Serum selenium concentration in a representative sample of the Canarian population

The concentration of serum selenium in 395 individuals (187 males + 218 females) living in the Canary Islands, Spain was determined by hydride generation atomic absorption spectrometry. The mean selenium concentration was 74.7 +/- 25.2 microg/l ranging between 7.86 and 182.3 microg/l. Twenty-two adults (7.2% of the total) had serum selenium concentrations under 45 microg/l. It is widely accepted that below this selenium serum concentration (45 microg/l) there is an increased risk of cardiovascular disease and cancer. Our results fall within data recently published in other Spanish and European regions and are much lower than data observed in USA or seleniferous regions. The estimated Se intakes of our population were lower than the Recommended Dietary Allowances for American people. Individuals from Lanzarote had a mean Se concentration significantly higher than individuals from the other islands. This could be attributed to differences in Se content of soil and/or differences in dietary habits of the populations. Serum selenium concentration did not vary with the sex of the subjects. Individuals younger than 14 years old had a serum selenium concentration significantly lower than the rest of the individuals. No relationship with socio-economic status, educational level, smoking habits, physical exercise or beer consumption was found. However, individuals who consume wine more than three times a week showed higher selenium concentrations than individuals with lower consumption. Also, individuals with consumption above seven units of spirit drinks a week had the highest mean selenium concentration.     

Selenium mass balance in the Great Salt Lake, Utah

A mass balance for Se in the south arm of the Great Salt Lake was developed for September 2006 to August 2007 of monitoring for Se loads and removal flows. The combined removal flows (sedimentation and volatilization) totaled to a geometric mean value of 2079 kg Se/yr, with the estimated low value being 1255 kg Se/yr, and an estimated high value of 3143 kg Se/yr at the 68% confidence level. The total (particulates + dissolved) loads (via runoff) were about 1560 kg Se/yr, for which the error is expected to be ± 15% for the measured loads. Comparison of volatilization to sedimentation flux demonstrates that volatilization rather than sedimentation is likely the major mechanism of selenium removal from the Great Salt Lake. The measured loss flows balance (within the range of uncertainties), and possibly surpass, the measured annual loads. Concentration histories were modeled using a simple mass balance, which indicated that no significant change in Se concentration was expected during the period of study. Surprisingly, the measured total Se concentration increased during the period of the study, indicating that the removal processes operate at their low estimated rates, and/or there are unmeasured selenium loads entering the lake. The selenium concentration trajectories were compared to those of other trace metals to assess the significance of selenium concentration trends.     

Distribution and mobility of arsenic in soils of a mining area (Western Spain)

High levels of total and bioavailable As in soils in mining areas may lead to the potential contamination of surface water and groundwater, being toxic to human, plants, and animals. The soils in the studied area (Province of Salamanca, Spain) recorded a total As concentration that varied from 5.5 mg/kg to 150 mg/kg, and water-soluble As ranged from 0.004 mg/kg to 0.107 mg/kg, often exceeding the guideline limits for agricultural soil (50 mg/kg total As, 0.04 mg/kg water-soluble As). The range of As concentration in pond water was < 0.001 μg/l-60 μg/l, with 40% of samples exceeding the maximum permissible level (10 μg/l) for drinking water. Estimated bioavailable As in soil varied from 0.045 mg/kg to 0.760 mg/kg, around six times higher than water-soluble As fraction, which may pose a high potential risk in regard to its entry into food chain. Soil column leaching tests show an As potential mobility constant threatening water contamination by continuous leaching. The vertical distribution of As through soil profiles suggests a deposition mechanism of this element on the top-soils that involves the wind or water transport of mine tailings. A similar vertical distribution of As and organic matter (OM) contents in soil profiles, as well as, significant correlations between As concentrations and OM and N contents, suggests that type and content of soil OM are major factors for determining the content, distribution, and mobilization of As in the soil. Due to the low supergenic mobility of this element in mining environments, the soil pollution degree in the studied area is moderate, in spite of the elevated As contents in mine tailings.     

