快速连续提取沉积物中还原性无机硫的实验方法与应用

Experimental Method and Application of Rapid and Continuous Extraction of Reduced Inorganic Sulfur from Sediments

还原性无机硫是沉积物硫中最活跃的部分,其含量变化控制沉积物中铁、磷及重金属等元素的地球化学行为,在地质过程和环境污染方面都具有至关重要的影响。化学连续提取法是目前沉积物中硫形态提取基本方法,但常用的冷扩散法处理单个样品耗时长,难以实现对大批量样品的快速连续提取。为实现快速、准确地测定沉积物样品各形态还原性无机硫的含量,本文采用热蒸馏法,改进基于前人的三步提取过程,通过优化实验装置预先制备实验所需的二氯化铬溶液,实现了样品还原性无机硫形态的快速连续提取;以过氧化氢为氧化剂,将提取的各形态硫氧化为SO2-4后采用离子色谱进行检测。选取三峡库区沉积物样品进行重复实验检验,得到提取酸挥发性硫、黄铁矿硫、元素硫的标准偏差(RSD,n=3)分别为5.26%、1.22%和3.09%,重复性较好。进一步对酸挥发性硫、黄铁矿硫、元素硫的加标回收率进行测定,得到这三种硫形态的回收率分别为92.8%、93.6%、94.1%。本实验方法采用的热蒸馏法对单个硫形态提取时间为1.5h,用时较短,玻璃装置连接便捷、操作简单,分析检测准确度好,实现了一套装置对沉积物还原性无机硫形态的连续提取,可适用于大批量样品的硫形态快速提取与检测。

BACKGROUND:Sulfur is an active element with multiple chemical forms,which plays a vital role in the regulation of redox chemistry.Reduced inorganic sulfur(RIS)including acid volatile sulfur(AVS),elemental sulfur(ES)and pyrite sulfur(CRS)is the most active part of sulfur species in sediments and plays an important role in controlling the geochemical behavior of iron,phosphorus and heavy metals in sediments.Separation and determination of reduced inorganic sulfur in anoxic sediments are critical to ecological and geological studies of sulfur cycles.Both distillation and diffusion methods can be effectively used to separate AVS,ES,and CRS in sediments.However,the current methods for extracting sulfur species are difficult to adapt to the large number of samples in geological and environmental research.Due to the reaction time,requirements of 24h for single sulfur species in the diffusion method limits the number of samples that can be processed on a timely basis.This limitation presents a problem for analyzing fresh anoxic sediment samples which have to be processed immediately to minimize the risk of sulfide re-oxidation.The detection method has the disadvantages of having a cumbersome testing process,long analysis time,and easy loss of sulfur components.