典型喀斯特小流域石灰土和黄壤硫同位素分布特征及其影响因素

Characteristics and Influencing Factors of Sulfur Isotope Distribution in Calcareous Soil and Yellow Soil of Typical Small Karst Catchments

分析了贵州普定陈旗和后寨河喀斯特小流域石灰土和黄壤剖面不同深度总硫、碳键硫、酯键硫酸盐、SO_(4)^(2-)和总还原态无机硫的含量及其δ^(34)S值、硫酸盐还原菌数量和采样坡地溪水SO_(4)^(2-)的δ^(34)S值,目的是阐明喀斯特流域土壤对大气酸沉降的响应。结果表明:在同等酸沉降水平下,石灰土和黄壤剖面中各形态硫含量、δ^(34)S值及硫酸盐还原菌数量有明显差异,同时溪水中有超过70%的SO_(4)^(2-)来自石灰土和黄壤剖面不同深度土壤的输出,指示石灰土和黄壤对大气酸沉降的不同响应。有机硫形成和SO_(4)^(2-)异化还原反应是石灰土和黄壤中都存在的硫滞留过程。黄壤剖面存在着SO_(4)^(2-)吸附并在底层累积,因此SO_(4)^(2-)吸附是黄壤硫滞留的主要原因。石灰土和黄壤剖面输出的SO_(4)^(2-)主要来自大气酸沉降输入的SO_(4)^(2-),不是土壤本身有机硫矿化。不过,有机硫是石灰土和黄壤主要的硫形态,在沉降的硫通量显著降低后,这两类剖面有机硫矿化会释放大量的SO_(4)^(2-)进入水体。

In this paper, we analyzed the contents and δ^(34)S values of total sulfur, carbon-bonded sulfur, ester-bonded sulfate, SO_(4)^(2-), total reduced inorganic sulfur and stream SO_(4)^(2-), and SRB quantity at different depths in calcareous soil and yellow soil profiles in Chenqi and Houzhaihe small karst catchments of Puding County in Guizhou Province, with the aim of elucidating the response of soils in karst catchments to atmospheric acid deposition. The results showed that under the same acid deposition level, there were significant differences in the sulfur content and δ^(34)S values of different sulfur forms and SRB numbers in the calcareous soil and yellow soil profiles. Also more than 70% of the SO_(4)^(2-)in the stream water of sampled slope came from soils at different depths in calcareous soil and yellow soil profiles. These results indicate the different response of calcareous soil and yellow soil to atmospheric acid deposition. The formation of organic sulfur and dissimilatory SO_(4)^(2-)reduction are sulfur retention processes that exist in both calcareous soil and yellow soil profiles. SO_(4)^(2-)adsorption exists in the yellow soil profile and accumulates in the bottom soil layers;therefore, SO_(4)^(2-)adsorption is the main cause of sulfur retention in yellow soil. The SO_(4)^(2-)exported from the calcareous soil and yellow soil profiles is mainly from SO_(4)^(2-)input from atmospheric acid deposition and not from organic sulfur mineralization of the soil itself. However, organic sulfur is the dominant sulfur form in calcareous soil and yellow soil, and organic sulfur mineralization in these two types of profiles may release a large amount of SO_(4)^(2-)into the surface water after the sulfur deposition flux is significantly reduced.