The effect of nitrate concentration on sulfide-driven autotrophic denitrification in marine sediment.

The effect of nitrate concentration on denitrification rate, microbial community and byproduct accumulation in sulfide-driven autotrophic denitrification, one of the dominant processes during anoxic marine sediment remediation, was investigated in this study. Microorganisms which were phylogenetically closely related with Sulfurimonas denitrificans of ε-Proteobacteria and Thiohalomonas denitrificans of γ-Proteobacteria were the major autotrophic denitrifiers in this study. Nitrate concentration was demonstrated to have selective effect on denitrifying microbial community as revealed by denaturing gradient gel electrophoresis. Denitrifiers enriched at 30 mM NO(3)(-) have higher diversity than other two groups (10, and 80 mM NO(3)(-)) according to Shannon index. Denitrification showed zero-order reaction kinetics when nitrate concentration was higher than 4mM. Neither absolute nitrate concentration nor overall nitrate/sulfide ratio acted as the determinant for denitrification byproduct (i.e. N(2)O and NO(2)(-)) accumulation. The limitation of sulfide due to low mass transfer might be the reason for the byproduct accumulation.