Heavy Metal Pollution Characteristics and Ecological Risk Analysis for Soil in Tea Core Plantations of Xinping County

Purposes To study the characteristics and sources of heavy metals, and to evaluate their ecological risk and early warning of tea plantations soil in Xinping County.

Methods We collected 30 samples of soil mixture to evaluate the heavy metal pollution and ecological risk of tea plantations soil in Xinping County by the pollution load index (PLI), potential ecological risk index (RI) and the ecology risk warning index (I_ER).

Results The average values of Cd, Pb, Hg, As, Cr, Cu and Zn in the soils were 0.11, 58.14, 0.142, 12.24, 83.01, 32.61 and 67.97 mg/kg, respectively; Hg, Cr and Pb concentrations were as 2.60, 1.15 and 1.11 times as the background values of soil in Yunnan Province, were mainly affected by human activities. But their concentrations were all lower than the threshold values II of the National Environmental Quality Standard for Soil (GB 15618—1995). Each single contamination factor (C_fⁱ) revealed that the level of heavy metal pollution in the soils was in order of Hg>Cr>Pb>As>Cd>Zn>Cu, Hg pollution was of moderate level while Cr and Pb pollution were slight. The average PLI was 0.81, there was no soil pollution caused by heavy metals. The sequence of potential ecological risk of heavy metal was Hg>Cd>Pb>Cr>Zn>Cu>As. The integrated factor RI of heavy metal pollution in the soils was 28.07, suggesting a low ecological risk. The RI of tea plantation soils in 8 villages or towns was in order of Jianxing Village (35.7)>Pingzhang Village (35.2)>Mosha Town (31.3)>Zhelong Village (25.2)>Gasa Town (25.1)>Shuitang Town (22.13)>Pingdian Village (22.07)>Xinhua Village (19.4). The average value of the soilI_ER was −4.36, which belonged to the no warning. Hg was the heavy metal element with the highest ecological risk level, the contribution of soil PLI, RI and I_ER in the research area was very large.

Conclusions The potential ecological risk analysis suggested a slight risk to local ecosystem originated from heavy metal contamination in the soils of tea plantation in Xinping, which belonged to the no-warning situation, and could develop high quality agriculture while maintaining the original ecological environment.