High Levels Of As Research Articles

Impact of Arsenite on the Bacterial Community Structure and Diversity in Soil.

The impact of arsenite (As[III]) on the bacterial community structure and diversity in soil was determined by incubating soil slurries with 50, 500, and 5,000 μM As(III). As(III) was oxidized to arsenate (As[V]), and the microbial contribution to As(III) oxidation was 70–100%. PCR-denaturing gradient gel electrophoresis revealed that soil bacterial diversity decreased in the presence of As(III). Bacteria closely related to the family Bacillaceae were predominant in slurry spiked with 5,000 μM As(III). The population size of culturable As(III)-resistant bacteria was 37-fold higher in this slurry than in unspiked slurry (p < 0.01), indicating that high levels of As(III) stimulate the emergence of As(III)-resistant bacteria. As(III)-resistant bacteria isolated from slurry spiked with 5,000 μM As(III) were mainly affiliated with the genus Bacillus; however, no strains showed As(III)-oxidizing capacity. An As(III)-oxidizing bacterial community analysis based on As(III) oxidase gene (aioA) sequences demonstrated that diversity was the lowest in slurry spiked with 5,000 μM As(III). The deduced AioA sequences affiliated with Alphaproteobacteria accounted for 91–93% of all sequences in this slurry, among which those closely related to Bosea spp. were predominant (48–86%). These results suggest that exposure to high levels of As(III) has a significant impact on the composition and diversity of the soil bacterial community, including the As(III)-oxidizing bacterial community. Certain As(III)-oxidizing bacteria with strong As(III) resistance may be enriched under high As(III) levels, while more sensitive As(III) oxidizers are eliminated under these conditions.

Behavior of Eucalyptus urophylla and Eucalyptus citriodora Seedlings Grown in Soil Contaminated by Arsenate

Persistent areas of tailings and deposits from coal and gold mining may present high levels of arsenic (As), mainly in the arsenate form, endangering the environment and human health. The establishment of vegetation cover is a key step to reclaiming these environments. Thus, this study aimed to evaluate the potential of Eucalyptus urophylla and E. citriodora seedlings for use in phytoremediation programs of arsenate-contaminated areas. Soil samples were incubated at increasing rates (0, 50, 100, 200 and 400 mg dm-3) of arsenic (arsenate form, using Na2HAsO4) for 15 days. The seedlings were produced in a substrate (vermiculite + sawdust) and were transplanted to the pots with soil three months after seed germination. The values of plant height and diameter were taken during transplanting and 30, 60 and 90 days after transplanting. In the last evaluation, the total leaf area and biomass of shoots and roots were also determined. The values of available As in soil which caused a 50 % dry matter reduction (TS50%), the As translocation index (TI) from the roots to the shoot of the plants, and its bioconcentration factor (BF) were also calculated. Higher levels of arsenate in the soil significantly reduced the dry matter production of roots and shoots and the height of both species, most notably in E. urophylla plants. The highest levels of As were found in the root, with higher values for E. citriodora (ranging from 253.86 to 400 mg dm-3). The TI and BF were also reduced with As doses, but the values found in E. citriodora were significantly higher than in E. urophylla. E. citriodora plants presented a higher capacity to tolerate As and translocate it to the shoot than E. urophylla. Although these species cannot be considered as hyperaccumulators of As, E. citriodora presented the potential to be used in phytoremediation programs in arsenate-contaminated areas due to the long-term growth period of this species.

Biomonitoring Heavy Metal Pollution Using an Aquatic Apex Predator, the American Alligator, and Its Parasites.

