic excretion to BSP, ICG and DEM were related, both proportionally and temporally, to the effects exerted by these agents on the hepatobiliary transport of GSH, as assessed by the biliary excretion of non-protein thiols. These findings indicate that the biliary excretion of arsenic after the administration of either arsenite or arsenate is dependent on the hepatobiliary transport of GSH. Transport of arsenic as a GSH complex may account for the GSH dependence of biliary arsenic excretion.

Transformation of arsenic compounds in a freshwater food chain

AbstractThe transport and transformation of arsenic were investigated in the food chain Chlorella and Phormidium sp. (autotrophic freshwater algae)–Moina sp. (zooplanktonic grazer)–Poecilia sp. (carnivorous guppy). The algae were grown for seven days in a modified Detmer medium containing 100 mg dm−3 arsenic as Na2HAsO4. The algae (Chlorella 0.64 mg g−1 dry mass; Phormidium 2.9 mg g−1 dry mass) were fed to Moina for seven days. Moina acquired arsenic concentrations of 76 μg g−1 (from Chlorella) and 111 μg g−1 (from Phormidium). The guppy feeding on Moina (with arsenic from Chlorella) had the lowest arsenic concentrations (5.6 μg g−1) among these organisms.Whereas the arsenic in the algae was almost all in inorganic form, 85% of the arsenic in the guppy was in di‐ and tri‐methylated form. The higher Percentages of methylated arsenic at the higher trophic levels could be the result of preferential uptake or retention of methylarsenic compounds or of methylation of arsenic compounds by the higher organisms.

Prevention of acid drainage from gold mining in the western United States and impacts on water quality

Water quality regulations recently adopted by states in the western USA have increasingly stringent limitations on allowable changes in the quality of surface water and groundwater. The “nondegradation of water” provisions in state regulations require accurate predictions and control of the quantity and quality of acid mine water and strictly limit the entry of acid water into natural water systems. Long-term water quality impacts from mine waste rock, spent ore from heap leaching, tailings and open pits must be considered in design, operation and reclamation of proposed or expanded mining operations. Acid-base testing, humidity cells, column testing and shake flask tests have been used with mixed success to predict the extent of acid water production. The types and forms of sulfide minerals present, bacterial catalysis of the sulfide oxidation reaction and configuration of the reclaimed facilities are all important elements in accurately predicting acid mine drainage. A critical factor in prediction of acid mine impacts is a pathway and fate analysis which includes geochemical reactions with aquifer materials and dilution and dispersion of parameters in the leachate plume. Of particular concern is the production and transport of arsenic, metals and residual cyanide from mined areas. Evaluation of three major operating gold mines in the northwestern United States shows the relationship between production of acidic water, movement of this water in aquifers and impacts on groundwater and surface water. Column testing showed reduction in concentrations of most metals by 50 to over 90 percent during travel through aquifers. Clays and silt zones were very effective in adsorbing metals. Operational control of water/rock reactions and reclamation design can significantly reduce or eliminate acid drainage. Soil cover, revegetation and slope are the major components that limit long-term acid drainage and metal contamination of surface water and groundwater. Compliance with water quality limits can be achieved only by design and operation of mining facilities to minimize the formation of acidic waters.

Effects of Benthic Flora on Arsenic Transport

Chemical and biological interactions involving arsenic (As) and phosphorus (P) appear to affect significantly As transport and distribution in Whitewood Creek, South Dakota. Data (first‐order uptake rate constants, standing crop, and accumulation factors) that can be used to predict As transport have been determined using algae collected in the creek along a transect from upstream of mine discharge down gradient through a 57‐km impacted reach. Cultures of Achnanthes minutissima (Bacillariophyceae) were isolated from four sites along a longitudinal gradient of dissolved As within the study reach and were maintained at ambient dissolved‐As concentrations. Arsenic sorption‐rate constants for cell surfaces of these isolates were estimated as a function of dissolved arsenate and orthophosphate. All isolates sorbed orthophosphate preferentially over arsenate. Initial sorption of both arsenate and orthophosphate appeared to follow a first‐order equation within media formulations but did not adequately describe o...

