土壤-水稻系统重金属空间异质性研究——以浙江省嵊州市为例

在嵊州农产品产地共采集94对土壤-水稻样品,研究重金属在土壤-水稻系统的污染特征及空间异质性.结果表明,土壤重金属Cd、Cu、Ni、Pb和Zn的平均含量分别为0.20、28.64、27.03、38.51和98.74mg/kg,与背景值相比较,这些重金属在研究区均有不同程度的累积,局部污染严重,但是水稻重金属没有超过国家规定的食品安全标准,仍处于安全水平.土壤重金属Cd、Cu、Ni、Pb和Zn都属于中等程度变异,其变异系数分别为45.00%、46.65%、81.54%、18.07%、32.47%.地统计学和局部Moran's I指数结果可识别出这五个重金属的污染分布情况.土壤Cd、Cu、Ni和Zn的空间分布较为相似,基本为东西部含量较低,中部较高,这与工业活动和其他的人为活动有关.土壤-水稻系统重金属的迁移、吸收主要受土壤重金属含量和土壤理化性状的影响.从长远来看,重金属污染对当地生态和居民健康仍有潜在的威胁.

Heavy metal contamination in soil-rice system and its spatial variation in Shengzhou City

There was a total of 94 pairs of soil and rice samples were collected from Shengzhou, Zhejiang Province. The results indicated that the mean soil concentrations of five heavy metals including Cd, Cu, Ni, Pb and Zn were 0.20, 28.64, 27.03, 38.51 and 98.74mg/kg, respectively. Compared with the National Guidelines, the heavy metals were enriched in paddy soils of the study area. Part of paddy farmland was seriously contaminated by heavy metals in Shengzhou city. However, the heavy metals in rice still remained at a safe level. The Cd, Cu, Ni, Pb, Zn concentrations in paddy soil had a moderate variability coefficients of 45.00%, 46.65%, 81.54%, 18.07%, 32.47%, respectively. Kriging interpolation and the Local Moran's I were used to identify the contaminated hotspots of these five metals. It was found out that the soil Cd, Cu, Ni, Zn had a very similar spatial pattern-higher concentrations located in the middle part of the study area while relatively lower levels in the eastern and western regions, which could be attributed to industrialization and other anthropogenic activities. The accumulation and bioavailability of heavy metals in the soil-rice system may be influenced by both soil heavy metal concentrations and soil physico-chemical properties. It may pose a potential threat to local ecosystem and human health as a long-term effect.