Total mercury,methylmercury and selenium in mercury polluted areas in the province Guizhou,China

The province of Guizhou in Southwestern China is currently one of the world's most important mercury production areas. Emissions of mercury from the province to the global atmosphere have been estimated to be approximately 12% of the world total anthropogenic emissions. The main objective of this study was to assess the level of contamination with Hg in two geographical areas of Guizhou province. Mercury pollution in the areas concerned originates from mercury mining and ore processing in the area of Wanshan, while in the area of Quingzhen mercury pollution originates from the chemical industry discharging Hg through wastewaters and emissions to the atmosphere due to coal burning for electricity production. The results of this study confirmed high contamination with Hg in soil, sediments and rice in the Hg mining area in Wanshan. High levels of Hg in soil and rice were also found in the vicinity of the chemical plant in Quingzhen. The concentrations of Hg decreased with distance from the main sources of pollution considerably. The general conclusion is that Hg contamination in Wanshan is geographically more widespread, due to deposition and scavenging of Hg from contaminated air and deposition on land. In Quingzhen Hg contamination of soil is very high close to the chemical plant but the levels reach background concentrations at a distance of several km. Even though the major source of Hg in both areas is inorganic Hg, it was observed that active transformation of inorganic Hg to organic Hg species (MeHg) takes place in water, sediments and soils. The concentration of Hg in rice grains can reach up to 569 microg/kg of total Hg of which 145 microg/kg was in MeHg form. The percentage of Hg as MeHg varied from 5 to 83%. The concentrations of selenium can reach up to 16 mg/kg in soil and up to 1 mg/g in rice. A correlation exists between the concentration of Se in soil and rice, indicating that a portion of Se is bioavailable to plants. No correlation between Hg and Se in rice was found. Exposure of the local population to Hg may occur due to inhalation of Hg present in air (in particular in Hg mining area) and consumption of Hg contaminated food (in particular rice and fish) and water. Comparison of intake through these different routes showed that the values of Hg considerably exceed the USA EPA Reference Concentration (RfC) for chronic Hg exposure (RfC is 0.0004 mg/m(3)) close to the emission sources. Intake of Hg through food consumption, particularly rice and fish, is also an important route of Hg exposure in study area. In general, it can be concluded that the population mostly at risk is located in the vicinity of smelting facilities, mining activities and close to the waste disposal sites in the wider area of Wanshan. In order to assess the real level of contamination in the local population, it is recommended that biomonitoring should be performed, including Hg and MeHg measurements in hair, blood and urine samples.     

Impacts of mercury contaminated mining waste on soil quality, crops, bivalves, and fish in the Naboc River area, Mindanao, Philippines

Rice paddy fields in the Naboc area, near Monkayo on the island of Mindanao, Philippines, have been irrigated four times a year over the last decade using Naboc River water contaminated with mercury (Hg) by artisanal gold mining in the Diwalwal area. Silt containing up to at least 90 mg Hg/kg (d.w.) has been deposited in rice paddy fields during the 1990s and this has been repeatedly mixed into the rice root zone through ploughing. Hg in the rice paddy field soils averages 24 mg Hg/kg and generally exceeds the UK and Canadian soil quality thresholds for agricultural soils as well as the proposed Dutch Intervention value and the USEPA soil ingestion Soil Screening Level (SSL) for inorganic Hg. Much lower Hg concentrations (0.05-0.99 mg/kg) within the range expected for uncontaminated soils, characterise soils on which corn and bananas are cultivated, largely because these are not irrigated with Hg-contaminated water from the Naboc River. The estimated total weekly MeHg intake for a person living in the Naboc area related to the weekly consumption of 2.1 kg of rice grown on Hg-contaminated soils (15 microg MeHg) in conjunction with 1 kg of fish (220 microg MeHg) and 100 g of mussels (50 microg MeHg) from the Naboc River, would total 285 microg MeHg (equivalent to 4.75 microg/kg bw for a 60 kg adult), which is nearly three times the JECFA PTWI of 1.6 microg/kg bw. This will significantly contribute to the population mercury exposure and might explain why 38% of the local inhabitants were classified as Hg intoxicated during a mercury toxicity assessment [Drasch GS, B?se, O'Reilly S, Beinhoff C, Roider G, Maydl S. The Mt. Diwata study on the Philippines 1999-assessing mercury intoxication of the population by small scale gold mining. Sci Total Environ 2001; 267(1-3): 151-168.].     

