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三峡库区丰都-忠县段消落带不同高程土壤镉及其形态的分布特征
钟志淋1, 邴海健1, 吴艳宏1, 祝贺1, 王晓晓2, 周俊1
1.中国科学院、水利部成都山地灾害与环境研究所;2.西华师范大学
摘要:
镉(Cd)是目前三峡库区消落带主要的污染物之一,其迁移和形态转化直接威胁水环境安全。选择库区丰都-忠县段消落带,按照高程差异分别于不同土地利用类型(农田、林地、果园和村庄)下采集土壤样品,利用化学连续提取法测定Cd的形态组成,探讨影响消落带土壤中Cd及其形态空间分布的关键因素。结果表明,消落带土壤中Cd的平均浓度为0.65 ± 0.04 mg/kg,可交换态及碳酸盐结合态是土壤中Cd的主要形态,占比达到41.21% ± 1.48%,残渣态和铁锰氧化物结合态次之,有机物及硫化物结合态占比最低。不同土地利用类型下消落带土壤Cd的浓度整体上不存在显著性差异(p < 0.05),表明当地人类活动对土壤Cd的直接贡献较弱。消落带土壤Cd及其形态的浓度与高程显著负相关(p < 0.05),且在160~165 m区域发生明显转变,水位变化导致的泥沙沉积可能是控制消落带Cd空间分布的主要因素。此外,土壤理化性质,尤其是细颗粒泥沙对Cd及其形态分布具有明显影响,将来需重点关注泥沙理化属性对Cd迁移及形态转化的影响。
关键词:  重金属  形态组成  土地利用类型  水位变化  三峡水库
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基金项目:中国科学院青年创新促进会项目
Distribution characteristics of soil cadmium along the altitude of riparian zone at the sections from Fengdu to Zhongxian in the Three Gorges Reservoir region
ZHONG Zhilin,BING Haijian,WU Yanhong,ZHU He,WANG Xiaoxiao,ZHOU Jun
The Key Laboratory of Mountain Surface Processes and Ecological Regulation,Institute of Mountain Hazards and Environment,Chinese Academy of Sciences
Abstract:
Cadmium (Cd) is one of the major pollutants in the water-level fluctuation zone of the Three Gorges Reservoir region. The migration and fraction transformation of Cd directly threat the safety of water environment. At the riparian zones from Fengdu to Zhongxian in the Three Gorges Reservoir, soil samples were collected according to altitudinal difference under four different land use types including farmland, woodland, orchard and residential zone. The fraction composition of Cd in the soils was determined by chemical sequential extraction, the key factors affecting the spatial distribution of Cd and its fractions in the riparian soils were deciphered. The results showed that the average concentration of Cd in the soil was 0.65 ± 0.04 mg/kg. The acid extractable fraction (41.21% ± 1.48%) of Cd was the dominant fraction in the soils, followed by residual fraction and reducible fraction, and the oxidizable fraction was the lowest. In general, the significant difference in the concentrations of Cd and its fractions in the soils under different land use types was not observed (p < 0.05), indicating slight local anthropogenic contribution to Cd in the riparian soils. Both the concentration of Cd and its fractions in the soils showed a significant negative correlation with altitude (p < 0.05), and their concentrations had a marked change at the altitude of 160-165 m. This indicates that sediment deposition caused by water-level fluctuation may be the main factor controlling the spatial distribution of Cd in the riparian soils. The physicochemical properties of soils, especially the fine particles, induce an important influence on the spatial distribution of Cd in the riparian soils. Further research should be focused on the effects of sediment properties on the migration and fraction transformation of Cd in the riparian soils.
Key words:  Heavy metal  fraction composition  land use type  water-level variation  Three Gorges Reservoir
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