武汉东湖沉积物中酸挥发性硫化物(AVS)的深度分布及其影响因素

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

沉积物中酸挥发性硫化物(AVS)是硫化物的生成、氧化和扩散等综合作用的反映,有机物的供给、硫酸盐的还原等因素都能影响其分布特征. 本文对武汉东湖三个污染程度不同站点的AVS深度分布特征进行了研究,结果表明,AVS含量在一定深度沉积物中具有最大值,东湖沉积物中AVS的深度分布具有两种不同的模式,I站和II站AVS浓度峰在5cm左右的表层沉积物中,且AVS还原层深度较狭窄,而III站AVS浓度峰处于10-20cm深度范围,沉积物中有机质负荷的差异是导致这种分布特征的重要原因. 沉积物中有机质含量对AVS的深度分布具有重要影响,高有机质负荷导致AVS浓度峰向表层迁移,且AVS还原层分布于较狭窄的深度范围. 对方涛等对流-扩散模型的应用表明,该模型在高有机质负荷沉积物中(I、II站)AVS深度分布的应用较为理想,然而低有机质负荷沉积物中(III站)不能准确反映AVS的深度分布特征,说明其应用范围具有一定的局限性.

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.