Heavy Metal Concentrations in Top Agricultural Soils around Ceramic and Pharmaceutical Industrial Sites in Niger State, Nigeria

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1 Research Journal of Environmental and Earth Sciences 4(2): , 2012 ISSN: Maxwell Scientific Organizational, 2012 Submitted: October 23, 2011 Accepted: November 15, 2011 Published: February 01, 2012 Heavy Metal Concentrations in Top Agricultural Soils around Ceramic and Pharmaceutical Industrial Sites in Niger State, Nigeria 1 Y.A. Iyaka and 2 S.E. Kakulu 1 Department of Chemistry, Federal University of Technology, Minna, Niger State, Nigeria 2 Department of Chemistry, University of Abuja, Abuja, F.C.T., Nigeria Abstract: Lead, copper, nickel and zinc contents in agricultural soils within the vicinity of ceramic and pharmaceutical industrial sites in Niger State, Nigeria were determined using Flame Atomic Absorption Spectrophotometry technique. Mean contents for all sample locations of the two industrial sites were 18±7.5, 15±5.7, 1.9±0.96 and 28±22 mg/kg for lead, copper, nickel and zinc, respectively. The obtained values were of higher contents than the background levels measured in control soil samples, thereby showing that studied heavy metals are mainly accounted for by anthropogenic activities, although nickel was less apparent. The findings of this study have also revealed the need for more constant monitoring of heavy metal concentrations in soils from the vicinity of industrial sites in developing nations in order to assess their possible potential hazard to life and environment. Key words: Contamination, developing nation, emission, land, trace toxic, elements INTRODUCTION Heavy metals occur naturally as chemical elements in the earth s crust and surface soils in varying concentrations (Ward, 1995; Alloway and Ayres, 1997), but of concern is their emissions through industrial, man s agricultural and urban activities into the environment and consequently into soils that serve as ultimate sink. Furthermore, the persistent accumulation of heavy metals in soils is of great concern because they constitute health threat and toxicity problems to human life and environment (Purves, 1985; Wild, 1994). Heavy metal contamination of soils through anthropogenic sources from the vicinity of industrial sites have also been reported by various researchers (Onianwa and Fakayode, 2000; Martley et al., 2004; Kachenko and Singh, 2006; Ngoc et al., 2009). However, in agricultural soils the anthropogenic input of trace metals can be enhanced by chemical applications such as fertilizers, herbicides, pesticides as well as applications of animal manure and sewage (Alloway and Ayres, 1997; Merrington et al., 2003; Montagne et al., 2007; Iyaka and Kakulu, 2009). The pace and scale of environmental contamination by industrial activities have steadily increased in the last two centuries due to the pronounced industrial revolution (Stigliani et al., 1991). Hence, 40% of the approximately 1000 contaminated super fund sites identified on the USEPA s National Priority List involved heavy metal contamination associated with industrial activities (Fostner, 1995), and 70% of all the metal-contaminated sites involve two or more heavy metals. The aim of this research, therefore, is to determine the extent of lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) contamination in cultivated farmlands in the vicinity of ceramic and pharmaceutical industrial sites in two major cities of Suleja and Minna respectively in Niger State, Nigeria. The study also aimed at providing a data base of Pb, Cu, Ni and Zn in this area in order to assess the influence of industrial activities on agricultural soils particularly within the cultivated farmlands, since such studies are scarce for soils in North- central zone of Nigeria. MATERIALS AND METHODS Soil sampling: Soil samples of topsoil were collected from 32 locations within the vicinity of ceramic and pharmaceutical industrial sites in two major cities of Suleja and Minna, respectively in Niger State. Control soil samples were collected from locations within the two cities that were far from any major pollution sources. The sampling approach was random and systematic; at each sampling location or point a stainless steel auger was used to collect five sub-samples from the top layer at a depth of 0-20 cm. The collected sub-samples were then pooled together to form a composite of each individual sample. Analytical methods: The soil samples were air-dried for one week, ground, passed through 2.0 mm sieve (for soil ph and particle size analysis), and some portion of the individual sieved sample was further pulverized to a fine Corresponding Author: Y.A. Iyaka, Department of Chemistry, Federal University of Technology, Minna, Niger State, Nigeria, Tel.:

2 Table 1: Soil properties of the vicinity of a ceramic industrial site % Sample Distance from ph Location factory (m) (H 2 O) OC Sand Silt Clay East East East South East South East South East South South West West North West North West North North North North East North East North East Table 2: Soil properties of the vicinity of a pharmaceutical industrial site % Sample Distance from ph location factory (m) (H 2 O) % OC Sand Silt Clay East East East South East South East South East South South South North North North North East North East powder (passed through 0.5 mm sieve) for the total metal content and organic carbon determination. Soil ph was measured in 1:1 (soil to water ratio) according to Tan (1996), organic carbon was determined by Walkley-Black titration method and particle size was determined using hydrometer method of soil mechanical analysis. Soil samples were digested with HNO 3 -H 2 O 2 -HCl using USEPA SW-846, method 3050(1986). The USEPA SW- 846, method 3050 developed for total sorbed heavy metals in soils, gives a reliable measure of the amount of the metals added to soils as nonsilicates (Risser and Baker, 1990) that is potentially available for natural leaching and biological processes. The concentrations of Pb, Cu, Ni and Zn in the digestion solution were determined with a Unicam 969 Atomic Absorption Spectrophotometer - solar in the flame mode. At least one reagent blank and one duplicate sample were run for every batch of 5 samples for background correction and to verify the precision of the method. Accuracy was however, assessed by analyzing three (3) replicates of certified reference materials, soil sample S0-1, obtained from Canada Centre for Mineral and Energy Technology (CANMET). Recoveries were satisfactory; average values being in excess of 90 % for Pb, Cu, Ni and Zn analyzed. RESULTS AND DISCUSSION Soil physico-chemical properties: The interpretation data for rating the obtained values of the soil physicochemical properties in this study were adapted from Baize (1993) and Kparmwang et al. (2000). Greater than 50% of the soil samples studied from the vicinity of the two industrial sites were weakly acid, with approximately more than 30% being neutral, and many few were acid (Table 1 and 2). The ph values ranged from and from with mean values of 6.0±0.8 and 6.1±0.8 for ceramic and pharmaceutical industrial sites respectively (Table 3). The general mean ph value of 6.0±0.8 obtained from this study is lower than the previously reported value by Iyaka and Kakulu (2009) in their study of cultivated farmlands in the vicinity of abandoned industrial sites in Niger State, but higher than the average ph value of 5.2 reported for some Nigerian soils by Onofiok and Ojobo (1993). The soil organic carbon contents ranged from % for the ceramic industrial site and from % for the pharmaceutical industrial site. Up to 55.5% and about 50% of the analyzed soil samples from the vicinities of the ceramic and pharmaceutical industrial sites respectively are within the medium range of % organic contents. Only 30.9% of ceramic and 35.7% of the pharmaceutical studied soils have low organic carbon concentrations. The clay contents for all the soil samples from the vicinities of the two studied industrial sites ranged between 7.1 and 13.2% with mean values of 9.8±1.9 and 9.6±1.4%, respectively for ceramic and pharmaceutical industrial sites. HEAVY METAL CONTENTS IN SOILS Lead: Table 4 and 5 indicated that Pb levels in the vicinity of the ceramic industrial site ranged from 7.7 mg/kg in North East ward direction (50.0 m) to 22 mg/kg in East ward direction (0.0 m), and in the pharmaceutical industrial site obtained values varied from 15 mg/kg in East ward direction (50.0 m) to 38 mg/kg in North East ward direction (50.0 m). The varied concentrations obtained in this study are within the normal range of 2-60 mg/kg reported by Scheffer and Schachtschabel (1992) for Pb in soils that are not exposed to direct air pollution, but the obtained Pb values for the soils from the vicinity of the pharmaceutical industrial site are generally higher than the background value of 10 mg/kg documented by Alloway (1990). Honk and Lock (2000) recognized ceramic industry as an important source of Pb and Cd pollution, thus the 172

3 Table 3: Ranges and Mean of the Soil properties from the two industrial sites studied % Industrial site ph (H 2 O) OC Sand Silt Clay Ceramic Range (n = 18) Mean SD a Pharmaceutical Range (n = 14) Mean SD All soils Range (n = 32) Mean SD a : Standard deviation Table 4: Heavy metal contents in soils from the vicinity of a ceramic industrial site mg/kg Sample Distance from location factory (m) Pb Cu Ni Zn East East East South East South East South East South South West West North West North West North North North North East North East North East Table 5: Heavy metal contents in soils from the vicinity of a pharmaceutical industrial site mg/kg Sample Distance from location factory (m) Pb Cu Ni Zn East East East nd b 12 South East South East South East South South South North North North North East North East nd 13 b : Not detected obtained values for Pb from the vicinity of the ceramic industrial site in this study show that Pb levels generally decreased with distance from the factory (Table4), thereby suggesting dispersion from a point source. The higher Pb contents obtained from West (30.0 m) and Northwest Table 6: Summary of the heavy metal contents (mg/kg) in soils from the vicinity of industrial sites studied Site Heavy metal Range Mean SD Ceramic Pb Cu Ni Zn Pharmaceutical Pb Cu Ni nd Zn All soils Pb Cu Ni nd Zn Control Pb nd Cu Ni nd Zn (50.0 m) directions when compared to their 0.0 m location values may probably be ascribed to passage of roadway along those sampling locations, and vehicular emissions have been identified with deposition of Pb in roadside soil by various authors (Tiller, 1989; Othman et al., 1997; Al- Chalabi and Hawker, 2000). Furthermore, the relatively low average content of Pb obtained from soils of ceramic industrial site in this study, much as it presents insignificant exposure risks; do not rule out the possibility of increase in Pb levels with time. Other previous findings by Madrid et al. (2002) had reported that the extent of heavy metal pollution varied with age, particularly for Cu and Pb (Chen et al., 2005). Copper: Levels of Cu in soil samples of the vicinity of the ceramic and pharmaceutical industrial sites are shown in Table 4 and 5 respectively. The Cu contents in studied soils from the vicinity of the ceramic Industrial site are within the normal range given in literature for soil in Europe (Besnard et al., 2001) and the obtained average value for soils from ceramic industrial site in this study is higher than 2.44 and 4.21 mg/kg, respectively reported for form and fertilizer blending companies by Harami et al. (2004) in their study of heavy metal levels in industrial estate of Bauchi, Nigeria. 173

