Analyzing soil contamination status in garage and auto mechanical workshops of Shashemane City: implication for hazardous waste management
© Demie. 2015
Received: 28 July 2015
Accepted: 27 August 2015
Published: 15 September 2015
Historically human being exist in harmony with their environment. However, the current rapid urbanization, industrialization and expansion of different economic activities were lead to contamination of environmental resources. Hence, the aim of this study was determining the level of heavy metal contamination of soil in garage and auto-mechanical workshops and comparing with existing national and international standards so as to now the impact they had on human being and environment.
To achieve objectives, a total of 36 soil sample were collected form 0–15, 15–30 and 30–45 cm soil depth using calibrated auger. Three control soil samples were also collected from undisturbed area for comparison of the result so as to know the level of pollution. The concentration of heavy metal in soil samples were determined using atomic absorption spectrometer and calculation of their contamination factor, geo-accumulation index and pollution load index were done using SPSS version 20.0. To check variability of the pollutant under different service year of garage and soil depth, correlation analysis and analysis of variance were tested at α (alpha) = 0.05 significance level.
The result of study showed that the overall mean concentrations of the heavy metals viz. chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd) and cobalt (CO) were 290.1, 782.1, 443.6, 133.1 and 331.0 ppm respectively which is extremely higher than US EPA and EU regulation standards.
The value of contamination factor and degree of contamination indicated that the study area is considerably polluted by heavy metals under investigation and hence require urgent remedial action for its reclamation.
KeywordsSoil contamination Contamination factor Degree of contamination Geoaccumulation index
Historically human beings live in harmony with their natural environment. However, the current rapid rate of industrialization and urbanization (Jiang et al. 2013) and economic activities like mining (Navarro et al. 2008), agriculture (Vaalgamaa and Conley 2008; Syed et al. 2012), industries and transportation (Jaradat et al. 2005; David and Sunday 2012) leads to contamination of environmental resources due to huge amount of waste they generate. For instance, gasoline, battery manufacture, metal plating, smelting, tanneries, petroleum refining, paint manufacture, pesticide, cosmetics, ceramics, pigment manufacture, printing and photographic industries, etc., are sources of heavy metal such as cadmium, zinc, copper, nickel, lead, mercury, cobalt, manganese and chromium (Kadirvelu et al. 2001; Alloway 1995). Furthermore, automobiles’ used oil, weared machinery, used batteries, organic and inorganic chemicals used in oil as additives were also release different heavy metals (EEA 2007) and these heavy metals enter the human being and environment through biomagnifications in food chains (Bradl 2005), ingestion, skin absorption, inhalation of volatile heavy metals, leaching, runoff, deposition of atmospheric particulate, disposal of metal enriched sewage sludges and effluents. Once entered food chain and ecosystem, heavy metals have capacity to pose a wide range of adverse health and environmental problems (Tamene 2008; Cai et al. 2011). For instance the study of Adela et al. (2012) confirmed that garage and automotive workers were in danger of impending lead toxicity and facing abdominal colic, constipation, fatigue and central nervous system dysfunction.
The study of Naser et al. (2011) and Itanna (2002) also confirmed that plants and leafy vegetables grown using wastewater and polluted soil can accumulate toxic heavy metals above maximum limit stated by FAO (1985) and USEPA (www.EPA.Gov.) causing serious risk to human health when consumed (Akinola et al. 2008). Generally, toxic metals cause enzyme inactivation, acute mental lapse (lead), kidney, liver, gastrointestinal tract (cadmium) and central nervous system damage (arsenic) (Landrigan 1994 cited in Adela et al. 2012).
Currently, the Shashemane City is characterized as one of the fastest growing city and center of business in Oromia region. Besides this, the number of garages are rapidly increasing and an individual may get garage in maximum of 1 km interval while is enjoying in the city. This implies that the, whether it is large or small scale garage, it releases different types of pollutant that have significant potential impact to environment (soil, water and air) (Adie and Osibanjo 2009; Olukanni and Adeoye 2012; Ololade 2014) undertaking different operational activities. These metals are none biodegradable and deposit themselves in environment resources and cause pollution. This was also the major challenges in Shashemane City due to absence of appropriate hazardous waste management and less emphasis given to garage and auto mechanical waste. To reverse the situations and inform concerned body, chemical analysis of soil and research are mandatory. However, there has not been agreed guidance and researches conducted on the heavy metal contamination of soils due to waste released form garages and auto mechanical workshops. Even the research studies conducted at different area were not directly related to garage waste and not complete rather specific to single types of metals while others depend on the source and types of waste. For instance, the Adela et al. (2012) focus on impact of exposure to lead by garage workers while the study of Itanna (2002) was about contamination of vegetables by wastewater; soil pollution by solid waste disposal sites Hunachew and Sandip (2011). Hence the objective of this research is to analyze soil pollution status in garage and auto mechanical workshops and compare the result with national and international standard.
