Removal of Se(IV) from aqueous solution using sulphuric acid-treated peanut shell

A carbonaceous sorbent was prepared from peanut shell via sulphuric acid treatment. Se(IV) removal from aqueous solution on the sorbent was studied varying time, pH, Se(IV) concentration, temperature and sorbent status (wet and dry). Se(IV) removal was faster using the wet sorbent than the dry sorbent following a pseudo-first-order model. Se(IV) removal increases at low pH values, and decreases as pH increases until pH 7. Sorption was found to fit the Langmuir equation and sorption capacity for the wet sorbent was higher than that for the dry one. Both sorbents showed an increased selenium sorption by rising the temperature. Redox processes between Se(IV) and the carbon sorbent are involved. Analysis by scanning electron microscope and X-ray powder diffraction for the sorbent after the reaction with acidified Se(IV) confirmed the availability of elemental selenium as particles on the sorbent surface as a result of Se(IV) reduction. Physicochemical tests showed an increase in sorbent acidity, cation exchange capacity (CEC) and surface functionality after the reaction with acidified Se(IV), indicating the oxidation processes occurring on the sorbent surface. Due to its reduction properties, the sorbent seems efficient for Se(IV) removal from aqueous solution.     

长三角典型地区土壤环境中Se的空间变异特征及其与人类健康的关系

农业土壤环境中硒（Se）的缺乏或过量都会通过食物链最终影响人类健康。在203个土壤采样点的基础上,利用GIS和地统计学相结合的方法,对江苏省如皋市农田土壤环境中Se的空间变异特征及其影响因素进行分析,同时,对土壤中Se的空间分布与长寿人口的空间分布进行空间叠加分析。研究结果表明,如皋市土壤环境中总Se及水溶态Se的平均含量分别为0.13 mg/kg和2.16 μg/kg,研究区处在相对低Se的土壤环境中。总Se的空间变异性不大,其空间分布比较均一;但水溶态Se的空间变异性较大,主要受成土条件及土壤母质、土壤类型及地形地貌等结构性因子的影响。水溶态Se对土壤的理化性质也比较敏感,特别是速效磷、有机质及全钾含量与水溶态硒的相关性较显著,因此在有机质及土壤养分含量较高、土壤颗粒组成较细的东部及北部地区水溶态硒的含量也较高。土壤水溶态Se的空间分异与长寿人口比率的空间分异呈极显著的正相关关系(〖WTBX〗P〖WTBZ〗<001),相关系数达〖WTBX〗r〖WTBZ〗=0325,表明人类的健康长寿现象与环境中水溶态硒的含量有很大关系,但人类长寿的本质和真正机理仍需进一步研究验证。     

溴酸钾—酸性铬红—CTMAB动力学光度法测定硒的研究

根据痕量硒（Ⅳ）对溴酸钾氧化酸性铬红的褪色催化作用,建立了一种测定硒的新方法。检出限为4μg／L,硒的含量在20～240μg／L内符合比耳定律。方法用于食品中硒的测定,结果满意。     

Biological effects of selenium and relationships with carcinogenesis†

Selenium is an element that is both essential, at low levels of dietary intake, and toxic, at high levels, to man and a wide range of animals. The purpose of the communication is to review the evidence for the involvement of hyper‐ and hypo‐selenosis in the aetiology of cancer. High levels of selenium intake have been blamed for an increase in cancer, dental caries and an array of other conditions. Critical evaluation of the evidence, however, leads to the conclusion that such claims have little substance. On the other hand, low levels of selenium intake may be associated with an increased incidence of certain forms of cancer and there appears to be an inverse relationship between blood selenium levels and cancer death rate in the United States. Keshan Disease, in the People's Republic of China has only been shown to occur in populations severely depleted of selenium. In well nourished populations there is no evidence to indicate that selenium supplements have any prophylactic or therapeutic benefit against human diseases such as cancer, cardiovascular disease or cystic fibrosis.     

The biogeochemistry of selenium in Sunan grassland,Gansu, Northwest China,casts doubt on the belief that Marco Polo reported selenosis for the first time in history

