Transfer of metals from soil to vegetables in an area near a smelter in Nanning, China

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Abstract

A field survey was conducted to investigate the metal contamination in soils and vegetables, and to evaluate the possible health risks to local population through foodchain transfer near a smelter in Nanning, southern China. Contamination levels in soils and vegetables with cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) were measured, and transfer factors (TF) from soils to vegetable plants and its health risk (risk index, RI) were calculated accordingly. Results showed that both soils and vegetables from villages 1 and 2 (V1 and V2, 1500 m and 500 m from the smelter) were heavily contaminated, compared to a village 50 km from the smelter. Geometric mean of Cd and Pb concentrations in vegetables for V1 and V2, respectively, were 0.15 and 0.24 mg Cd kg−1 and 0.45 and 0.38 mg Pb kg−1 (on fresh weight basis). Oral intake of Cd and Pb through vegetables poses high health risk to local residents. Risk indices for V1 and V2, respectively, were 3.87 and 7.42 for Cd, and 1.44 and 13.5 for Pb. The complexity of metal contamination and their health risks are also discussed.

Introduction

The accumulation of heavy metals and metalloids in agricultural soils is of increasing concern due to the food safety issues and potential health risks as well as its detrimental effects on soil ecosystems (McLaughlin et al., 1999). It also poses potential barriers for international trading of foodstuffs. Regulatory frameworks and guidelines for heavy metals in the environment and foodstuffs have been developed in many countries around the world, such as Australia and New Zealand (McLaughlin et al., 2000). Sources of heavy metals in soils mainly include natural occurrence derived from parent materials and human activities (anthropogenic sources). Anthropogenic inputs are associated with industrialization and agricultural activities such as atmospheric deposition, waste disposal, waste incineration, urban effluent, vehicle exhausts, fertilizer application and long-term application of sewage sludge in agricultural land Bilos et al., 2001, Hlavay et al., 2001, Koch and Rotard, 2001, McLaughlin and Singh, 1999, McLaughlin and Hamon, 2000.

Soil-to-plant transfer of heavy metals is the major pathway of human exposure to soil contamination. Health risk due to soil contamination with single heavy metal has been widely studied. For example, lifetime exposure to low level soil contamination with cadmium (Cd) has shown to cause renal dysfunction in residents living near the contamination sites in Japan (Ryan et al., 1982) and China Cai et al., 1990, Nordberg et al., 1997, Watanabe et al., 1998, Watanabe et al., 2000, Jin et al., 2002. However, in the reality, multiple contaminants often co-exist in the environment and health risk estimated on the basis of single contaminant may not be sufficient to predict the risk for mixed contaminants.

In this study, we conducted a dietary survey and collected samples of blood serum, urine, vegetables and soil in a multiple-metal contaminated area at Pingyang, near a smelter in Nanning, a city in southern China. The aim was to evaluate the potential health effect of metal polluted soil on the people in Pingyang through vegetable consumption. We determined cadmium, lead, iron, zinc, calcium and copper in all sample and also estimated indicators of renal dysfunction.

Section snippets

Study area

The study area was located near a smelter in the suburb of Nanning, the Capital of Guangxi Province in southern China. The smelter was established in 1965, producing 12 000 t of lead (Pb) and 4000 t of antimony (Sb) every year and dumping solid waste near to arable land. Two villages with metal contamination were selected in the area; village 1 (V1) was 1500 m and village 2 (V2) was 500 m from the smelter. As a reference uncontaminated area, village 3 (V3) was 50 km from the smelter in the same

Metals concentration in soils and vegetables

The geometric mean soil Cd concentrations in V1 and V2 were 0.87 and 22.06 mg kg−1, respectively, which were significantly higher than in the control village (V3, 0.12 mg kg−1), and soil Cd concentration in V2 was higher than in V1 (Table 1). Higher Cd concentration in V2 was probably due its shorter distance from the smelter (Fig. 1), therefore more atmospheric deposition. Concentrations of other metals in soils except Fe showed the similar trend between villages, there was no significant

Discussion

Soil contamination with metal mixtures is receiving increasing attention from the public as well as governmental agencies, particularly in developing countries (Yanez et al., 2002). Principally, there are two major pathways for human exposure to soil contamination: soil–plant–human (food chain pathway) and soil–human (incidental soil ingestion) pathways. In this study, we focus our attention on the foodchain pathway. Results presented here showed that in V1 and V2 both soils and vegetables were

Acknowledgements

This research was financially supported by the Natural Science Foundation of China (project numbers 20207012 and 40225002) and Ministry of Science and Technology (2002CB410808). We thank the two anonymous referees for their constructive comments.

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