Monitoring the bioaccumulation of chemical elements within various organismal tissues has become a useful tool to survey current or chronic levels of heavy metal exposure within an environment. In this study, we compared the bioaccumulations of As, Cd, Cu, Fe, Pb, Se, and Zn between the American alligator, Alligator mississippiensis, and its parasites in order to establish their use as bioindicators of heavy metal pollution. Concomitant with these results, we were interested to determine if parasites were more sensitive bioindicators of heavy metals relative to alligators. We found parasites collectively accumulated higher levels of As, Cu, Se, and Zn in comparison to their alligator hosts, whereas Fe, Cd, and Pb concentrations were higher in alligators. Interestingly, Fe levels were significantly greater in intestinal trematodes than their alligator hosts when analyzed independently from other parasitic taxa. Further analyses showed alligator intestinal trematodes concentrated As, Cu, Fe, Se, and Zn at significantly higher levels than intestinal nematodes and parasites from other organs. However, pentastomids also employed the role as a good biomagnifier of As. Interestingly, parasitic abundance decreased as levels of As increased. Stomach and intestinal nematodes were the poorest bioaccumulators of metals, yet stomach nematodes showed their ability to concentrate Pb at orders of magnitude higher in comparison to other parasites. Conclusively, we suggest that parasites, particularly intestinal trematodes, are superior biomagnifiers of As, Cu, Se, and Zn, whereas alligators are likely good biological indicators of Fe, Cd, and Pb levels within the environment.

Inhibition of arsenic accumulation in Japanese rice by the application of iron and silicate materials

There are many rice paddy fields with relatively high arsenic (As) concentrations in areas that have not been subjected to countermeasures because the As level was below the criterion value established by the Agricultural Land Soil Contamination Prevention Law in Japan. To reduce the risk of excessive As in rice paddy fields using agronomic methods applicable to common farming practices, we examined the effect of the application of iron (Fe) and silicate materials on As uptake by rice plants in bottomless concrete frames filled with soil collected from an area surrounding a former As-polluted region. Following the application of calcium silicate slag at a rate of 0.5kgm−2, no significant effect was observed on the As concentration in rice grain or straw, but the available silicate in the soil was increased. The application of Fe materials at a rate of 0.5kgm−2 resulted in a significant reduction of the As concentration in grain and straw, as shown by an analysis of variance. The lowest concentrations of As in both grain and straw were obtained with the application of a metal Fe powder (EM), followed by that with an Fe oxide material (FB), a converter furnace slag (FM), and the control. The EM and FB applications both significantly reduced the 1M HCl-soluble As concentration in soil compared to the control. The levels of both acid ammonium oxalate extractable Fe (Fe-ox) and citrate–bicarbonate–dithionite extractable Fe (Fe-CDB) in the soil were significantly increased by the application of EM and that of FB compared to the FM and the control. A negative significant correlation was obtained between the amount of 1M HCl-soluble As and two types of free Fe oxide. These results suggest that the available As in soil was strongly fixed with the Fe oxides that were increased by the application of Fe materials, and that the decrease of available As in the soil induced a decrease in the As uptake by rice plants. The application of Fe materials will thus be effective to lower or prevent the risk of the rice cultivation in paddy fields with relatively high levels of As.

Toxic elements and speciation in seafood samples from different contaminated sites in Europe

The presence of cadmium (Cd), lead (Pb), mercury (THg), methylmercury (MeHg), arsenic (TAs), inorganic arsenic (iAs), cobalt (Co), copper (Cu), zinc (Zn), nickel (Ni), chromium (Cr) and iron (Fe) was investigated in seafood collected from European marine ecosystems subjected to strong anthropogenic pressure, i.e. hotspot areas. Different species (Mytilus galloprovincialis, n=50; Chamelea gallina, n=50; Liza aurata, n=25; Platichthys flesus, n=25; Laminaria digitata, n=15; and Saccharina latissima, n=15) sampled in Tagus estuary, Po delta, Ebro delta, western Scheldt, and in the vicinities of a fish farm area (Solund, Norway), between September and December 2013, were selected to assess metal contamination and potential risks to seafood consumers, as well as to determine the suitability of ecologically distinct organisms as bioindicators in environmental monitoring studies. Species exhibited different elemental profiles, likely as a result of their ecological strategies, metabolism and levels in the environment (i.e. seawater and sediments). Higher levels of Cd (0.15–0.94mgkg−1), Pb (0.37−0.89mgkg−1), Co (0.48–1.1mgkg−1), Cu (4.8–8.4mgkg−1), Zn (75–153mgkg−1), Cr (1.0–4.5mgkg−1) and Fe (283–930mgkg−1) were detected in bivalve species, particularly in M. galloprovincialis from Ebro and Po deltas, whereas the highest content of Hg was found in P. flesus (0.86mgkg−1). In fish species, most Hg was organic (MeHg; from 69 to 79%), whereas lower proportions of MeHg were encountered in bivalve species (between 20 and 43%). The highest levels of As were found in macroalgae species L. digitata and S. latissima (41mgkg−1 and 43mgkg−1, respectively), with iAs accounting almost 50% of the total As content in L. digitata but not with S. latissima nor in the remaining seafood samples. This work highlights that the selection of the most appropriate bioindicator species is a fundamental step in environmental monitoring of each contaminant, especially in coastal areas. Furthermore, data clearly shows that the current risk assessment and legislation solely based on total As or Hg data is limiting, as elemental speciation greatly varies according to seafood species, thus playing a key role in human exposure assessment via food.

