Objective The aims were to understand the status of heavy metal pollution in the Tieguanyin tea garden soils of Anxi County, in order to provide a scientific foundation for the health evaluation of tea garden soils.

Method A total of 111 soil samples were collected from tea gardens across 23 towns in Anxi County to investigate the concentrations of eight heavy metals: arsenic (As), mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb), copper (Cu), zinc (Zn), and nickel (Ni). The degree of contamination was assessed by comparing the measured concentrations against the national standard, the "Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land (GB 15618-2018)", as well as the local soil background values of Fujian Province. Pollution risks were evaluated using the single-factor pollution index and the Nemerow comprehensive pollution index. Furthermore, a non-carcinogenic health risk model was employed to assess potential health impacts, and principal component analysis (PCA) was conducted to identify the potential sources of these heavy metals.

Result Although the average concentration of all elements was lower than the national risk control standards for agricultural land, the mean levels of As, Hg, Cd, Pb and Zn showed enrichment by exceeding the background values for Fujian Province. Except Pb, the average value of the single factor pollution index of the other 7 kinds of heavy metals was less than 0.7, and the average value of the comprehensive pollution index was 0.62, which indicated that 72.97% of the soil quality grade of the tea garden was safe. Hg and Cd were the elements with the highest potential ecological risk, with 49.55% and 29.73% of the samples in the medium high risk, respectively. The average value of the comprehensive potential ecological risk index was 112.50, and the soil heavy metals were in the medium risk. The non-carcinogenic health risk index of heavy metals was far less than 1, so the risk of non-cancer diseases of local residents was small because of heavy metals in tea garden soil. But there is a carcinogenic risk that the human body can tolerate, and Cr is the main element that increases the carcinogenic risk. The results of principal component analysis showed that Cr, Cu and Ni mainly came from soil parent materials (contribution rate 30.91%), Cd, Pb and Zn mainly came from traffic pollution (contribution rate 24.09%), and As and Hg mainly came from agricultural production activities (contribution rate 14.04%).

Conclusion In Anxi County, the heavy metal concentrations in tea garden soils generally comply with agricultural land safety standards. Nevertheless, anthropogenic enrichments of As, Hg, Cd, Pb, and Zn are observed, necessitating concern over their long-term accumulation. An assessment reveals a moderate ecological risk, predominantly driven by Hg and Cd. Although no significant health risk is currently identified, ongoing monitoring of the dynamics of these highly enriched elements is crucial. Source apportionment indicates that parent materials, traffic emissions and agricultural activities are the main pollution sources, highlighting the need for targeted management strategies for traffic and agricultural sources.