| The history of tea planting dates back to two thousand years ago in Ya’an. With the rapid development of economy and the increasing growth of population, the negative effects on environment caused by environmental pollution and ecocide through human behaviour have been got more and more attention. The ecological environment of some tea-producing areas has been destroyed, resulting in the heavy metal content exceed the standard in tea, people pay more and more attention to tea security. Therefore, The surveys and research on heavy metal content of Ya’an tea garden’s soil,fresh tea leaves and commodity tea, not only provide a scientific reference for constructing of the green tea and organic tea base, but also provide a scientific basis for improving the quality of Ya’an tea and evaluate the quality of tea.Based on the consumer survey, the eight heavy metals were analysed in tea gardens’ soil,fresh tea leaves and commodity tea from the main tea-producing region of Ya’an; The tea and soil’s pollution situation and the health risks of commodity tea were evaluated by the national standards.The single contamination index method,synthetical index method,Muller’s index method and enrichment index method were used.Researched on the correlation of pH and heavy metals in soil, the correlation between heavy metals in soil, the heavy metals enrichment capability of fresh leaves from soil, the heavy metals relevance of the fresh leaves-soil. Study reached the following conclusions:(1) The consumer survey of tea, determination and assessment the pollution of heavy metal in siol-fresh tea leaves-the commodity tea.Through the consumption survey of Ya’an tea showed that the main consumers drunk green tea with 4 times a week, aged from 20 to 50 years. we assumed lOg/d for drinking based on the health risk model.Ya’an tea gardens soil’s pH ranged of 4.0 to 5.7 which was suitable for the growth of tea trees. The average content of heavy metals in soil was belowe the non-pollution tea soi’sl environment quality standards, the quality of Ya’an tea’s soil reached the national secondary standards. But Hg, Cd, As, Zn, Cr and Ni in Baoxing soil were the highest levels among all regions.The research on the fresh tea leaves showed that the total amount of Hg was low. The content of Pb, Cd, As in fresh tea leaves were highest in Baoxing,we should pay more attention to the soil pollution in Baoxing.The content of Pb, Cd, As, Cu, Cr were belowe the national limits quality standard in commodity tea, The content of Pb in Tianquan one sample site detected 5.705 mg/kg,which was beyond the limits (5 mg/kg). Compared to tea quality grading standards,6 sites were reached the national firstly standards by used the single contamination index method.The result indicated the values of pollutants was closed to the background value or slightly higher.In general, the whole Ya’an’s tea has less pollution and hold a good quality.The six counties daily intake of heavy metals volume was much lower than recommended of the U.S. EPA by reference the average body weight and tea intakes intake. The investigation of individual counties’HRI and THQ were significantly less than 1, showed the commodity tea was no health risk for the population.(2) The tea planting soil’s pH effected on heavy metals and interaction.The correlation analysis between heavy metals in soils and pH showed that Hg with pH was significantly correlated(P<0.01), and Hg was negatively correlated in all areas; Pb, As were negative correlated with pH; Cu, Cd, Cr, Ni, Zn was positively correlated with pH.The correlation analysis between soil heavy metals, Cu-Cr-Zn-Ni showed a extreme significant positive correlation (P<0.01), a synergistic effect; Cd-Pb showed a significant positive correlation (P<0.05), a synergistic effect; while the relationship between As, Hg and other heavy metals was not significant.(3)The tea planting soil’s heavy metals effeced on fresh leaves.The study of the fresh tea leaves, the content of eight kinds of heavy metals:Zn> Cu> Pb> Ni> Cr> As> Cd> Hg. According to the enrichment factor, fresh tea leaves enrich heavy metals’capability:Cd> Cu> Zn> Ni> Hg> Pb> As> Cr. The strong enrich capability was on Cd which was 100% in Baoxing, the biggest difference of enrichment factor about eight elements in 6 counties was Cd.The content of Cr was the biggest differences between fresh tea leaves and soil among the eight elements, Cr was the minimum enrich coefficient.The correlation analysis between fresh tea leaves and soil, the correlations of Cd, Cu, Hg in fresh tea leaves and soil was extreme significantly correlated (P<0.01),Cd was positively correlated, Cu, Hg were negatively correlated. The correlations of Ni in fresh tea leaves and soil was significantly positive correlated (P<0.05). Pb, Cr were negative correlation but no significant; As and Zn were positively correlated but no significant. |
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