Methyl mercury exposure in Swedish women with high fish consumption

We studied the exposure to methyl mercury (MeHg) in 127 Swedish women of childbearing age with high consumption of various types of fish, using total mercury (T-Hg) in hair and MeHg in blood as biomarkers. Fish consumption was assessed using a food frequency questionnaire (FFQ), including detailed information about consumption of different fish species, reflecting average intake during 1 year. We also determined inorganic mercury (I-Hg) in blood, and selenium (Se) in serum. The average total fish consumption, as reported in the food frequency questionnaire, was approximately 4 times/week (range 1.6-19 times/week). Fish species potentially high in MeHg, included in the Swedish dietary advisories, was consumed by 79% of the women. About 10% consumed such species more than once a week, i.e., more than what is recommended. Other fish species potentially high in MeHg, not included in the Swedish dietary advisories, was consumed by 54% of the women. Eleven percent never consumed fish species potentially high in MeHg. T-Hg in hair (median 0.70 mg/kg; range 0.08-6.6 mg/kg) was associated with MeHg in blood (median 1.7 microg/L; range 0.30-14 microg/L; rs = 0.78; p < 0.001). Hair T-Hg, blood MeHg and serum Se (median 70 microg/L; range 46-154 microg/L) increased with increasing total fish consumption (rs = 0.32; p < 0.001, rs = 0.37; p < 0.001 and rs = 0.35; p = 0.002, respectively). I-Hg in blood (median 0.24 microg/L; range 0.01-1.6 microg/L) increased with increasing number of dental amalgam fillings. We found no statistical significant associations between the various mercury species measured and the Se concentration in serum. Hair mercury levels exceeded the levels corresponding to the EPA reference dose (RfD) of 0.1 microg MeHg/kg b.w. per day in 20% of the women. Thus, there seems to be no margin of safety for neurodevelopmental effects in fetus, for women with high fish consumption unless they decrease their intake of certain fish species.     

Survey of arsenic and other heavy metals in food composites and drinking water and estimation of dietary intake by the villagers from an arsenic-affected area of West Bengal,India

An investigation of arsenic, copper, nickel, manganese, zinc and selenium concentration in foodstuffs and drinking water, collected from 34 families and estimation of the average daily dietary intake were carried out in the arsenic-affected areas of the Jalangi and Domkal blocks, Murshidabad district, West Bengal where arsenic-contaminated groundwater (mean: 0.11 mg/l, n=34) is the main source for drinking. The shallow large diameter tubewells, installed for agricultural irrigation contain an appreciable amount of arsenic (mean: 0.094 mg/l, n=10). So some arsenic can be expected in the food chain and food cultivated in this area. Most of the individual food composites contain a considerable amount of arsenic. The mean arsenic levels in food categories are vegetables (20.9 and 21.2 microg/kg), cereals and bakery goods (130 and 179 microg/kg) and spices (133 and 202 microg/kg) for the Jalangi and Domkal blocks, respectively. For all other heavy metals, the observed mean concentration values are mostly in good agreement with the reported values around the world (except higher zinc in cereals). The provisional tolerable daily intake value of inorganic arsenic microg/kg body wt./day) is: for adult males (11.8 and 9.4); adult females (13.9 and 11); and children (15.3 and 12) in the Jalangi and Domkal blocks, respectively (according to FAO/WHO report, the value is 2.1 microg/kg body wt./day). According to WHO, intake of 1.0 mg of inorganic arsenic per day may give rise to skin lesions within a few years. The average daily dietary intake of copper, nickel and manganese is high, whereas for zinc, the value is low (for adult males: 8.34 and 10.2 mg/day; adult females: 8.26 and 10.3 mg/day; and children: 4.59 and 5.66 mg/day) in the Jalangi and Domkal blocks, respectively, compared to the recommended dietary allowance of zinc for adult males, adult females and children (15, 12 and 10 mg/day, respectively). The average daily dietary intake of selenium microg/kg body wt./day) is on the lower side for the children (1.07 and 1.22), comparable for the adult males (0.81 and 0.95) and slightly on the higher side for the adult females (1.08 and 1.26), compared to the recommended value (1.7 and 0.9 microg/kg body wt./day for infants and adults, respectively).     

