Investigation on the origin of Se-rich soils in Yutangba： Evidence from selenium speciation and native selenium

Yutangba has been known as a typical high-Se area in China since a sudden incidence of human Se poisoning occurred in 1963. The surface exposed Se-rich rocks of the Maokou and Wujiaping Formations were genereally considered to be the main source of Se that was enriched in soils of Yutangba and other places in Enshi Prefecture. However, little study was conducted to comfirm the origin of Se-rich soils in Yutangba.     

Geochemistry of the Yutangba Se Deposit in Western Hubei, China

1IntroductionThecontentsofSeinthecrustareextremelylow ,onlyabout0 .0 5mg/kg .Innatureitishardtoformindependentminerals,insteaditisdispersedinothermineralsandmedia.Althoughitscon tentsarefarhigherthanthoseofTeinthecrust,seleniumisusuallydispersedinsulfidesinitsas cendingandformingprocesses (D’yachkovaandKhodakovskiy ,1 968) .Thisisthereasonwhyse leniummineralsarefarlessthantelluriummineralsandsulfidesinnature (Simonetal.,1 997) .Forthisreason ,thegeochemicalstudyofseleniumdidnotattractanyat…     

Selenium contamination in the Colorado River Basin, western USA： Remediation by leaching and nanof＇dtration membranes

Selenium （Se） is an essential micronutrient to biota, but can become a potent toxicant at elevated concentrations. The natural sources and chemical properties of Se species make the boundary between deficiency and toxicity narrow for some biota, with both phenomena common around the globe. Large areas of farmland in the Colorado River Basin （CRB） generate salinized drainage water with Se concentrations much higher than 5 μg/L, the U.S. Environmental Protection Agency chronic water-quality criterion for the protection of aquatic life. We have carried out detailed field and laboratory studies to investigate Se geochemistry and remediation in two of these areas： the Middle Green River Basin, Utah and the Salton Sea Basin, California, located respectively in the Upper and Lower CRB. Results from these and other studies show that approximately 90% of the dissolved Se in the Colorado River and its tributaries originally is derived from the Upper Cretaceous Mancos Shale and equivalent pyritic marine units that outcrop in the Upper CRB. Selenium is mobilized commonly by biogeochemical oxidation of this pyritic shale and is concentrated mainly as selenate （SeO4^2-） in soils and agricultural drainage water of dry climates by evaporation. Minor （0%-5%） amounts of Se are present as the selenite species （HSeO3^-） and （SEO3^2-）, but these species and the more reduced species, elemental Se （SeO） and selenide （Se^2-）, have much lower solubility and/or have high sorptive affinity towards organic matter, clay minerals and iron oxyhydroxides. The concentration of dissolved Se （-2.5 μg/L） and salinity in the Lower Colorado River water are among the highest of the world major rivers. Because of low precipitation （7 cm/a） and extreme evapotranspiration （-1.8 m/a） rates in the Salton Sea Basin, California, Se values in irrigation water imported from the Colorado River increase to 〉300 μg/L in drainage wastewater. Removal of Se from contaminated wastewater by nanofiltration membranes was demonstrated in laboratory and pilot-scale field experiments.     

Geochemical Evaluation of Soil Quality in Menyuan County of Qinghai Province北大核心CSCD

青海省门源县内林草地面积大于44万公顷,耕地仅不到4.2万公顷,林草地资源丰富。2016年在门源县地区开展了1：25万土地质量地球化学评价工作,是青海省首次在大面积林草地区开展1：25万土地质量地球化学调查工作,具有较好的示范作用。通过评价土壤养分、土壤环境等级划分了土壤质量地球化学综合等级,结果表明：门源县土壤质量一等优质土壤占比92.4%,二等良好土壤占0.8%,三等中等土壤占5.6%,四等差等土壤占0.9%,五等劣等土壤占0.3%。通过项目实施可服务门源县土地资源管理,为门源县土地规划利用、农业种植结构调整及生态环境治理等提供依据,助力门源县绿色有机农畜产品输出地建设。     

Environmental Geochemistry of Fluorine in the Rock—Soil—Water System in the Karst Region of Central Guizhou Province

