Enrichment characteristics and risk assessment of Hg in bird feathers from Caohai wetland in Guizhou Province,China

Based on the analysis of the enrichment characteristics of Hg and Me Hg in bird feathers from Caohai National Nature Reserve in Guizhou, the risks of Hg pollution to the birds from Caohai wetland have been evaluated. The total Hg content of bird feathers ranges from 40 to 5058 ng/g with an average of 924 ng/g. The content of Me Hg is significantly correlated with total Hg(r = 0.68,p<0.01), and the content are among 0.75 and 113 ng/g.The total Hg content in the birds feathers is significantly dependent on their feeding habits, which is mainly in accordance with the following rule: carnivorous birds [ omnivorous birds that are mainly carnivorous [ omnivorous birds that are mainly herbivorous.There are also differences in the Hg enrichment ability in the different parts of bird feathers, and the total Hg and Me Hg content in the wing feathers are significantly higher than that in the other parts of feathers. The bioaccumulation coefficients of aqueous Hg and Me Hg by bird feathers are 0.9×10~4–112.13×10~4(mean value is 20.47×10~4) and 0.47×10~4–70.4×10~4(mean value is 9.52×10~4),respectively. Although the whole Hg level in Caohai bird feathers is not too high, the Hg content in some carnivorous birds exceeds over or approaches the abnormal threshold when birds are breeding(5 μg/g), which indicates that the birds in Caohai wetland are faced with some risks of ecological Hg pollution.

Effects of soil properties on production and bioaccumulation of methylmercury in rice paddies at a mercury mining area,China

Rice paddy soil is recognized as the hotspot of mercury（Hg） methylation, which is mainly a biotic process mediated by many abiotic factors. In this study, effects of key soil properties on the production and bioaccumulation of Hg and methylmercury（MeHg） in Hg-contaminated rice paddies were investigated. Rice and soil samples were collected from the active Hg smelting site and abandoned Hg mining sites（a total of 124 paddy fields） in the Wanshan Mercury Mine, China. Total Hg（THg） and MeHg in soils and rice grains, together with sulfur（S）,selenium（Se）, organic matter（OM）, nitrogen（N）, phosphorus（P）, mineral compositions（e.g., SiO2, Al2O3 and Fe2O3） and pH in soils were quantified. The results showed that long-term Hg mining activities had resulted in THg and MeHg contaminations in soil-rice system. The newly-deposited atmospheric Hg was more readily methylated relative to the native Hg already in soils, which could be responsible for the elevated MeHg levels in soils and rice grains around the active artificial Hg smelting site. The MeHg concentrations in soils and rice grains showed a significantly negative relationship with soil N/Hg, S/Hg and OM/Hg ratio possibly due to the formation of low-bioavailability Hg–S（N）–OM complexes in rhizosphere. The Hg–Se antagonism undoubtedly occurred in soil-rice system, while its role in bioaccumulation of MeHg in the MeHg-contaminated rice paddies was minor. However, other soil properties showed less influence on the production and bioaccumulation of MeHg in rice paddies located at the Wanshan Mercury Mine zone.

Effects of sulfate-reducing bacteria on methylmercury at the sediment–water interface

Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.

中国西部贫困农村孕期微营养素补充对出生体重、分娩孕周和围产儿死亡影响的研究：双盲整群随机对照试验

目的以单纯补充叶酸为对照，评价孕期补充多种微营养素或铁／叶酸对出生体重、分娩孕周和孕晚期血红蛋白的影响。设计采用整群随机双盲对照试验设计。地点中国陕西省的两个贫困县（长武县和彬县）。研究对象5828名孕妇及其分娩的4697名活产新生儿。干预措施以村为单位整群随机化，同一个村的孕妇孕期每天补充叶酸（对照组）、铁／叶酸或多微营养素。多微营养素含15种推荐量的维生素和矿物质。主要结局指标测量出生体重、身长、头围在产后72小时内测量。通过产后42天访视收集新生儿生存情况。结果与单纯补充叶酸比较，多微营养素可显著提高出生体重42g（95％CI7—78g）；孕期补充多微营养素和铁／叶酸均可显著增加分娩孕周（铁／叶酸：0．23周，95％CI0．10～0．36周；多微营养素：0．19周，95％CI0．06～0．32周）。铁／叶酸可显著减少34周以内的早产（RR0．50，95％CI0．27～0．94，P=0．031）。相对于纯叶酸组，多微营养素和铁／叶酸均可显著增加孕妇孕晚期的血红蛋白水平（铁／叶酸：5．0g／L，95％CI2．0～8．0g／L，P=0．001；多微营养素：6．9g／L，95％CI4．1～9．6g／L，P〈0．001）。孕期营养素补充对围产儿死亡没有明显影响，但铁／叶酸可减少54％（RR0．46，95％CI0．21～0．98）的7天内新生儿死亡。结论与对照组（叶酸）比较，在中国贫困农村孕期补充铁／叶酸可延长分娩孕周从而减少早期新生儿死亡；多微营养素可适当增加出生体重，尽管如此，对早期新生儿死亡并无明显影响。在孕期微营养素干预中，剂量充足的铁对于降低发展中国家的新生儿死亡是最关键的。