4 Table 7: Correlation coefficients of elemental content with soil properties of the studied sites Industrial site ph OC Sand Silt Clay Ceramic Pb Cu ** Ni Zn 0.551* Pharmaceutical Pb Cu ** Ni ** Zn ** All soils Pb ** ** Cu Ni ** Zn 0.543** 0.554** 0.355** *: Correlation is significant at the 0.05 level; **: Correlation is significant at the 0.01 level The mean Cu content of 16 mg/kg obtained from soils of the pharmaceutical industrial site in this study is similar to mg/kg reported for agricultural topsoils in Spain by Rodríguez-Martin et al. (2006). However, the highest value of 34 mg/kg from the Eastward direction may probably be ascribed to the passage of industrial waste water along that sampling area. Generally, the obtained mean value of 15 mg/kg from the soils of the vicinity of the two industrial sites of this study is less than the 28.7 mg/kg reported as mean Cu level by Belivermis et al. (2008) in their study of heavy metal contents in urban soils of Istanbul. Nickel: The Ni concentrations varied considerably for the two industrial sites (Table 4 and 5) with soil samples from two locations of the vicinity of pharmaceutical industrial site having Ni contents that were too low to be detectable. Peris et al. (2008) had reported higher mean values of Ni in their study than obtained in this study. However, the findings of this research revealed that Ni contents in the studied soil samples from the vicinity of the two industrial sites decrease with increase in distance from the point source, which may probably be ascribed to the observation by Nriagu (1990), that the burning of fossil fuels to generate energy needed to sustain industrial activities account for more than 80% of pollutant Ni. Zinc: Table 4 and 5 revealed that only few sampling points had zinc contents of less than 10 mg/kg in the soils of the vicinity of the two industrial sites studied. However, higher Zn values were obtained from the pharmaceutical industrial site than in the ceramic industrial site, probably due to the observation that the whole surrounding environment of the pharmaceutical industrial site has been converted to cultivated farmlands. Several researchers such as Andreu and Gimeno (1996) as well as Alloway and Ayres (1997) had stated that agricultural chemicals or materials such as impurities in fertilizers, pesticides and wastes from intensive poultry production constitute the very essential non-point sources of metal pollutants such as Zn in soils. Furthermore, the mean Zn contents of 36±28 and 22±14 mg/kg obtained from the soil samples of the pharmaceutical and ceramic industrial sites respectively are within the natural concentration range of Zn in surface soils of mg/kg recommended by Ward (1995). However, the obtained mean values from the two industrial sites of this study are less than average value of 42.4 Zn mg/kg reported by Golia et al. (2009) in their study of Zn and Cu in surface soils of Central Greece. Nevertheless, higher range Zn content of mg/kg than mg/kg obtained from this study has been reported by Asaah et al. (2006) in their study of surface soils of the Bassa Industrial Zone. Correlation Analysis: Correlation studies of the analyzed heavy metals with soil properties (Table 6) indicated that for ceramic industrial site only Cu and Zn correlated positively with silt and ph respectively. Moreover, for pharmaceutical industrial site, there was positive correlation between organic carbon and Cu, Zn and Ni. Furthermore, Table 7 depicts that there is positive correlation between Cu and Ni, as well as between Zn and Pb in all the soils studied. CONCLUSION Cu and Zn contents in the soils from the vicinity of the two industrial sites studied were substantially higher than twice that of the control soils. Although, the Pb and Ni concentrations in background levels were too low to be detectable, the extent of contamination was not well pronounced for Ni with average content of 1.9±0.96 mg/kg for all the studied soils. However, the obtained mean value of 18±7.5 mg/kg for Pb from all the soil samples studied signifies enrichment or accumulation of Pb above background levels in the urban soils of this study. Hence, the need for public awareness and monitoring of possible risks that could arise through the food chain from heavy metal contamination of soils. 174

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