长江口沙洲表层沉积物中生物硅分布特征

Distribution of Biogenic Silica in Surface Sediments from the Shoals in the Yangtze Estuary

利用生物硅（BSi）8 h连续提取法，分析了长江口南支沙洲表层沉积物中BSi的分布特征，并探讨了BSi分布与沉积物理化性质之间的相关关系.研究结果发现，沙洲沉积物中BSi含量的变化范围为0.47%-1.02%，平均含量为0.75%.高潮滩沉积物中BSi含量的变化范围在0.47%-0.91%之间，中潮滩在0.48%-1.02%之间，低潮滩则是0.47%-0.96%.沉积物理化性质与BSi之间的相关分析揭示，沉积物中BSi含量与粘土和粉砂含量呈极显著正相关，这表明沉积物中BSi的赋存对沉积物机械组分具有明显的依赖性；沉积物中的BSi与有机碳、氮（OC、ON）之间存在极显著的正相关关系，表明在富含有机质的沉积物中易于BSi的累积；OC/BSi和ON/BSi的变化范围分别为0.28-2.59和0.05-0.21，都低于Redfield比值，说明沙洲沉积物中BSi的溶解速率要远低于有机质的分解速率.此外，还发现沉积物中BSi与叶绿素之间存在弱的正相关关系，反映了硅质藻类等初级生产者对沉积物中BSi累积也有一定的贡献.

Distributions of biogenic silica（BSi） in surface sediments from the shoals in the Yangtze Estuary were investigated using an 8-hour sequential extraction method, and the relationships of BSi with the sediment physio-chemical characteristics were also discussed. The findings indicated that the BSi contents in the shoal sediments varied from 0.47% to 1.02%, and the average content was 0.75%. The BSi contents range of the high, middle and low intertidal flats was 0.47% -0.91%, 0.48% - 1.02% and 0.47% - 0.96%, respectively. The significant positive relationships were found between BSi and the clay and silt contents in sediments, which indicated that the accumulation of BSi in sediments closely depended on sediment compositions. There also existed the remarkable positive relationships between BSi and organic carbon （OC） and nitrogen （ON）. This implied that BSi was apt to accumulate in sediments enriched in organic matter. Compared with Redfield ratios, the ratios of OC/BSi and ON/BSi in shoal sediments were relatively lower and in the range of 0.28 - 2.59 and 0.05 - 0.21, respectively. Therefore, it was shown that the dissolution rate of BSi in shoal sediments was lower than the rate of organic matter decomposition. In addition, it was also found that there was the weak positive correlation between BSi and chlorophyll in the sediments, reflecting that primary productivity such as diatoms, to some certain, made contribution to the storage of BSi.