Environ Monit Assess (2014) 186:8063–8080 DOI 10.1007/s10661-014-3987-z
Evaluation of the impact of asbestos wastes on soils in Emene-Enugu, Southeastern Nigeria O. Igwe & O. V. Omonona & O. S. Onwuka & O. D. Nnebedum
Received: 18 December 2013 / Accepted: 25 July 2014 / Published online: 7 August 2014 # Springer International Publishing Switzerland 2014
Abstract This study investigated the impacts of asbestos wastes on soils in Emene-Enugu, southeastern Nigeria, generated by the activities of a major asbestos products manufacturing company in southeastern Nigeria. The methods of investigation included vertical electrical sounding (VES), 2-D horizontal resistivity profiling (HRP), induced polarization (IP) survey, chemical analysis of plant tissues and standard penetration tests of soil samples. The 2-D HRP and IP identified six closed waste pits alongside the two active pits. The VES revealed four geoelectrical layers in the area: from bottom to top; the inferred lithologies included dark shale, clay, gravel and recent sands. The geochemical data results revealed that Cd concentration of the soils of the waste pits is above the contaminated land exposure assessment soil guideline value for residential and allotment land uses. The geochemical pollution indices classified the soils as “unpolluted” to “extremely polluted”. Bioconcentration factor of Pb in plant tissues was found to be above recommended limits of 0.045. The geotechnical parameters indices revealed that the soils varied from “very soft” to “stiff”
O. Igwe : O. S. Onwuka : O. D. Nnebedum Department of Geology, University of Nigeria, Nsukka, Nigeria O. V. Omonona (*) Department of Physics/Geology/Geophysics, Federal University, Ndufu Alike, Ikwo, Nigeria e-mail: [email protected]
and “very loose” to “medium”. Soils of the active pits have very low strength and bearing capacity while closed pits have high strength and bearing capacity. It may be safe, therefore, to conclude that as the wastes are completely turned into soils, they will assume geotechnical properties similar to those of natural soils. Keywords Asbestos . Emene-Enugu . Enrichment factor . Geoaccumulation index . Waste dump pit . Pollution . Standard penetration test
Introduction The environment has emerged as one of the most important issues of contemporary times. This is in realization of the ever-increasing negative environmental impacts of rapid industrial development. Therefore, public and private organizations all over the world have come under increasing pressure to take account of the environmental implications of their activities. An asbestosproduct manufacturing industry in southeastern Nigeria that releases large amount of asbestos wastes into the environment annually is located at Emene-Enugu. It started operation in the year 1963 and produces a wide range of products: roofing products (standard corrugated sheets and Dura tile), ceiling products (Emulex, Dura ceil, Emceil sheets) and garden exquisites items (flower pots and vases). Raw materials used by factory include cement, asbestos, calcium carbonate, cellulose fibre and kaolin.
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Environ Monit Assess (2014) 186:8063–8080
Fig. 1 Location and geologic map of Enugu metropolis
Asbestos, however, has been replaced with polyvinyl alcohol (PVA) since the year 2000. The company generates waste at two stages: the production and the finishing stages. The wastes generated over the years include asbestos–cement waste, fibre–cement or new
Fig. 2 Google Earth map showing survey and sampling points
technology waste (from PVA), wastewater, plastic sheeting, disposable coveralls, disposable respirators and rags. Over 1,000 tons of these wastes are generated annually. The asbestos–cement and fibre–wastes are stored temporarily in decantation basins before
Environ Monit Assess (2014) 186:8063–8080
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Table 1 Summary of the results of resistivity and layer thicknesses from VES surveys Layer thickness (m) h1
h2
Layer resistivity (Ωm)
Curve type
h3
h4
ρ1
ρ2
ρ3
ρ4
VES 1
3
6
141
–
1,000
30
12
300
QH
VES 2
1.2
19
80
–
80
30
100
0.02
HK
h = thickness; ρ = resistivity
they are finally deposited at the waste disposal site about 2.6 km away from the factory site. The other
waste types are disposed immediately after they are generated.
