Zn, Ni, Mn, Cr, Pb and Cu in soil-tea ecosystem: The concentrations, spatial relationship and potential control.

Excessive accumulation of heavy metals in tea has certain health risk to the consumers. To discuss the spatial relationship between heavy metals in tea leaves and soil in a county scale, 74 samples of tea leaves and corresponding subsoil (15-30 cm) were collected in the tea plantations of Lishui, Nanjing, China. The total Zn, Ni, Mn, Cr, Pb and Cu in both tea leaves and soil samples, as well as pH value in soil were analyzed. The results of regression showed that the Mn and Cr in tea leaves were increased when the Mn and Cr in soil were at high levels, and higher pH decreased Zn, Ni, Mn and Cu contents in tea leaves. Moreover, distance to village and metal industry had negative impacts on the Mn level in soil. It is necessary to control the pH of soil in tea plantations which are close to villages or metal industries, as well as, to search more appropriate areas, where are far away from villages or metal industries, to plant tea should be taken into consideration. In addition, 17.57% of the samples have higher concentration of Pb than the maximum limits was found in tea plantation of Lishui. Heavy metals (Cr) standards regarding leafy vegetables is used for reference in this study, as there are no maximum levels of contaminants (MLC) in tea. It is significant to construct a targeted standard of heavy metals contents that could applicable throughout the world for reduce the health risks to the consumers.