Sulfur Speciation in the Surface Sediments of Lakes from Different Regions, China: Characterization by S K-Edge XANES Spectroscopy

Wang Jingfu,Ma Chenyan,Yang Haiquan,Dai Zhihui,Chen Jingan

doi:10.1155/2016/3672348

Wang Jingfu, Ma Chenyan + Show 3 more

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https://doi.org/10.1155/2016/3672348

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Abstract

X-ray absorption near edge structure (XANES) spectroscopy affords the opportunity to determine redox status for element S in the aquatic ecosystems. However, there have been relatively few studies of S XANES spectroscopy in the terrestrial aquatic ecosystems. In this study, XANES technology was used to examine changes in S speciation in the sediments collected from Taihu Lake, Qinghai Lake, Dianchi Lake, Caohai Lake, and Hongfeng Lake located in distinct geological background areas of China. The results showed that sedimentary S in Qinghai Lake has a high proportion of sulfate averaged 88.9% due to physical weathering of watershed rocks, while deposited S in Taihu Lake has a high fraction of intermediate S (36.5%), which may be the response of the agricultural nonpoint source pollution in drainage basin. The three lakes located in Southwest China have similar composition characteristics of S species, indicating similar S sources including chemical weathering of carbonate and atmospheric deposition. 60–90% of S compounds in the surface sediments were in the form of sulfate and FeS. In deeper layers, the ratio of FeS2and the intermediate S significantly increased, suggesting rapid processes of sulfate reduction and sulfide reoxidation with the increasing depths.

Highlights

Sediment is an important repository and sink for sulfur (S) [1]
Two major absorption bands were observed in these K-edge XANE spectra: one near 2472 eV region for the reduced S compounds (e.g., Fe monosulfide (FeS) and FeS2) and another near 2483 eV region for oxidized S species (e.g., SO42−), suggesting that sulfate and FeS were the most important component of elemental S in all lakes
The vertical distributions of sulfur speciation in sediment cores collected from five lakes of China were investigated using X-ray absorption near edge structure (XANES) spectroscopy

Summary

Introduction

Sediment is an important repository and sink for sulfur (S) [1]. The biogeochemical cycles of S in sediments were highly complex, because the aquatic ecosystems have anaerobic zones which strongly affect the chemical forms of S [2, 3]. The wet-chemical speciation method was generally used to analyze the S speciation in sediments and reveal its geochemical processes in the aquatic ecosystems [4,5,6,7,8,9]. Often neglected, S in natural samples existed in a large variety of organic and inorganic forms with different electronic oxidation states, ranging from −2 (inorganic sulfide) to +6 (sulfate) [10]. This made traditional wet-chemical S speciation complicated [11]. The method has become especially attractive for the speciation of S in sediments and other environmental samples, most prominently at the S Kedge [10, 12, 14, 15]

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