呼伦湖沉积物生物硅的分布特征

以Si的生物地球化学特征为基础,结合本小组前期研究成果,探讨了我国纬度最高湖泊呼伦湖沉积物中生物硅(BSi)的分布特征以及有机质与BSi的相关性。研究表明,呼伦湖表层沉积物中BSi的含量介于4.04~18.30 mg.g-1之间,平均11.81 mg.g-1;受陆源输入和沉积物粒度分异的影响,呼伦湖表层沉积物中BSi的空间分布由北西向南东呈现明显递减趋势,BSi的高值区出现在北西部湖区。3个柱芯沉积物中BSi的含量均在10 cm处达到峰值,这可能与20世纪60年代出现的大规模厄尔尼诺现象对湖泊水体中营养盐及藻类繁殖带来的影响有关。沉积物中有机碳与生物硅呈显著正相关关系,OC/BSi值介于0.89~7.22之间,平均2.74,远远小于Redfield比值(106/16),揭示相同条件下,有机质的分解速率远远大于生物硅的溶解速率,颗粒物表层有机质对BSi起到了很好的保护作用,使沉积物中BSi的大部分不参与再循环。

Characteristics of Biogenic Silica Distribution in the Sediment of Hulun Lake

On the basis of Biogenic silica(BSi) geochemistry characteristics,the spatial distribution of BSi and the correlation between BSi and TOC in sediments from Hulun Lake were studied in this work.The results showed that BSi concentrations in the surface sediments from Hulun Lake were ranged from 4.04 to 18.30 mg·g-1 with a mean value of 11.81 mg·g-1.In terms of spatial distribution,the concentration of BSi was decreased from northwest to southeast in spatial distribution,and the high-concentration areas were found in the northwest of the lake which might result from terrestrial inputs and particle size fractionation.The maximum concentration values of BSi in sediment cores were observed at 10 cm reflecting the nutrients accumulation and alga bloom in the aquatic environments at this stage,which may be related to the large scale EI Nino in 1960s.Furthermore,the concentration of BSi showed a positive correlation with organic carbon in sediment cores,and the ratios of OC to BSi were in the range of 0.89~7.22 with a mean value of 2.74 which was far less than the Redfield ratio(106/16).All of the mentioned above indicated that the decomposition rate of organic matter was far greater than the dissolution rate of biogenic silica under the same conditions.Accordingly,BSi tended to accumulate in sediments which limited its bio-geochemistry cycle.