Groundwater quality in the vicinity of a dumpsite in Lagos metropolis,Nigeria

Inappropriate management of municipal solid waste dumpsites is a major cause of groundwater contamination in developing countries,but the extent of the problem is not known.This study investigated groundwater quality in the vicinity of Olusosun dumpsite in Lagos,Nigeria,the most populous city in sub-Saharan Africa.During 2020,monthly groundwater samples were collected in 17 wells and boreholes used as drinking water sources,and analysed for 20 physico-chemical parameters.Differences between sites and seasons were statistically assessed,together with changes in water quality index(WQI).The results indicated that heavy metals(Pb^(2+),Ni^(+),Mn^(2+),Fe^(2+),Cr^(6+)),cations(Ca^(2+),Mg^(2+),K^(+)),total hardness and pH were the main parameters impairing water quality.Drinking water quality standards from both the World Health Organization and Nigeria government were exceeded more often in the wet season than in the dry season.Some groundwater properties were negatively correlated with distance to dumpsite(e.g.,Fe^(2+),Pb^(2+),NO_(3)^(−)).Significant differences between sites were identified,but with no clear spatial trend.WQI varied from excellent(6%-24%of the sites over the study period)to unsuitable for drinking water purposes(12%-18%),with good quality prevailing at most sites(35%-47%).Although groundwater quality declined at 24%of the sites over 2020,the results indicated improvements compared with previous decades.Remediation strategies must be implemented to safeguard public health and the sustainability of water resources.

Environmental and Health Impact of Solid Waste Disposal in Developing Cities: A Case Study of Granville Brook Dumpsite, Freetown, Sierra Leone

Indiscriminate disposal of solid waste in dumpsites located within urban areas has proved to be a problem to nearby residents in most developing cities of the world, Freetown is no exception. Open dumps have environmental safeguards;they can pose major public health threats and environmental effects in urban cities. Therefore, this paper presents the findings of a research carried out in Freetown municipal area in Sierra Leone to determine the environmental and health impacts of solid waste disposal at Granville Brook dumpsite on the surrounding human settlements. Data were collected from three hundred and ninety eight nearby dumpsite household residents (less than fifty metres) and two hundred and thirty three far away household residents (more than fifty metres) through the use of structured self-administered questionnaires. Interviews and personal observations were also used to collect some of the data. Descriptive statistics involving tables, graphs and figures were used to present and analyze the data. Results show that both nearby residents and far away residents suffered from related diseases such as malaria, chest pains, diarrhea and cholera, due to the location of the dumpsite closer to their settlements. As a result, this study highlights the need for the Freetown City Council to properly manage and relocate the dumpsite to a safe distance from all human settlements, and provide resettlement and environmental education programmes for all persons living less than fifty metres away from the dumpsite as interim measures.

Integrated Geophysical and Geochemical Methods for Environmental Assessment of Municipal Dumpsite System

Leachate originating from open refuse dumpsite systems can be delineated through an integration of qualitative and quantitative methods. This study was designed to examine extent of leachate and pollution from one of the numerous open refuse dumpsites in Lagos metropolis. Qualitative assessment was determined using electrical resistivity tomography (ERT), vertical electrical sounding (VES) and induced polarization geophysical methods. Both ERT and VES methods revealed persistent low resistivity (1 - 20 Ωm) of leachate to the depth above 35 m. The two methods were projected to produce 3-D view of the site which shows a NW-SE flow pattern of the leachate and possibly, the groundwater. IP values observed over the polluted zone was -2.9 - 8 ms, indicating a sandy layer. Quantitative assessment was achieved by analysis of geochemical substances in the water samples taken from wells and boreholes in the precinct of the dumpsite. Here, we examine the macroelements, salts (sulphates, nitrates and chlorides), heavy metals, radioactive metals contents and physical parameters of the water samples. The analyses reveal the presence of these substances in the water and their strong correlations justified the provenance as the same. As part of the quantitative evaluation, physical parameters (pH, TDS, DO, salinity, total hardness, turbidity, electrical conductivity EC and temperature) of the water samples were also determined. The samples pH plotted in the acidic domain unsuitable for human consumption. Leachate flow direction was generated from the decreasing concentration of measured parameters (geochemical elements and physicals properties) in NW-SE direction which agrees with similar flow pattern deduced from ERT results.

System Dynamics Modeling of Dumpsite Leachate Control in Ogbomosoland, Nigeria

Leachate pollution from landfills is a major source of environmental hazard in many Nigerian municipalities and there is the need to mitigate its effects. The aim of this study is to examine the leachate pollution and determine the effectiveness of liner system in leachate management of dumpsites in Ogbomosoland. The method of modeling us ing principles of system dynamics was employed to determine the interrelationships of leachate generation components for 50 years. Causal loops indicating the linkage of population, economic status, waste generation per capita and weather conditions to wastes and leachate generation were developed. A set of state model equations for Gas Produced (Gp), Precipitation (Pt), Degradation water-loss (Wg), Leachate Quantity (LQn), were formulated. Leachate management strategies of liner systems were studied, and the effectiveness of Compacted Clay (CC), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Geosynthetic Clay (GC), Silt (SI), Sandy loam (SL), and Sand (SA) liners were examined. A user-friendly computer program for estimating leachate generation per time and breakthrough time for liners was then developed. The results showed that a direct relationship exists between leachate and Gp, Pt, Wg and LQn. Average leachate breakthrough times for the liners, in years, were CC (41.5), HDPE (14.0), LDPE (10.0), GC (1.1), SI (0.1), SL (0.01), and SA (0.00002). In conclusion, dumpsite leachate pollution was established as having negative effects on the groundwater resource. Compacted Clay liner is therefore recommended for use in curtailing its menace.

