贵州阿哈湖物质循环过程的微量元素地球化学初步研究

A Primary Geochemical Study on Trace Metals During Biogeochemical Cycling in Aha Lake,Guizhou,China

对贵州阿哈湖夏季和冬季分层湖水的水化学参数、溶解态微量元素和悬浮颗粒物微量元素进行了对比研究。结果显示:阿哈湖湖水夏季热分层和化学分层均较明显,而冬季湖水处于混合状态。夏季湖泊物质循环过程对生源要素Si、DOC以及Mn、Fe、Cr、Co、Ni、Zn和Mo等微量元素的分布和迁移转化均产生了重要影响。夏季湖泊底层水体中溶解态Mn、Fe、Co和Ni的含量较高,主要受有机质降解和Fe、Mn氧化还原循环的影响,而且Mn的循环强度高于Fe循环,溶解态Cr在底层水体中仅有小幅升高;另外,沉积物孔隙水向上覆水体的释放作用对底层水体中溶解态重金属浓度的升高可能也有一定的影响。溶解态Zn和Mo在夏季底层水体中的含量呈现逐渐降低的趋势,主要受到金属硫化物形成以及钼酸盐沉淀的影响。夏季悬浮颗粒物的Mn、Fe、Cr、Co、Ni、Zn和Mo均在氧化还原界面附近呈明显富集趋势,主要受铁锰氧化物/氢氧化物吸附/解吸、氧化还原作用等水-粒相互作用过程的控制和影响;此外,金属硫化物的形成可能也对底层水体中悬浮颗粒物Zn、Mo和Ni含量的升高有一定贡献。

Physico-chemical parameters,dissolved trace metal ions and particulated trace metals were investigated for their distributions and transformations during summer and winter in Aha Lake,Guizhou province.In summer,thermal and chemical stratifications were well established while water overturn occurred during winter.The biogeochemical cycling probably play an important role in the distribution of dissolved Si,dissolved organic carbon（DOC）,Mn,Fe,Cr,Co,Ni,Zn and Mo during summer stratification.In summer,significant increase of dissolved Mn,Fe,Co and Ni were clearly observed in the bottom as a result of degradation of organic matter and the redox cycling of Fe and Mn.The Mn concentration was much higher than Fe concentration,indicating that Mn cycling is stronger than that of Fe.Only a slight increase of Cr concentration occurred in Aha Lake in summer.Besides,metal diffusions from sediment porewaters may also have some contribution to the increase of metal ions in the bottom.In contrast,strong decrease of Zn and Mo concentrations appeared in the bottom due to the formation of metal sulfides and metal molybdates.There were significant enrichments of particulated Mn,Fe,Cr,Co,Ni,Zn and Mo just near the redox boundary,which were induced by water-particle interactions including adsorption/desorption,redox cycling of Fe and Mn oxides and hydroxides.As for Zn,Mo and Ni,the formation of metal sulfides seems to be another contributor to the increase of pariculated Zn,Mo and Ni.