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JOURNAL OF RESEARCH IN NATIONAL DEVELOPMENT VOLUME 8 NO 2, DECEMBER, 2010

 

THE DISTRIBUTION OF SOME HEAVY METALS IN SOILS AROUND INDUSTRIAL WASTES DUMP SITES IN KADUNA ENVIRONMENT

 

H.A. Zakari, M. Shimbayev, D.Autamashi and O. Julius

Department of Agricultural Engineering, Kaduna Polytechnic, Kaduna

E-mail: zakariharuna1964@gmail.com

 

Abstract

This study examined the distribution of Cu, Pb, Cd and Zn in soils around Kudenda, Gonigora Kakuri, Dirkaniya, Nasarawa industrial wastes dump sites. The study revealed the distribution of these metals as affected by distance away from the dumped wastes. Areas close to the highest concentration of the wastes exhibited high content of the metals when compared to the control sites.

 

Keyword: Dump sites, Cu, Cd, Pb and Zn.

 


Introduction

Traditional soil fertility and plant nutrition studies have concentrated on essential trace elements particularly Fe, Mn, Cu, Zn B and Mo (Adriano, 1986). The non-essential trace elements, with the exception of Cd, Pb and to some extent As, have received little or no attention despite their potential to contaminate food chains and the associated health risks to animals and humans in environments where soil rich in these trace elements might be inhaled (Reimann and de caritat, 1998). This is particularly relevant to the savanna where, during the ‘Harmattan’ period (November – March), the atmosphere is covered with dust particles. Inhalation of dust particles contaminated with Pb, Cd, over a long time, might lead to acute and chronic disorders in animals and humans (Briggs and Fowler, 1991). Long –term exposure to U dusts leads to dermatitis, renal damage and acute arterial lesions (Burkhart, 1991). The renal toxicity of U has been attributed to the precipitation of hexavalent U in the proximal kidney tubules (Burkhart, 1991). Thorium and U have natural radioactivity, and thus emit ionizing radiation. All substances which emit ionizing radiation have to be treated as mutagens and carcinogens. Rats receiving 5 mg Nb Kg -1 body weight died of respiratory paralysis (Georing and Fowler, 1991). In humans, Cu has been associated with Willson, disease. Several processes affect the mobilization and redistribution of primary minerals, formation of secondary solid phases, redox potential, erosion, co-precipitation and cation exchange reactions (Nesbitt, 1979; Middelburg et al., 1988).

 

There are growing concerns of trace metal pollution of soils and cation ground water with increasing applications of organic manures, inorganic fertilizers, pesticides and other agrochemicals. Xing and Dudas (1993) studied the concentration of trace and rare earth elements in some Chinese soils, and reported that  those trace element associated with clay minerals had elevated levels in the soil sample while those having affinity for Mn and Fe-oxyhydroxides were concentrated in the illuvial horizon. Those present in resistant minerals were uniformly distributed in the profiles.  However, the study did not indicate the extent to which pedogenic enrichment and depletion of these trace elements had occurred in the region, and the possible role of agricultural activities.

 

In a recent study of the Nigerian savanna, Ewa et al. (1999) examined the vertical and horizontal distribution of some trace element and concluded that the soils were contaminated with Ti, V, U and Th but the contamination level were ill-defined in the study. Furthermore, Ewa et al. (1999) hypothesized that long-term application of phosphate fertilizer could have been responsible for the elevated concentrations of these elements. Compared with temperate regions, widespread applications of inorganic fertilizers are fairly recent in the savanna and probably not more than 30 – 40 years. In this study, distribution of some heavy metals in soils around industrial wastes disposal sites were determined.

 

 

 

 

 

Materials and methods

The soil samples were obtained at the various industrial wastes dump sites in kaduna. The sample were taken at an interval of 1m, 10m, 20m and 50m away from the area of high  concentration of the industrial waste.

