The influence of ionic strength, index cations and competing anions on arsenate (AsV) adsorption–desorption kinetics was studied in an Alfisol soil. A flow-through reactor system similar to that developed by
Carski and Sparks (Soil Sci Soc Am J 49:1114–1116, 1985) was constructed for the experiments. Arsenate adsorption kinetics
for all the treatments were initially fast with 58–91% of AsV adsorbed in the first 15 min. Beyond 15 min, AsV adsorption continued at a slower rate for the observation period of the experiments. Changes in the solution composition
had differing effects on the cumulative amount of AsV adsorbed by the soil. Ionic strength and different index cations had little effect on the amount of AsV adsorbed, while the presence of phosphate decreased the amount of AsV adsorbed from 169 to 89 and 177 to 115 g AsV μg−1 in 0.03 M sodium nitrate and 0.01 M calcium nitrate, respectively. Considerably less AsV was desorbed than was adsorbed, with only between 2 to 17% of the adsorbed AsV desorbed. The presence of phosphate increased the amount of AsV desorbed by 17%, but other changes in the solution ionic strength or index cation had little effect on the amount of AsV desorbed. 相似文献
The effects of arsenic (As) species, such as As(III), As(V) and dimethylarsinic acid (DMA), on the accumulation of As in cucumber (Cucumis sativus), as well as on its growth in a soil mesocosm were evaluated. When Cucumis sativus was cultivated in soils contaminated with 20 and 50 mg/kg of As(III), As(V) or DMA for 40 days, the growth was markedly inhibited by the inorganic As (As(III) and As(V)) rather than the organic As (DMA). Irrespective of the As species, the As concentrations accumulated in Cucumis sativus increased with increasing As concentration in the soil. The As bioaccumulation factors from soil into the tissue of Cucumis sativus were 17.5-35.4, 29.3-42.7 and 17.6-25.7 for As(III), As(V) and DMA, respectively. In addition, the As translocation factors from the roots to shoots were 0.025-0.031, 0.018-0.032 and 0.014-0.026 for As(III), As(V) and DMA, respectively. In conclusion, Cucumis sativus mainly accumulated As in its roots rather than its shoots and easily accumulated inorganic rather than organic As from the soil into its tissue. 相似文献
This review will focus primarily on ohe effects of the inorganic arsenicals (arsenate and arsenite forms) that are present in drinking water. They are acutely toxic to both humans and animals, an effect that may be related to their bioavailibility. In humans, arsenicals have been reported to cause dermatitis and mucous membrane irritation upon exposure. They have also been reported to cause skin lesions and peripheral neurotoxicity in smelter workers and in patients treated with Fowler's Solution. When humans are exposed to arsenic in drinking water, effects such as hyperkeratosis, electromyographic abnormalities and vascular effects have been reported. In experimental animals, arsenic has been demonstrated to affect the liver and kidneys. In mice, arsenic has also been reported to decrease the animal's resistance to certain viral infections. The arsenite (+3) and arsenate (+5) forms have different modes of action. Arsenite binds to sulphhydryl groups and has been reported to inhibit over 100 different enzymes, while the arsenate can substitute for phosphate in various high energy intermediates, resulting in arsenolysis. In addition, when arsenate is reduced to arsenite in the body, it can also cause toxicity as that species. 相似文献
This study measured activities of serum enzymes alkaline phosphatase, acid phosphatase, glutamic oxaloacetic transaminase (SGOT), and glutamic pyruvic transaminase (SGPT), markers of liver function in albino rats after continuous ingestion of arsenic trioxide (As203). For the study, treated animals were given AS2O3 (0.2 mg/100 g/day) orally for 180 days. After the completion of treatment, the blood was collected for the estimation of serum biochemical markers. The results obtained were compared with control group. Data showed a significant increase in SGOT and SGPT activity after 60 days of As203 administration. The level of alkaline phosphatase and acid phosphatase increased significantly after 90 and 120 days, respectively. Since the elevation of these serum enzymes is an indicator of hepatic damage, data indicate that As2O3 produces hepatotoxicity. When taken continuously, arsenic was also deposited in liver and blood and affected the enzymatic pathways. Total accumulated arsenic was determined by HG-AAS at 193.7 nm. 相似文献
Arsenic is one of the few human carcinogens for which there is not yet a reliable animal cancer model. As such, the classification of arsenic as a carcinogen is based upon data derived from human epidemiologic studies. Although the mechanisms of action of arsenic as a toxic agent have been known for many years, the inability to produce cancer with arsenic in laboratory animals has confounded the operational characterisation of arsenic as initiator, promoter, complete carcinogen, or cocarcinogen for humans. Arsenic is clearly a genotoxic agent that induces chromosomal aberrations, micronuclei and sister chromatid exchange in mammalian cells as well as neoplastically transforms Syrian hamster embryo cells; however, it is not a classical point mutagen. This paper reviews some of the scientifically based issues relating to arsenic and risk assessment. 相似文献
Although numerous studies with rats, hamsters, minipigs, goats and chicks have indicated that arsenic is an essential nutrient, the physiological role of arsenic is open to conjecture. Recent studies have suggested that arsenic has a physiological role that affects the formation of various metabolites of methionine metabolism including taurine and the polyamines. The concentration of plasma taurine is decreased in arsenic-deprived rats and hamsters. The hepatic concentration of polyamines and the specific activity of an enzyme necessary for the synthesis of spermidine and spermine, S-adenosylmethionine decarboxylase, are also decreased in arsenic-deprived rats. Thus, evidence has been obtained which indicates that arsenic is of physiological importance, especially when methionine metabolism is stressed (e.g. pregnancy, lactation, methionine deficiency, vitamin B6 deprivation). Any possible nutritional requirement by humans can be estimated only by using data from animal studies. The arsenic requirement for growing chicks and rats has been suggested to be near 25 ng g–1 diet. Thus, a possible human requirement is 12 g day–1. The reported arsenic content of diets from various parts of the world indicates that the average intake of arsenic is in the range of 12–40 g. Fish, grain and cereal products contribute most arsenic to the diet. 相似文献
