集硒与非集硒植物中硒,硫元素间相互作用的研究

比较了溶液ＳｅＯ４，ＳＯ及它们之间相互作用对非集硒植物（苜蓿）和集硒植物（Ａ．ｂｉｓｕｌｃａｔｕｓ）吸收硒和硫的影响，测定了较长生长周期（２１天以上）内这两类植物对化学特性相似的两类阴离子的吸收的误差，结果表明，虽然ＳＯ４对植物吸收ＳｅＯ４有竞争作用，但原生集硒植物具有优先吸Ｓｅ（与吸Ｓ相比）能力，甚至生长在高ＳＯ４土壤中，这类植物含Ｓｅ量也很高。因上，原生集硒植物在生物改良盐化的硒污染土壤与沉积     

硒和硫相互作用对烟草硫吸收与积累的影响

以第四纪红色粘土为母质的红壤和下蜀黄土为母质的黄褐土为供试土壤 ,进行盆栽试验 .结果表明 ,施硫可提高烟草各部位硫含量 ,烟叶硫含量高于根部 .施硒对烟草中硫含量影响不明显 ,但对硫积累量的影响比较明显 .红壤施低硒 (Se<3.71 μg/ g)时烟草地上部积累增加 ,高硒 (Se >3.71 μg/ g)时有降低趋势 ;黄褐土上则随施硒增加而下降     

不同硫水平下土壤对SeO32-的吸附

Selenium (Se) in the environment and food chains was greatly related to animal development and human health. Soils are the main sources of Se in ecosystem. Numerous studies have been carried to investigate relationships between Se and S in soils. Xu (1992) reported that Se and S had similar chemical and physical properties so some factors influencing the uptake and toxicity of Se are attributed to the interaction of Se withs .     

土壤硒与硒中毒的防治

在已知的生命所必需的微量元素中,硒是较引人注目的一种,人体缺硒或富硒都会引起疾病。在硒含量特别高时,可导致硒中毒,硒中毒分地方性中毒和职业性中毒两类。前者系由于某些地区的土壤、食物中硒含量过高而引起的,其症状为毛发脱落,指甲、皮肤和神经系统受损害,最后发展为四肢瘫痪。     

土壤中硒的形态及其区分

用６个土样进行土壤中硒形态分组的研究，并应用ＸＡＤ－７树脂消除富里酸中有机物质的干扰后，测定其中的无机态硒，采用凝胶色谱技术研究富里酸组分中的有机态硒，本方法成功地定量区分了土壤中各种形态的硒。     

影响土壤中硒有效性的若干因子

本文以砖红壤、红壤和黄棕壤为供试土样,研究了它们的氧化还原状况、酸度以及氧化铁的含量对亚硒酸盐有效性的影响。结果表明:(1)土壤对亚硒酸盐的吸附量以还原态高于氧化态,但速效态Se是氧化态高于还原态,而潜在有效态Se则是还原态高于氧化态;(2)随土壤pH升高,土壤对亚硒酸盐吸附量降低,水溶性Se增加,交换态Se降低,而潜在有效态Se变化则不明显;(3)土壤中氧化铁对亚硒酸盐的吸附及其有效性右着重要的影响。     

土壤耐硒菌株筛选及其硒活化能力评价研究

  目的  从湖北省恩施市双河镇新塘乡渔塘坝硒矿床采集矿渣、淤泥、农田土壤,从中筛选分离出耐硒菌株,并对筛选出菌株的活化土壤硒的能力进行评价。  方法  采用稀释涂布平板法和平板划线法分离、筛选出耐受亚硒酸钠浓度较高的菌株,根据菌株形态学特征和用分子生物学方法对其进行分类鉴定,再将分离得到的耐硒菌株分别接种于酸性富硒赤红壤中进行培养,通过测定培养后土壤中的硒含量评价两菌株活化土壤硒的能力。  结果  筛选出了细菌B-1和真菌B-2两耐硒菌株;细菌B-1被鉴定为嗜麦芽寡养单胞菌（Stenotrophomonas maltophilia）,其可耐亚硒酸钠浓度为17000 μg mL?1,在温度20 ~ 35 ℃、pH 5 ~ 9、盐浓度0 ~ 3%条件下可正常生长;真菌B-2被鉴定为聚多曲霉（Aspergillus sydowii）,该菌株可耐亚硒酸钠浓度为6000 μg mL?1,在温度25 ~ 30 ℃、pH 4 ~ 7、盐浓度2% ~ 5%条件下可正常生长。添加两耐硒菌株培养后土壤的可溶态硒和可交换态硒含量均显著提高。  结论  筛选出具有较高的硒耐受性和较强的活化酸性富硒土壤中硒的能力的菌株,可为富硒土壤资源开发利用提供生物种质资源和技术手段,对富硒微生物肥料研发、富硒农产品生产和硒污染土壤环境修复也有重要意义。     

