Content and Bioavailability of Hg in a Soil–Tea Plant System in Anxi Area, Southeast China

Abstract

Many studies on the bioavailability of Hg in soil–plant systems have been conducted. However, studies on the soil–tea plant system are still limited. In this study, we collected soil and tea leaf samples from 69 tea gardens in the Anxi area in China. We investigated the Hg contents in tea leaves and soil, and the bioavailability of Hg from soil to tea leaves. The results showed the following: (1) The Hg content in soil was equivalent to the background value in Fujian province and was 2.6–2.9 times higher of the national background value in China. For different geological backgrounds, the Hg contents differed. In addition, we found a negative correlation between the total Hg content and pH value (r = −0.196) and a positive correlation between total Hg and soil organic carbon (SOC) content (r = 0.116) in surface soil. (2) Compared with young leaves, Hg content in older leaves was higher. The transfer factor (TF) of Hg from soil to tea leaves ranged from 0.25% to 24.76%. (3) The correlation between Hg content in tea leaves and total Hg content in soil was not statistically significant. However, we found a statistically significant positive correlation between the Hg content in tea leaves and the extracted amount of Hg both in surface and subsurface soil. The SOC and pH value were also statistically significantly positively correlated with the Hg content in tea leaves. Our findings show that the Hg content in tea leaves does not only depend on the total Hg content in soil: it is also affected by other factors.