Mercury contaminations from historic mining to water, soil and vegetation in Lanmuchang, Guizhou, southwestern China

Concentrations of total mercury and methylmercury (MeHg) were measured in soil and vegetation samples collected from a small area with a long history of Hg-mining. Hg distributions were determined in stream-waters during two sampling periods. Total Hg concentrations in soil and vegetation samples were highly elevated ranging from 0.41 to 610 mg kg(-1) and from 0.02 to 55 mg kg(-1), respectively. MeHg concentrations varied from 0.41 to 8.8 microg kg(-1) in soil samples and from 0.65 to 5.5 microg kg(-1) in vegetations. The concentrations of total Hg in stream waters varied from 55.0 to 7020 ng L(-1) in the flood-flow regime and from 24.8 to 679 ng L(-1) in the base-flow regime, respectively. Average dissolved Hg concentration was 15.7 ng L(-1) in the wet season and 21.0 ng L(-1) in the dry season. However, particulate Hg was typically >70% of total Hg in the flood-flow regime. Higher concentrations of particulate Hg primarily originated from summer floods were the major pathway of Hg transportation, which were evidenced by the positive correlation between particulate Hg and total suspended solids (TSS). The contaminated soils and distribution patterns of Hg in the stream-waters may serve as an important source of Hg to the local environment in the study area.     

Environmental assessment of mercury contamination from the Rwamagasa artisanal gold mining centre, Geita District, Tanzania

This study presents the results of an environmental assessment of mercury (Hg) contamination in the Rwamagasa artisanal gold mining area, northwest Tanzania, and the potential downstream dispersion along the River Malagarasi to Lake Tanganyika. At the time of sampling, generally low concentrations of Hg (<0.05 mg/kg) occurred in most cultivated soils although higher Hg (0.05-9.2 mg/kg) was recorded in urban soils and vegetable plot soils where these are impacted by Hg-contaminated water and sediment derived from mineral processing activities. Hg in vegetable and grain samples is mostly below the detection limit of 0.004 mg/kg Hg, apart from 0.007 and 0.092 mg/kg Hg in two yam samples and 0.011 to 0.013 mg/kg Hg in three rice samples. The standardized (i.e., standardized to 10 cm length) Hg concentrations in Clarias spp. increase from about 0.01 mg Hg/kg for the River Malagarasi delta to 0.07, 0.2, and 1.6 mg/kg, respectively, for the Rwamagasa 'background', moderately and most contaminated sites. For piscivorous (Lates, Brycinus, and Hydrocynus spp.), insectivorous (Barbus spp.), and planktivorous (Haplochromis spp.) fish species, the 10-cm standardized Hg concentrations increase from about 0.006 mg/kg for the River Malagarasi-Lake Tanganyika area to 0.5 and 3.5 mg/kg, respectively, for the Rwamagasa moderately and most contaminated sites. The low concentrations of Hg in fish from the Malagarasi River delta and Lake Tanganyika indicate that Hg contamination from the Rwamagasa area does not have a readily discernible impact on the biota of Lake Tanganyika. Many of the fish samples from Rwamagasa exceed guidelines for human consumption (0.5 mg/kg) as well as the WHO recommended limit for vulnerable groups (0.2 mg/kg). Tissue total Hg (THg) of all fish collected from the River Malagarasi-Lake Tanganyika subarea is well below these guidelines. Potential human exposure through consumption of 300 g/day of rice grown on Hg-contaminated soils is 5.5 microg/week. Consumption of 250 g Nile perch (Lates spp.), 500 g tilapia (Oreochromis spp.), and 250 g of catfish (Clarias spp.) each week would result in an intake of 65 microg Hg/week for people consuming only fish from the Mara and Mwanza regions of Lake Victoria and 116 microg Hg/week for people in the Rwamagasa area consuming tilapia and Nile perch from Lake Victoria and catfish from mining-impacted streams. This is lower than the Provisional Tolerable Weekly Intake (PTWI) of 300 microg for Hg in the diet set by the WHO and the FAO. Inadvertent ingestion of soil containing 9 mg Hg/kg at a rate of 80 mg/day would give an additional estimated weekly intake of 5 microg THg, whereas the persistent and purposeful consumption of soil (geophagia) at a rate of 26 g soil/day would produce an additional chemical exposure of 230 microg Hg/day.     

