• 关键词：砷  红壤  粒级组分  X射线吸收近边结构光谱(XANES)

• 基金项目：国家自然科学基金项目(No. 40810180,40921061);江苏省自然科学基金创新学者攀登项目(No. BK2009016)

• 李士杏
• 1. 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008;
  2. 中国科学院研究生院,北京 100049

• 骆永明
• 1. 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008;
  2. 中国科学院研究生院,北京 100049

• 章海波
• 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008

• 黄玉娟
• 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008

• 李柱
• 1. 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008;
  2. 中国科学院研究生院,北京 100049

• 韦婧
• 1. 中国科学院土壤环境与污染修复重点实验室(南京土壤研究所),南京 210008;
  2. 中国科学院研究生院,北京 100049

• 摘要：土壤固相由不同大小的土壤颗粒构成.研究砷在土壤不同粒级组分中的形态,有助于深入了解土壤中砷的生物有效性、移动性及其环境风险.本文以砷吸附能力很强的红壤为研究对象,采用传统化学提取法研究了砷在各粒级组分(50~250 μm,5~50 μm,1~5 μm和<1 μm)中的含量和形态,并采用X射线吸收近边结构(XANES)光谱法表征了不同铁氧化物对红壤砷吸附的贡献.结果表明:红壤粒级组分中砷含量随着粒径减小而增加.铁铝元素含量和颗粒比表面积是影响不同粒级组分中砷含量的主要因素.在各粒级组分中,仅有0.6%以下的砷以非专性吸附态存在,有25.0%~38.5%的砷以可被磷酸盐交换的专性吸附态存在,有31.0%~50.8%的砷以较稳定的铁铝氧化物结合态存在,稳定的残留态砷的比例为17.8%~40.2%.随粒径减小,粒级组分中铁铝氧化物结合态砷的比例减小,而残留态砷比例增加.X射线吸收近边结构(XANES)光谱的分析结果显示,1~5 μm和<1 μm的粒级组分中砷的形态类似,主要与针铁矿和无定形氧化铁相结合.

• Abstract：Solid phase soil is made up of particles of different sizes. Speciation of arsenic in particle-size fractions is useful to understand the bioavailability, mobility and environmental risk of arsenic. The present study focused on the red soil with high arsenic adsorption capacity. Total concentration and chemical fractionation of arsenic in particle-size fractions (50~250 μm, 5~50 μm, 1~5 μm and <1 μm) were investigated by acid digestion and sequential extraction procedure. X-ray absorption near edge structure spectroscopy (XANES) technique was used to study the contribution of different iron oxides to arsenic adsorption on soil particles. The results suggested that arsenic concentration increased as the soil particle size decreased. The concentrations of Fe and Al and the specific surface area of soil particles were main factors to influence the concentration of arsenic in different particle-size fractions. Among all particle-size fractions, non-specifically adsorbed arsenic accounted for less than 0.6%, while the specifically adsorbed arsenic which could be exchanged by phosphate varied from 25% to 38.5%. The stable form of arsenic species associated with Fe/Al hydroxides ranged from 31.0% to 50.8%. The most stable form of residual arsenic varied from 17.8% to 40.2%. As the particle size decreased, the proportion of arsenic associated with Fe/Al hydroxides decreased, and that of residual arsenic increased. Arsenic species were characterized using XANES spectroscopy. It showed that arsenic species were similar on 1~5 μm and <1 μm fractions, and arsenic was mainly adsorbed on ferrihydrite and goethite.

• Key words：arsenic  red soil  particle-size fraction  X-ray absorption near edge structure (XANES)

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