粤东凤凰山茶区土壤镉赋存形态特征及茶叶有效性

通过对粤东凤凰山茶区12个大型茶园土壤和茶叶进行采样,采用连续提取法将茶园土壤Cd分为可交换态、碳酸盐结合态、铁锰氧化物结合态、有机束缚态和残渣态,探讨了茶园土壤Cd的5种化学形态组成特征及其与土壤理化性质和茶叶Cd积累的关系。结果表明:(1)茶区土壤中镉的化学形态分布受到土壤pH值和有机质含量的影响,土壤中Cd的5种化学形态分布的规律为:残渣态>碳酸盐结合态>可交换态>铁锰氧化物结合态>有机束缚态;茶区土壤可交换态Cd和残渣态Cd与土壤中的pH值呈极显著负相关性关系,而有机结合态Cd与土壤pH值呈显著正相关关系;有机质含量与氧化物结合态Cd和有机束缚态Cd呈显著正相关关系,而与可交换态Cd和残渣态Cd呈显著负相关关系。(2)茶叶中Cd含量在0.30~0.98mg/kg,平均含量为0.65mg/kg;茶叶中的Cd含量与土壤中可交换态Cd有显著正相关关系,而与土壤pH值呈显著负相关关系。因此,可以通过调节茶园土壤pH值,影响土壤中Cd的化学形态分布,最终达到降低茶叶中Cd含量,提高茶叶品质的目的。

Distribution Characteristics and Tea Leaf Bioavailability of Cd in Tea Garden Soil from Fenghuang Mountain of East Guangdong Province

The content and fractions of Cd in tea garden soils,and their relationships with soil properties and Cd content in tea leaves were studied.The tea garden soils samples from 12tea gardens were collected from Fenghuang Mountain in east of Guangdong Province.The result showed that the distribution of chemical fractions of Cd in the tea garden soils were:residual-Cd>carbonate-Cd>exchangeable-Cd>Fe/Mn oxides-Cd>organic-Cd.Soil pH value showed significant negative relationships with exchangeable-Cd and residual-Cd,while it showed a significantly positive correlation with organic-Cd.Soil organic matter was positively correlated with Fe/Mn oxides-Cd and organic-Cd,while it was negatively correlated with residual-Cd and exchangeable-Cd.The Cd content in tea leaves was 0.30~0.98mg/kg,and 0.65mg/kg in average.Moreover,a significantly positive correlation was found between the Cd content in tea leaves and exchangeable-Cd,while significantly negative correlation was found between Cd content and soil pH value.In conclusion,the content of Cd in soil and tea leaves in Fenghuang Mountain was not exceed the relevant standards,and the Cd chemical form of soil was mainly influenced by soil pH value and organic matter.This study highlight that Cd content in tea leaves can be adjusted by adjusting soil pH value and the organic matter,by doing this,the quality of tea can be improved.