Trace-Metal Enrichment and Pollution in Coastal Sediments in the Northern Tyrrhenian Sea, Italy.

This study evaluated the distribution pattern and pollution of chromium, arsenic (As), manganese (Mn), nickel, lead, and copper in surface sediments along the northern Latium coast of the Tyrrhenian Sea in Italy. The enrichment factor, geoaccumulation index, and potential toxicity response index were used to evaluate the degree of contamination. These results show As and Mn contamination. The high enrichment and contamination levels of As and Mn are located in two hot spots. These elevations are due to naturally high levels of As and Mn in the Mignone River and the Marangone Stream as well as the intense human activity in the area including the largest energy production site in Europe (Torrevaldaliga Nord coal-fired power plant) and of one of the most important ports for cruise traffic in the Mediterranean Sea.

Arsenic in freshwater ecosystems of the Bengal delta: status, sources and seasonal variability

The study aimed to examine the contamination status of arsenic (As) in excavated small water bodies, commonly known as ponds – the integral part of daily life in the arsenic-affected rural areas of West Bengal, India in comparison to the unaffected areas. The ponds of the contaminated area had higher levels of As: water 2–174 µg L−1 (mean 31 ± 2 µg L−1) and sediment 1.3–37.3 mg kg−1 (mean 10.3 ± 0.4 mg kg−1), than those from the unaffected area: water 1–8 µg L−1 (mean 4 ± 0 µg L−1) and sediment 1.4–5.3 mg kg−1 (mean 3.0 ± 0.1 mg kg−1). A moderate positive correlation was observed between the water and sediment arsenic content of the ponds of the arsenic-affected region (r = 0.688, n = 277, p < 0.0001). Contaminated ground water, either as direct input or through agricultural washings, was found to be the major contributor of arsenic pollution to these ecosystems. Seasonal variations were not prominent. This study emphasized the beneficial role of using the studied ecosystems over the highly contaminated ground water for various livelihood activities in the Gangetic delta region.

Metalloid Attenuation from Runoff Waters at an Historic Orogenic Gold Mine, New Zealand

The metalloids arsenic and antimony are mobilised through the decomposition of arsenopyrite, pyrite, and stibnite at the historic Big River Mine. Their content in the solid substrates reach levels up to ≈25 wt% As and 3.6 wt% Sb, but their concentrations in the mine water are only elevated locally, up to 0.85 mg/L dissolved As and 0.007 mg/L dissolved Sb. Water draining the waste rock are characterised by neutral pH, but at the mine’s former processing site, the oxidation of sulphide concentrates has produced acidic conditions, both in the water (pH 3.8) and solid mining residues (paste pH 2–4). Dissolved metalloid concentrations are being effectively attenuated on site through the formation of secondary As phases in the mining residues, including scorodite, iron sulphoarsenate, and amorphous iron arsenate. Attenuation is also occurring by co-precipitation and adsorption onto iron oxides or hydroxides, and adsorption onto clay mineral surfaces. These processes are complemented by dilution of the dissolved As and Sb by the Big River. Therefore, despite the extremely high levels of As and Sb in the mining residues, metalloid mobilisation is limited, resulting in relatively low concentrations in water leaving the site.

