Elsevier

Food Chemistry

Volume 111, Issue 4, 15 December 2008, Pages 811-815
Food Chemistry

Heavy metal accumulation in vegetables irrigated with water from different sources

https://doi.org/10.1016/j.foodchem.2008.04.049Get rights and content

Abstract

The present study was carried out to assess levels of different heavy metals like iron, manganese, copper and zinc, in vegetables irrigated with water from different sources. The results indicated a substantial build-up of heavy metals in vegetables irrigated with wastewater. The range of various metals in wastewater-irrigated plants was 116–378, 12–69, 5.2–16.8 and 22–46 mg/kg for iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn), respectively. The highest mean levels of Fe and Mn were detected in mint and spinach, whereas the levels of Cu and Zn were highest in carrot. The present study highlights that both adults and children consuming vegetables grown in wastewater-irrigated soils ingest significant amount of these metals. However, the values of these metals were below the recommended maximum tolerable levels proposed by the [Joint FAO/WHO Expert Committee on Food Additives (1999). Summary and conclusions. In 53rd Meeting, Rome, June 1–10, 1999]. However, the regular monitoring of levels of these metals from effluents and sewage, in vegetables and in other food materials is essential to prevent excessive build-up of these metals in the food chain.

Introduction

Industrial or municipal wastewater is mostly used for the irrigation of crops, mainly in periurban ecosystem, due to its easy availability, disposal problems and scarcity of fresh water. Irrigation with wastewater is known to contribute significantly to the heavy metals content of soil.

Heavy metals are very harmful because of their non-biodegradable nature, long biological half-lives and their potential to accumulate in different body parts. Most of the heavy metals are extremely toxic because of their solubility in water. Even low concentrations of heavy metals have damaging effects to man and animals because there is no good mechanism for their elimination from the body. Nowadays heavy metals are ubiquitous because of their excessive use in industrial applications. Wastewater contains substantial amounts of toxic heavy metals, which create problems (Chen et al., 2005, Singh et al., 2004). Excessive accumulation of heavy metals in agricultural soils through wastewater irrigation, may not only result in soil contamination, but also affect food quality and safety (Muchuweti et al., 2006).

Food and water are the main sources of our essential metals; these are also the media through which we are exposed to various toxic metals. Heavy metals are easily accumulated in the edible parts of leafy vegetables, as compared to grain or fruit crops (Mapanda, Mangwayana, Nyamangara, & Giller, 2005). Vegetables take up heavy metals and accumulate them in their edible (Bahemuka & Mubofu, 1991) and inedible parts in quantities high enough to cause clinical problems both to animals and human beings consuming these metal-rich plants (Alam, Snow, & Tanaka, 2003). A number of serious health problems can develop as a result of excessive uptake of dietary heavy metals. Furthermore, the consumption of heavy metal-contaminated food can seriously deplete some essential nutrients in the body causing a decrease in immunological defences, intrauterine growth retardation, impaired psycho-social behaviour, disabilities associated with malnutrition and a high prevalence of upper gastrointestinal cancer.

The present study was conducted with an aim to compare the heavy metals (copper, manganese, zinc and iron) accumulation potential of some of the commonly grown vegetables in Rajasthan, India. Irrigation of crops with wastewater is a very common practice in India. The effect of irrigation with wastewater is also studied in these crops to observe the concentration of accumulated metals to which human beings are exposed. Furthermore, the daily intake of these metals is calculated for both adults and children.

Section snippets

Study area and sampling

All the experiments were conducted at the environmental science laboratory of Maharishi Dayanand College, Sri Ganganagar, Rajasthan, India. Samples of some commonly grown vegetables, i.e., radish (Raphanus sativus), spinach (Spinacia oleracea), turnip (Brassica rapa), brinjal (Solanum melogena), cauliflower (Brassica oleracea var. botrytis), lotus stem (Nelumbium nelumbo), mint (mentha), coriander (Coriandrum sativum), methi (Trigonella foenum-graecum), and carrot (Daucus carota), were

Metal accumulation in plants

The application of wastewater generally led to changes in the physicochemical characteristics of soil and consequently heavy metal uptake by vegetables. The heavy metals concentrations in edible parts of vegetables in Sri Ganganagar District, Rajasthan are shown in Fig. 1, Fig. 2. It can be clearly observed that the concentration of all the heavy metals is higher in wastewater-irrigated vegetables than freshwater-irrigated plants. Table 1 shows a very high concentration of heavy metals in

Conclusion

Heavy metals show a significant build-up with continuous irrigation with wastewater and long-term irrigation of farmlands with wastewater has led to contamination of food crops in the study area. Wastewater-irrigated spinach has shown significantly (p < 0.05, p < 0.01) higher accumulation of iron, manganese, copper and zinc, compared to the freshwater-irrigated spinach, indicating the highest metal absorption for this vegetable. All the vegetables contained heavy metals were lower than the

Acknowledgements

The authors would like to place on record their sincere thanks to Dr. R. S. Poonia and Dr. B. M. Kanwar for their valuable help.

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