| Nowadays, there is an increasing concern for food safety. Rice is the most important agricultural crop in China. The quality of rice directly influences human health. With the rapid development of industrialization, urbanization and agricultural modernization, more and more heavy metals discharge to water, soil and atmosphere. Up to date, electronic waste has become a growing source of heavy metal pollution. It has made a serious threat to the ecological environment. Soil heavy metal contamination is especially dangerous due to its toxicity, non-biodegradability and persistence. Once the heavy metals are greatly accumulated in plant, it will not only seriously affect the growth of plants, but also pose potential threat to human health through food chain. Good production environment, is important to determine the safety of agricultural products. Therefore, the study for heavy metals in rice is of great significance. Heavy metal bioavailability and accumulation in paddy soils has been studied extensively,and most of the research is based on pot experiments. Field crop conditions are more complex and results are often different from pot experiment result. Little information is available on heavy metal accumulation in paddy fields at regional scales. Therefore, it is quite necessary to carry out some investigations on the contamination and relationship of heavy metals in the soil-rice system at a regional scale. The results will provide guidelines to distribution of rice plant and ensure the safety of agricultural products.In this study, a total of 90 pairs of soil and rice samples were collected from Wenling, Zhejiang Province. Geostatistical methods have been successfully applied to investigate the spatial variability of environment variables. Semivariogram, one of the geostatistical methods, combined with Moran’s I is considered a useful method to explore the spatial variation of Cd, Cu, Ni and Zn. The main results were summarized as follows:(1) Compared with the background values of soils in Zhejiang province and the Environmental Quality for Soil in China, the heavy metals were accumulated in paddy soils of the study area and some areas showed certain contaminate characteristic. However, the quality of the paddy soils in the study area met the requirement of crop production. According to the survey, e-waste dismantling activities and development of the industrialization, urbanization, chemical fertilizer and pesticide applying, is an important source of causing the accumulation of heavy metals in the soil.(2) The heavy metals in rice still remained at a safe level. However, some rice had been polluted by Cd, indicating that the study area has a certain potential health risks. Therefore, the positive measures should be taken into account to control soil heavy metal pollution in Wenling. The Cd, Ni concentrations in rice had a high variability coefficients,while Cu, Zn 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 index were used to identify the contaminated hotspots of these heavy metals, and display the spatial distribution.(3) Enrichment index(EI) was determined as a measure of the availability of heavy metals in soil and rice. The reasults showed that the enrichment capability of heavy metals in rice was generally in the order of Cd>Zn>Cu>Ni. Compared with other heavy metals, the stronger enrichment ability of Cd resulted in the high potential Cd risk in the study areas.(4) Rice geno-types and soil properties were also the important factors to influence the transfer and bioavailability of heavy metals in soil-rice system.It may pose a potential threat to local ecosystem and human health as a long-term effect. Therefore,the positive measures should be taken into account to control soil heavy metal pollution in Wenling,with an attempt to minimize local human exposure to heavy metals via food chain. |
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