Description of study area
Sampling and analytical procedures
According Tomlinson et al. (1980), a pollution load index (PLI) <1 denote perfection; PLI = 1 present that only baseline levels of pollutants are present and PLI > 1 would indicate deterioration of site quality.
Result and discussion
Chemical concentration of studied element
Average heavy metal concentration in mg kg−1 per sample within study area
Mean ± SD
290.1 ± 248.8
782.1 ± 754.7
443.6 ± 378.3
133.1 ± 77.5
331.0 ± 472.7
1.1 ± 1.5
48.8 ± 11.5
904.6 ± 557.5
Correlation coefficient matrix for the metals in soil in garage of Shashemane city
The mean concentrations of the heavy metals were varying per sample and within the study area. As indicated in Table 1, the concentration of chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd) and cobalt (CO) were 290.1, 782.1, 443.6, 133.1 and 331.0 mg kg−1 respectively. Accordingly, the trend of metals on the basis of their mean concentration was: Pb > Ni > CO > Cr > Cd. The variation of heavy metals mean concentration was also observed across the different soil sampling depth as indicated in Fig. 2. These indicate that the concentration of lead is relatively very high compared to the other heavy metals within study area. This was in line with the finding of Endale et al. (2012) at Addis Ababa City. The possible reason for high concentration of lead within study area might be in appropriate use and disposal of leaded gasoline, body repair activity using metal welding and other garage wastes.
ANOVA table for testing the significance of the concentration of different element with service year of garages
Sum of squares
Cr × service year
Pb × service year
Ni × service year
Cd × service year
CO × service year
pH × service year
EC × service year
SOM × service year
Comparing the value of heavy metals in study area with other studies in the country and outside the country including standards
Study in Ethiopia (in mg kg−1)
Study in other county (in mg kg−1)
USEPA stand (mg kg−1)f
EU Reg (mg kg−1)g
Addis Ababa Cityb
The mean concentration of lead (782.1 ± 248.8 mg kg−1), nickel (443.6 ± 378.3 mg kg−1) and cobalt (331.0 ± 472.7 mg kg−1) are also very high compared to studies conducted by Itanna et al. (2008); Hunachew and Sandip (2011); and Melaku et al. (2005) in Ethiopia. It is also extremely higher than maximum tolerable standard of USEPA (1993) and European regulation standards (Ewers 1991) as in Table 4. The highest concentration of lead observed in study area is most likely from vehicle emissions and leaded gasoline combustion. As pin pointed by Atuanya and Oseghe (2006), higher lead concentration in soils has toxic effect on soil microorganisms which can in turn influence the presence of flora and fauna. It also leads to impaired mental and physical development, liver and kidney damage, brain and central nervous system damage, decreased hemi biosynthesis and serum levels of vitamin D in children (Needleman et al. 1990).
The chromium concentration relatively elevated compared to the finding of Itanna (2002) in soil sample taken from adjacent Bulbula and Kera river of Addis Ababa City and European regulation standards. However, it is lower than the united state environmental protection agency standards (1993). In general, the area is extremely polluted by toxic metals under investigation and requires urgent response.
Index of geoaccumulation (Igeo)
The result of data analysis showed that the Igeo was distinctively variable and suggests that soil in garages of Shashemane City ranged from uncontaminated to extremely contaminated with respect to the analyzed heavy metals. Igeo revealed that except sample 8, 10 and 11 (which falls in class 1—uncontaminated/moderately contaminated), the remaining sampling points were falling in Class O (uncontaminated) with respect of chromium and sampling point 6 and 7 for nickel. In case of lead, among the 12 sampling point 8 of them were falling under extremely contaminated class. This high index is caused mainly by inappropriate disposal of hazardous waste like used oil and metallurgical activity.