The role of three species of benthic invertebrates in the transport of arsenic from contaminated estuarine sediment

We examined the transport of arsenic out of contaminated sediments by three burrowing organisms with different burrowing habits, Nereis succinea (Frey et Leuckart), Macoma balthica (L.) and Micrura leidyi (Verrill). All three species caused measurable flux of arsenic out of the sediment which was not measurable in the absence of infauna. Arsenic released from the sediment was primarily arsenate and arsenite, with trace amounts of methylated arsenic compounds. Nereis and Micrura were approximately equal at facilitating arsenic flux on a per individual basis while Macoma was less than half as active. On a weight basis, however, Micrura was over five times more active than Nereis and > 25 times as great as Macoma. Macoma in contaminated sediment increased their arsenic body burdens by a factor of ≈ 50, much greater than either Nereis or Micrura. When relative activities and potential for trophic transfer are considered, we suggest that smaller active organisms may be more important as facilitators of direct flux to the water column but larger, less active, benthic organisms contribute more to uptake of contaminants through food chain pathways.

Chemical speciation and distribution of arsenic in water, suspended solids and sediment of Xiangjiang River, China

The forms of arsenic in the Zuzou Zone of the Xiangjang River are evaluated. Nine fractions of arsenic, consisting of soluble arsenic(III) and total soluble arsenic, loosely bound arsenic, aluminium arsenate, iron arsenate, calcium arsenate, arsenic occluded on iron oxide, organic compounds of arsenic and residual arsenic, were separated from suspended solids and sediments by sequential chemical extraction. All arsenic fractions were determined by ASV and AFS. The distributions of arsenic and arsenic fractions in water, sediments and suspended solids are discussed in terms of the mechanisms of arsenic transport and deposition in aquatic ecosystems.

The effect of biological and physical disturbances on the transport of arsenic from contaminated estuarine sediments

From the distribution of dissolved and solid arsenic species in a contaminated estuarine sediment and measured rates of flux of the various arsenic species we propose an empirical model for the cycling of arsenic between sediments and water column. The chemical form of arsenic in the sediment was largely determined by the redox state of the sediment. Arsenite was the dominant dissolved and solid species in the deeper reduced sediment, and arsenate was dominant in the oxidized surface layer. Arsenite in the interstitial water diffused toward the surface layer, where it was mostly oxidized to arsenate prior to leaving the sediments. Some arsenate adsorbed to the surface sediments and produced a surface layer enriched in arsenic. Small concentrations of methyl and dimethyl arsenic were produced in the sediments, and these also diffused into the overlying water. Nereis succinea, a burrowing polychaete, affected distribution and flux of arsenic from the sediments by its production of irrigated burrows. These burrows increased both the effective surface area of the sediment and the diffusion of arsenic by a factor of five. When the relative effects of the activities of Nereis succinea and physical resuspension are compared, results indicate that although physical resuspension can produce large pulses of materials from contaminated sediments, continuous biological activity is likely to be more important in the mobilization of contaminants from sediments in many estuarine environments.

Sources, transport and alterations of metal compounds: an overview. I. Arsenic, beryllium, cadmium, chromium, and nickel.

An overview is presented of the current state of knowledge of the salient aspects of the sources, transport, and alterations of arsenic, beryllium, cadmium, chromium, and nickel. This information is considered vital for a better assessment of the scope of potential human hazard to these ubiquitous toxicants and their compounds. Stress is focused on both natural and industrial activities, particularly on the latter's projected trends. Increasing use patterns per se of most of these metals, as well as aspects of waste disposal and the anticipated increased combustion of fossil fuels for power generation and space heating (particularly in the United States), are major causes of potential health concern. Additionally, attention is drawn to the need for increased research to fill the gaps in our knowledge in these vital areas, all in the hope of permitting a more facile identification and quantification of the potential hazard to exposure to these agents.

Transport of arsenic in grassland microcosms and field plots

Two sizes of excised microcosms (15 and 30 cm in diameter) and 30 cm diameter homogenized microcosms were compared with field plots to assess the transport of As in a grassland ecosystem. The purpose of the experiment was to determine the suitability of using microcosms for measuring the transport of toxic substances through grassland ecosystem components (soil, grass, and soil water). Arsenic was applied to each set of microcosms and the field plots, at rates of 0, 0.5, and 5.0 mg cm−2. Results show that As was highly assimilated by grass, with the greatest concentration being 720 ppm. The microcosms were found to represent the field plots in terms of As transport, and offer several advantages over field testing of toxic substances.