The Accumulation and Subcellular Distribution of Arsenic and Antimony in Four Fern Plants

In the present study, Pteris cretica ‘Albo-Lineata’ (PC), Pteris fauriei (PF), Humata tyermanii Moore (HT), and Pteris ensiformis Burm (PE), were selected to explore additional plant materials for the phytoremediation of As and Sb co-contamination. To some extent, the addition of As and Sb enhanced the growth of HT, PE, and PF. Conversely, the addition of As and Sb negatively affected the growth of PC and was accompanied with the accumulation of high levels of As and Sb in the roots. The highest concentration of Sb was recorded as 6405 mg kg−1 in the roots of PC, and that for As was 337 mg kg−1 in the rhizome of PF. To some degree, As and Sb stimulated the uptake of each other in these ferns. Arsenic was mainly stored in the cytoplasmic supernatant (CS) fraction, followed by the cell wall (CW) fraction. In contrast, Sb was mainly found in the CW fraction and, to a lesser extent, in the CS fraction, suggesting that the cell wall and cytosol play different roles in As and Sb accumulation by fern plants. This study demonstrated that these fern plants show a good application potential in the phytoremediation of As and Sb co-contaminated environments.

A rice ABC transporter, OsABCC1, reduces arsenic accumulation in the grain.

Arsenic (As) is a chronic poison that causes severe skin lesions and cancer. Rice (Oryza sativa L.) is a major dietary source of As; therefore, reducing As accumulation in the rice grain and thereby diminishing the amount of As that enters the food chain is of critical importance. Here, we report that a member of the Oryza sativa C-type ATP-binding cassette (ABC) transporter (OsABCC) family, OsABCC1, is involved in the detoxification and reduction of As in rice grains. We found that OsABCC1 was expressed in many organs, including the roots, leaves, nodes, peduncle, and rachis. Expression was not affected when plants were exposed to low levels of As but was up-regulated in response to high levels of As. In both the basal nodes and upper nodes, which are connected to the panicle, OsABCC1 was localized to the phloem region of vascular bundles. Furthermore, OsABCC1 was localized to the tonoplast and conferred phytochelatin-dependent As resistance in yeast. Knockout of OsABCC1 in rice resulted in decreased tolerance to As, but did not affect cadmium toxicity. At the reproductive growth stage, the As content was higher in the nodes and in other tissues of wild-type rice than in those of OsABCC1 knockout mutants, but was significantly lower in the grain. Taken together, our results indicate that OsABCC1 limits As transport to the grains by sequestering As in the vacuoles of the phloem companion cells of the nodes in rice.

Increase of As release and phytotoxicity to rice seedlings in As-contaminated paddy soils by Si fertilizer application

Silicon (Si) was shown to be able to reduce arsenic (As) uptake by rice in hydroponic culture or in low As soils using high Si application rates. However, the effect of Si application on As uptake of rice grown in As-contaminated soils using Si fertilizer recommendation rate has not been investigated. In this study, the effect of Si application using Si fertilizer recommendation rate on As release and phytotoxicity in soils with different properties and contents of As was examined. The results show that the concentrations of As in soil solutions increased after Si applications due to competitive adsorption between As and Si on soil solids and the Si concentrations in soil solutions were also elevated to beneficial levels for rice growth. The rice seedlings accumulated more As and its growth was inhibited by Si application in As contaminated/spiked soils. The results indicate that there is an initial aggravation in As toxicity before the beneficial effects of Si fertilizing to rice were revealed when Si application based on fertilizer recommendation rate to As-contaminated paddy soils. Therefore, for As-contaminated paddy soils with high levels of As, the application of Si fertilizer could result in increasing As phytotoxicity and uptake by rice.

Main and Interactive Effects of Anxiety Sensitivity and Physical Distress Intolerance with Regard to PTSD Symptoms Among Trauma-Exposed Smokers

The present study examined the roles of anxiety sensitivity (AS; the tendency to misinterpret physical internal sensations of harmful) and distress tolerance (the capacity to tolerate aversive stimuli) in terms of the expression of posttraumatic stress disorder (PTSD) symptoms among a sample of trauma-exposed, treatment-seeking tobacco smokers (n = 137; Mage = 37.7 years, 48.2% female). It was hypothesized that higher AS and lower physical distress tolerance would interact to predict greater PTSD avoidance and hyperarousal symptoms. Results were partially consistent with this prediction. Specifically, there was a significant interactive effect of AS by physical distress tolerance in terms of PTSD hyperarousal symptom cluster severity. The form of the interaction was in the expected direction, with the highest levels of PTSD hyperarousal symptoms reported among smokers with higher levels of AS and a lower capacity to tolerate physical distress. Findings underscore the importance of considering AS and physical distress tolerance in terms of better understanding mechanisms underlying the expression of PTSD symptoms among trauma-exposed smokers.

