| The environmental quality of tea garden is very important to tea safety. With the growth of economic and population, the tea economy is developed rapidly. But at the same time, Suzhou tea garden environment is at the risk of pollution. It has great significance for protection of Suzhou agriculture environment and continuance of Suzhou tea production by strengthening the study and research of Suzhou tea garden soil and heavy metal content of tea.Heavy metal contents in soils of tea gardens, marketed made tea samples and tea plants were analyzed. Their contents were then compared to standards of Non-pollution Tea Codes and Organic Tea Codes respectively. The correlation of heavy metal contents among the soil, made tea samples and different organs of tea plants were evaluated. Spatial variability of Pb contents in soil of two areas was further analyzed by GIS software via Kriging interpolation.The results of the present study are given as follows:(1) The average contents of heavy metals in the tea products were lower than the magnitudes given by the Organic Tea Code. But the Pb content of some samples were close to, though still less than, the critical value given by the code.(2) There were obvious differences of heavy metals content in different organs of tea plant. The contents of Zn, Cu and Ni were highest in new shoots. The contents of Cd, Cr and Pb had the highest values in the branches. The content of As was highest in old leaves. The contents of Cd, Cr, Pb and As in the roots had the second highest values.(3) Generally speaking, the heavy metal contents of tea garden soils in the study area were at low levels compared to the permitted values given by the Codes. The comprehensive pollution index was between 0.2758 and 0.7130, averaged at 0.4738. The comprehensive pollution indexes of a few samples were close to or even higher than the critical standard.(4) There were significant positive correlations between the contents in the soil of Cd with Zn and Pb, Zn with Cu, Ni with Cu, Cr and As. The content of Ni had significantly negative correlation with that of Pb. The pH had no correlation with the heavy metals contents. Principal component analysis showed that the heavy metals in soil of study area can be separated into two group by PC loads, which was explained as their contents being influenced mainly by two factors, the soil parent material for elements Ni, Cu, Cr, Zn and As; and the effect of human activities for Cd and Pb.(5) The variation coefficients of the heavy metals content in study area were Pb>Cd>As>Ni>Cu>Zn>Cr. The variation coefficient of Pb content was the highest. In the whole study area the Pb content was 4.51~66.0 mg/kg, it also had a strong spatial correlation.(6) The maps of Pb contents in soils from area A and area B were drawn by Kriging interpolation. In area A, the Pb content had a lower level and gradually decreased from center to milieu. The range of high-value points was 16~20mg/kg. In area B, the Pb contenr was lower in southeast-northwest and higher in northeast-southwest. The high-value points concentrated in northeast and southwest, and its range was 20~29 mg/kg. |
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