Selenate removal in methanogenic and sulfate-reducing upflow anaerobic sludge bed reactors

This paper evaluates the use of upflow anaerobic sludge bed (UASB) bioreactors (30 degrees C, pH=7.0) to remove selenium oxyanions from contaminated waters (790 microg Se L(-1)) under methanogenic and sulfate-reducing conditions using lactate as electron donor. One UASB reactor received sulfate at different sulfate to selenate ratios, while another UASB was operated under methanogenic conditions for 132 days without sulfate in the influent. The selenate effluent concentrations in the sulfate-reducing and methanogenic reactor were 24 and 8 microg Se L(-1), corresponding to removal efficiencies of 97% and 99%, respectively. X-ray diffraction (XRD) analysis and sequential extractions showed that selenium was mainly retained as elemental selenium in the biomass. However, the total dissolved selenium effluent concentrations amounted to 73 and 80 microg Se L(-1), respectively, suggesting that selenate was partly converted to another selenium compound, most likely colloidally dispersed Se(0) nanoparticles. Possible intermediates of selenium reduction (selenite, dimethylselenide, dimethyldiselenide, H(2)Se) could not be detected. Sulfate reducers removed selenate at molar excess of sulfate to selenate (up to a factor of 2600) and elevated dissolved sulfide concentrations (up to 168 mg L(-1)), but selenium removal efficiencies were limited by the applied sulfate-loading rate. In the methanogenic bioreactor, selenate and dissolved selenium removal were independent of the sulfate load, but inhibited by sulfide (101 mg L(-1)). The selenium removal efficiency of the methanogenic UASB abruptly improved after 58 days of operation, suggesting that a specialized selenium-converting population developed in the reactor. This paper demonstrates that both sulfate-reducing and methanogenic UASB reactors can be applied to remove selenate from contaminated natural waters and anthropogenic waste streams, e.g. agricultural drainage waters, acid mine drainage and flue gas desulfurization bleeds.     

Lead contamination in shooting range soils from abrasion of lead bullets and subsequent weathering

Contamination of shooting range soils from the use of Pb bullets is under increasing scrutiny. Past research on Pb contamination of shooting ranges has focused on weathering reactions of Pb bullets in soil. The objective of this study was to determine the significance of abrasion of Pb bullets in contributing to soil Pb contamination. This was accomplished by firing a known mass of bullets into sand and analyzing for total Pb after removing bullets, through field sampling of a newly opened shooting range, and a laboratory weathering study. Forty-one mg of Pb were abraded per bullet as it passed through the sand, which accounted for 1.5% of the bullet mass being physically removed. At a shooting range that had been open for 3 months, the highest Pb concentration from the pistol range berm soil was 193 mg/kg at 0.5 m height, and from the rifle range berm soil was 1142 mg/kg at 1.0 m height. Most soils from the field abrasion experiment as well as soil collected from the rifle range had SPLP-Pb >15 microg/l (Synthetic Precipitation Leaching Procedure). Typically, Pb concentration in the rifle range was greater than that of the pistol range. Based on a laboratory weathering study, virtually all metallic Pb was converted to hydrocerussite (Pb3(CO3)2(OH)2), as well as to a lesser extent cerussite (PbCO3) and massicot (PbO) within one week. Our study demonstrated that abrasion of lead bullets and their subsequent weathering can be a significant source of lead contamination in soils of a newly opened shooting range.     

Selenium in the belgian soils and its uptake by rye-grass

Data obtained by atomic absorption spectroscopy showed a selenium concentration of only 0.11 ppm as an average value for the most representative agricultural soils in Belgium. The selenium content in rye-grass grown on different soil types was between 0.05 and 0.11 ppm, and positively correlated with the soil selenium level.Addition of selenium in the form of selenite to the different soil types resulted in an increased selenium uptake by the plant. The ultimate concentration in the plant depended on the structural and chemical composition of the soil. Twelve other elements were determined in the soils by energy-dispersive X-ray fluorescence; none showed a strong correlation with the soil selenium content or with the selenium uptake by ryegrass.     

