Distributive Characteristics and Relationship of Soil pH-value and Heavy Metal Content in Tobacco Leaves in Qujing Tobacco-planting Area

Taking 1427 soil samples and the corresponding 1427 flue-cured tobacco leaf samples from Qujing tobacco-planting area in the year 2010 as test materials,the distributive characteristics and relationships of soil pH-value and the contents of 5 heavy metal elements(As,Hg,Pb,Cd and Cr) in tobacco leaves were analyzed.The results indicated that:(1) The pH-value in the soil ranged from 4.28 to 8.37,and the soil samples with the pH-value which was within the most appropriate range for the growth of flue-cured tobacco accounted for 37.7% of the total soil samples.Among different types of soil,alluvial soil had the maximum coefficient of variation in pH-value;while yellow loam had the smallest one.(2) The maximum coefficient of variation was found in Cd content among five heavy metal elements,and the contents of five heavy metal elements in tobacco leaves all had the following order: lower leaf middle leaf upper leaf.(3) The contents of As,Pb,Hg and Cd in tobacco leaves all had obvious regressive relationship and correlation with the soil pH-value.The changes in the content of heavy metals in different parts of tobacco leaves were highly consistent with the changes in soil pH-value.Along with the increase in soil pH-value,the contents of As,Hg and Cr in tobacco leaves gradually decreased,and that of Pb and Cd gradually increased.