土壤硒的形态及有效硒的提取

本文研究了陕西省几种主要土壤中硒的形态,并提出了一种土壤有效硒的浸提方法。土壤无机态硒的易溶部分依照杰克逊对无机磷分级方法被分为NH₄Cl-Se、Al-Se和Fe-Se三类。三部分硒总量占全硒含量的37—65%,平均为48%。三者的比例大致为Fe-Se>Al-Se>NH₄Cl-Se,它们与全硒和NaHCO₃-Se均呈显著相关,与水溶态硒相关不显著;由盆栽试验证明,土壤有效硒的NaHCO₃浸提法可以用作判断土壤对作物供硒能力的指标,而水溶态硒在本试验范围内与作物吸收性不一致。     

Fractionation and distribution of selenium in soils

Abstract

A modified selenium (Se) fractionation procedure was used to study Se distribution in three soils (two silt loams and one silty clay). This sequential procedure consisted of: i) 0.2 M potassium sulfate (K₂SO₄)‐soluble fraction, ii) 0.1 M potassium dihydrogen phosphate (KH₂PO₄)‐exchangeable fraction, iii) 0.5 M ammonium hydroxide (NH₃H₂O)‐soluble fraction, iv) 6 M hydrochloric acid (HCl)‐extractable fraction, and v) residual fraction digested with perchloric (HClO₄) and sulfuric (H₂SO₄) acids. The fractionation procedure had high recovery rates (92.5 to 106%). The Se distribution in soil was controlled by soil properties, such as pH, oxide, clay, and calcium carbonate (CaCO₃) contents. In the untreated soil samples, residual Se fraction was dominant. In the Se‐enriched soils, the silty clay had significantly more Se in the NH₃H₂O and residual fractions while in the two silt loams the largest were KH₂PO₄ and residual fractions. The Se availability in the two silt loams was higher than in the silty clay. The Se availability pattern in the untreated soils was: unavailable (HCl + residual fractions) >> potentially available (KH₂PO₄ + NH₃H₂O fractions) > available (K₂SO₄ fraction), while in the Se‐enriched soils it was potentially available > unavailable > available.     

Effects of sulfur and selenium oxyanions on Hg-toxicity in turnip seed germination

Water, Air, & Soil Pollution - The phytotoxicity of Hg-ion, as measured by inhibition of turnip seed germination, is antagonized by Group Vla oxyanions. The effects of S0 4 = and Se0 4 = are...     

Modeling excess sulfur deposition on wetland soils using stable sulfur isotopes

Freshwater wetlands exposed to excess S deposition can potentially store significant amounts of reduced S in soils by dissimilatory sulfate reduction. If this storage is permanent, the harmful environmental effects of S deposition and the accompanying acidity are reduced, particularly on surface waters into which wetlands drain. Total non-sulfate S in freshwater peat is divided into three fractions: reduced inorganic S, ester sulfate and carbon-bonded sulfur (CBS). Each fraction is further divided based on its origin: assimilatory via plant and microbial uptake, and dissimilatory via microbial reduction. The CBS fraction dominates in peat, so the amount of dissimilatory CBS in the soil is a direct measure of the beneficial effect of storage of reduced S. Unfortunately, there is no way to directly measure dissimilatory CBS. A model is developed which, with three assumptions, provides a method to calculate dissimilatory CBS using S pool size and stable isotope measurements. Application of the model to a wetland in the New Jersey Pinelands, U.S.A., shows that large amounts of reduced dissimilatory S are stored in the soil. As a consequence, the impact of S deposition and acidity on the surface water environment is significantly reduced.     

