The Impact of Pesticide Application on Heavy Metal (Cd, Pb and Cu) Levels in Spinach

 

Timothy Musa CHIROMA, Bala Isah ABDULKARIM, Haruna Mavakumba KEFAS

 

Chemical Engineering Department, Federal University of Technology, Yola, Nigeria

timobaba12@yahoo.com, balisa76@yahoo.com, hmkefas@yahoo.com

 

Abstract

The impact of Pesticides (DELVAP 1000EC) application on the levels of Cd, Pb and Cu in two species of Spinach (maroon and green) was investigated. The results shows highest accumulation in leaves compared to stem and roots for both species. The levels of Cd, Pb and Cu in leaves of maroon Spinach treated with pesticides are 6.8, 1.4 and 18.6 times respectively higher than the maximum tolerable levels of 30μg/g, 300μg/g and100μg/g for Cd, Pb and Cu respectively in plants, while in green Spinach treated with pesticides the levels of Cd and Cu in leaves are 4.9 and 14.7 times respectively higher than the maximum tolerable levels. The concentration of Cd, Pb and Cu in leaves, stem and roots of maroon Spinach treated with pesticides are 163%, 222% and 178%; 364%, 325% and 449%; and 254%, 363%and 224% respectively higher than the untreated Spinach while their corresponding concentration in green Spinach treated with pesticides are 1! 56%, 238% and 150%; 163%, 454% and 462%; and 156%, 407% and 346% respectively higher than the untreated green Spinach.

Keywords

Spinach; Pesticides; Heavy Metal; Critical Concentration.

 

Introduction

 

With global heavy metal concentration increasing throughout the World due to various human and natural activities, ecosystems have been and are being contaminated with heavy metals. Activities such as controlled and uncontrolled disposal of wastes, accidental and process spillages, use of Agricultural fertilizers, herbicides, insecticides and pesticides, and migration of contaminants into a non contaminated land as vapors and leacheate through soil, or as dust, or spreading of sewage sludge, contributes towards contamination of the ecosystem. A wide range of materials which cause contamination includes, heavy metals, inorganic and organic compounds, oils and tars, toxic and explosive gases, combustible and putrescible substances, hazardous wastes and explosives. It has already been shown from studies that contamination levels of easily extractable copper, zinc, lead and cadmium are present in surface soils, and contamination levels of copper, zinc and iron occur in herbage n! otably around heavy industry areas [2]. The use of pesticides in the treatment of vegetables and the presence of heavy metals in pesticides is one of the sources of heavy metal pollution of vegetables. The objectives of the present study therefore, was to establish the effects of pesticides (DELVAP 1000EC) which is one of the commonest pesticides used by vegetable farmers in Yola, on the heavy metals (Cu, Cd and Pb) levels in two species of Spinach (maroon and green) grown in Yola.

 

 

Materials and method

 

A pilot garden was prepared consisting of four beds, and two species of spinach (maroon and green) were planted. The beds were irrigated with clean tap water. Three weeks after planting, two of the beds (one maroon and one green) were sprayed with pesticide (DELVAP 1000 EC). The application of the pesticide was repeated weekly until maturity of the spinach after 12 weeks. All the four beds were harvested and separated accordingly. Samples were taken from each of the four beds, and were thoroughly cleaned and washed to remove dust, dirt and possible parasites or their eggs [5]. Each sample was divided into three parts (stem, leaves and roots).the samples were reduced to fine powder on a grinder prior to drying at 60°C in an oven (LTE Greenfield) to a constant weight.

Half gram of the fine powder samples were weighed into conical flask and digested in a mixture of 4 ml of HClO₄, 25 ml of HNO₃, 2 ml of concentrated H₂SO₄ and 1 ml of 60% H₂O₂ at 100°C on a hot plate for two hours in a fume cupboard. The resulting solution was left over night and made up to 100 ml with deionized distilled water [3]. The heavy metals under study were determined using Atomic Absorption Spectrophotometer (Pye Unicam Model sp - 9).

 

 

Results and Discussion

 

The results of the analyses of the different parts of the spinach samples from the four beds are summarized in Table 1 and 2.

 

Table 1. Variation of heavy metals (Cd, Pb and Cu) concentrations in different parts of Maroon Spinach treated and untreated with pesticides

 

Table 2. Variation of heavy metals (Cd, Pb and Cu) concentrations in different parts of Green Spinach treated and untreated with pesticides

 

The variation of Cd, Pb and Cu concentrations in the different parts of the two species of spinach under study are shown in Tables 1 and 2.The maximum tolerable levels of Cd, Pb and Cu in plants proposed by countries are 5 - 30μg/g; 30 - 300μg/g and 20 - 100μg/g respectively which are commonly referred as critical concentrations in plants, above which toxicity are likely to occur [1,4]. The variations of the heavy metal concentrations in all the samples analyzed show highest accumulation in the leaves compared to other parts, although copper tends to show substantial accumulation in the roots. The high concentrations of Cu in the roots may be linked to its low translocation within plants, compared to other elements [6]. Copper also has the highest concentration in all in all the samples as shown in Figures 1 to 4 below.