Selenium status in Greenland Inuit

In Greenland, the human intake of selenium has always been relatively high and is closely connected to intake of the traditional food of marine origin. Analyses of historic and present day human and animal hair samples have indicated that the selenium level in the marine environment has been constant over time, while the levels in humans have declined corresponding to a decrease in intake of traditional food. The Inuit population in Greenland is in dietary transition where western-style food will increasingly dominate. As a consequence, the ample supply of selenium may not be sustained in the future. We report here the selenium status in three Greenlandic population groups, Ittoqqortoormiit and Tasiilaq on the east coast and Uummannaq on the west coast. Mean whole blood concentrations ranged from 178 microg/l in Tasiilaq men to 488 microg/l in Uummannaq men. Plasma concentrations ranged from 79 microg/l in Tasiilaq women to 113 microg/l in Uummannaq men. With increasing Se concentrations in whole blood, the plasma concentrations increased but tended to stabilise a level approximately 140 microg/l. Selenium blood levels were highly significantly correlated with long chain marine fatty acids. Dietary survey and food composition data from the west coast showed that whale skin, muktuk, is the main source of Se followed by birds, seal meat and organs, and fish. Terrestrial animals contributed only insignificantly to the selenium intake. In West Greenland, daily Se intake (235 microg/day) was estimated by dietary survey; it corresponded well with a calculated intake (220 microg/day) based on the mean blood concentration.     

Selenium and its redox speciation in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores.

The determination of the total concentration of selenium does not provide sufficient information about its toxicity and its bioavailability. The determination of its chemical forms is the basis for understanding the biogeochemical cycle in terrestrial and aquatic ecosystems and for detecting the species which might be toxic to biota. In this work we describe an analytical procedure to carry out the redox speciation of selenium present at ultratrace levels in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores. A simple preconcentration step of the rainwater sample on a rotavapor system, in vacuum at low temperature permits the concentration of the different redox selenium species until levels quantifiable by sensitive techniques such as differential pulse cathodic stripping voltammetry or by spectrometric techniques, based on the hydride generation and detection by atomic absorption or atomic fluorescence spectrometry. These techniques coupled to redox chemical reactions allow the redox speciation of selenium. The results show that the open evaporation system can be used to concentrate water samples when the aim of the analysis is the determination of the total selenium concentration. On the contrary, to carry out its redox speciation only the preconcentration performed on rotavapor system, in vacuum can be used. When synthetic solutions containing different redox species of selenium, at ultratrace levels, were slowly evaporated on open system, Se(II) and Se(IV) were oxidized. The optimized procedure was then applied to the selenium determination and its redox speciation in rainwater samples collected in sites impacted by mining activities of copper ores. It was found that the amounts of total selenium in rainwater, as copper, from Puchuncavi valley decrease exponentially with the distance from the source, indicating that these elements in this region arise from the industrial complex Las Ventanas. In the redox speciation of selenium, Se(IV) and Se(VI) were the species found in all rainwater samples analyzed, providing selenium in species which are most favorable for their uptake by the vegetation grown in these soils.     

Effect of moisture and casein on demethylation of trimethylselenonium in soil

Trimethylselenonium ion (TMSe+) is a major urinary selenium (Se) metabolite of animals. The effect of soil moisture and casein on the demethylation of TMSe+ were examined in three California soils [Tulare Basin (TL), Losthill (LH) and Five Points (FP) upland areas] treated with 20 microg/g TMSe+. Results showed that soil moisture positively affected the demethylation of TMSe+ to volatile dimethylselenide (DMSe). In the non-saline TL and FP soils, the highest demethylation rates were 0.169-0.454, 0.646-2.71, and 3.15-6.01 microg/g per day from a 10, 20, and 100% moisture soil, respectively. During 51 days of the experiment, approximately 75.4-80.2% of added TMSe+ was demethylated to volatile DMSe. In contrast, in a saline LH soil, the demethylation rate was < 0.2 microg/g per day, and only 7% of the added TMSe+ was demethylated to volatile DMSe. Addition of casein stimulated the demethylation of TMSe+ in a 10% moisture TL soil. Dissolved DMSe, dimethylselenoxide (DMSeO) and TMSe+, and adsorbed TMSe+ were found in the three experimental soils. Concentrations of dissolved and adsorbed TMSe+ were much higher in the LH soil than in the TL and FP soils. This study showed that demethylation of TMSe+ dominates in the FP and TL soils, and adsorption of TMSe+ is a more important process in the LH soil.     