INAA for determination of trace elements in bottom sediments of the Selenga river basin in Mongolia

Instrumental neutron activation analysis (INAA) was used for the determination of major, minor and trace elements in samples of bottom sediments of the inflows of the Selenga river basin to assess the impact of the contamination from the industrial complex Erdenet and other industrial enterprises in Mongolia. A total of 42 elements (Na, Mg, Cl, K, Ca, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Rb, Sr, Zr, Nb, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Dy, Tm, Hf, Ta, W, Au, Hg, Th, and U) was determined by combination of conventional and epithermal neutron activation analysis at the IBR-2 reactor, FLNP JINR, Dubna. For the first time such a large set of elements was used for characterization of the bottom sediments as accumulating media which may reflect industrial contamination of the water basin. The concentrations of heavy metals and other trace elements in the samples from three inflows of the Selenga river basin were compared with data from the previous studies. It was shown that the industrial zone of the Erdenet Mining Corporation (EMC) and gold mining zone Zaamar are the sources of strong environmental contamination. The concentrations of Cu and Sb determined in sediment samples of the River Khangal and Govil near the EMC exceed average crustal rock and soil values by factors of 50 and 15, respectively. In the area of the gold mining zone Zaamar concentrations of Au, As, and Sb exceed crustal rock and soil values by factors of 4, 25, and 6, respectively. The relatively high levels of As, V, Zn, V, and Sr in the sediments of the studied rivers are obviously due to the discharges of untreated wastewater of desalination plant, electrical power station, textile industry and mining activities as well as domestic wastewater.

Immunological alterations in individuals exposed to metal(loid)s in the Panasqueira mining area, Central Portugal

Environmental studies performed in Panasqueira mine area (central Portugal) identified high concentrations of several metal(loid)s in environmental media, and individuals environmentally and occupationally exposed showed higher levels of As, Cr, Mg, Mn, Mo, Pb and Zn in blood, urine, hair and nails when compared to unexposed controls. To evaluate the presence of immunological alterations attributable to environmental contamination, we quantified neopterin, kynurenine, tryptophan, and nitrite concentrations in plasma, and analysed the percentage of several lymphocytes subsets, namely CD3+, CD4+ and CD8+ T-cells, CD19+ B-cells, and CD16+56+ natural killer (NK) cells in a group of individuals previously tested for metal(loid) levels in different biological matrices. The environmentally exposed group had significantly lower levels of %CD8+ and higher CD4+/CD8+ ratios, whereas the occupationally exposed individuals showed significant decreases in %CD3+ and %CD4+, and significant increases in %CD16+56+, when compared to controls. Analysed biomarkers were found to be influenced by age, particularly neopterin, kynurenine and kynurenine to tryptophan ratio (Kyn/Trp) with significantly higher levels in older individuals, and %CD3+, %CD8+ and %CD19+ with significantly lower values in older individuals. Males environmentally exposed showed significantly lower values of %CD19+ when compared to control females. The concentration of Pb in toenails was associated to the level of neopterin, kynurenine and Kyn/Trp ratio (all direct), and the concentration of Mn in blood to the level of %CD8+, %CD19+ (both inverse) and CD4+/CD8+ ratio (direct). Overall our results show that the metal(loid) contamination in Panasqueira mine area induced immunotoxic effects in exposed populations, possibly increasing susceptibility to diseases.

