Effect of selenium on the growth of Lemna minor

The effect of selenium on the vegetative reproduction of cultured Lemna minor was investigated. Cultures were grown for 28 days at a temperature of 23 ± 3°C and under a constant (24 h) light cycle. Growth was monitored every seven days. The growth of L. minor was inhibited at high concentrations (>5mg/L [Se]), but stimulated at low concentrations (0.2—2mg/L [Se]). This stimulation of growth at low selenium concentrations has significant implications for the use of selenium enriched superphosphate fertilisers on selenium deficient pastures.     

Effects of seasonal climatic variability on several toxic contaminants in urban lakes: Implications for the impacts of climate change

Climate change is supposed to have influences on water quality and ecosystem. However, only few studies have assessed the effect of climate change on environmental toxic contaminants in urban lakes. In this research, response of several toxic contaminants in twelve urban lakes in Beijing, China, to the seasonal variations in climatic factors was studied. Fluorides, volatile phenols, arsenic, selenium, and other water quality parameters were analyzed monthly from2009 to 2012. Multivariate statistical methods including principle component analysis, cluster analysis, and multiple regression analysis were performed to study the relationship between contaminants and climatic factors including temperature, precipitation, wind speed, and sunshine duration. Fluoride and arsenic concentrations in most urban lakes exhibited a significant positive correlation with temperature/precipitation, which is mainly caused by rainfall induced diffuse pollution. A negative correlation was observed between volatile phenols and temperature/precipitation, and this could be explained by their enhanced volatilization and biodegradation rates caused by higher temperature. Selenium did not show a significant response to climatic factor variations, which was attributed to low selenium contents in the lakes and soils. Moreover, the response degrees of contaminants to climatic variations differ among lakes with different contamination levels. On average, temperature/precipitation contributed to 8%, 15%, and 12% of the variations in volatile phenols, arsenic, and fluorides,respectively. Beijing is undergoing increased temperature and heavy rainfall frequency during the past five decades. This study suggests that water quality related to fluoride and arsenic concentrations of most urban lakes in Beijing is becoming worse under this climate change trend.     

Two selenium tolerant Lysinibacillus sp. strains are capable of reducing selenite to elemental Se efficiently under aerobic conditions

Microbes play important roles in the transport and transformation of selenium (Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides, respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations (MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L. xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles (SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra- or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized SeNPs would have potential applications in agriculture, food, environment and medicine.     

生物体内汞与硒的相互作用

对硒与汞在生物体内相互作用的一般规律进行了综合评述，概括介绍了生物体内汞与硒相互拮抗关系的实验研究基础，汞与硒拮抗作用的影响因素以及汞与硒拮抗机制的研究进展。     

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.     

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。     

桂中典型碳酸盐岩区水稻及根系土硒含量特征

硒对人体的健康具有重要意义。水稻作为中国南方的主要粮食作物,研究水稻籽实与根系土硒含量特征及其影响因素,可为富硒水稻种植、富硒产业开发、提升土地利用价值提供科学依据。本文以桂中典型碳酸盐岩地区为研究区,通过采集、测试400套水稻籽实及对应的根系土样品,研究讨论其含硒水平及影响因素。结果表明:(1)水稻根系土硒含量为0.11～3.82 mg/kg,平均值为0.61 mg/kg,明显高于全国其他省份表层土壤硒含量值。(2)根系土中Cd、Cr、Hg、S元素含量高于全国土壤背景值,Cd、Cr、Hg富集现象显示了广西典型碳酸盐岩区土壤重金属高背景属性,碳酸盐岩区Se与Cd等重金属元素次生富集特征近似。(3)根系土中硒含量主要受成土母质岩系控制,土壤中Se高含量主要与石炭系、泥盆系、二叠系、三叠系地层碳酸盐岩、硅质岩的分布密切相关。此外,与土壤有机质呈明显正相关,土壤中的有机质能对硒起吸附固定作用,使得硒在土壤表层富集。(4)研究区水稻籽实硒最小值为0.015 mg/kg,最大值为0.532 mg/kg,平均值为0.08 mg/kg,富硒率高达81.5%。水稻籽实硒含量除了与根系土硒含量有关外,还与土壤中的有机质、S、pH呈显著负相关性。     

硒镉联合作用对大、小鼠精子畸形率的影响

通过对小鼠腹腔注射硒、镉化合物和大鼠经口摄入低硒加镉粮,来观察高剂量镉,高、低剂量硒单独和联合作用的遗传学效应。结果表明,不仅氯化镉和亚硒酸钠能引起精子畸形率的明显升高,长期摄入低硒粮也能引起精子畸形率的明显升高。当高硒高镉联合作用时,亚硒酸钠可明显对抗氯化镉的遗传毒性,而低硒高镉联合作用时,则加重了氯化镉和亚硒酸钠的遗传毒性。     

贵州丹寨县土壤-水稻中硒和重金属的积累及迁移特征

通过测定贵州丹寨县主要水稻种植区30件水稻土及对应的水稻中硒和重金属的含量,分析硒和重金属Cd、Hg、As、Pb在根系土及对应水稻中的分布特征,研究了土壤有机质和pH对硒和重金属在土壤-水稻系统中迁移的影响。结果表明：该地区水稻根系土中硒含量变化范围为0.27～0.98 mg/kg,平均值为0.65 mg/kg, 70%的样品达到富硒土壤标准,但是仅23.3%水稻籽实样品达富Se大米标准。土壤重金属污染风险较大,特别是Hg和Cd,其中80%的样品Hg超《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB 15618—2018)中污染风险筛选值,但水稻籽实中尚无重金属超标现象。水稻根系对硒的富集能力相对最强,其次为茎、叶和籽实。重金属也主要积累在根系中。水稻籽实Se含量与土壤Se总量的相关性不显著,与土壤pH和有机质含量呈显著负相关。水稻籽实中Cd与土壤Se和pH呈显著的负相关关系。土壤中As和Hg向水稻的迁移则主要受总量的控制。水稻各部位Se的吸收能力与土壤重金属存在极显著负相关性,据此可采取措施如降低土壤中的重金属尤其是Cd和Hg的含量及减少有机肥的施用来提高Se在籽实中的积累。