Content of Copper in Maize and Soil Collected from Selected Agricultural Areas in Kaduna, Nigeria

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1 British Journal of Pharmacology and Toxicology 3(3): , 2012 ISSN: Maxwell Scientific Organization, 2012 Submitted: May 11, 2012 Accepted: May 29, 2012 Published: June 30, 2012 Content of Copper in Maize and Soil Collected from Selected Agricultural Areas in Kaduna, Nigeria S.S. Mohammed, M.B. Mohammed and N. Musa Department of Applied Science, College of Science and Technology, Kaduna Polytechnic, Kaduna, Nigeria Abstract: This study was conducted to determine the content of maize in soil so as to evaluate its mobility, bioavailability and eco-toxicity. The copper content of maize and soil samples was determined using Flame Atomic Absorption Spectrometry (FAAS). The soil samples related to the maize were digested and extracted using different digestion and extraction reagents. The results indicated that the soil samples collected from various locations contain varying amounts of Cu and was distributed between Residual, Oxide and Carbonate/Organic fractions. The result of the study also showed that, in some of the sampling locations, the Cu content in the soil was above the tolerance limit of 100 mg/kg and the ANOVA (p = 0.000<0.05) indicated a significant difference in both the copper concentrations across the various maize crops and maize grown soils. Keywords: Atomic absorption spectrometry, copper content, kaduna metropolis, maize, soil INTRODUCTION Concerns over the possible build-up of heavy metals in soils resulting from large applications of sewage sludge has prompted research on the fate of these chemicals in soils. Most attention has been given to Zinc, Copper, Nickel, Cadmium and Lead which are present at significant levels in sludge (Jones, 1991). Heavy metal contamination in arable soils through industrial and anthropogenic activities is a serious problem in Nigeria. Metals uptake by plants may pose risks to human health when such plants are grown on or near contaminated areas. Metal accumulation in plants depends on plant species, growth stages, types of soil and metals, soil conditions, weather and environment (Chang et al., 1984; Petruzzelli, 1989). A large number of extracting solutions have been used to assess plant available trace elements (Gupta and Aten, 1993; He and Singh, 1993; Mohammed and Ayodele, 2011). In this research, the extractable Cu in soil samples was determined by Flame Atomic Absorption Spectrometry (FAAS). The soil samples were extracted using the chemical reagents, 0.05 M EDTA, 1.0 M acetic acid and 1.0 M oxalic acid. The relation between the maize and soil extracts lead contents was investigated. MATERIALS AND METHODS A flame atomic absorption spectrophotometer model 8010 Young Lin was used for the Cu determination. In the extraction procedures, 1.0 M oxalic acid, 0.05 M Na 2 EDTA and 1.0 M acetic acid were used. Preparation of samples: The research covered seven agricultural sites in Kaduna, Nigeria. The sites are: Nasarawa (NS), Sabon Tasha (ST), UnguwarMuazu (UM), Tudun Wada (TW), Kakuri (KK), Mando (MD), Kabala (KB) west and Kachia (KC). The samples were collected during the harvest season (Oct-Nov., 2008, 2009 and 2010). The soil samples were collected from the different areas enumerated at a depth of about 10 cm below the surface (Yaman et al., 2005). The cereal samples were collected at each of the locations. Guinea corn was chosen for the purpose of this research study as it is the staple food being produced and consumed in these areas. Kachia, a town situated about 130 km away from Kaduna was taken as a control Fig. 1. The cereal was thoroughly washed with water and allowed to drain on a filter paper. Both the cereal and soil samples were dried at 85ºC. All the analyses were carried out in the analytical laboratory of the department of Applied Science, College of Science and Technology, Kaduna Polytechnic, Kaduna-Nigeria. Wet ashing of cereal: Five (5) g of oven dried guinea corn sample was accurately weighed into an evaporating dish and ashed at 480 C in an ashing furnace for 4 h. Ten cm³ of a mixture of nitric acidhydrogen peroxide (2+1) was added to the ashed sample and dried with occasional shaking on a hot plate Corresponding Author: S.S. Mohammed, Department of Applied Science, College of Science and Technology, Kaduna Polytechnic, Kaduna, Nigeria 140