Systematic determination of and adsorption experiment on fluorine in the carbonate rock-soil-water system in the karst region studied in Guzhou Province,in conjunction with the mineral surface and soil chemistry data,have revealed the geochemical characteristics of F and the mechanisms of its transport and entrichment in the rock-soil-water-system of the karst region central guizhou province,Deep-seated underground waters(-100m or lower)and soil layers in the karst region of central Guizhou are characterized by high-F anomalies whereas shallow-level underground and surface waters by low contents of F(mostly lower than 05mg/L).Fluorine in soil and water in the region studied comes largely from Triassic marine strata dominated by gypsum-bearing carbonate rocks.The special adsorption and desorption of F on the surface of geothite in soil layers are the important mechanisms of its transport and enrichment in the rock-soil-water system of the karst region studied.     

Distribution and Variation of Ribonucleic Acid （RNA） and Protein and Its Hydrolysis Products in Lake Sediments

Protein and RNA in lake sediments tend to be decomposed progressively with time and sedimentation depth. Their concentrations tend to decrease starting from the sedimentation depth of 17 cm and that of 19 cm, respectively. However, the products of their decomposition —amino acids and nucleotides show different rules of variation. At the depth from 27 cm to 30 cm the amino acids are most abundant in the pore waters of lake sediments. Such variation tendency seems to be related to the extent to which microbes utilize amino acids and nucleotides. Due to polymerization in the geological processes and the adsorption of protein on minerals and organic polymers, below the sedimentation depth of 17 cm there is still a certain amount of protein in the sediments. With the time passing by, protein has been well preserved in various sediment layers, indicating that its decomposition is relatively limited. The peak values of protein content in the sediments of the two lakes are produced in the surface layers at the depth of 10 cm, implicating that the surface sediments are favorable to the release of protein. The contents of amino acids in the pore waters of lake sediments are closely related to the activities of microbes. Below the depth of 27 cm, the amino acids are significantly accumulated in Lake Aha sediments, probably indicating the weakening of microbial activities. The research project was financially supported jointly by the Ntional Natural Science Foundation of China (No. 40173038) and the Guizhou Provincial Foundation (No. 3090) and the Chinese Academy of Sciences Knowledge-Innovation Foundation (KZCX2-105).     

Spatial Distribution of Contourites in Global Ocean and Its Paleoclimatic Significance—The Contribution of International Ocean Drilling to the Studies of Contourites

Contourite is one of the most important type of sediments in the global ocean, which has recorded significant information on paleoclimatic changes. It is also of great importance for ocean engineering and marine hydrocarbon exploration. The development of scientific ocean drilling, especially the “Integrated Ocean Drilling Program” and the undergoing “International Ocean Discovery Program”, has made great contribution in mapping the spatial distribution of contourites and revealing contourite-related paleoclimatic information, through coring and geophysical exploration in the global ocean. It is found that the global distribution of contourites is controlled predominantly by the global deep-water circulation while its distribution in a specific region can be affected by the intensity of deep currents, tectonic activities, sediment supply, and so on. The geological changes in the global deep-water circulation is, however, further affected by tectonic activities, origins of water masses, as well as climate changes, e.g. the Cenozoic global cooling, changes in the size of the northern hemisphere ice caps, and intensity of monsoon. The main controlling factors of deep water circulation vary with different regions.     

Importance of measurement of rare-earth elements from the Soil Information and Monitoring System： A normalization method for detection of chromium contamination in soils

The Soil Information and Monitoring System （TIM） is an independent subsystem of the integrated Environmental Information and Monitoring System in Hungary. Based on physiographical-soil-ecological units 1202 representative observation points were selected and exactly defined by geographical coordinates using GPS. The first sampling was done in 1992. Some soil parameters are measured every year, some others every 3 years or every 6 years depending on their changeability （stability）. Toxic element, heavy metal and rare earth element contents in soil samples were determined after hot and strong acid digestion by ICP-OES equipment. The rare earth elements were measured in TIM soil samples and some of them can be found in a relatively high amount, e.g. cerium and neodymium concentration are 3-4 times higher than the very often-measured copper concentration. Close correlation was found among some of the rare earth element concentrations. The Y-Yb correlation is the strongest, its r-value is higher than 0.95. The reason of difference among the yttrium concentrations of samples is not the deviation of ICP-OES measurement that is much smaller than the difference among the individual soil samples. Similar, close correlation was obtained between the soil yttrium and chromium concentration. The amount of chromium contamination can be calculated as the distance from the Y-Cr trend line. We call this method yttrium normalization. The principle of this method is described as follows： such elements than chromium and yttrium insist in the soil in a strongly bonded form. Therefore, in a non-contaminated area there is a close correlation between the yttrium and chromium concentrations. If the measured chromium concentration in a sample is not on the Cr-Y trend line than the distance it indicates the amount of antropogenic chromium. Contamination can be detected in that case of course if the contaminant does not contain yttrium.     

