广西西江流域土壤镉含量特征及风险评估

Accumulation of Cd and Its Risks in the Soils of the Xijiang River Drainage Basin in Guangxi

为了解广西西江流域土壤Cd含量分布特征及风险,结合土地利用方式进行大规模抽样调查,采集有色金属矿区土壤、农田土壤(水田土壤和旱地土壤)和自然土壤共2 512个样品,测试其Cd含量.结果表明,西江流域土壤Cd的背景值为0.514mg·kg^(-1),显著高于前人研究结果(0.148 mg·kg^(-1))和广西土壤背景值(0.267 mg·kg^(-1));旱地、水田、矿区土壤Cd含量分别为0.559、0.787、5.71 mg·kg^(-1),水田土壤和矿区土壤Cd含量显著高于自然土壤;以西江流域土壤Cd含量背景值和基线值为限定值,超标率分别为51.2%、66.7%、77.8%和35.2%、39.6%、71.4%,矿区土壤和农田土壤都有明显的Cd积累趋势;从土壤Cd空间分布及污染特征来看,西江流域总体土壤Cd含量为0.726 mg·kg^(-1),高Cd含量斑块主要集中在西江流域上游河池地区的南丹县、大化县、都安县、环江县和宜州市,以及柳江县、武宣县和象州县等地区,这些地方出现了重度甚至极重度污染、中等-强污染累积程度和高等-极高等潜在生态风险.总体上,广西西江流域上游地区的农业土壤、矿区土壤Cd污染问题突出,属于高Cd风险区域,土壤生态状况不容乐观,这主要与上游矿业密集区的矿业活动和地质高背景Cd有关,长期居住在矿区及周边地区的居民,以及食用这一区域生产的农产品,可能对部分当地居民的健康产生危害.建议进一步通过土壤-植物-人体体系展开镉风险评估,同时采取相应措施以控制风险.

To understand the distribution and risk of soil cadmium（ Cd） in the Xijiang River drainage basin in Guangxi,a total of2512 soil samples were collected nonferrous metal mining area,farmland（ paddy soils and dryland soils） and the background soils,in the Xijiang River drainage basin in Guangxi. The results showed that Cd concentration was 0. 514 mg·kg^-1 in background soils significantly higher than previously resulted（ 0. 148 mg·kg^-1） and that in Guangxi background soil（ 0. 267 mg·kg^-1）. The geometric average concentration of Cd in dryland soils,paddysoils and mining soils was 0. 559,0. 787,5. 71 mg·kg^-1,respectively,which were significantly higher than background soils. The Cd concentration exceeded the background soils and baseline by 51. 2% and 35. 2% in dryland soil,66. 7% and 39. 6% in paddy soil,77. 8% and 71. 4% in mining soil,high Cd concentration occurred in the Nandan County,Dahua County,Duan County,Huanjiang County and Yizhou City,as well as Liujiang County,These regions have developed severe and even extremely serious pollution,medium-high pollution accumulation and higher-extremely high potential ecological risks.The Cd-pollution in soils in agricultural and mining soils in upstream of Xijiang River in Guangxi is serious,due to mining activities and high Cd geological background. People in the mining area and surrounding areas who live on local crops,vegetables,may expose to the Cd-pollution. It is recommended to further develop a Cd risk assessment through a soil-plant-human system,taking appropriate measures to control risk.