2 Fig. 1: Map of Kaduna metropolis showing the sampling sites 141

3 and cooled, 4 cm³ of 1.5 mol/l nitric acid was then added and centrifuged. Sixty cm³ water was added to the clear digest and was filtered. This was analysed for Cu using FAAS model 8010 Young Lin. A blank digest was carried out in the same way. Digestion and extraction of soil: Soil ph was measured (1:5, w/v) by digital ph meter. A modified Tessier et al. (1979) extraction method developed by Yaman et al. (2005) was used. Ten cm³ of a mixture of nitric acid-hydrogen peroxide (2+1) was added to 5 g of soil sample and dried with occasional shaking on a hot plate and cooled. Four cm³ of 1.5 mol/l nitric acid was added to the remainder, centrifuged and diluted to 60 cm³ with water and filtered. The clear digest was analysed for Cu using FAAS model 8010 Young Lin. A blank digest was carried out in the same way. Soil extracts were obtained by shaking separately, 5 g of soil samples with 10 cm³ of 0.05 mol/l Na 2 EDTA (for carbonate and organically bound phases), 1.0 mol/l oxalic acid (for oxide phases) and 1.0 mol/l acetic acid (for carbonate phases). The mixture was evaporated with occasional shaking on a hot plate. Four cm³ of 1.5 mol/l nitric acid was added to the remainder and centrifuged. This is referred to as hot extraction. The digest was diluted to 60 cm³ and analyzed for Cu using FAAS model 8010 Young Lin. A blank digest was carried out in the same way. RESULTS Copper content in maize and soils: The copper content for the sample collected from the sampling locations is shown in Table 1-8. The results of the Cu concentration in maize and soil varied from one location to the other. The results of the Cu concentrations in KB, MD, KK, TW, UM and KC indicate higher concentrations of the metal in maize than in corresponding soil samples. This could be due to agricultural processes and other human activities in the sampling locations. Similar results were reported by other workers working under similar conditions (Ana- Irina et al., 2008; Urunmatsoma et al., 2010). A higher Cu concentration was observed in soil than the corresponding maize samples in NS and ST (Takac et al., 2009; Urunmatsoma et al., 2010). In some of these sampling locations, the Cu concentration in the soil was above the tolerance limit of 100 mg/kg (Lindsay and Norvell, 1978). The Cu highest concentration in the areas is not only a problem to plant nutrition and food chain; it may constitute a direct health hazard as well Seward and Richardson (1990). The ANOVA (p = 0.000<0.05) indicated a significant difference in the Copper concentrations across the various maize crops. The differences in Copper concentrations can further be deduced by a post-hoc test using the Duncan Multiple range test where means of homogeneous subgroups are clearly displayed. Moreover, the mean plots that follow will clearly depict the mean values of the Copper concentrations across the various maize crops. The Duncan multiple range tests showed that, Kakuri, Nasarawa, among others had the least Copper concentration in maize crops. While Sabon Tasha and Ungwan Muazu had the highest copper concentration as depicted in Fig. 2. Metal speciation: The Cu distribution in the soil samples from the sampling locations varied from one sampling site to another. The metal exists in the forms; the residual, oxide and carbonate/organic. The concentration of the metal bound to carbonate/organic phase is highest in KB, TW. The copper in these soils was organically bound and hence bioavailable and mobile (Hickey and Kittrick, 1984; Urunmatsoma et al., 2010). Table 1: Results of Cu concentrations in maize and soil samples at Kabala Metal conc in Metal conc in soil KB nd nd 1.15± ± ±0.5 KB ± ± ± ± ±1.2 KB ± ± ± ± ±0.6 KB ± ± ± ± ±0.6 KB ± ± ± ± ±0.6 KB ± ± ± ± ±0.6 KB ± ± ± ± ±1.2 KB ± ± ± ± ±

4 Table 2: Results of cu concentrations in maize and soil samples at Nasarawa - NS nd nd 3.46± ± ±0.6 NS ± ± ± ± ±0.6 NS ± ± ± ± ±1.2 NS ± ± ± ± ±1.2 NS ± ± ± ± ±1.2 NS ± ± ± ± ±1.2 NS ± ± ± ± ±1.2 NS ± ± ± ± ±0.6 Table 3: Results of cu concentrations in maize and soil samples at Mando MD nd nd 2.31± ± ±0.6 MD ± ± ± ± ±1.2 MD ± ± ± ± ±0.6 MD ± ± ± ± ±2.9 MD ± ± ± ± ±5.9 MD ± ± ± ± ±5.9 MD ± ± ± ± ±5.9 MD ± ± ± ± ±2.9 Table 4: Results of Cu concentrations in maize and soil samples at Kakuri KK nd nd 1.73± ± ±0.6 KK ± ± ± ± ±1.2 KK ± ± ± ± ±1.2 KK ± ± ± ± ±0.6 KK ± ± ± ± ±1.2 KK ± ± ± ± ±0.6 KK ± ± ± ± ±0.6 KK ± ± ± ± ±0.6 Table 5: Results of cu concentrations in maize and soil samples at T/WADA TW nd nd 1.73± ± ±0.6 TW ± ± ± ± ±0.6 TW ± ± ± ± ±0.6 TW ± ± ± ± ±0.6 TW ± ± ± ± ±0.6 TW ± ± ± ± ±1.2 TW ± ± ± ± ±1.2 TW ± ± ± ± ±

