Chemical endemic diseases and their impact on population in china

This paper deals with some endemic diseases related to selenium, iodine and fluoride in eco-environment. Keshan disease and Kaschin-Beck disease are associated with low selenium, they mainly occur in a belt zone across China ranging from North-East to South-West. Selenium contents in food grains and human hair from the disease affected areas are usually below 0.020ppm and 0.20ppm respectively. The endemic goitre caused by iodine deficiency distributes extensively in China, mainly in mountainous and hilly districts, swamp and peat areas, some sand soil and limestone areas. Also there is another kind of endemic goitre which caused by iodine excess in interior and coast areas. Endemic cretinism usually occurs in the endemic goitre seriously affected areas. Endemic fluorosis is also widely distributed in China, but mainly occurs in dry or semi-dry areas of north China. The fluoride sources for causing endemic fluorisis are drinking water and food grains polluted by coal smoke in the backing process of maize     

Selenium speciation in acidic environmental samples: application to acid rain-soil interaction at Mount Etna volcano

Speciation plays a crucial role in elemental mobility. However, trace level selenium (Se) speciation analyses in aqueous samples from acidic environments are hampered due to adsorption of the analytes (i.e. selenate, selenite) on precipitates. Such solid phases can form during pH adaptation up till now necessary for chromatographic separation. Thermodynamic calculations in this study predicted that a pH < 4 is needed to prevent precipitation of Al and Fe phases. Therefore, a speciation method with a low pH eluent that matches the natural sample pH of acid rain-soil interaction samples from Etna volcano was developed. With a mobile phase containing 20 mM ammonium citrate at pH 3, selenate and selenite could be separated in different acidic media (spiked water, rain, soil leachates) in <10 min with a LOQ of 0.2 μg L⁻¹ using ⁷⁸Se for detection. Applying this speciation analysis to study acid rain-soil interaction using synthetic rain based on H₂SO₄ and soil samples collected at the flanks of Etna volcano demonstrated the dominance of selenate over selenite in leachates from samples collected close to the volcanic craters. This suggests that competitive behavior with sulfate present in acid rain might be a key factor in Se mobilization. The developed speciation method can significantly contribute to understand Se cycling in acidic, Al/Fe rich environments.     

Relations between mercury, methyl-mercury and selenium in tissues of Octopus vulgaris from the Portuguese Coast

Mercury, methyl-mercury (MeHg) and selenium were determined in digestive gland and mantle of Octopus vulgaris, from three areas of the Portuguese coast. To our knowledge these are the first data on MeHg in cephalopods. Concentrations were higher in the digestive gland and percentage of MeHg in mantle. Enhanced Hg and MeHg levels were obtained in digestive gland of specimens from Olhão (3.1-7.4 and 2.0-5.0 μg g⁻¹, respectively). Differences between areas may be partially related to Hg availability. Relationships between concentrations in mantle and digestive gland pointed to proportional increases of Hg and MeHg in tissues of specimens from Matosinhos and Cascais, but relatively constant values in mantle of individuals from Olhão (higher contamination). Se:Hg molar ratio in digestive gland was 32 and 30 in octopus from Matosinhos and Cascais, respectively, and 5.4 from Olhão. The proximity to the unit suggests demethylation as response to elevated MeHg levels in digestive gland.     

Year-to-year correlations in blood metal levels among individuals of two species of North American sea ducks

Sea duck populations have declined in North America. Contaminants, especially metals, have been listed as possible contributing factors. Sea ducks are long-lived. Thus, individuals chronically exposed to elevated metal levels may be at greatest risk. Information about long-term exposure (> or =1year) of individuals to metals is absent. To address this information gap, we examined year-to-year correlations among individual White-Winged Scoters and King Eiders in levels of blood cadmium, lead, mercury and selenium. Positive correlations (r> or =0.43), were found in six, five, five and two of seven correlations for cadmium, selenium, lead and mercury. Thus, certain individuals of these species may be exposed over two or more years to higher levels of cadmium, selenium and lead (but apparently not mercury) than other individuals. Single blood samples are appropriate metrics of exposure for studies that examine long-term effects of certain metals on these birds.     