Arsenic solubility and distribution in poultry waste and long-term amended soil

The purpose of this study was to quantify the solubility and distribution of As among solid-phase components in poultry wastes and soils receiving long-term poultry waste applications. Arsenic in the water-soluble, NaOCl-extractable (organically bound), NH(2)OH x HCl-extractable (oxide bound) and residual fractions were quantified in an Upper Coastal Plain soil (Neshoba County, MS) that received annual waste applications. After 25 years, As in the amended soil had a mean of 8.4 mg kg(-1) compared to 2.68 mg kg(-1) for a non-amended soil. Arsenic in the amended soil was mainly in the residual fraction (72% of total), which is generally considered the least bioavailable fraction. Arsenic in poultry waste samples was primarily water-soluble (5.3-25.1 mg kg(-1)), representing 36-75% of the total As. To assess the extent of spatial heterogeneity, total As in a 0.5-ha area within the long-term waste-amended field was quantified. Soil surface samples were taken on 10-m grid points and results for total As appeared negatively skewed and approximated a bimodal distribution. Total As in the amended soil was strongly correlated with Fe oxides, clay and hydroxy interlayered vermiculite concentrations, and negatively correlated with Mehlich III-P, mica and quartz contents.     

Mercury and selenium concentrations in hair samples of women in fertile age from Amazon riverside communities

The aim of the present study was to evaluate mercury and selenium concentrations in hair samples of reproductive age women from riverside communities of the Tapajós River basin. We studied 19 pregnant and 21 non-pregnant women, 13 to 45 years old, living in the region for at least 2 years, and having a diet rich in fish. The analysis of Se and total Hg were performed in the Instituto de Pesquisas Energéticas e Nucleares (IPEN, S?o Paulo, Brazil) by using a Varian AA220-FS atomic absorption spectrometer with a flow injection system. There were no differences between the two groups - pregnant and non-pregnant -- concerning age (23.80 +/- 6.92 and 26.60 +/- 9.60 years old, respectively) and residential time (20.21 +/- 8.30 and 22.20 +/- 10.90 years, respectively). The geometric means and ranges for total Hg concentration were similar (p > 0.05): 8.25 microg/g (1.51-19.43) in pregnant and 9.39 microg/g (5.25-21.00) in non-pregnant women, respectively. Total Hg concentrations were also similar in different gestational stages. However, there was a significant difference between the two groups (p < 0.05, Student t test) in relation to Se concentration: 0.61 microg/g (0.40-2.33) in pregnant and 2.46 microg/g (0.92-5.74) in non-pregnant women, respectively. We concluded that Hg exposure levels in reproductive age women were only slightly higher than a provisional tolerable weekly intake of MeHg would provide, that Hg concentration in maternal hair samples was independent of gestational age, and that low Se concentration in pregnant women indicates high mineral consumption by fetal organism to satisfy their metabolic requirements raised during pregnancy, including as a protective mechanism for Hg cytotoxic effects.     

PAH and metal mixtures in New Orleans soils and sediments.

The purpose of this study is to determine the degree of PAH contamination and the association of PAHs with inorganic substances in soils and sediments of New Orleans. Bonnet Carré Spillway (BCS) (n = 5) provides modern baseline data, while urban soil samples (CTY) (n = 27) and sediment samples from Bayou St. John (BSJ) (n = 11) provide experimental data for New Orleans. Soil samples were collected from the top 2.5 cm of the surface, air-dried, and sieved (2 mm). Sediments samples were collected with a Wildco-Ekman bottom dredge, air-dried and finely ground. Accelerated solvent extraction (ASE) was used to release PAHs from the samples and analysis was conducted with gas chromatography-mass spectrometry (GC-MS). Metals were extracted using a 5:1 ratio of 1 mol/L nitric acid (room temperature) for soil and sediment samples, shaken for 2 h, centrifuged (1000 x g for 15 min) and filtered. Metal analysis was done by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Mann-Whitney tests show PAH differences (P < 0.001). Ranking of total PAHs is, BSJ sediments (10.3 mg/kg) > CTY soils (3.7 mg/kg) > BCS alluvium (0.28 mg/kg). The sum of the metals are similar for BSJ sediments (698 mg/kg) and CTY soils (679 mg/kg) and significantly lower for BCS (189 mg/kg). Manganese of these samples is similar for each site. For paired samples, Pearson Product Moment Correlation tests reveal that many PAHs are strongly associated with each other at all locations. For BCS alluvium and BSJ sediments, total PAHs are not significantly associated with total metals. For CTY, most pairs of metals are significantly associated, and total soil PAHs are strongly associated with total soil metals (correlation 0.78, P = 4.9 x 10(-4)). The linear model, total soil PAH = 136.3 + 6.25 (total soil metals) forms the basis for a predicted PAH map of New Orleans. Previous empirical research demonstrates an association between soil lead and children's lead exposure. This study indicates that PAHs are part of the soil mixture of accumulated substances and by-products of industrial society that presents exposure potential in cities.     

