河北平原土壤硒异常成因及其生态效应

河北平原多目标区域地球化学调查在唐山开滦煤田及石家庄-邯郸一带发现了以Se元素为主的土壤地球化学异常。本文利用相关分析、多元统计分析等地球化学方法,对土壤Se异常成因、来源、生态环境效应等问题进行解释与评价。结果表明,燃煤产生的大气降尘是形成土壤Se异常的主要原因。土壤Se异常区小麦、玉米中Se元素含量明显高于非异常区,且有害元素含量不超标。     

紫外分光光度法测定大米中微量元素硒的含量

以市售大米为检测对象,采用凯氏烧瓶消解-紫外分光光度法测定了样品中微量元素硒的含量。结果表明:富硒大米、五常大米、白城大米、泰国香米及龙江县大米的含硒量分别为:0.258、0.054、0.051、0.033、0.045mg/kg(干基)。富硒大米的硒含量明显高于普通大米。标准曲线的相关系数r为0.9998,加标回收率在98.6%～102.7%之间,精密度RSD为2.25%,因此该法具有灵敏度高、稳定性好、工作曲线线性关系好的显著优点,可用于大米中微量元素硒的测定。     

连续流动氢化物发生原子荧光法测定水中硒

文章介绍连续流动一氢化物发生一原子荧光测定水中硒的方法,研究了盐酸浓度、硼氢化钾浓度、灯电流、光电倍增管负高压、泵速、载气和屏蔽气流量等对测定硒的影响,找出测定水中硒最佳条件,在最佳条件下,校准曲线相关系数为0.9999.方法检出限为0.0095μg/L,方法的测量范围为0.038-300μg/L,回收率在91.8%-...     

硒对镉胁迫下菠菜生理特性、元素含量及镉吸收转运的影响

为了探讨硒(Se)对菠菜中的镉(Cd)胁迫造成毒害的缓解作用,采用盆栽试验,研究了不同浓度Se(0、0.5、2.0、4.0 mg·L-1)对不同浓度Cd(0.5和2.0 mg·kg-1)胁迫下菠菜生理特性、元素含量及Cd吸收转运的影响.结果表明:不同浓度的Se可使丙二醛(MDA)积累量显著降低,最佳作用下分别为两种浓度Cd单一胁迫下的53.93%和41.79%;不同浓度的Se可以缓解Cd胁迫对菠菜地上部和根部的抑制作用,最佳缓解条件下,菠菜地上部和根部的鲜重分别为两种浓度Cd单一胁迫时的1.13倍、1.29倍和1.31倍、1.37倍,干重分别为1.78倍、2.09倍和3.03倍、4.36倍;叶绿素含量显著提高,在最佳缓解浓度下分别是两种浓度Cd单一胁迫时的1.51倍和1.35倍;与两种浓度Cd单一胁迫相比,最佳缓解浓度下超氧化物歧化酶(SOD)活性分别提高了36.0%和42.8%;外源Se可以使地上部和根部的K、Na、Ca和Mg等元素的含量不同程度的增加;施Se可以有效的抑制菠菜根部对Cd的吸收、富集和向地上部的转运,使菠菜地上部和根部Cd含量显著降低,分别为两种浓度Cd单一胁迫下的65.77%、75.92%和46.11%、70.01%,表明外源Se能有效的减轻Cd胁迫对菠菜的毒害作用.对本研究所用的两种浓度Cd来说,最佳的缓解浓度为2.0 mg·L-1和4.0 mg·L-1.     

地表水和地下水中的砷、硒同时测定

通过利用双道原子荧光法,同时对地表水和地下水样品中砷、硒进行测定,具有操作更加简单、监测分析速度快、节省试剂等优点。     

广州市32种水产品的Se含量特征分析

通过酸消解,原子荧光-氢化物发生法测定了广州市部分市售水产品中Se的含量,由标准物质(GBW 08551猪肝)和回收率控制检测质量.结果表明,不同水产品中Se含量有较大差异,含量范围为(34.-1117.)×10-9,平均含量为(345.±149.)×10-9,不同类型水产品中Se含量变化特征是:甲壳类(544.±107.)×10-9＞海水鱼类(392.±86.)×10-9＞软体类(244.±89.)×10-9＞淡水鱼类(238.±97.)×10-9.     

Institutional Constraints on Cost‐Effective Water Management: Selenium Contamination in Colorado's Lower Arkansas River Valley

Ground and surface water selenium (Se) contamination is problematic throughout the world, leading to harmful impacts on aquatic life, wildlife, livestock, and humans. A groundwater reactive transport model was applied to a regional‐scale irrigated groundwater system in the Lower Arkansas River Basin in southeastern Colorado to identify management practices that remediate Se contamination. The system has levels of surface water and groundwater Se concentrations exceeding the respective chronic standard and guidelines. We evaluate potential solutions by combining the transport model with an assessment of the cost to employ those practices. We use a framework common in economics and engineering fields alike, the Pareto frontier, to show the impact of four different best management practices on the tradeoffs between Se and cost objectives. We then extend that analysis to include institutional constraints that affect the economic feasibility associated with each practice. Results indicate that although water‐reducing strategies have the greatest impact on Se, they are the hardest for farmers to implement given constraints common to western water rights institutions. Therefore, our analysis shows that estimating economic and environmental tradeoffs, as is typically done with a Pareto frontier, will not provide an accurate picture of choices available to farmers where institutional constraints should also be considered.     

