title: [Sulfur isotopic ratios indicating sulfur cycling in slope soils of karst areas].
abstract: Sequential extraction methods for soil sulfur were used to determine delta34 S ratios and sulfur contents of total sulfur, organic sulfur, SO4(21) and FeS2 in slope soils of karst areas. In general, FeS2 has the lowest delta34 S ratios, ranging from -6.86% per hundred to -4.229% per hundred, followed in ascending order by SO4(2-) (-2.64% per hundred - -1.34% per hundred), total sulfur (-3.25% per hundred - -1.03% per hundred) and organic sulfur (-1.63% per hundred -0.50% per hundred) in surface soils of profiles, and delta34 S ratios in different sulfur forms all show increasing trend with profiles deepening. Covariations of delta34 S ratios of SO4(2-) and FeS2 with increasing depth are related to SO4(2-) dissimilatory reduction, while the increase in parallel of delta34 S ratios of total sulfur and organic sulfur could be resulted from organic sulfur cycling. delta34 S ratios have been extensively used to indicate sulfur sources, moreover, SO4(2-) dissimilatory reduction and organic sulfur mineralization result in significant sulfur isotopic fractionation, and sulfides oxidation and SO4(2-) assimilation have no isotopic fractionation occurred, the vertical variations of delta34 S ratios in different sulfur forms can therefore be good records for depth-dependant sulfur cycling processes. Furthermore, by comparing depth distributions of sulfur contents and delta34 S ratios in different sulfur forms, it is easily to discuss the migration of SO4(-1) and organic sulfur fractions in soil profiles.
authors.affiliation: Key Laboratory for Water Environment and Resources, Tianjin Normal University, Tianjin 300387, China. zhw1258@126.com
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Cong-qiang
authors.initials: CQ
authors.lastname: Liu
authors.forename: Xiao-dong
authors.initials: XD
authors.lastname: Li
authors.forename: Tao-ze
authors.initials: TZ
authors.lastname: Liu
authors.forename: Li-li
authors.initials: LL
authors.lastname: Zhang
mesh_terms: D015258:Acid Rain / Q000032:analysis*; D002681:China; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D012987:Soil / Q000032:analysis*; D013431:Sulfates / Q000032:analysis* / Q000737:chemistry; D013455:Sulfur / Q000032:analysis* / Q000737:chemistry; D013460:Sulfur Isotopes / Q000032:analysis
chemical_list: D015258:Acid Rain; D012987:Soil; D013431:Sulfates; D013460:Sulfur Isotopes; D013455:Sulfur