Of the necessity of knowledge of the natural pedo-geochemical background content in the evaluation of the contamination of soils by trace elements

In order to evaluate the contamination of the Dornach (Switzerland) site within the framework of the CEEM-Soil project, each participating team was allowed to take a maximum of 15 samples. The French team's sampling was organized in such a way as to answer the following questions: (i) what is the natural concentration of the soils at this site (local pedo-geochemical background content)?; (ii) what are the levels of Cd, Cu, Pb and Zn contamination of the soil?; (iii) what is the depth reached by the surface contamination that is derived from atmospheric fallout?; (iv) how is the contamination spread along the longest axis of the area under study? The relationships between total Fe and the trace metals have allowed local variations in the natural pedo-geochemical background content to be detected and thus permitted the anthropogenic contamination to be estimated. There would appear to be a low level of Pb contamination over all the site investigated (an increase of the order of 5-10 mg kg(-1) on the background level), limited to the surface humus-bearing layers. There is also a significant contamination by Cu over all of the site (an increase of the order of 30-40 mg kg(-1)). This contamination has remained in the surface horizons (0-20 cm). Very high Zn and Cd concentrations have been found in the four surface (0-4 cm) and deep horizons (15-70 cm) taken under the forest and very much lower values in the samples taken from cultivated soils. The most likely explanation is an unequal inheritance between the upper part of the site (wooded with thinner very clayey soils) and the lower cultivated part of the site (with thicker less clayey soils developed in a loamy material). For various reasons, it seems unlikely that a contamination of the wooded part should be so much higher than the cultivated part due to the interception of atmospheric dust by the trees. The local pedo-geochemical background Cd and Zn content of the upper wooded part proved to be clearly higher than that which would be encountered in most soils of Switzerland and France. Given this evaluation of the background content, it seems that only the surface horizons have been affected by Zn contamination (an addition of approx. 60-100 mg kg(-1)). In the case of Cd, the increase in concentrations is only 0.5-1 mg kg(-1) for the ploughed horizons, as well as the for the A horizons.     

Effects of soil compaction and irrigation on the concentrations of selenium and arsenic in wheat grains

Arsenic is a known human carcinogen, whereas Se is essential to human health and human Se intake in some European countries has decreased in recent decades. There have been few reports on the potential effect of soil physical conditions on the uptake of Se and As by food crops. Field experiments were conducted to evaluate the effects of soil compaction and irrigation on Se and As concentrations in wheat grains in two seasons. Grain Se concentration varied from 10 to 115 microg kg(-1), whereas the concentration of As in grain was low (<20 microg kg(-1)). Irrigation significantly decreased grain Se concentration by 30-75%, and the effect was likely due to a dilution as a result of increased grain yield, a competition of sulfate added in the irrigation water on Se uptake and increased leaching losses. Soil compaction significantly decreased grain Se concentration in one season. In contrast, soil compaction increased grain As concentration significantly when the crop was irrigated. The contrasting effects of soil compaction on As and Se uptake are explained by the difference in their mobility in soil and the pathway of ion transport to roots. The observed effect on grain Se is significant for human and animal nutrition, because the concentration varied from sufficient to very low levels in response to the alternation of soil physical conditions in the field. Soil physical conditions have to be taken into account when assessing the bioavailability of the contaminant As or the essential nutrient Se.