Contamination factor, degree of contamination, modified degree of contamination and pollution load index
Contamination factors, degree of contamination, modified degree of contamination and pollution load index of the five elements studied within study area
Contamination factors and degree of contamination categories with their terminologies for description
Cf and Cd terminologies
Cf < 1
Low Cf indicating low contamination/low Cd
Cd < 8
1 ≤ Cf < 3
Moderate Cf/moderate Cd
8 ≤ Cd < 16
3 ≤ Cf < 6
16 ≤ Cd < 32
Cf ≥ 6
Very high Cf/Cd
Cd ≥ 32
Modified degree of contamination classification and their description
mCd < 1.5
Nil to very low degree of contamination
1.5 ≤ mCd < 2
Low degree of contamination
2 ≤ mCd < 4
Moderate degree of contamination
4 ≤ mCd < 8
High degree of contamination
8 ≤ mCd < 16
Very high degree of contamination
16 ≤ mCd < 32
Extremely high degree of contamination
mCd ≥ 32
Ultra high degree of contamination
The assessment of soil contamination was carried out using the contamination factor and degree of contamination based on four classification categories proposed by Hakanson (1980) while seven classification categories recognized by Abrahim and Parker (2008) were used for modified degree of contamination classification and description as presented in Tables 6 and 7 respectively.
Based on the contamination factor values, the overall contamination of soils within study area were moderately contaminated by chromium and very highly contaminated by lead, nickel, cadmium and cobalt. The result of modified degree of contamination also indicates that the study area is extremely contaminated. This may be due to different activities viz. dewaxing and cleaning of vehicles; the storage, use and disposal of polluting liquids such as oils, paints, solvents, antifreeze and other coolant additives, brake fluids and solid waste such as oil filters, exhaust systems, batteries and tyres taking place within garage and auto-mechanical workshops. In order to minimize the effect of spikes of individual elements and to have accurate interpretation of the mCd result, the calculation of pollution load index was carried out and its result reveals that the soil quality of study area were deteriorated. Thus urge for immediate interventions to ameliorate the pollution within study area.
Pearson correlation analysis (Edwards 1976) was performed between all the variables to check their interaction with one another in the study area. The level of significance (P ≤ 0.05, p ≤ 0.01) of heavy metals correlation for soil samples was determined and the results were given in Table 2. The Pearson correlation (r) values showed that there is strong negative correlation and statistically significant relation between depth of soil sample and soil organic matter within study area. There is also weak to moderate correlation between service year (year of establishment) of garage and heavy metals under investigation. For instance, chromium and nickel show positive and statistically significant relation with year of garage establishment. The correlation coefficient matrix of pH, electrical conductivity and soil organic matter indicated extremely weak to weak relation with heavy metals under study. The metallic–metallic correlation coefficient in the soil samples with p < 0.01 was observed between cobalt and nickel metal; which indicates that they inter the soil from rechargeable batteries and repair of automobiles within garage. In other vine they come from common anthropogenic sources.
Conclusion and recommendation
Soil is the major repository of different pollutant emitted from different sources especially from anthropogenic activity and leading to deterioration of quality of soil resources. This was greatly aggravated by current rate of industrialization and urbanization that release huge amount of heavy metals to surrounding environment. Garage and auto-mechanical workshops are also another source of hazardous pollutant for soil resource and causing disruption of normal function of soil resources. Thus, the pollution of soil resource is calling for great concern though it is characterized by the problems of developed countries. The impact of soil pollution is found to be more hazardous for developing countries like Ethiopia due to lack of proper consideration and management. The wittiness for this conclusion may be allocation of trade license carried out by trade and industry bureau for garage workers here and their within vicinity of individual residences. The result of this study also proofed that garage and auto-mechanical workshops have the potential to emit huge amount of heavy metal pollutant to soil resource. This may in turn leads to several health related hazards when individuals are exposed to these polluted soil around and within garage areas. A lots of study showed, exposure to heavy metal would result in reduced oxygen flow in red blood cells, disruption of ecosystem function, increased risk of chest pain for person with heart disease and death. Therefore, in order to reduce the contamination of soil by heavy metals around garage, appropriate areas should be selected like developing garage and auto-mechanical zone, regulation and management of hazardous waste released from garage should be carried out by environmental authority and trade and industry bureau as well. Furthermore, application of phytoremediation is also required in order to reclaim extremely contaminated soils.
atomic absorption spectrophotometer
analysis of variance
- Cd :
degree of contamination
- Cf :
degree of freedom
- Igeo :
index of geoaccumulation
- mCd :
modified degree of contamination
pollution load index
Statistical Package for Social Science
Getachew Demie: Lecturer at Hawassa University Wondo Genet College of Forestry and Natural Resources. He mainly teaches courses related to Environmental resource management, water pollution, land degradation and Rehabilitation; and undertake research on Soil pollution, water accessibility and impact of open landfill.
I would like to thank Research and development office of Wondo Genet College of Forestry and Natural Resources for providing financial support to conduct this research.
Compliance with ethical guidelines
Competing interest The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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