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.

本研究测定了南海冷泉沉积物中的甲烷、硫酸盐、溶解无机碳（dissolved inorganic carbon, DIC）与硫化物浓度，总有机碳（total organic carbon, TOC）、酸挥发性硫化物（acid volatile sulfur, AVS）、铬还原态硫化物（chromium reducible sulfur, CRS）及活性铁的含量，同时分析了DIC与TOC的碳同位素δ¹³C值、硫酸盐、AVS及CRS的硫同位素δ³⁴S值，并测定了硫酸盐还原（sulfate reduction, SR）与甲烷厌氧氧化（anaerobic oxidation of methane, AOM）的速率。
2022年5月，依托“东方红3号”（R/V Dongfanghong 3）科考船航次，在南海（South China Sea, SCS）东北坡的F站位（22°06.922'N；119°17.130'E）采集了沉积物样品。
本研究采用放射性示踪法，通过分别定量测定添加的³⁵S-SO₄²⁻示踪剂向产物³⁵S-H₂S的转化量，以及¹⁴C-CH₄示踪剂向产物¹⁴C-CO₂的转化量，完成了SR与AOM速率的测定。