5 Table. 6: Results of cu concentrations in maize and soil samples at S/TASHA ST ND ND 2.88± ± ±0.6 ST ± ± ± ± ±0.6 ST ± ± ± ± ±0.6 ST ± ± ± ± ±1.2 ST ± ± ± ± ±0.6 ST ± ± ± ± ±0.6 ST ± ± ± ± ±0.6 ST ± ± ± ± ±0.6 Table 7: Results of cu concentrations in maize and soil samples at U/Muazu UM ND ND 1.15± ± ±0.6 UM ± ± ± ± ±11.5 UM ± ± ± ± ±1.2 UM ± ± ± ± ±0.6 UM ± ± ± ± ±5.8 UM ± ± ± ± ±1.2 UM ± ± ± ± ±0.6 UM ± ± ± ± ±0.6 Table 8: Results of cu concentrations in Maize and soil samples at Kachia KC ± ± ± ± ±1.2 KC ± ± ± ± ±0.0 KC ± ± ± ± ±2.9 KC ± ± ± ± ±0.6 KC ± ± ± ± ±1.2 KC ± ± ± ± ±1.2 KC ± ± ± ± ±0.6 KC ± ± ± ± ±1.2 The concentration of the metal bound to oxide fraction is highest in MD. The copper in these locations is said to be oxide species. Thus, it is bioavailable and mobile. Similar findings were reported by Hickey and Kittrick (1984), Takac et al. (2009) and Urunmatsoma et al. (2010). The concentration of Cu bound to carbonate fraction is highest in UM. The metal is said to be organically bound or carbonate species and hence bioavailable and mobile. This is in agreement with other results (Hickey and Kittrick, 1984; Urunmatsoma et al., 2010). The concentration of the metal bound to residual fraction is highest in NS, KK, ST and KC. The metal is said to be residual species in these areas. Thus, it is bioavailable and mobile (Hickey and Kittrick, 1984; Chamon et al., 2009; Takac et al., 2009; Urunmatsoma et al., 2010). The HNO 3 /H 2 O 2 extractable, EDTA extractable, CH 3 COOH extractable, COOH) 2 extractable and C 6 H 8 O 7 extractable are considered as available Cu in these locations. The ph of the soil samples is acidic. Due to the various agricultural processes (Kashem et al., 2007; Chamon et al., 2009). The bioavailability of the metal decreases with increasing ph (Moraghan and Mascani, 1991; Morel, 1997). The acidity of the soils increases 144

6 Mean of copper concentration in maize sample (mg/kg) Fig. 2: Mean plot for copper concentration in maize crops Mean of copper concentration in soil sample (mg/kg) Kabala west K aba la west Nasarawa Nasarawa Mando Mando Kakuri Sites Kakuri Sites Tudun wada Tudun wada Sabon tasha Ungwan muazu Sabon tash a Ungwan m ua zu K achi a Fig. 3: Mean plot for copper concentration in maize grown soil the solubility and mobility of the metal in the soils. Thus, increasing the availability of the metal for plant uptake (Baranowski et al., 2002; Takac et al., 2009). The ANOVA (p = 0.000<0.05) indicated a significant difference in the Copper concentrations across the various maize soils. The differences in Copper concentrations can be deduced by a post-hoc test using the Duncan Multiple range test where means of homogeneous subgroups are clearly displayed. Moreover, the mean plots that follow will clearly depict the mean values of the Copper concentrations across the various maize soils. The Duncan multiple range tests showed that Kabala West had the least Copper concentration in maize grown soils. While Mando had the highest Copper concentration in soil as depicted in Fig. 3. Kachia CONCLUSION Total trace metal composition of soil is of little importance in determining its uptake by plants and consequently, in contaminating the food chain since the different forms have different mobilities, bioavailabilities and potential environmental contamination potential. The results on heavy metal speciation in the study indicated that the soil samples collected from various areas contain varying amounts of the metal. The metal was distributed between residual, oxide and carbonate fractions. An increase of the metal concentration in some areas suggests that heavy use of agrochemical materials for planting activities could cause increase in the content of heavy metals in the soil. ACKNOWLEDGMENT The authors show great appreciation to Kaduna Polytechnic, Nigeria for providing facilities to analyze thesamples and to Kabiru Shehu and Yusuf Abdul Raheem, for the help in sample collection, metal and statistical analyses. REFERENCES Ana-Irina, S.H. Vasile, O. Vasile, J. Jozsef and P. Elena, Studies on transfer and bioaccumulation of heavy metals from soil into lettuce. Env. Eng. Manage. J., 7(5): Baranowski, R., A. Rybak and I. Baranowska, Speciation Analysis of Elements in Soil Samples by XRF. Pol. J. Environ. Stud., 2(5): Chamon, A.S., M.N. Mondol, B. Faiz, M.H. Rahman and S.F. Elahi, Speciation analysis of nickel in the soils of tejgaon industrial area of Bangladesh. Bangladesh J. Sci. Ind. Res., 44(1): Chang, A.C., A.L. Page, J.E. Warneke and E. Grgurevic, Sequential extraction of soil heavy metals following a sludge application. J. Environ Qual., 1: Gupta, S.K. and C. Aten, Overview of the use of leaching/extraction tests for risk assessment of trace metals in contaminated soils and sediments. Int. J. Environ. Anal. Chem., 51: He, Q.B. and B.R. Singh, Plant availability of cadmium in soils. I. extractable cadmium in newly and long term cultivated soils. Acta Agric. Scand. Sect. B. Soil Plant Sci., 43: Hickey, M.G. and J.A. Kittrick, Chemical partitioning of cadmium, copper, nickel and zinc in soils and sediments containing high levels of heavy metals. J. Environ. Qual., 13:

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