不同耕作方式下土壤—川芎系统中镉、铅的累积特征及污染评价

Assessment of Accumulation Characteristics and Pollution of Lead and Cadmium in Soil-Ligusticum chuanxiong System Under Different Tillage Methods

为了研究耕作方式对川芎不同部位重金属含量的影响以及探明道地产区川芎栽培环境的质量,为川芎药材的优质生产提供理论依据,以彭州川芎种植区的菜—药、稻—药(翻耕)、稻—药(免耕)和旱地(未种过川芎和蔬菜)种植方式下的土壤为研究对象,采用污染指数法、地积累指数法和富集因子法对4种耕作方式下的土壤Cd、Pb污染状况和土壤—川芎系统中Cd、Pb的富集特征进行了探讨。结果表明:川芎种植土壤未受Pb污染,但存在不同程度的Cd污染。菜—药种植方式下土壤Cd、Pb含量显著高于其他3种方式,且Pb含量具有随土壤pH增大而降低的趋势,依次为菜—药>免耕>免耕>旱地。川芎根茎和叶片中Cd的含量基本符合WM/T2—2004标准要求(除菜—药方式外),均表现为菜—药>免耕>免耕>旱地;根茎和叶片中的Pb含量均超标,平均含量分别为6.16 mg/kg和8.63 mg/kg,具有随土壤pH增加而增大的趋势。川芎叶片对Cd、Pb的富集能力上均大于根茎且对Cd的富集大于Pb。

In order to clarify the effect of different tillage methods on heavy metal content in different parts of Ligusticum chuanxiong, four types of soil with different previous crops as vegetable-herb, rice-no tillage, rice-conventional tillage and dry land（with other crops） were studied to explore characteristics of cadmium（Cd） and lead（Pb） accumulation in soil- Ligusticum chuanxiong system and the pollution status. Three evaluation methods, including Nemerow index（P） method, geo-accumulation index（Igeo） method and enrichment factor （EF） method, were adopted in the study. The results showed that the current situation of soil was out of danger by Pb but in danger by Cd in varying degrees. Contents of Cd and Pb in soil were significantly different in vegetable-herb planting pattern than in the other three planting patterns, and contents of Pb had a decreasing tendency with the increase of soil pH value. The content of Pb in the four planting patterns showed an order as vegetable-herb rice-no tillage rice-conventional tillage dry land. Contents of Cd in Ligusticum chuanxiong rhizomes and leaves were up to the standard of WM/T 2-2004（except in vegetable-herb pattern）,showed an order as vegetable-herb 〉rice-no tillage 〉rice-conventional tillage 〉dry land. Contents of Pb exceed the standard with average concentration of 6.16 mg/kg in rhizomes and 8.63 mg/kg in leaves, and increased with the rise of soil pH value. Among different parts of Ligusticum chuanxiong, the leaves had a higher enrichment capacity of Cd and Pb than the rhizomes, the herb has a higher enrichment capacity of Cd than Pb, too.