Mercury is one of the primary contaminants of global concern.As anthropogenic emissions of mercury are gradually placed under control,evidence is emerging that biotic mercury levels in many aquatic ecosystems are increasingly driven by internal biogeochemical processes,especially in ecosystems that have been undergoing dramatic environmental changes.Here we review the unique properties of mercury that are responsible for the exceptional sensitivity of its biogeochemical cycles to changes in climatic,geochemical,biological and ecological processes.We show that,due to rapid climate warming,a shift from sources-driven to processes-driven mercury bioaccumulation is already happening in the Arctic marine ecosystem.We further suggest that such a shift might also be operating in the Three Gorges Reservoir due to changes in these biogeochemical processes induced by the damming.As a result,the effectiveness of mercury emission control is expected to be followed by long delays before ensuing reduction is seen in food-web levels,making it all the more pressing to control and reduce mercury emissions to the reservoir.Long-term monitoring and targeted studies are urgently needed to understand how biotic mercury levels in the reservoir are responding to changes in mercury emissions and in biogeochemical processes.
Organoarsenics are widely used as growth promoters in poultry industry,resulting in arsenic(As)accumulation in poultry litter.A greenhouse pot study was implemented to investigate the fate of arsenic originated from poultry litter and their effects on the growth of Brassica napus(oilseed rape),and assess their potential health risks.Five poultry litter application rates(0,5%,10%,20%and 40%)were used,dividing into two groups:one for soil incubation(SI)and the other for plant cultivation(PC).Experimental results indicated that the total arsenic for composted poultry litter was(10.94±0.23)mg/kg,As(V)and As(III)decreased while methylated arsenic increased after 21 d in SI and PC treatments.Seed germination rates were negatively correlated with monomethylarsenic acid(MMA,R2=0.63,p<0.05).The length and biomass of roots and shoots were significantly inhibited by poultry litter,but plant length of 5%treatments was slightly stimulated.Within an average weekly intake of 0.5 kg Brassica napuss,the risk quotient(RQ)values induced from roots nearly all surpassed the acceptable limit(1),were two orders magnitude higher than shoots.According to the potential risk to order,child exhibited the highest risk,adolescent ranked secondly,and adult exhibited the lowest risk.Hence,people should better avoid intake Brassica napus roots to reduce arsenic potential risk.
邻苯二甲酸二甲酯(DMP)作为一种在环境中广泛存在的有毒化合物,已被中国列为优先控制污染物。采用无机盐培养基从长期覆盖农膜的黑土中分离鉴定了一株能够以DMP为碳源的菌株QD-9-10,根据菌落的形态特征及16S r DNA碱基序列同源性分析,鉴定QD-9-10为Bacillus sp.。正交实验结果表明,菌株QD-9-10的最优降解条件为p H 8.0,温度35.0℃,摇床转速124.0 r·min-1,DMP初始浓度100.4 mg·L-1,在32 h时内可将DMP完全降解。底物利用能力测试表明,菌种QD-9-10具有可降解多种邻苯二甲酸酯(PAE)的能力。由此可见,Bacillus sp.QD-9-10在修复PAEs污染环境方面有一定应用前景。
