环境地球化学国家重点实验室知识库

Silicon (Si) is one of the main biogenic elements in the aquatic ecosystem of lakes,significantly affecting the primary productivity of lakes. Lake sediment is an important sink of Si,which exists in different Si forms and will be released and participate in the recycling of Si whenthe sediment environment changes. Compared to carbon (C), nitrogen (N) and phosphorus (P),the understanding of different Si forms in sediments and their biogeochemical cycling is currentlyinsufficient. Dianchi Lake, a typical eutrophic lake in southwest China, was selected as an example,and the contents of different Si forms and biogenic silicon (BSi), as well as their correlations withtotal organic carbon (TOC), total nitrogen (TN), and chlorophyll a in the surface sediments, weresystematically investigated to explore Si’s recycling characteristics. The results showed that thecoupling relationship of the four different Si forms in the surface sediments of Dianchi Lake waspoor (p > 0.05), indicating that their sources were relatively independent. Moreover, their formationmay be greatly influenced by the adsorption, fixation and redistribution of dissolved silicon bydifferent lake substances. The contents of different Si forms in the surface sediments of DianchiLake were ranked as iron-manganese-oxide-bonded silicon (IMOF-Si) > organic sulfide-bondedsilicon (OSF-Si) > ion-exchangeable silicon (IEF-Si) > carbonate-bound silicon (CF-Si). In particular,the contents of IMOF-Si and OSF-Si reached 2983.7~3434.7 mg/kg and 1067.6~1324.3 mg/kg,respectively, suggesting that the release and recycling of Si in surface sediments may be moresensitive to changes in redox conditions at the sediment–water interface, which become the mainpathway for Si recycling, and the slow degradation of organic matter rich in OSF-Si may lead tolong-term and continuous endogenous Si recycling. The low proportion (0.3~0.6%) and spatialdifferences of biogenic silicon (BSi) in the surface sediments of Dianchi Lake, as well as the poorcorrelation between BSi and TOC, TN, and chlorophyll a, indicated that the primary productivityof Dianchi Lake was still dominated by cyanobacteria and other algal blooms, while the relativeabundance of siliceous organisms such as diatoms was low and closer to the central area of DianchiLake. Additionally, BSi may have a faster release capability relative to TOC and may participate inSi recycling.