The effects of microcosm size and substrate type on aquatic microcosm behavior and arsenic transport

The chemical and biological characteristics of 12 freshwater microcosms of two different sizes (7-L and 70-L) and substrate types (sand and lake mud), and the fate of an introduced test contaminant (74As) were explored as part of a larger study of the feasibility of using microcosms for assessing the probable fate and effects of contaminants in natural ecosystems. An inoculum of local pond algae with attendant organisms was introduced into each microcosm. Substrate type influenced chemical and biological conditions and arsenic distribution profoundly, while size had lesser effects which were probably due to differences in surface area to volume ratio. Lake sediment contributed to significantly greater algal productivity as reflected by biomass, pH, dissolved oxygen, dissolved nutrients, and chlorophyll-a. Most of the arsenic moved into the mud of the lake sediment microcosms, but remained in the water of the sand microcosms. Bioaccumulation ratios for algae ranged from 370 for 7-L sand microcosms to 4300 for lake mud microcosms. Arsenic concentrations in snails were directly proportional to substrate arsenic concentrations. Transport of arsenic in the microcosms was in good agreement with published field data. The results of the experiment emphasized the importance of selecting components for test microcosms from the specific environments most likely to incur introduction of a particular contaminant.

Emissions of arsenic in Sweden and their reduction.

The role of arsenic in Sweden is generally described, including raw materials, exports/imports, products, consumption, etc. An attempt was also made to estimate the transport of arsenic in Sweden. The quantities of arsenic in raw materials, the emissions of arsenic from such processes as copper smelters and chemical industries, and the amounts of products containing arsenic were calculated. The studies show that a copper smelter is the main user of arsenical materials, the very largest emitting source and also the plant which manufacturers most arsenic products. A summary of measurements of arsenic in air, water and soil in Sweden has also been made. The concentrations near a smelter, in the Baltic, in cities and in "clean-air areas" are given. The efforts made to date to reduce the emissions of arsenic and the measures planned for the next few years are described. A reduction has already been achieved and a further rather large decrease will come, especially in arsenic levels in water. The possibilities of minimizing the use of materials and products containing arsenic is also discussed.

Effect of metabolic alkalosis and acidosis on renal transport of arsenic.

Effect of metabolic alkalosis and acidosis on renal transport of arsenic.

RENAL MECHANISM FOR EXCRETION AND TRANSFORMATION OF ARSENIC IN THE DOG.

Studies have been performed in female dogs on the renal tubular transport of arsenate and arsenite and on the intrarenal conversion of arsenate to arsenite. During the infusion of arsenate there is a net reabsorption of arsenate and a net secretion of arsenite. The rate of arsenite secretion varies directly with the rate of arsenate reabsorption. The transport of both ions is inhibited by phosphate and glucose. Renal arteriovenous concentration differences show a net production of arsenite from arsenate. Stop-flow studies localize the major site of arsenic transport in the proximal tubule. During arsenite infusion both arsenate and arsenite undergo net reabsorption. The data are interpreted as representative of a tubular reabsorption of arsenate with intracellular conversion of arsenate to arsenite and subsequent diffusion of arsenite across both luminal and antiluminal faces of the tubular cell.

Holcocrinus, a new inadunate crinoid genus from the lower Mississippian [Upper Mississippi Valley

Hundreds of millions of people world-wide are exposed to unacceptable levels of arsenic in drinking water. This is a public health crisis because arsenic is a Group I (proven) human carcinogen. Human cells methylate arsenic to monomethylarsonous acid (MMA^III), monomethylarsonic acid (MMA^V), dimethylarsinous acid (DMA^III), and dimethylarsinic acid (DMA^V). Although the liver is the predominant site for arsenic methylation, elimination occurs mostly in urine. The protein(s) responsible for transport of arsenic from the liver (into blood), ultimately for urinary elimination are unknown. Human multidrug resistance protein 1 (MRP1/<i>ABCC1</i>) and MRP2 (<i>ABCC2</i>), are established arsenic efflux pumps, but unlike the related MRP4 (<i>ABCC4</i>), are not present at the basolateral membrane of hepatocytes. MRP4 is also found at the apical membrane of renal proximal tubule cells making it an ideal candidate for urinary arsenic elimination. In the current study, human MRP4 expressed in HEK293 cells reduced the cytotoxicity and cellular accumulation of As^V, MMA^III, MMA^V, DMA^III, and DMA^V while two other hepatic basolateral MRPs (MRP3 and MRP5) did not. Transport studies with MRP4-enriched membrane vesicles revealed that the diglutathione conjugate of MMA^III [MMA(GS)₂] and DMA^V were the transported species. MMA(GS)₂ and DMA^V transport was osmotically sensitive, allosteric (Hill coefficients of 1.4 ± 0.2 and 2.9 ± 1.2, respectively), and high affinity (K_0.5 of 0.70 ± 0.16 μM and 0.22 ± 0.15 μM, respectively). DMA^V transport was pH dependent with highest affinity and capacity at pH 5.5. These results suggest human MRP4 could be a major player in the elimination of arsenic.

Early organic chemistry of america

Early organic chemistry of america