On the Vertical Distribution and Influencing Factors of Acid-Volatile Sulfide in the Sediments of Donghu Lake (Wuhan)

Abstract

Lake Donghu(Wuhan), a subtropical shallow lake near the Yangze River, is polluted heavily by some sewage inputs. Based on total phosphorus (TP) and chlorophyll-a, Station I is defined as a hypertrophic lake, and Station II is defined as a eutrophic lake, and Station III is defined as mesotrophic lake. The main purposes of this paper are to describe the vertical distribution of acid volatile sulfide (AVS) in the sediments of three stations with different trophic levels in Lake Donghu, and to discuss the possible mechanisms underlining these patterns with emphasis on the possible effects of organic matter. The results indicate that AVS peak appeared in anoxic sediments in all three stations. Two patterns of AVS distribution were found. The AVS profiles in cores of Station I and II showed a maximum concentration at about 5-cm depth, and then a drop down at a lower level. On the contrary, the AVS profile in the cores of Station III showed AVS peak between 10 cm to 20 cm depths. There was closer relationship between OM and AVS in the sediment with high concentration of OM than with low concentration of OM, and AVS/OM ratio was in the order of Station I II III. This indicates that organic matter exerted great effects on the distribution of AVS in the sediment. The content of AVS in sediments is mainly affected by decompose of organic matter, deposition, dissolution and oxidation of AVS. High organic matter flux shifted AVS peak into the surface sediment, and narrowed the depth interval over which the accumulation of AVS became maximized at the more eutrophic Stations I and II. The convection-diffusion model of AVS reported by Fang et al was tested. The vertical distribution of AVS accorded with the model better in eutrophic lake with high concentration of OM than with low concentration of OM.