Selective determination and formation of elemental selenium in soils

A selective method for the determination of elemental selenium in soil was developed and was applied to the study of elemental selenium in soil. (1) Elemental selenium extracted with carbon disulfide from soil was selectively transformed into selenocyanate ion by reacting with potassium cyanide in carbon disulfide. The selenocyanate ion formed was recovered into an aqueous solution and the amount of selenium in the aqueous solution was determined. This method was specific to elemental selenium and did not interfere with the other selenium compounds and soil components. The method was also highly sensitive and enable to determine more than 0.1 μg kg^-1 of elemental selenium in soil. (2) The formation of elemental selenium was confirmed, when a soil was submerged and the redox potential of the soil decreased. The amount of elemental selenium formed was proportional to the selenite content of the soil, indicating that elemental selenium is transformed from selenite upon its reduction.     

Effects of previous elemental sulfur applications on oxidation of additional applied elemental sulfur in soils

Oxidation of elemental sulfur (S⁰) in 20 Chinese agricultural soils was tested and the effects of previous S⁰ applications on the oxidation of additional applied S⁰ in selected soils were investigated using laboratory, greenhouse, and field experiments. Results showed that sulfur oxidative capacities presented great variability among 20 tested soils, with a coefficient of variation of 92.4%. There were no significant relationships between S⁰ oxidation and physical and chemical properties of the selected soil. Previous S⁰ amendment significantly increased the oxidation rate of additional applied S⁰. These stimulatory effects after the first applications of S⁰ were greater than those after two applications. The percent increase in S⁰ oxidation rate due to S⁰ pretreatment was negatively correlated with the oxidation capacities of soils before S⁰ pretreatments. The significant reduction of sulfur oxidation in autoclaved soils and significant increase in S⁰ oxidation after inoculation with S⁰-treated soil suspension demonstrated that microbial oxidation was mainly responsible for the enhancement of soil oxidation ability after previous S⁰ amendments.     

Characterization of sulfur retained by soils exposed to sulfur dioxide

Abstract

Soils have substantial capacity for sorption of sulfur dioxide (SO₂) but little is known about the nature of the sorbed S. Three surface soils varying in pH, organic matter, CaCO₃ equivalent and surface area were exposed to air containing 5% SO₂ and subsequently analyzed by ten different procedures to characterize the sorbed S. Most of the sulfur retained by soils after exposure to SO₂ could be recovered as CaCl₂‐extractable S, Ca(H₂PO₄)₂‐extractable S, or S released as H₂S by hydriodic acid (HI). Only small amounts of sulfur could be recovered as tetrachloromercurate (TCM)‐extractable S, S released as SO₂ by HCl, or S released as H₂S by HCl + Zn, HCl + Sn, or Raney Ni and NaOH. However, large amounts of S released as SO₂ by HCl were recovered from the air‐dry Webster and the moist Storden soils indicating that SO₂ sorption is influenced by organic matter in air‐dry soils and by CaCO₃ in moist soils.     

Analysis of sulfur compounds in acid sulfate soils and other recent marine soils

Abstract

A refined scheme for the semi micro chemical analysis of sulfur fractions in soils is presented. Pyrite is analyzed, as iron, after extraction in HNO₃. Non‐pyrite iron is excluded by a pretreatment with HF/H₂SO₄. Water‐soluble sulfate and jarosite [KFe₃(SO₄)₂(OH)₆], the other dominant sulfur fractions in acid sulfate soils, are analyzed turbidimetrically, as sulfate, after successive extractions by EDTA.3Na (water soluble plus exchangeable SO₄) and by hot 4 M HCl (jarosite). These methods are simpler, less bulky and more specific than most existing procedures.

Introduction of elemental sulfur analysis permits estimation of organic sulfur fraction as well. Sums of individual sulfur fractions agree well with separate total sulfur determinations.

The proposed analysis of pyrite permits also distinction of the components Fe₂O₃, FeO and FeS₂ in soils and rocks².     