Seasonal differences in the dissolved arsenic concentration and speciation in a contaminated urban waterway in northwest England have been determined using a coupled ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS) technique. Waters sampled in the vicinity of an industrial works during relatively dry conditions in April 2000 were found to contain total arsenic concentrations (As) of up to 132 g L–1, more than an order magnitude greater than the 4 g L–1 maximum found in December 2000. The difference in As between the April and December sampling periods is speculated to be largely due to the irregular anthropogenic supply of arsenic to the watercourse. For both sampling periods, the dissolved arsenic was exclusively inorganic in nature and had an As(V)/As ratio of between 0.6 and 0.8. Analysis of samples taken downstream of the industrial site, after the confluence with a relatively As-poor stream, revealed that As(III), As(V) and As concentrations were lower than would be expected from conservative mixing. The As(V)/As ratio was also observed to decrease markedly. The loss of arsenic from solution is thought to be due to adsorption on the iron oxyhydroxide-rich sediment observed to coat the riverbed downstream of the confluence. The reduction in the As(V)/As ratio is believed to be due to the more rapid adsorption of As(V) compared to that of As(III). Deviations from conservative behaviour were more marked during the relatively dry April 2000 sampling period and suggest the increased importance of adsorption processes controlling arsenic availability during this time. 相似文献
In this review paper, various methods for arsenic removal from water have been described by explaining the related mechanisms
of each methods. Advantages and drawbacks were discussed. Membrane methods were suggested as reliable methods for elimination
of arsenic from water in addition to other conventional separation methods. 相似文献
There is a lack of information on arsenic metabolism in children exposed chronically to low levels of arsenic (<50 µg L?1). The objective of this study was to determine the methylation profile of urinary arsenic metabolites in children exposed to low-level concentrations of arsenic via their drinking water. A cross-sectional study was undertaken in 50 children from four towns in the Yaqui Valley, Sonora, with total arsenic values of 39.9, 16.8, 7.3, and 5.5 µg L?1 in their drinking water, respectively. First morning void samples were analyzed for inorganic-As (InAs), mono and dimethyl arsenic (MMA and DMA). The total arsenic excreted in urine ranged from 23.1 to 99.1 µg L?1 and these levels did not vary by sex. Children with the highest level of total arsenic in their drinking water excreted the highest amount in urine and the length of residence and age also had significant contribution. Children with a lower range of arsenic exposure (16.8–5.5 µg L?1) had similar amounts of arsenic in urine with values of 23.1, 28.2, and 32.6 µg L?1, respectively. DMA had the highest proportion in urine (52.1–74.7%), followed by InAs (16.3–34.9%) and MMA (4.4–8.4%). Compared to other reports, these children excreted a low %MMA (6.1%), and children from the towns with the lowest levels of arsenic had the highest %InAs and the lowest %DMA. This variability in arsenic methylation was partially explained by arsenic concentration in drinking water, years of residence and age, and may reflect genetic differences or more contribution from different exposure routes. In conclusion, our results show that at low levels of exposure the children's ability to metabolize InAs did not have a linear association with the levels of arsenic, and overall children from the Yaqui Valley excrete a lower %MMA than expected. 相似文献
The arsenic levels of 23 mineral waters on sale to the public in the United Kingdom were measured. The arsenic content of most waters was below 1 g L–1 but the statutory limits of 50 ug L–1 for natural mineral waters and 100 g L–1 for non-alcoholic beverages were exceeded by the French mineral water, Vichy Célestins (220 ug L–1). Regular consumption of mineral water of such elevated concentration could make a significant contribution to the intake of the more toxic inorganic species of arsenic, with possible adverse long-term effects on the health of some individuals. The general need for analytical speciation studies of dietary arsenic is emphasised. 相似文献
Arsenic (As) is a pervasive environmental toxin and carcinogenic metalloid. It ranks at the top of the US priority List of Hazardous Substances and causes worldwide human health problems. Wetlands, including natural and artificial ecosystems (i.e. paddy soils) are highly susceptible to As enrichment; acting not only as repositories for water but a host of other elemental/chemical moieties. While macroscale processes (physical and geological) supply As to wetlands, it is the micro-scale biogeochemistry that regulates the fluxes of As and other trace elements from the semi-terrestrial to neighboring plant/aquatic/atmospheric compartments. Among these fine-scale events, microbial mediated As biotransformations contribute most to the element’s changing forms, acting as the ‘switch’ in defining a wetland as either a source or sink of As. Much of our understanding of these important microbial catalyzed reactions follows relatively recent scientific discoveries. Here we document some of these key advances, with focuses on the implications that wetlands and their microbial mediated transformation pathways have on the global As cycle, the chemistries of microbial mediated As oxidation, reduction and methylation, and future research priorities areas.