环境样品中铅、锑、汞、硒形态分析研究进展

综述了环境样品中铅、锑、汞、硒形态分析的研究进展,以及光谱法、色谱法、毛细管电泳及其联用技术在形态分析中的应用,展望了环境样品痕量元素形态分析的发展前景。     

异丙醇增感电感耦合等离子体质谱法直接测定土壤和沉积物中硒

提出了沸水浴混合酸法消解,以异丙醇为增感剂,电感耦合等离子体质谱直接测定土壤和沉积物中硒的方法。实验表明2mol/L硝酸-4mol/L盐酸混酸能有效溶出土壤和沉积物中各种形态的硒。相对于1%硝酸基体,4%(V/V)异丙醇基体中硒的ICP-MS响应值提高了12.1倍;而且4%(V/V)异丙醇基体可有效抑制硒的质谱干扰。ICP发射功率和雾化气流速是影响异丙醇在ICP-MS测定过程增敏效应的主要因素。以78硒为测定同位素,方法检出限为0.005mg/kg,实际样品测定精密度均小于5%。用于测定土壤和沉积物国家标准样品并对其消解液进行加标回收实验,结果令人满意。     

Selenium speciation and localization in chironomids from lakes receiving treated metal mine effluent

A lake system in northern Saskatchewan receiving treated metal mine and mill effluent contains elevated levels of selenium (Se). An important step in the trophic transfer of Se is the bioaccumulation of Se by benthic invertebrates, especially primary consumers serving as a food source for higher trophic level organisms. Chironomids, ubiquitous components of many northern aquatic ecosystems, were sampled at lakes downstream of the milling operation and were found to contain Se concentrations ranging from 7 to 80 mg kg⁻¹ dry weight. For comparison, laboratory-reared Chironomus dilutus were exposed to waterborne selenate, selenite, or seleno-DL-methionine under laboratory conditions at the average total Se concentrations found in lakes near the operation. Similarities in Se localization and speciation in laboratory and field chironomids were observed using synchrotron-based X-ray fluorescence (XRF) imaging and X-ray absorption spectroscopy (XAS). Selenium localized primarily in the head capsule, brain, salivary glands and gut lining, with organic Se species modeled as selenocystine and selenomethionine being the most abundant. Similarities between field chironomids and C. dilutus exposed in the laboratory to waterborne selenomethionine suggest that selenomethionine-like species are most readily accumulated, whether from diet or water.     

Total arsenic and selenium analysis in Marcellus shale, high-salinity water, and hydrofracture flowback wastewater

Trace levels of arsenic and selenium can be toxic to living organisms yet their quantitation in high ionic strength or high salinity aqueous media is difficult due to the matrix interferences which can either suppress or enhance the analyte signal. A modified thiol cotton fiber (TCF) method employing lower flow rates and centrifugation has been used to remove the analyte from complex aqueous media and minimize the matrix interferences. This method has been tested using a USGS (SGR-1b) certified reference shale. It has been used to analyze Marcellus shale samples following microwave digestion as well as spiked samples of high salinity water (HSW) and flow back wastewater (WRF6) obtained from an actual gas well drilling operation. Quantitation of arsenic and selenium is carried out by graphite furnace atomic spectroscopy (GFAAS). Extraction of arsenic and selenium from Marcellus shale exposed to HSW and WRF6 for varying lengths of time is also reported.     

EFFECTS OF SELENIUM AND MERCURY ON THE ENZYMATIC ACTIVITIES AND LIPID PEROXIDATION IN BRAIN,LIVER, AND BLOOD OF RATS

Recent studies have reported on the toxicity and related oxidative stress of selenium and mercury. The present study compares the effects of Se as sodium selenite (Na₂SeO₃) and Hg as mercuric chloride (HgCl₂) separately and in combination. Rats received repeated oral doses of Se (0.5 μmol/ml), Hg (0.5 μmol/ml), or Se in combination with Hg (0.5 μmol/ml of each) for 5 consecutive days. Rat serum, brain and liver samples were collected for biochemical assays. The following biochemical alterations occurred in response to Hg treatment: protein content (brain and liver), acetylcholinesterase (AChE) (brain and serum), acid and alkaline (AcP and AlP) phosphatases (plasma and liver) and glutathione S-transferase (GST) (plasma and liver) activities were significantly (P<0.05) decreased, while lactate dehydrogenase (LDH) (plasma, brain and liver), aspartate and alanine aminotransferase (AST, ALT) (serum and liver) activities were significantly increased. Thiobarbituric acid reactive substances (TBARS) was significantly increased in brain and liver. Effect of Se alone included decreased AcP, AlP and GST (serum and liver) activities. However, LDH (serum, brain and liver) and AST (liver) and TBARS (brain and liver) increased. Selenium in combination with Hg partially or totally alleviated the toxic effects of Hg on different studied enzymes. It is concluded that Se could be able to antagonize the toxic effects of mercury.