 

Soil analysis

The bulk densities of the sampled horizons were determined by the cove method described by blake and Hartge (1986). The Amorphas  Fe and Al (Fe, and Al) were determined by ammonium oxalate in the davk (Jackson et al 1986). While the free Fe and Al oxlides were determined by the dithionite citrate bicarbonate (Fe and Al) method of mehra and Jackson (1960). The particle size distribution of the soils was determined by the pipette method (Gee and Bauder, 1986) table 1 gives the range of selected properties of the soil profiles. The soil samples for the determinations of Cu, Cd, Pb, and Zn were pulverized and these elements in the powder sample (pulverized samples) were determined by x- ray fluorescence (Konhauser et al 1994).


 

Table 1 the means and standard of selected physico-chemical of soils averaged across the profiles

Selected soil

 Properties

Sites

Control

Gonigora

Kudenda

Kakuri

Dirkaniya

Nasarawa

Sand (%)

29.2 ±7.3

46.2 ±14

35.8 ±13

24.8±8

35.8 ±13

24.8±8

Silt (%)

Clay(%)

41 ±5

30±6

30.4±6

25±5

38±6

32±6

445±6

33±6

38±6

32±6

445±6

33±6

B.d (gcm-3)

1.60±o.1

1.59±0-6

1.64±0.4

1.66±0.2

1.64±0.4

1.66±0.2

Oc (gkg-1)

3.0±0.4

4.0±0.6

4.0±0.6

3±0.2

4.0±0.6

3±0.2

Fe3 (gkg-1)

1.6±0.6

1.8±0.2

1.2±0.2

1.4±0.1

1.2±0.2

1.4±0.1

 


Data handling

To assess the impact of cultural practices (cultivation) and management  on the changes in the metals, a reference against which the measured concentrations and amounts can be compared has to be established, for this purpose, an adjacent site free of industrial wastes was chosen as a reference condition to compare the distribution of the metals in these soils.

 

Element concentration in a soil can be affected by cultivation due to changes in bulk densities and soil mass.

 

Thus the mass of a given element in an area – basis was calculated to determined the fluxes induced by long – term cultivation activities and management practices. In assessing these changes, firstly, we determined the element masses on an area basis up to a depth of 20cm because cultivation and management inputs and plant root activities are most intense within this layer. The area based changes in the element mass induced by cultivation was calculated as follows:

 

ê% = [(Xe- Xn)/Xn] X 100 where Xe is the mass of an element on the cultivated site, Xn is the mass of the same element in the native (reference site) or uncultivated site. The element mass per unit areas was calculated by multiplying the concentration by the bulk density and the sampling depth.

 

The association of the trace elements with soil constituents was evaluated by sample correlation analysis since incorporation of trace elements into Fe oxides, Fe-oxyhydroxide and mineral resistant to weathering determine the extent of depletion and enrichment in a soil (Middelburg et al., 1988).

 

 

 

Result and discussion

The concentrations of Cu in soils ranged from 2 to 100mg/kg-1 with a mean of 20mg/kg -1 (Agbenin2002).

In these soils Cu ranged from 17 - 185 to 18mg/kg-1 and increased with soil depth (Fig1). The increasing

concentration with depth might suggest mobilization and translocation with clay consistent with its

correlation with clay content (v=0-59++).

 

Lead ranged from  to 2 - 300mg/kg in these savanna soils with a fairly uniform profile distribution (fig2b) suggesting that Pb is associated with resistant mineral fractions in the soil. (Agbennin 2002)


Figure

 

 

 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

 

 


The concentration of the soils in the research area is 2 – 3 times higher than the mean concentrations. The high concentration was found in soils that received industrial wastes for a long term. The high concentration of Pb in the soils must be viewed with concern since Pb has been linked with reproductive dysfunction. The probability of exposure to Pb is high where dust inhalation particularly during the Harmattan season. Dust inhalation has been identified as a major avenue for human exposure to heavy and toxic metals in soils (Agbennin, 2002). The relatively high concentration on the surface horizon is of health concern in this our region where exposure to dust is high. Cd concentration in soil varied between 0.01 and 1.4mg/kg with the highest in soil close to the dump sites (lm) (fig1a). The concentration of Zn the the study area range from 20 – 220mgkg-1 but the concentration Zn in agricultural soil worldwide is approximately 10 - 100mg/kg-1 (Bowen, 1979).