Fig. 3 a Interpreted model of VES 1 (RS—ohm m; IP—ms). b Interpreted model of VES 2 (RS—ohm m; IP—ms)
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Asbestos dusts and fibers are released into the air and environment when wastes containing asbestos are poorly handled during removal and transport for disposal, and at disposal sites. Asbestos wastes are highly hazardous when inhaled, and they are associated with mesothelioma, asbestosis and some lung cancers (EPA 2013).
Environ Monit Assess (2014) 186:8063–8080
England and Wales consider asbestos waste as “hazardous waste” when it contains more than 0.1 % asbestos, while Scotland considers wastes containing 0.1 % asbestos as “special wastes”. This study investigated the impact of asbestos wastes on soils at the dumpsite for waste generated by the asbestos factory.
Fig. 4 a Line one resistivity profile. b Line one induced polarization profile
Environ Monit Assess (2014) 186:8063–8080
Description of the study area Emene is a major suburb of Enugu City, an old metropolis in southeastern Nigeria. It is, however, the industrial hub of the city. Enugu lies between
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latitudes 6.405°N and 6.500°N and longitudes 7.475°E and 7.500°E (Fig. 1). The vegetation is the tropical Guinea Savannah, characterized by scattered trees and grasses. The Enugu Shale (Fig. 1) underlies the area. The formation consists of soft grey-blue to dark grey
Fig. 5 a Line two resistivity profile. b Line two induced polarization profile
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Environ Monit Assess (2014) 186:8063–8080
shales and mudstones. Intercalations of sandstones and sandy shales occur in the formation (Reigers 1996). The shales are fractured, and they weather to blackish and greyish laterites, which serve as clay cap over the bedrock. This laterized overburden is about 20 m thick, porous and permeable, and constitutes the only known aquifer in the study area (Onwuka et al. 2004, 2013).The unweathered shale is hard and has good bearing capacity when dry, but may deteriorate in strength rapidly when infiltrated by water (Reigers 1996). The waste disposal site is located at the northeastern section of Enugu metropolis, a few kilometers from the Akanu Ibiam
International Airport. It covers an area of 129,330 m2. The Ekulu River bounds the southern side of the waste disposal site. Eight of the waste pits were identified, six are filled and closed and two are active and in use. The closed waste pits sites were already obliterated. Each of the waste pits measures 4.5 m×3.5 m×2.5 m.
Materials and methods Three principal methods (geophysical investigations, geochemical analysis and geotechnical survey) were
Table 2 Mean physico-chemical properties of the soils Depth (m)
pH
C (%)
N (%)
P (mg/kg)
Ca
Mg
Na
K
H+
Al3+
THC
Closed pit 1
2
Active pit 1 Control 1
Closed pits 1
2
Active pit 1
0
7.1
0.41
0.04
0.84
16.35
1.99
0.83
0.31
ND
ND
19.48
1.5
7.3
0.23
0.03
ND
12.82
1.17
0.32
0.27
ND
ND
14.58
4.5
7.0
0.10
0.02
ND
4.31
0.63
0.25
0.11
ND
ND
5.3
0
7.80
0.35
0.03
1.04
13.20
2.08
0.94
0.20
ND
ND
16.42
1.5
8.10
0.22
0.02
ND
14.48
1.28
0.27
0.20
ND
ND
16.23
4.5
8.00
0.07
0.01
ND
2.15
0.84
0.21
0.07
ND
ND
3.27
1.5
7.80
0.61
0.04
0.74
52.72
8.16
0.94
3.98
ND
ND
65.8
4.5
7.91
0.32
0.02
0.25
29.31
2.54
0.48
2.11
ND
ND
34.44
Depth (m)
Depth (m) 0
5.3
1.22
0.08
ND
2.08
2.72
0.75
0.46
0.60
ND
6.01
1.5
5.2
0.42
0.04
ND
1.28
0.82
0.26
0.25
0.45
ND
2.61
4.5
5.0
0.15
0.01
ND
0.94
0.45
0.12
0.10
0.02
ND
1.61
Depth (m)
Pb
Cd
As
Cr
Co
Ni
V
Fe
Hg
THC
0
90.21
20.51
Evaluation of the impact of asbestos wastes on soils in Emene-Enugu, Southeastern Nigeria O. Igwe & O. V. Omonona & O. S. Onwuka & O. D. Nnebedum
Received: 18 December 2013 / Accepted: 25 July 2014 / Published online: 7 August 2014 # Springer International Publishing Switzerland 2014
