沉积物中硅释放的影响因素研究

为揭示沉积物中硅的迁移转化机制及其生物地球化学循环规律,给湖泊富营养化发生机制及水环境治理与保护研究积累基础数据,以乌梁素海为研究对象,深入探讨了p H、微生物和低分子量有机酸等环境因子对沉积物中Si释放的影响机制。结果表明,随着p H的升高(7.0~9.5),乌梁素海上覆水中Si浓度降低,沉积物中生源硅(BSi)含量升高,显示乌梁素海的偏碱性环境使硅在水-沉积物界面的扩散矢量方向指向沉积物。方差分析表明,有微生物体系和无微生物体系之间上覆水Si浓度具有显著差异,可能与微生物的捕食作用和降解作用有关。菖蒲区上覆水中Si浓度整体高于对应季节芦苇区上覆水,而菖蒲区沉积物中BSi含量低于对应季节芦苇区沉积物,主要是由于芦苇和菖蒲根基分泌的低分子量有机酸不同,进而对硅酸盐矿物的溶解能力存在差异导致的。沉水植物区沉积物冬春季和夏秋季整体表现为上覆水的硅汇,上覆水共向沉积物中转移约15.62 t Si;挺水植物区沉积物冬春季和夏秋季整体表现为上覆水的硅源,沉积物共向上覆水中释放约33.15 t Si。

Factors influencing silicon releases fromlake sediments

Diatoms greatly control the water''s capacity to store CO₂. Silicon(Si) level in water impacts diatom growth. In this work, the influences of pH, microorganism and low molecular weight organic acids on silicon releases from the sediments of Wuliangsuhe(WLSH) Lake were investigated under simulating experiments. Results showed that concentrations of Si in overlying water decreased along with pH increases(7.0~9.5), while the content of BSi in sediments increased. This indicated that the diffusion direction of Si released was towards the sediments at the water-sediment interface under weak-alkaline environment. Silicon concentrations were higher in microorganism system than in non-microorganism system in both overlying water and sediments. The differences in Si concentrations in both overlying water and sediments among different hydrophyte areas were resulted from the differences of low molecular weight organic acids excreted by hydrophytes. Sediments from both submerged and emergented plant areas acted as Si sink and source, depositing and releasing 15.62 t and 33.15 t Si in the whole year, respectively. This work would advance the understanding of the transformation, migration and biogeochemical cycle of Si in lake sediments as well as protection of terrestrial aquatic environment.