Abstract:
The content and distribution of lead (Pb) in the soil and parts of a tea plant from 8representative tea plantations in central Fujian were determined using theinductively coupled plasma mass spectrometry (ICP-MS). Correlations among thesoil physiochemical properties were studied. A preliminary assessment on thehealth risk of Pb in the brewed tea made from theplants grown in the same areas were conducted according to the method of targethazard quotient (THQ) to arrive at the proposed safety limits of Pb in tea leavesand plantation soil. In the soil, the average Pb content wasfound to be 82.91 mg·kg
-1, which was 2.38 times higher than the standardfor the province, indicating a substantial accumulation of the metal ion in theregion. The average available Pb in soil was15.20 mg·kg
-1 and the activation rate of Pb was 17.57 %. The Pbpollution indices of the plantation soils ranged from 0.40 to 4.05, averaging1.18, with two specimens scored beyond the national standards. On the teaplants, the amount and enrichmentcoefficients of Pb differed in different tissues that generally ranked in theorder of lateral roots>main stem>taproot≈side-stems>oldleaves>young leaves. It appeared that most of the Pb absorbed by a tea planttended to accumulate in the roots and stems, and that the Pb uptake in theleaves, which are the raw material made into teas, might not exceed the safety limitunder normal conditions. The Pb contents in the old leaves, side-stems, and mainstem of a plant correlated significantly or extremely significantly with the total and available Pb in soil .The total available phosphorus inverselycorrelated with the available Pb, Pb in the tea organs, Pb enrichmentcoefficient, and Pb transfer coefficient in soil. The average Pb content in thebrewed tea was 22.84 μg·L
-1, which was well below the safety standardfor drinking water (GB5749-2006). As the solubility of Pb in water being 20.98%,the target THQ for brewed tea being 2.06×10
-2, and that for tea leaves being 1.07×10
-1 (which are one to two order of magnitudelower than those for safety standards), only minimal risk for personalconsumption was expected. Nonetheless, when the Pb content in tea leaves was upto 82.36 mg·kg
-1 or the daily tea drinking reached 550.98g, the risk index will be greater than 1,and a risk on human health may become a realistic concern.