Abstract This study investigated the impacts of asbestos wastes on soils in Emene-Enugu, southeastern Nigeria, generated by the activities of a major asbestos products manufacturing company in southeastern Nigeria. The methods of investigation included vertical electrical sounding (VES), 2-D horizontal resistivity profiling (HRP), induced polarization (IP) survey, chemical analysis of plant tissues and standard penetration tests of soil samples. The 2-D HRP and IP identified six closed waste pits alongside the two active pits. The VES revealed four geoelectrical layers in the area: from bottom to top; the inferred lithologies included dark shale, clay, gravel and recent sands. The geochemical data results revealed that Cd concentration of the soils of the waste pits is above the contaminated land exposure assessment soil guideline value for residential and allotment land uses. The geochemical pollution indices classified the soils as “unpolluted” to “extremely polluted”. Bioconcentration factor of Pb in plant tissues was found to be above recommended limits of 0.045. The geotechnical parameters indices revealed that the soils varied from “very soft” to “stiff”
O. Igwe : O. S. Onwuka : O. D. Nnebedum Department of Geology, University of Nigeria, Nsukka, Nigeria O. V. Omonona (*) Department of Physics/Geology/Geophysics, Federal University, Ndufu Alike, Ikwo, Nigeria e-mail: [email protected]
and “very loose” to “medium”. Soils of the active pits have very low strength and bearing capacity while closed pits have high strength and bearing capacity. It may be safe, therefore, to conclude that as the wastes are completely turned into soils, they will assume geotechnical properties similar to those of natural soils. Keywords Asbestos . Emene-Enugu . Enrichment factor . Geoaccumulation index . Waste dump pit . Pollution . Standard penetration test
Introduction The environment has emerged as one of the most important issues of contemporary times. This is in realization of the ever-increasing negative environmental impacts of rapid industrial development. Therefore, public and private organizations all over the world have come under increasing pressure to take account of the environmental implications of their activities. An asbestosproduct manufacturing industry in southeastern Nigeria that releases large amount of asbestos wastes into the environment annually is located at Emene-Enugu. It started operation in the year 1963 and produces a wide range of products: roofing products (standard corrugated sheets and Dura tile), ceiling products (Emulex, Dura ceil, Emceil sheets) and garden exquisites items (flower pots and vases). Raw materials used by factory include cement, asbestos, calcium carbonate, cellulose fibre and kaolin.
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Environ Monit Assess (2014) 186:8063–8080
Fig. 1 Location and geologic map of Enugu metropolis
Asbestos, however, has been replaced with polyvinyl alcohol (PVA) since the year 2000. The company generates waste at two stages: the production and the finishing stages. The wastes generated over the years include asbestos–cement waste, fibre–cement or new
Fig. 2 Google Earth map showing survey and sampling points
technology waste (from PVA), wastewater, plastic sheeting, disposable coveralls, disposable respirators and rags. Over 1,000 tons of these wastes are generated annually. The asbestos–cement and fibre–wastes are stored temporarily in decantation basins before
Environ Monit Assess (2014) 186:8063–8080
8065
Table 1 Summary of the results of resistivity and layer thicknesses from VES surveys Layer thickness (m) h1
h2
Layer resistivity (Ωm)
Curve type
h3
h4
ρ1
ρ2
ρ3
ρ4
VES 1
3
6
141
–
1,000
30
12
300
QH
VES 2
1.2
19
80
–
80
30
100
0.02
HK
h = thickness; ρ = resistivity
they are finally deposited at the waste disposal site about 2.6 km away from the factory site. The other
waste types are disposed immediately after they are generated.