 

Area-based changes Induced by human activity.

We have already alluded in this report that the intention of this investigation was to compare the levels of some heavy metals in native and cultivated soils around industrial waste dump sites. In making this comparisons, no formal statistical power test was employed. Several investigators have expressed misgiving on the importance of statistical power in environmental protection and conservation studies, (Peter man, 1991). These investigators pointed out that in environmental and conservation studies, the practical consequence of failure to detect a difference which indeed, occurred in nature (type ll ewor), might be much more dire than the consequences of detecting a difference which did not occur in nature (type l error). Thus, the area-based changes in the amounts of heavy metals were simply expressed as percentage changes (ê%).  Changes in masses of Cu (16%), Zn (14%) were pronounced in area, lm away from the dump sites. The changes in Cd and Pb were less than 5%.

 

Table 2

The masses and the area-based changes of the metals induced by long term exposure to industrial metal containing wastes in the 0-20cm depth


 

Metals lm        ê%     10m     ê%     20m     ê%     50m     ê%     control ê%

Cd(gm-2)  4.0   -           3.3       -23      3.3       -18       4.2      -           4.3             -

Cu (gm-2)         1.6       18        8.1       6.3      5.3       -          12                   11.6           14

Zn (gm-2)          5.9       1.1       16.7   - 1.1       1.4       6                      5.8            75

Pb(gm-2)           1.2       -           1.1       1.1       12.5     18        1.1                   1.2            15

 

 


Changes ≤% were omitted because these were considered to be within experimental error.

Soil 1m  away from the dump sites had increased masses of Cu (16%) and Zn (14%) in the surface kg horizon  (o-20)cm). The changes in the masses of Cd and Pb were less than 5%. Changes less than 5% were considered within the experimental error.

 

At 10m away from the area with high concentration of the wastes, Cd decreased by 21% but Cu and Pb increased by 61% and 51% respectively. The % of Cd was found to decrease by 18% at distance 20m away from the dump site, while Zn and Pb increased by 14% and 18% respectively. In the control, there were net increases in Cu (14%), Zn (71% ) and Pb (14%). The drastic net increase in Zn (71%) in the control was rather surprising. However, assessment of human activity like cultivation – induced changes on the masses of these metals on surface horizons might be misleading, because of translocation and redistribution of these metals within profiles during cultivation

 

Summary and recommendation

The result of the study indicated that soils 1m away from dump sites had the highest accumulation of Cu, Zn. Traces of some of the metals in the control site was attributable to aelian deposition.

 

It is therefore recommended that a further research that will cover all other heavy metals at a deeper profile be conducted. Close and regular monitoring of all industries by the agencies concerned should be ensured in order to avoid indiscriminate disposal of industrial waste close to human habilitation because of the inherent health risks arising there from.

 

References

Adriano, D.C.(1986): Trace elements in the terrestrial environment.New York: Spinger.

 

Agbenin, J.O, de Abreu C.A, Raij B. (1999): Extraction of phytoavailable trace metals from tropical soils by mixed ion exchange resins modified with inorganic and ligads. Sci Total Environ 227:187-198.

 

Blake, G.R, Hartge, K.H.91986): Bulk density. In: Klute A, editor, Methods of soil analysis. Part 1. Physical and mineralogical methods, Madison, Winsconsin: American society of Agronomy.

Bowen, H.J.M.(1986): Environmental chemicals. London: Academic Press.

 

Bowen H.J.M.(1979): Environmental chemistry of elements. London: Academic Press.

 

Burau R.G.(1982): Lead in, Page Al, Miller RH, Keeney  DR, editor. Methods of soil analysis. Part 1. Chemical and microbiological properties. Madison Wissconsin: American society of Agronomy, pp347-365

 

Chang F-H, Broardbent F.E.(1982): Influence of trace metals on some soil nitrogen transformation. J Env Qual11:1-4.

 

Davies B.E. (1995): Lead.in: Alloway BJ, editor. Heavy metals in soils. Glasgow: Blackie Academic and professional, pp 206-223.