不同岩性背景区关键带土壤地球化学特征及生态风险

Soil geochemistry characteristics and ecological risks in critical zones of different lithologic backgrounds

以贵州普定陈旗流域和福建九龙江流域作为研究对象,比较两个不同岩性背景区土壤重金属和稀土元素的分布特征及其控制因素,探究了地球关键带土壤元素的地球化学循环过程和环境效应。结果显示,普定浅层土壤重金属Cr、Zn、Ni、Cu和Pb含量均高于九龙江流域,主要受淋滤作用和地质背景控制。普定土壤中大部分重金属在耕地、灌丛和弃耕地高于草地和次生林地,九龙江流域部分重金属含量在废弃茶园高于林地,与两个流域大气沉降和农业活动密切相关。普定土壤稀土含量(145~248 mg·kg^(-1))高于九龙江流域(51~173 mg·kg^(-1)),普定土壤稀土与喀斯特成土作用密切相关,而九龙江流域土壤稀土含量主要由成土母质决定。生态风险评估显示,普定土壤为轻微生态危害,九龙江流域林地也为轻微生态危害,而九龙江流域废弃茶园地表现出中等生态危害,重金属Cd生态风险较高。

We compared the distribution and influencing factors of heavy metals and rare earth elements in soils of Chenqi catchment in Puding, Guizhou and Jiulong River catchment in Fujian, China, and investigated the geochemical cycling processes and environmental effects of soil elements in both Earth’s critical zones. The results showed that Cr, Zn, Ni, Cu, and Pb contents in topsoils from Puding were higher than that from Jiulong River catchment, which were mainly associated with the leaching and geological background of the catchments. The contents of most heavy metals in cropland, shrub land, and abandoned cropland were higher than that in grassland and secondary forest in Puding, while the contents of some heavy metals in abandoned tea plantation were higher than that in forest in Jiulong River catchment. This may be related to atmospheric deposition and agricultural activities. The contents of rare earth elements in Puding soils(145-248 mg·kg^(-1)) were higher than that in Jiulong River catchment(51^(-1)73 mg·kg^(-1)), which was attributed to the formation process of karst soil in Puding and parent rock in Jiulong River catchment. Results of the ecological risk analyses showed low ecological risk in Puding soils and forest soils in Jiulong River catchment, while moderate ecological risk occurred in abandoned tea plantation in Jiulong River catchment, with a high ecological risk of Cd.