Sorption of sulfur gases by soils

Gas Chromatographie studies showed that air-dry and moist soils have the capacity to sorb dimethyl sulfide (CH₃SCH₃), dimethyl disulfide (CH₃SSCH₃). carbonyl sulfide (COS) and carbon disulfide (CS₂), but do not sorb sulfur hexafluoride (SF₆). Moist soils sorb larger amounts of CH₃SCH₃. CH₃SSCH₃. COS or CS₂, than do air-dry soils, but the capacity of moist (or air-dry) soils for Sorption of these gases is much smaller than their capacity for sorption of H₂S. SO₂ or CH₃SH. The ability of moist soils to sorb COS is considerably greater than their ability to sorb CH₃SCH₃, CH₃SSCH₃ or CS₂. and sorption of COS by moist soils is accompanied by release of small amounts of CS₂.Experiments with sterilized (autoclaved) soils indicated that soil microorganisms are partly responsible for the sorption of CH₃SCH₃. CH₃SSCH₃. COS and CS₂ by moist soils. Support for this conclusion was obtained from experiments showing that the rate of sorption of these gases by moist soils increases with time.The work reported provides further evidence that soil is an important natural sink for gaseous atmospheric pollutants, but indicates that soils have little, if any, potential value for removal of CH₃SCH₃. CH₃SSCH₃. COS or CS₂, from industrial emissions polluted by these gases. The finding that soils have no capacity for sorption of SF₆ is significant in relation to use of this gas as a tracer for atmospheric research and as an internal standard for gas Chromatographie studies of evolution and sorption of gases by soils.     

Total selenium content of agricultural soils in Japan

To evaluate the selenium (Se) level in agricultural soils in Japan and to investigate its determining factors, 180 soil samples were collected from the surface layer of paddy or upland fields in Japan and their total Se contents were determined. Finely ground soil (50 mg) was wet-digested with HNO₃ and HClO₄ solution and the released Se was reduced to Se(IV). The concentration of Se(IV) was then determined by high-performance liquid chromatography with a fluorescence detector after treatment with 2,3-diaminonaphthalene and extraction with cyclohexane. The total Se content ranged from 0.05 to 2.80 mg kg⁻¹ with geometric and arithmetic means of 0.43 and 0.51 mg kg⁻¹, respectively. The overall data showed a log-normal distribution. In terms of soil type, volcanic soils and peat soils had relatively high Se content and regosols and gray lowland soils had relatively low Se content. In terms of land use, upland soils had significantly higher Se content than paddy soils. Among regions, soils in the Kanto, Tohoku, Hokkaido and Kyushu regions had relatively high content. The total Se content had a significant positive correlation with the organic carbon content ( P  < 0.01) and the equation for the estimation of total Se content with organic carbon suggested that on average approximately 48% (0.24 mg kg⁻¹) of the total Se was in inorganic forms and approximately 52% (0.25 mg kg⁻¹) was in organic forms. Soil pH, on the contrary, did not show a significant relationship with the total Se content. In conclusion, the organic matter content, in combination with volcanic materials, was the main determining factor of the total Se content of agricultural soils in Japan.     

Sorption and desorption of selenium in different soils of the mediterranean area

Abstract

The adsorption of selenium (Se) in the selenate form and its desorption by phosphate in four soils with different physiochemical properties were studied in the laboratory. To determine adsorption isotherms for selenate 25 mL of solutions containing 1 to 100 ppm of Se were added to 2.5 g of soil. Desorption isotherms were determined by resuspending the samples in phosphate solution. The selenate sorption process was adequately described by the Freundlich equation. In pine forest and woodland soils, characterized by the highest organic matter content and cation exchange capacity (CEC) values, the isotherms were classified as L type, since the amount of Se sorbed appeared to move towards saturation. The organic matter content played the most important part in the adsorption of Se, while pH appeared to have a small effect on the ability of the soil to adsorb Se. The high CaCO₃ content of the pine forest soil may have contributed in increasing the Se adsorption notwithstanding the high pH value. The cultivated and arable soils showed a reduced sorption capacity. The sorption could be described by an S type curve. At low concentrations of Se the affinity of the solid phase was less than that of the liquid phase. By increasing the concentration of Se in solution, the affinity of the solid phase increased and the sorption was favored. Selenate desorption by water was negligible, whereas the amount of Se desorbed by phosphate varied among the different soils. The desorption experiments indicated that a significant portion of the sorbed Se was irreversibly retained. This suggests the existence of linkages which allow the release of Se in the soil solution only after physico‐chemical variation such as exchange with phosphate ions.