 

Figure 1. Variation of mean metal concentration in parts of Maroon Spinach treated with pesticides

 

Figure 2. Variation of mean metal concentration in parts of Green Spinach treated with pesticides

 

Figure 3. Variation of mean metal concentration in parts of Maroon Spinach untreated

Figure 4. Variation of mean metal concentration in parts of Green Spinach untreated

 

The concentrations of Cd, Pb and Cu in stem, leaves and roots of the two varieties of the spinach treated with pesticides are higher compared to the untreated samples as shown in Tables 1 and 2. These suggest that application of pesticides on spinach increases the Cd, Pb and Cu concentrations. It was also observed that the maroon spinach has a higher heavy metal absorption compared with the green variety. This may be ascribed to its large interfacial area of the leaves compared to the green variety.

The concentration of Cd, Pb and Cu in leaves of maroon Spinach treated with pesticides are 6.8, 1.4 and 18.6 times respectively higher than the maximum tolerable levels of 30mg/g, 300mg/g and 100mg/g for Cd, Pb and Cu respectively in plants, while in green spinach treated with pesticides, the concentration of Cd, and Cu in leaves are 4.9 and 14.7 times respectively higher than the maximum tolerable level, but Pb concentration is within tolerable limit in plants [1,4], thus suggesting toxicity of these metals in the leaves of both species of the spinach.

The concentration of Cadmium (Cd) in the leaves, stem and roots of the maroon spinach treated with pesticides are about 163%, 222% and 178% respectively higher than their corresponding concentration ii untreated maroon spinach. The Pb concentrations are 346%, 325% and 449% respectively higher than the untreated, while the Cu concentrations are 2545, 263 and 224% respectively higher than the untreated maroon spinach as shown in Table 1.

As for green spinach the concentration of Cd in stem, leaves and roots are about 156%, 238% and150% respectively higher than their corresponding concentrations in untreated green spinach. The Pb concentrations in stem, leaves and roots of treated green spinach are 163%, 454% and 462% respectively higher than the untreated while Cu concentrations are 156%, 407% and 346% respectively higher than the untreated green spinach as shown in Table 2. This result shows that the application of pesticides (DELVAP 1000 EC) contributed largely the contamination of spinach with the heavy metals Cd, Pb and Cu.

 

 

Conclusion

 

The results revealed that the application of pesticides (DELVAP 1000EC) increases the concentration of Cd, Pb and Cu in Spinach. The maroon specie of Spinach has higher tendency to accumulate Cd, Pb and Cu compared to the green specie. The leaves of spinach also accumulate higher concentration of the heavy metals (Cd, Pb and Cu) compared to the stem and roots. The concentration of Cd, Pb and Cu in leaves of maroon Spinach treated with pesticides are 6.8, 1.4 and 18.6 times respectively higher than the maximum tolerable levels of 30μg/g, 300μg/g and 100μg/g for Cd, Pb and Cu respectively in plants; while the green spinach treated with pesticides, the concentration of Cd and Cu in leaves are 4.9 and 14.7 times respectively higher than the maximum tolerable levels.

 

 

References

 

1.              Alloway B. J., Heavy metals in soils, Blackie Glasgow, UK, pp. 222 - 225, 1990.

2.              Beavington F., Heavy metal contamination of vegetables and soils in domestic gardens around smelting complex, J. Environmental Pollution 1975, 9, p. 211-217.

3.              Chiroma T. M., Hymore F. K., Ebewele R. O., Heavy metal contamination of vegetables and soils irrigated with sewage water, Nigerian Journal of Engineering Research and Development, 2003, 2(2), p. 60-68.

4.              Kabata - Pendias A., Pendias H., Trace elements in soils and plants, CRC Press, Boca Raton, Fla, 1984, 85, p.107-129.

5.              Sonhmacher M., Domingo J. L., Liobet J. M., Conbella I. J., Chromium, Copper and Zinc concentrations in edible vegetables grown in Tarragona Province, Spain, J. Environment contamination and Toxicity, 1993, 58, p. 515-521.

6.              Voutsa D., Grimanis A., Samara C., Trace elements in vegetables grown in an industrial area in relation to soil and air particulate matter, J. Environmental Pollution, 1996, 94(34), p. 325-335.