Mineralization during Collisional Orogenesis and Its Control of the Distribution of Gold and Other Deposits in the Junggar Orogen, Xinjiang, China

The Junggar orogen, Xinjiang, China, is an important part of the Ural-Mongolian orogen.The collisional orogenesis in this region occurred primarily in the Carboniferous and Permianwith an evolutional process of early compression and late extension. Mineralization of gold andother metals in the Junggar orogen occurred mainly in the Permian and in a few cases in theLate Carboniferous. The deposits are largely distributed in areas where collisional orogenesiswas intensive and formed in a transitional stage from compression to extension. Therefore, goldmineralization in the Junggar orogen is fully consistent with the collisional orogenesis in time,space and geodynamic setting. This indicates that the mineral deposit model of collisionalorogenesis is applicable to prospecting and study of ore deposits in the Junggar orogen.Furthermore, the factual distribution of gold and other deposits in this region is just the same asthe collisional orogenic model presents.     

Liquid Immiscibility of Boninite in Xiangcheng, Southwestern China, and Its implication to Genetic Relationship between Boninite and Komatiitic Basalt

Boninitic rocks and associated high-magnesian basalt and high-iron tholeiite in the Xiangcheng area constitute the basal horizon of the arc volcanic sequence in the Triassic Yidun Island-Arc, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well-developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low-Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (>1000 ppm) and Ni (>250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low-Ca modern boninites and SHMB in the Archaean and Proterozoic.As a mechanism of ocellar texture, liquid immiscibility in boninite is supported by the following lines of evidence: (a) sharp contact between ocelli and matrix, (b) constant volumetric ratios of ocelli/matrix and common coalescence of ocelli in ocellar rocks, (c) identical micro-spinifex textures and mineral asse     

渔塘坝微地域硒分布的景观地球化学研究

选取迄今世界上唯一发生过人群硒中毒爆发性流行的地区－－湖北恩市双河乡渔塘坝为研究区。研究表明,在表生中－－强风化环境中,硒是个相当活泼的元素。在渔塘坝０．０１ｋｍ＾２的微地域内,土壤硒、玉米硒的分布存在着显著的不均一性。微地形、淋失条件是影响二者硒贪主其分布的主要因素。土壤硒含是基本决定了玉米硒含量。渔塘坝中硒在玉米中的基本分布规律是雄花、雌蕊〉叶〉籽〉根〉茎,上部叶片〉下部叶片、上部茎节〉下部茎     

Occurrence of native selenium in Yutangba and its environmental implications

Rare native Se has been discovered in Yutangba, Enshi City, Hubei Province, China, where a sudden incidence of Se poisoning occurred in the early 1960s. It was first found in a small area where native Se was produced on a large scale and was diverse in forms due to different formation mechanisms. Genetically, native Se can be divided into 3 categories: the primary native Se occurring in carbonaceous-siliceous rocks and tiny Se crystals formed in cracks of rocks during tectonic activities; micro-Se crystals formed in the weathering processes of Se-rich rocks; and larger Se crystals derived from natural burning of stone coal on the subsurface of abandoned stone coal spoils. The different forms of native Se found in Yutangba demonstrate that Se can be activated, transformed, remobilized and enriched at special sites such as in the unsaturated-subsurface zone or in the saturated zone. This discovery of native Se has not only resolved a long-standing controversial question on modes of occurrence of Se, which has puzzled many researchers in China, but has provided new possible evidence for the pathogenic explanation of the sudden prevalence of Se poisoning in Yutangba. The research results also have important implications for studying the mineralogy, ore geochemistry and environmental geochemistry of Se.     