In order to clarify the historic academic problem of whether or not livestock poisoning in ancient Suzhou of Northwest China, recorded by Marco Polo in 1295, was selenosis, this study deals with the biogeochemistry of selenium in Sunan County in the Hexi Corridor, which is part of ancient Suzhou in China. It was found that quite a number of farm animals had suffered from intoxication and died as a result of grazing poisonous grasses, mostly Oxytropis DC, Stellera chamaejasme, and Achnatheru inebrians. Toxic symptoms of livestock grazing on Oxytropis DC are similar to those of selenium toxicity, for instance, hair loss and hoof lesions as described by Marco Polo. Therefore, we thought that toxic grass, probably Oxytropis DC, led to the intoxication of livestock recorded by Marco Polo. Average Se concentrations in two members of this species were 0.112 +/- 0.038 mg/kg for the root of Oxytropis glabra, 0.102 +/- 0.027 mg/kg for the stem and leaf of Oxytropis glabra, and 0.066 +/- 0.009 mg/kg for Oxytropis ochrocephala. The average soil selenium concentration was 0.205 +/- 0.127 mg/kg on grassland producing Oxytropis glabra and 0.152 +/- 0.024 mg/kg on grassland producing Oxytropis ochrocephala. The average Se concentration in other plants was 0.076 mg/kg in the root of Ephedra monosperma Mey, 0.029 mg/kg in the root of Rheum palmatum, 0.031 mg/kg in the root of Stellera chamaejasme, 0.037 mg/kg in Achnatherum inebrians, and 0.067 mg/kg in forage grass (Achnatherum splendens ohwi). Selenium concentrations in soils and plants in Sunan County are far less than the thresholds causing selenium toxicity in livestock. As a result, this study concludes that the livestock poisoning recorded by Marco Polo in 1295 might not have been selenosis.     

X-ray absorption and photoelectron spectroscopy investigation of selenite reduction by Fe-bearing minerals

The long-lived radionuclide ⁷⁹Se is one of the elements of concern for the safe storage of high-level nuclear waste, since clay minerals in engineered barriers and natural aquifer sediments strongly adsorb cationic species, but to lesser extent anions like selenate (Se^VIO₄²⁻) and selenite (Se^IVO₃²⁻). Previous investigations have demonstrated, however, that Se^IV and Se^VI are reduced by surface-associated Fe^II, thereby forming insoluble Se⁰ and Fe selenides. Here we show that the mixed Fe^II/^III (hydr)oxides green rust and magnetite, and the Fe^II sulfide mackinawite reduce selenite rapidly (< 1 day) to FeSe, while the slightly slower reduction by the Fe^II carbonate siderite produces elemental Se. In the case of mackinawite, both S^−II and Fe^II surface atoms are oxidized at a ratio of one to four by producing a defective mackinawite surface. Comparison of these spectroscopic results with thermodynamic equilibrium modeling provides evidence that the nature of reduction end product in these Fe^II systems is controlled by the concentration of HSe⁻; Se⁰ forms only at lower HSe⁻ concentrations related to slower HSeO₃⁻ reduction kinetics. Even under thermodynamically unstable conditions, the initially formed Se solid phases may remain stable for longer periods since their low solubility prevents the dissolution required for a phase transformation into more stable solids. The reduction by Fe²⁺-montmorillonite is generally much slower and restricted to a pH range, where selenite is adsorbed (pH < 7), stressing the importance of a heterogeneous, surface-enhanced electron transfer reaction. Although the solids precipitated by the redox reaction are nanocrystalline, their solubility remains below 6.3 × 10^− 8 M. No evidence for aqueous metal selenide colloids nor for Se sorption to colloidal phases was found. Since Fe^II phases like the ones investigated here should be ubiquitous in the near field of nuclear waste disposals as well as in the surrounding aquifers, mobility of the fission product ⁷⁹Se may be much lower than previously assumed.     

Comparative on Causes and Accumulation of Selenium in the Tree-rings Ambient High-selenium Coal Combustion Area from Yutangba, Hubei, China

Toxic trace elements emitted during coal combustion are the main sources of air pollution. They are released into the atmosphere mainly in the forms of fine ash, smoke and flue, and thus adversely affect plant, animal and human health. Selenium is one of toxic and the most volatile in coal. Large amount of atmospheric emission of selenium, as well as selenium present and scrubber stockpiles in ash may create serious environmental problems. In the paper, on the basis of investigating the abundance and distribution of selenium in plant-rings during recent 20 years, the bioaccumulation of selenium is explained that selenium in plant, which were collected from the village of selenium-rich coal combustion, is much higher than that in plants collected away from the village of selenium-rich coal combustion. The main origins of selenium are selenium-rich coal combustion and high-selenium rock weathered. The selenium recycle by food chain and selenium will accumulate and redistribute in environments.     

混合酸消解变化对土壤和沉积物中痕量硒分析影响

基于各3种采集环境样本、国家标准物质的土壤和沉积物,以当前环境监测行业常用的3种消解方法,探讨20种混合酸系统条件在消解条件变化中对复杂样本硒元素测定的影响.确定了最佳土壤和沉积物消解的组合为王水系统(盐酸∶硝酸∶氢氟酸∶过氧化氢∶高氯酸=3∶1∶1∶1∶1),各消解法的处理结果部分(n=5):水浴法消解时间仅需0.5...     

石墨炉原子吸收法测定水与废水中硒

采用石墨炉原子吸收法测定水与废水中硒,以镍盐为基体改进剂,提高了灰化温度,消除了基体干扰。方法的最低检出浓度为1.4ppb,废水测定的变异系数为2.9％～7.5％,加标回收率为95.0％～105.4％     

“The Kesterson effect”

Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the “Kesterson effect.” At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California. In California, selenium, as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.