Reduced inorganic sulfur in surface sediment and its impact on benthic environments in offshore areas of NE China.

Geochemical cycling and biological toxicity of sulfur in marine sediments is closely related to the activity of organisms. This study investigated the distribution and potential impact on benthic environments of acid volatile sulfur (AVS), chromium(II)-reducible sulfur (CRS), elemental sulfur (ES), total S, C, N and Fe in superficial sediments across the Bohai Sea, Yellow Sea and East China Sea. The composition of reduced inorganic sulfur in the three study areas was dominated by CRS (averaging 72% of total reduced inorganic sulfur). The low AVS content (average of 1.12 µmol g(-1)) of the sediments and the low values of AVS/CRS (average 0.34 µmol g(-1)), degree of pyritization and degree of sulphidization indicate that there is sufficient available iron in the sediment to restrict the threat of sulphide toxicity to benthic organisms in most of the study areas. However, high organic matter loads in parts of the study areas have resulted in enhanced accumulation of AVS, resulting in a higher toxicity risk.