~(35)SO_4~(2-)示踪法测定九龙江河口沉积中硫酸盐还原速率

在2011年7月利用35SO2-4培养示踪法测定九龙江河口两个站位(A站位位于咸淡混合区,盐度3~5;B站位位于海相区,盐度20~25)沉积柱中硫酸盐还原速率的垂直分布。结果显示A站位沉积柱中硫酸盐还原速率变化范围为54~2 345nmol/(cm3·d),从表层到底部先增大后减小,最大值出现在20cm深度附近;B站位硫酸盐还原速率在24~987nmol/(cm3·d)之间,分别在10cm和78cm深度附近出现两个峰值,分别为876nmol/(cm3·d)和987nmol/(cm3·d)。综合分析两个站位孔隙水中SO2-4、甲烷浓度和沉积物中总有机碳、温度和氧化还原电位的垂直变化趋势与其硫酸盐还原速率的分布规律,表明A站位沉积物中硫酸盐还原以有机矿化为主;B站位受到有机质矿化和甲烷厌氧氧化的共同作用;两个站位硫酸盐还原速率及垂直分布趋势受孔隙水中SO2-4浓度、有机质活性和温度的共同影响;根据各个层位硫酸盐还原速率估算两个站位硫酸盐还原通量(以硫计)分别为527.9mmol/(m2·d)和357.1mmol/(m2·d),表明硫酸盐还原是九龙江河口有机质厌氧矿化的重要路径。

Measurement of sulfate reduction rate in coastal sediments of Jiulong River Estuary with a radiotracer technique

Sulfate reduction rates were measured experimentally with ³⁵SO₄^2- in sediment of A and B cores in coastal of Jiulong River Estuary in July of 2011. A and B cores were situated in the upper estuarine coast and seaward boundary respectively,with low salinity (3-5) and high salinity (20-25). Sulfate reduction rates volume-based values ranged from 54 to 2 345 nmol/(cm³·d) in vertical profile of A core,and the highest sulfate reduction rates occurred at 20 cm depth. Sulfate reduction rates varied from 24 to 987 nmol/(cm³·d) in B core,two peaks in sulfate reduction rates profiles obviously appeared on the top 10 cm and at 78cm depth,with significantly high value of 876 nmol/(cm³·d) and 987 nmol/(cm³·d),respectively. Based on trends on the vertical profile of SO₄^2-,methane concentration in pore water and total organic carbon,temperature and oxidation reduction potential in sediments of two cores,sulfate reduction is mainly dominated by organic mineralization in A Core,however sulfate reduction is controlled by the combination of organic matter mineralization and anaerobic methane oxidation in B Core. Meanwhile sulfate reduction rates and the vertical distribution trends of it were affected by the availability of active organic matter,temperature and SO₄^2- concentration in the pore water in two cores. The depth-integrated sulfate reduction rates were 527.9 mmol/(m²·d) and 357.1 mmol/(m²·d) within sulfate reduction zone in A Core and B Core respectively. Sulfate reduction is one of the major processes contributing to the mineralization of organic matter in this estuary.