杭州龙井茶田土壤酸化过程分析

针对杭州龙井茶田土壤酸化趋势日益加重的现状，通过矿物表征、室内试验等技术方法，研究了茶田土壤酸性来源及产酸机制. 在茶田现场采集6组20个土壤样品及对应岩样，茶田土壤pH稳定在4左右；通过XRD和XRF对土壤样品和岩石样品中的化学成分和矿物成分进行测定，结果显示茶田土壤中的常规阳离子含量远低于全国土壤元素丰度值；土壤和岩样动态淋滤试验结果表明，土壤酸性类型为HNO₃和H₂SO₄，基岩风化过程中产生的Ca2+含量较大，且易发生淋溶，土壤成土后K+、Ca2+、Na+、Mg2+等盐基阳离子淋失快且淋失量大，是造成酸化的主要原因. 茶树在多年种植条件下，由于盐基阳离子淋失，使得土壤盐基饱和度降低，从而导致土壤缓冲能力降低，造成土壤酸化. 

Soil acidification process in Longjing tea field,Hangzhou

Increasing trend of soil acidification has been identified in Longjing tea field in Hangzhou. Therefore in this paper we studied the source of soil acidity and possible mechanism of acid production by mineral characterization and leaching tests. Six groups of 20 soil samples and 4 bedrock samples were collected from the tea fields. The pH value was determined by potentiometry, which was found to be stable at 4. XRD and XRF found conventional soil cations to be far lower than national soil element abundance. Dynamic leachings of soil and rock samples revealed acidity types of HNO₃ and H₂SO₄. Ca2+ content generated in the process of bedrock weathering was found to be relatively large and tended to leach from soil to water. Salinity cation leaching of K+, Ca2+, Na+ and Mg2+ was found to be fast and large after soil formation, which were likely the main causes of acidification. After planting tea trees for many years, the base cation leaching reduced soil base saturation, leading to reduction in soil buffer capacity therefore resulting in soil acidification.