Geochemical characteristics, stable isotope compositions and microbial activities in cold seep sediments of South China Sea

We measured the concentrations of methane, sulfate, dissolved inorganic carbon (DIC) and sulfide, the contents of total organic carbon (TOC), acid volatile sulfur (AVS), chromium reducible sulfur (CRS) and reactive iron, the δ¹³C values of DIC and TOC, the δ³⁴S values of sulfate, AVS and CRS, and the rates of sulfate reduction (SR) and anaerobic oxidation of methane (AOM) in cold seep sediments of South China Sea. Sediment samples were collected from Site F (22°06.922'N; 119°17.130'E) on the northeastern slope of South China Sea (SCS) during an expedition on board the R/V Dongfanghong 3 in May 2022. The SR and AOM rates were determined using a radiotracer approach through quantifying the conversion of added ³⁵S-SO₄^2- and ¹⁴C-CH₄ tracer to the product ³⁵S-H₂S and ¹⁴C-CO₂, respectively.