Method for assessing lead, cadmium, mercury and arsenic in high-density polyethylene packaging and study of the migration into yoghurt and simulant

The purpose of this paper was to assess the concentration of lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) in high-density polyethylene (HDPE) packaging intended for contact with yoghurt and the migration of these elements using the food itself and 3% acetic acid as a food simulant in accordance to ANVISA, the Brazilian Health Surveillance Agency. In order to perform this study, it was necessary to develop and validate a method by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. For method validation, the parameters linearity, limits of detection (LODs) and quantification (LOQs), accuracy and precision were determined. Fifteen commercial samples of yoghurt, marketed in Campinas – São Paulo (Brazil), were used for the analysis. The packaging and yoghurt were digested in high-pressure ashing equipment (HPA) and the migration of the elements into simulant were determined directly in the solution. The validated method proved adequate and the results obtained showed that all the packaging had levels of Hg and Cd below the LOQ, corresponding to 1.0 and 1.5 μg l−1, respectively. The highest levels of As and Pb were 0.87 and 462.3 mg kg−1, respectively. The migration of these elements to the yoghurt after 45 days of contact at 4ºC was below the LOQ for all the samples assessed. The results of specific migration into 3% acetic acid simulant showed the concentrations of Cd, Hg and As below 5, 5 and 10 µg kg−1, respectively, which are the maximum limits set by ANVISA. However, for three samples the packaging lid showed migration of Pb into simulant ranging from 30.6 to 40.2 μg kg−1, exceeding the limit set by ANVISA of 10 μg kg−1.

Distribution of arsenic, cadmium, lead, and nickel levels in biological samples of Pakistani hypertensive patients and control subjects.

The abnormal metabolism of metal ions plays an important role in health and disease conditions, and studies about them have been attracting significant interest. The aim of our study was to assess the toxic elements arsenic (As), cadmium (Cd), nickel (Ni), and lead (Pb) in biological samples (scalp hair, blood, urine) of 387 hypertensive males and females, aged between 30 and 60 years, from an urban population together with 439 non-hypertensive subjects, of the same age group and residential areas. The element concentrations were measured by means of an electrothermal atomic absorption spectrophotometer after microwave-induced acid digestion. The validity and accuracy was checked by conventional wet acid digestion method and using certified reference materials. The overall recoveries of all elements were found in the range of 96.8 - 99.4% of certified values. The results indicated significantly higher levels of As, Cd, Ni, and Pb in the biological samples (scalp hair, blood and urine) of hypertensive patients, when related to controls of both genders. The high exposure of toxic elements may be synergistic with risk factors associated with hypertension. These data present guidance to clinicians and other professionals who will be investigating the toxicity of heavy elements in biological samples (scalp hair and blood) of hypertensive patients.

Sediment baseline study of levels and sources of polycyclic aromatic hydrocarbons and heavy metals in Lake Nicaragua

Selected metals and polycyclic aromatic hydrocarbons (PAHs) were analyzed in sediment samples from 24 sites in Lake Nicaragua sampled May 2010 to provide a baseline of pollution levels. Cu exceeded the Consensus-Based Sediment Quality Guideline (CBSQG) Threshold Effect Concentrations (TECs) at 21 sites while Ni exceeded the value at one site. Comparison of the sampling sites showed that the south-eastern shore and a central part of the lake contained the highest levels of As, Cd, Cr, and Ni, while the western part of the lake contained the highest levels of Cu, Pb, and Zn. Analysis of PAH levels showed that the CBSQG TECs were exceeded by naphthalene at five sites. The sum concentrations of the 16 US EPA priority PAHs (∑PAH16) ranged from 0.01mgkg−1dw to 0.64mgkg−1dw. The highest ∑PAH16 concentration was found upstream in River Mayales and the PAH composition revealed a heavy PAH fraction (e.g., creosote). The main sources of PAHs in Lake Nicaragua were determined as of diffuse petrogenic and pyrogenic origin as well as diagenetic produced perylene. The relative importance of these PAH sources was determined by interpretation of loading and score plots from a principal component analysis. This study concluded that areas of Lake Nicaragua represent an important pollution baseline for future studies in this lake and other tropical lakes.

