喀斯特小流域黄壤硫形态和硫酸盐还原菌分布特征

Distributions of sulfur forms and sulfate-reducing bacteria in yellow soil of small karst catchment

本文分析了黄壤中总硫、SO_4^(2-)、总还原态无机硫(TRIS)和有机硫的含量,以及硫酸盐还原菌(SRB)类群和数量,目的是阐明西南酸沉降地区土壤中硫形态和SRB的分布特征。结果表明:有机硫是主要的硫形态,SO_4^(2-)是主要的无机硫形态;黄壤剖面不同深度均检出脱硫弧菌属-脱硫微菌属,指示脱硫弧菌属-脱硫微菌属是黄壤中SRB的优势类群;黄壤剖面中SRB数量与TRIS含量增加的深度与SO_4^(2-)-S含量降低的深度基本一致,指示黄壤中存在SO_4^(2-)异化还原反应,并且TRIS是主要产物;生物滞留后剩余SO_4^(2-)的吸附、解吸、淋溶迁移及深层吸附与累积导致剖面底层SO_4^(2-)-S含量增加;酸沉降输入的SO_4^(2-)主要以有机硫和吸附态SO_4^(2-)滞留在黄壤中,在硫的年沉降速率大幅降低后,在较长时期内,黄壤中有机硫矿化和吸附态SO_4^(2-)解吸可能释放大量SO_4^(2-)进入地表和地下水体,与之相关的土壤理化性质变化和水体化学组成改变等方面的环境效应值得关注。

We analyzed the contents of total sulfur （S）, SO42--S, total reduced inorganic sulfur （TRIS）, organic S, and sulfate-reducing bacteria （SRB） groups and quantities in yellow soil to examine the distribution patterns of sulfur forms and SRBs in soils under acid deposition in the karst areas of Southwest China. The results showed that organic sulfur was the major sulfur form, and SO42- was the major inorganic sulfur form in yellow soil. Desulfovibrio-Desulfomicrobium was detected at different soil depths, indicating that Desulfovibrio-Desulfomicrobium is the domi-nant SRB group in yellow soil. The soil depths of increasing SRB quantity and TRIS contents corre- sponded well to the depths of decreasing SO42--S contents, indicating that dissimilatory SO42 re- duction occurred in yellow soil with TRIS as the main product. The residual SO42- after biological S retention was firstly adsorbed and then desorbed; desorbed SO42- could transport downward and was subsequently re-adsorbed and accumulated in deep soil layers. This explained the increasing SO42--S contents in bottom layers of yellow soil profiles. The deposited SO42- was retained as or- ganic sulfur and adsorbed SO42- in yellow soil, then yellow soil may release more S into rivers by organic sulfur mineralization and desorption of the adsorbed SO42- in a long period after a large decrease in annual sulfur deposition rate. Therefore, the environmental implications such as chan- ges of soil properties and chemical compositions of river water in southwest China should be in- vestigated in the future.