湖北恩施硒中毒区土壤硒的分布及其控制因素

将湖北恩施地区高硒环境的土壤划分为（1）高总硒高水溶性硒，（2）低总硒高水溶性硒，（3）低总硒低水溶性硒。前两种类型可定义为高硒中毒危险区土壤，后一种类型为非中毒区正常土壤这种分类便于对高危险区的预测和制定预防措施，控制高硒区不同类型分布的因素主要有土壤母质和出露的岩石型、产状。     

三江平原西部土壤硒分布特征及其影响因素

近年来在黑龙江三江平原局部地区发现有珍贵的富硒土地,但对三江平原土壤硒的分布以及土壤硒含量的控制因素研究较少.三江平原西部地区土地质量地球化学调查发现,该区表层土壤主要以足硒为主,未见硒中毒土壤,富硒土壤主要分布于完达山山前至沿挠力河之间的冲湖积低平原地区,少量分布于萝北县城北部的湖成剥蚀台地,硒不足或硒潜在不足地区主...     

Votalization of selenium in selenium-rich black rock series in Yutangba

Votalization of selenium in selenium-rich black rock series in Yutangba is discussed at 400, 500, 600, 700, 800 and 900℃.Votalization of selenium tends to increase when the temperature is high. So environmental influence of selenium-rich black rock series combustion needs to be considered.     

恩施渔塘坝富硒碳质岩中硒的赋存状态

在渔塘坝富硒碳质岩中发现了自然硒及其系列硒矿物的组合.这些硒矿物有自然硒、方硒铜矿、硒铜蓝、水硒铁石、硒银矿、含硒黄铁矿、含硒黄铜矿和难以确定名称的Fe-Se矿物.其中自然硒、方硒铜矿和硒铜蓝的矿物组合主要分布在断层面附近的碳质硅质岩中,自然硒与方硒铜矿的矿物组合主要分布在高碳质泥岩中,水硒铁石及未确定的Fe-Se矿物主要赋存于露头处的富硒碳质岩中.硒矿物中除自然硒较普遍地存在外,其他矿物并不是均匀地分布于富硒碳质岩中,而是局部性地出现.Cu-Se矿物的大量发育表明铜可能在硒的表生迁移转化中起着某种重要的作用.     

鄂西南双河渔塘坝硒矿区硅质岩地球化学特征

双河渔塘坝硒矿位于扬子准地台、上扬子台褶带的北部 ,受双河向斜构造控制。本区硅质岩的稀土元素特征表明 :稀土总量低 ,其平均值为 38.945× 10 -6,富集轻稀土元素 ,呈现负的Ce异常和正的Eu异常 ,表现出一定的热水成因的属性。说明本区含硒的硅质岩主要形成于浅海滞留盆地、缺氧的还原环境 ,是属于热水成因的一类硅质岩。     

湖北恩施渔塘坝自然硒的分布及其环境意义

自然硒在渔塘坝富硒碳质岩层及其附近的土壤、废弃“石煤”堆中广泛发育。渔塘坝自然硒的空间分布与富硒碳质岩层密切相关，其纵向分布整体与富硒碳质岩层的走向一致，局部地段呈片状或环带状；横向上沿着富硒碳质岩层的倾向方向，从二叠纪茅口组的碳质硅质岩层到吴家坪组的碳质页岩层，自然硒的发现由易到难。渔塘坝当前的地质环境有利于自然硒的形成和保存，且一旦在表生环境形成后将会在特殊的地段发生次生富集。但是，自然硒形成的地质环境一旦被人类活动打破，暴露于地表的自然硒也能够发生迅速的氧化而再次迁移，进入河流和当地居民的食物链系统。因此，渔塘坝及恩施地区广泛分布的富硒碳质岩层为硒中毒的发生提供了必要条件，当荒地开垦或开挖“石煤”等人类活动为自然硒的氧化和迁移提供充分条件时，硒中毒的发生仍将不可避免。     

鄂西南渔塘坝沉积型硒矿化区概况

这是个正在工作的地区,文中描述的状况可供有关人员研究。该矿赋存于二叠系茅口组硅质岩段(孤峰层)中,层位稳定,并有一定品位和规模。伴生组分钒、铝可供综合利用。硒主要呈分散状态分布于有机碳中,推测硒以吸附状态存在,少部分硒呈类质同象形式分布于黄铁矿中。