The relationships between mercury and selenium in plankton and fish from a tropical food web

Background, aim, and scope  Selenium (Se) has been shown to reduce mercury (Hg) bioavailability and trophic transfer in aquatic ecosystems. The study of methylmercury (MeHg) and Se bioaccumulation by plankton is therefore of great significance in order to obtain a better understanding of the estuarine processes concerning Hg and Se accumulation and biomagnification throughout the food web. In the western South Atlantic, few studies have documented trace element and MeHg in fish tissues. No previous study about trace elements and MeHg in plankton has been conducted concerning tropical marine food webs. Se, Hg, and MeHg were determined in two size classes of plankton, microplankton (70–290 μm) and mesoplankton (≥290 μm), and also in muscle tissues and livers of four fish species of different trophic levels (Mugil liza, a planktivorous fish; Bagre spp., an omnivorous fish; Micropogonias furnieri, a benthic carnivorous fish; and Centropomus undecimalis, a pelagic carnivorous fish) from a polluted estuary in the Brazilian Southeast coast, Guanabara Bay. Biological and ecological factors such as body length, feeding habits, and trophic transfer were considered in order to outline the relationships between these two elements. The differences in trace element levels among the different trophic levels were investigated. Materials and methods  Fish were collected from July 2004 to August 2005 at Guanabara Bay. Plankton was collected from six locations within the bay in August 2005. Total mercury (THg) was determined by cold vapor atomic absorption spectrometry (CV-AAS) with sodium borohydride as a reducing agent. MeHg analysis was conducted by digesting samples with an alcoholic potassium hydroxide solution followed by dithizone-toluene extraction. MeHg was then identified and quantified in the toluene layer by gas chromatography with an electron capture detector (GC-ECD). Se was determined by AAS using graphite tube with Pin platform and Zeeman background correction. Results and discussion  Total mercury, MeHg, and Se increased with plankton size class. THg and Se values were below 2.0 and 4.8 μg g⁻¹ dry wt in microplankton and mesoplankton, respectively. A large excess of molar concentrations of Se in relation to THg was observed in both plankton size class and both fish tissues. Plankton presented the lowest concentrations of this element. In fish, the liver showed the highest THg and Se concentrations. THg and Se in muscle were higher in Centropomus undecimalis (3.4 and 25.5 nmol g⁻¹) than in Micropogonias furnieri (2.9 and 15.3 nmol g⁻¹), Bagre spp (1.3 and 3.4 nmol g⁻¹) and Mugil liza (0.3 and 5.1 nmol g⁻¹), respectively. The trophic transfer of THg and Se was observed between trophic levels from prey (considering microplankton and mesoplankton) to top predator (fish). The top predators in this ecosystem, Centropomus undecimalis and Micropogonias furnieri, presented similar MeHg concentrations in muscles and liver. Microplankton presented lower ratios of methylmercury to total mercury concentration (MeHg/THg) (34%) than those found in mesoplankton (69%) and in the muscle of planktivorous fish, Mugil liza (56%). The other fish species presented similar MeHg/THg in muscle tissue (of around 100%). M. liza showed lower MeHg/THg in the liver than C. undecimalis (35%), M. furnieri (31%) and Bagre spp. (22%). Significant positive linear relationships were observed between the molar concentrations of THg and Se in the muscle tissue of M. furnieri and M. liza. These fish species also showed significant inverse linear relationships between hepatic MeHg and Se, suggesting a strong antagonistic effect of Se on MeHg assimilation and accumulation. Conclusions  Differences found among the concentrations THg, MeHg, and Se in microplankton, mesozooplankton, and fishes were probably related to the preferred prey and bioavailability of these elements in the marine environment. The increasing concentration of MeHg and Se at successively higher trophic levels of the food web of Guanabara Bay corresponds to a transfer between trophic levels from the lower trophic level to the top-level predator, suggesting that MeHg and Se were biomagnified throughout the food web. Hg and Se were positively correlated with the fish standard length, suggesting that larger and older fish bioaccumulated more of these trace elements. THg, MeHg, and Se were a function of the plankton size. Recommendations and perspectives  There is a need to assess the role of selenium in mercury accumulation in tropical ecosystems. Without further studies of the speciation of selenium in livers of fishes from this region, the precise role of this element, if any, cannot be verified in positively affecting mercury accumulation. Further studies of this element in the study of marine species should include liver samples containing relatively high concentrations of mercury. A basin-wide survey of selenium in fishes is also recommended.     

DIFFERENTIAL ACCUMULATION OF SELENIUM AMONG AXIAL MUSCLE,REPRODUCTIVE AND LIVER TISSUES OF FOUR WARMWATER FISH SPECIES1

Bluegill (Lepotmis macrochirus), largemouth bass (Micropterus salmoides), white catfish (Ictalurus catus), and channel catfish (Ictalurus punctatus), collected from an electric power plant cooling reservoir and a municipal water supply reservoir near Roxboro, North Carolina, were analyzed for selenium concentrations in axial muscle, reproductive and liver tissues. Fishes from the municipal water reservoir had lower selenium concentrations (≤0.2-2.1 μg/g - wet weight) than found in the cooling reservoir fishes (1.6-70.0 μg/g - wet weight) but similar distributions of concentrations among the tissues was evident. Selenium was differentially accumulated, with higher concentrations in liver tissues (0.7-70.0 μg/g - wet weight), followed by female reproductive tissues (0.7-25.0 μg/g - wet weight), axial muscle tissues (≤0.2-23.0 μg/g - wet weight) and male reproductive tissues (0.2-7.2 μg/g - wet weight).     

生态环境中镉对生物体毒性作用机理及硒对该毒性拮抗作用的研究进展

本文综述了生态环境中镉对生物毒性作用机理及硒对镉毒性拮抗作用研究的进展。镉的毒性作用与镉诱发自由基、诱导脂质过氧化以及对其它化学元素的干扰有关，同时也与金属硫蛋白（MT）有着密切关系。硒对镉的拮抗作用与硒的抗氧化作用、与镉形成硒镉复合物以及改变镉在体内的分布有关。