Skin lesion is one of the important health hazards caused by high intake of arsenic through drinking water and diet, and the other hazards include several types of cancers (viz. skin, lung and urinary bladder), ischemic heart disease, hypertension, etc. Two most important biomarkers to measure arsenic intake in a human body are arsenic concentration in urine and hair. The primary interest of this paper is the association between skin lesion and arsenic concentration in hair for participants with chronic arsenic exposure from West Bengal, India, using bivariate regression model based on copula function. The result showed participants with high arsenic concentration in hair had higher incidence of developing skin lesion. Arsenic concentration in hair was significantly higher for the participants with an arsenic concentration in water?>?10 mg/L. 相似文献
Magnetites (MEBWx) were prepared by precipitation in 1-butanol/water mixtures of various mole ratios of 1-butanol to water.
It was found that the magnetites prepared in the mixture with high mole ratio of 1-butanol to water have high specific surface
area. The adsorption isotherms of As(III) and As(V) with the magnetites at 303 K fitted the Langmuir model well. The adsorption
capacities of the magnetite prepared in the mixtures were higher than those of the magnetite prepared without 1-butanol. Their
adsorption capacities increased with increasing specific surface area. 相似文献
A Pseudomonas aeruginosa–Caenorhabditis elegans pathogenesis model was utilized to assess immunotoxic effects of arsenic trioxide (As2O3). After 2 h of As2O3 exposure, 500 µmol L?1 and 1 mmol L?1 As2O3 treatment significantly decreased median survivals of C. elegans (10 h after L4/adult molt). However, 2 h of As2O3 exposure caused no significant changes in the survivals rates of C. elegans (2 h after L4/adult molt). Notably, a significant dose-related immunoenhancement was observed in C. elegans (2 h after L4/adult molt) after 12 h of arsenite exposure. 相似文献
Arsenic (As) is found in waters such as seawater, warm springs, groundwater, rivers, and lakes. In aquatic environments, As occurs as a mixture of arsenate and arsenite, with arsenate usually predominating. The unrestricted application of As pesticides, industrial activities, and mining operations has led to the global occurrence of soluble As above permissible levels of 0.010 mg/L. Continuous exposure of freshwater organisms including fish to low concentrations of As results in bioaccumulation, notably in liver and kidney. As a consequence As induces hyperglycemia, depletion of enzymatic activities, various acute and chronic toxicity, and immune system dysfunction. Here we review arsenic chemistry, the occurrence of arsenic in aquatic system, the transformation and metabolism of arsenic; arsenic bioaccumulation and bioconcentration; behavioral changes; and acute and other effects such as biochemical, immunotoxic, and cytogenotoxic effects on fish. 相似文献
This paper describes risk assessment methods for two chronic exposure pathways involving arsenic contaminated soil, namely inhalation of fugitive dust emissions over a lifetime, and inadvertent soil/house dust ingestion. The endpoint in the first case is assumed to be lung cancer and in the second case skin cancer. In order to estimate exposures, inhalation rates and soil/dust ingestion rates are estimated for different age groups; indoor/outdoor time budgets for different age groups are developed; and indoor surface dust and air arsenic concentrations are estimated based on outdoor concentration measurements. Differences observed in indoor/outdoor ratios and arsenic containing dust particle size among different types of communities are noted, as well as possible relationship of particle size to bioavailability. Calculations of risk are presented using cancer potency factors developed by the U.S. Environmental Protection Agency, and uncertainties in these toxicity estimates are described based on: (1) evidence that arsenic may be neither a cancer initiator nor promotor, but may act instead as a late stage carcinogen and (2) evidence that the arsenic dose-response relationship for ingestion may be nonlinear at low doses due to increasing methylation of inorganic arsenic. The first of these considerations influences the relative importance ascribed to arsenic doses in different age groups. The latter consideration indicates that the risk estimates described here are probably very conservative. 相似文献