Contamination and spatial variation of heavy metals in the soil-rice system in Nanxun County, Southeastern China.

Keli Zhao,Weijun Fu,Chaosheng Zhang,Zhengqian Ye

doi:10.3390/ijerph120201577

Abstract

There is an increasing concern about heavy metal contamination in farmland in China and worldwide. In order to reveal the spatial features of heavy metals in the soil-rice system, soil and rice samples were collected from Nanxun, Southeastern China. Compared with the guideline values, elevated concentrations of heavy metals in soils were observed, while heavy metals in rice still remained at a safe level. Heavy metals in soils and rice had moderate to strong spatial dependence (nugget/sill ratios: 13.2% to 49.9%). The spatial distribution of copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) in soils illustrated that their high concentrations were located in the southeast part. The high concentrations of cadmium (Cd) in soils were observed in the northeast part. The accumulation of all the studied metals is related to the long-term application of agrochemicals and industrial activities. Heavy metals in rice showed different spatial distribution patterns. Cross-correlograms were produced to quantitatively determine the spatial correlation between soil properties and heavy metals composition in rice. The pH and soil organic matter had significant spatial correlations with the concentration of heavy metals in rice. Most of the selected variables had clear spatial correlation ranges for heavy metals in rice, which could be further applied to divide agricultural management zones.

Highlights

With the rapid development of industry and increasing release of agrochemicals into the environment, the potential accumulation of heavy metals in agricultural soils has caused a growing public concern about food security worldwide [1]
The quality of rice greatly affects human health, as consuming rice contaminated by cadmium (Cd), lead (Pb) and other metals can seriously deplete body stores of iron (Fe), vitamin C and other essential nutrients, leading to decreased immunological defenses, impaired psycho-social faculties and disabilities associated with malnutrition [7]
The main objectives of this study were: (1) to characterize heavy metal concentrations and spatial patterns of surface soil and rice grains; (2) to study the spatial dependence and relationship of heavy metals in the soil-rice system; (3) to determine the soil properties influencing the availability of heavy metals to rice

Summary

Introduction

With the rapid development of industry and increasing release of agrochemicals into the environment, the potential accumulation of heavy metals in agricultural soils has caused a growing public concern about food security worldwide [1]. Recent rapid economic growth in China has led to an increasingly serious problem of heavy metal contamination in agricultural soils [5,6]. Rice (Oryza sativa L.) is one of the most important agricultural crops in China. The quality of rice greatly affects human health, as consuming rice contaminated by cadmium (Cd), lead (Pb) and other metals can seriously deplete body stores of iron (Fe), vitamin C and other essential nutrients, leading to decreased immunological defenses, impaired psycho-social faculties and disabilities associated with malnutrition [7]. It is of great importance to protect agricultural soils and ensure its sustainability.

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Conclusion