Arsenic concentration variability, health risk assessment, and source identification using multivariate analysis in selected villages of public water system, Lahore, Pakistan

This paper reports high levels and variability in arsenic (As) levels at locations identified as one of the highest As-contaminated locations in Pakistan. Groundwater pollution related to arsenic has been reported since many years in the areas lying in outskirts of District Lahore, Pakistan. A comparative study is done to determine temporal variations of As from three villages, i.e., Kalalanwala (KLW), Manga Mandi (MM), and Shamki Bhattian (SKB). Seventy-three percent of the 30 investigated samples ranging in depth from 20 to 200 m, show an increasing trend in variations of As concentration over a time span of 4 years and 87% of samples exceeded the WHO standard of 10 μg/L for As while 77% of samples have As concentration >50 μg/L (national standard). Further results indicate that high levels of As is accompanied with increase pH (r = 0.8) favoring desorption of As from minerals at higher pH under oxidizing conditions. For health risk assessment of arsenic, the average daily dose, hazard quotient (HQ), and cancer risk were calculated. The residents of the studied areas had toxic risk index in the order of SKB>KLW>MM, with 87% of samples exceeding the typical toxic risk index 1.00 (ranging from 2.3-48.6) which was 83% (ranging from 0.3-41) 4 years before. The results of the present study therefore indicate that arsenic concentrations are increasing in the area, which needs an immediate attention to provide alternate sources of water to save people at risk.

A comparison of the nutritional value and food safety of organically and conventionally produced wheat flours

Growing interest in organic agriculture has prompted this study aiming to evaluate nutritional content of wheat flours originating from organic and conventional production systems. Obtained results showed that organic samples had significantly lower protein content and lower levels of Ca, Mn and Fe compared to conventional samples. Protein digestibility and levels of K, Zn and Mo were significantly higher in organic than in conventional wheat flours. Regarding undesirable metals, significantly higher levels of As and Cd were found in conventional compared to organic wheat flours. Although the mean concentrations of zearalenone and ochratoxin A were higher in conventional than in organic flours, this difference was not significant. This study revealed that organic agriculture has the potential to yield products with some relevant improvements in terms of high quality proteins and microelements contents, while the reduction in contamination with toxic elements and mycotoxins may be accomplished.

Evidence for an Intrabasinal Source and Multiple Concentration Processes in the Formation of the Carbon Leader Reef, Witwatersrand Supergroup, South Africa

Laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) trace element maps of pyrite and gold from the Carbon Leader Reef in the Witwatersrand basin provide new evidence that a significant proportion of the pyrite and gold was intrabasinal, derived from the West Rand Group or equivalent shales stratigraphically below this reef. Rounded detrital pyrite grains in the Carbon Leader Reef vary from compact to porous to sooty, with similar textures and composition to diagenetic pyrites reported from sedimentary rocks in the West Rand Group. Detrital porous and sooty pyrites contain 0.4 to 11.3 ppm solid-solution gold, sulfur isotope δ34S values from -17 to +16%, and high levels of As and Te, plus a wide range of other trace elements (in decreasing order: Ni, Co, Sb, Cr, Cu, U, Pb, Bi, Mo, Zn and Ag). The sooty pyrite is the most Au, Te, and Mo rich and is intergrown with alumino-silicates and organic matter. The detrital pyrite textures, S-isotopes and geochemistry resemble diagenetic pyrite developed under suboxic to anoxic bottom water conditions. The LAICP-MS maps also show that the detrital pyrite grains have euhedral hydrothermal pyrite overgrowths containing micro-inclusions of gold, brannerite, and Ni-As sulfides. The pyrite overgrowths are also enriched in solid-solution gold, tellurium, and other trace elements including, in decreasing order, As, Co, Ni, Cr, Cu, Mn, Pb, Bi, and Ag. Fractured and brecciated pyrite associated with brittle bedding-parallel fracture zones in the Carbon Leader Reef are also enriched in these elements due to alteration of pyrite surrounding the fractures. Laser ICP-MS Pb isotope determinations on the cores of detrital pyrite indicate an age between 2750 and 2950 Ma with hydrothermal overgrowths originating between 2100 and 2020 Ma incorporating highly radiogenic Pb. This study demonstrates that both of the two competing theories for the origin of the Witwatersrand gold reefs are likely to be correct. We suggest that the hydrothermal event was widespread (kilometer scale) and involved basinal fluids that scavenged gold, tellurium, arsenic, and trace elements (Co, Ni, Cr, Cu, Mn, Pb, Bi, Ag) from gold-bearing sedimentary units in the Central Rand Group. © 2013 Society of Economic Geologists, Inc.