Fig. 3 a Interpreted model of VES 1 (RS—ohm m; IP—ms). b Interpreted model of VES 2 (RS—ohm m; IP—ms)
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Asbestos dusts and fibers are released into the air and environment when wastes containing asbestos are poorly handled during removal and transport for disposal, and at disposal sites. Asbestos wastes are highly hazardous when inhaled, and they are associated with mesothelioma, asbestosis and some lung cancers (EPA 2013).
Environ Monit Assess (2014) 186:8063–8080
England and Wales consider asbestos waste as “hazardous waste” when it contains more than 0.1 % asbestos, while Scotland considers wastes containing 0.1 % asbestos as “special wastes”. This study investigated the impact of asbestos wastes on soils at the dumpsite for waste generated by the asbestos factory.
Fig. 4 a Line one resistivity profile. b Line one induced polarization profile
Environ Monit Assess (2014) 186:8063–8080
Description of the study area Emene is a major suburb of Enugu City, an old metropolis in southeastern Nigeria. It is, however, the industrial hub of the city. Enugu lies between
8067
latitudes 6.405°N and 6.500°N and longitudes 7.475°E and 7.500°E (Fig. 1). The vegetation is the tropical Guinea Savannah, characterized by scattered trees and grasses. The Enugu Shale (Fig. 1) underlies the area. The formation consists of soft grey-blue to dark grey
Fig. 5 a Line two resistivity profile. b Line two induced polarization profile
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Environ Monit Assess (2014) 186:8063–8080
shales and mudstones. Intercalations of sandstones and sandy shales occur in the formation (Reigers 1996). The shales are fractured, and they weather to blackish and greyish laterites, which serve as clay cap over the bedrock. This laterized overburden is about 20 m thick, porous and permeable, and constitutes the only known aquifer in the study area (Onwuka et al. 2004, 2013).The unweathered shale is hard and has good bearing capacity when dry, but may deteriorate in strength rapidly when infiltrated by water (Reigers 1996). The waste disposal site is located at the northeastern section of Enugu metropolis, a few kilometers from the Akanu Ibiam
International Airport. It covers an area of 129,330 m2. The Ekulu River bounds the southern side of the waste disposal site. Eight of the waste pits were identified, six are filled and closed and two are active and in use. The closed waste pits sites were already obliterated. Each of the waste pits measures 4.5 m×3.5 m×2.5 m.
Materials and methods Three principal methods (geophysical investigations, geochemical analysis and geotechnical survey) were
Table 2 Mean physico-chemical properties of the soils Depth (m)
pH
C (%)
N (%)
P (mg/kg)
Ca
Mg
Na
K
H+
Al3+
THC
Closed pit 1
2
Active pit 1 Control 1
Closed pits 1
2
Active pit 1
0
7.1
0.41
0.04
0.84
16.35
1.99
0.83
0.31
ND
ND
19.48
1.5
7.3
0.23
0.03
ND
12.82
1.17
0.32
0.27
ND
ND
14.58
4.5
7.0
0.10
0.02
ND
4.31
0.63
0.25
0.11
ND
ND
5.3
0
7.80
0.35
0.03
1.04
13.20
2.08
0.94
0.20
ND
ND
16.42
1.5
8.10
0.22
0.02
ND
14.48
1.28
0.27
0.20
ND
ND
16.23
4.5
8.00
0.07
0.01
ND
2.15
0.84
0.21
0.07
ND
ND
3.27
1.5
7.80
0.61
0.04
0.74
52.72
8.16
0.94
3.98
ND
ND
65.8
4.5
7.91
0.32
0.02
0.25
29.31
2.54
0.48
2.11
ND
ND
34.44
Depth (m)
Depth (m) 0
5.3
1.22
0.08
ND
2.08
2.72
0.75
0.46
0.60
ND
6.01
1.5
5.2
0.42
0.04
ND
1.28
0.82
0.26
0.25
0.45
ND
2.61
4.5
5.0
0.15
0.01
ND
0.94
0.45
0.12
0.10
0.02
ND
1.61
Depth (m)
Pb
Cd
As
Cr
Co
Ni
V
Fe
Hg
THC
0
90.21
20.51