Assessment of the Impact of Solid Waste Dumpsites on Some Surface Water Systems in the Accra Metropolitan Area, Ghana

Water samples from four water bodies that flow through some solid waste dump sites in the Accra metropolitan area of Ghana were analysed over a period of six months for Cd, Pb, Cu, Zn and Mn contents;coliform bacteria and helminth eggs. Other water quality parameters such as BOD, DO, suspended solids and turbidity were also assessed. Cd, Pb, Zn, Mn, and Cu were determined using flame atomic absorption spectrometry (FAAS). Faecal coliforms, total coliforms and helminth eggs were determined by the membrane filtration (MF) method. The water samples contain various levels of Cd, Pb and Mn;Zn and Cu levels were low and found to be below the detection levels of the instrument in most cases. Helminth egg counts in water samples were high;an indication that the water bodies were polluted with pathogens. It has been observed that the major sources of pollutants into the water bodies were organic waste as well as coliform bacteria derived from these waste dumps. The elevated levels of bacteria make the water bodies unsafe for both primary and secondary contacts.

Evaluating Anaerobic Digestion Technology in Reducing the Quantity of Solid Waste: Case of Kigali Dumpsite

Biodegradable organic matter constitutes a great portion of Municipal solid waste and comprises organic material which can be broken down by bacteria like paper, card, green waste, food waste, miscellaneous items with an organic element and fine materials. This paper mainly evaluated the potential of anaerobic digestion technology in reducing the quantity of solid waste destined to the dumpsite in Kigali city. The paper evaluates the viability of using biodegradable waste meant to the land where the biogas is produced and undertaking its cost & benefit analysis for chemical, physical and biological characteristics of municipal solids waste on anaerobic digestion technology. The quantity of municipal waste generated in Kigali city was used for designing the biodigester required. The paper indicates that the organic waste in Kigali city produces 457 L/kg DM of methane and the overall assessed value of methane was 51,384,375 L with the electricity derived from the methane of 180,873 KWh which is 54% of the daily demand in Kigali city. The volume of the biodigester was found to be 58,065 m3. Based on the energy recovered, revealed that cities will benefit this research for the population demand for the increased electricity.

Antimicrobial Resistance Encountered in Garbage Collection Areas and Dumpsites in Nairobi, Kenya Using <i>Escherichia coli</i>and <i>Klebsiella</i>as Indicator Species

Dumpsites and garbage collection areas can act as reservoirs of highly resistant bacterial strains and facilitate the dissemination of Multidrug resistant strains to those living and work on or near the dumpsites and garbage collection areas. The objective of this study was to determine the potential of garbage collection areas and dumpsites in different parts of Nairobi as possible sources of resistant strains using E. coli and Klebsiella as indicator species. The study design was a cross-sectional survey. Sample collection was carried out at different days in seventeen different areas. A total of 126 samples were collected during the sampling period. The samples were then transported to the laboratory for analysis. The samples were cultured on MacConkey agar. Gram staining was done on discrete isolates based on colony characteristics. Biochemical tests were performed on colonies from primary cultures for final identification of the isolates. Antimicrobial disc susceptibility tests and pathogenicity tests were also carried out on the indicator isolates. A total of 121 E. coli and 165 Klebsiella were isolated from all the sampled sites. The highest bacterial burden was recorded from Muthurwa estate dumpsite, with a mean viable count of 8.2 × 1010 cfu/gm while the least was from Dandora dumpsite with a mean count of 1.1 × 1011 cfu/gm. Overall, gentamicin was the most effective antibacterial agent on Klebsiella and meropenem was the most effective on both E. coli and Klebsiella strains. The isolates showed high resistance to ampicillin, streptomycin, and trimethoprim-sulfamethoxazole. It is concluded that municipal waste dumpsites and garbage collection areas bear heavy burdens of potentially resistant bacteria which may constitute major public health hazards, not only to the immediate communities but also to the families of such site workers.

A Comparative Investigation of Groundwater Contamination in Typical Dumpsites and Cemetery Using Ert and Physicochemical Analysis of Water in Benin Metropolis, Nigeria

This paper investigated the comparative analysis of groundwater contamination in Third Cemetery and Costain Dumpsite in Benin Metropolis, South South of Nigeria, using Electrical Resistivity Tomography (ERT) and Physicochemical analysis of water. The implications of land utilization for burial of dead human bodies in the form of cemeteries, many cases associated with coffin and caskets used for interment of remains and the location of refuse dump have received no consideration in Nigeria. Interment of bodies in cemeteries and dumping of refuse in dumpsites remain widespread practice and the only alternative endpoint to dead bodies and disposal of wastes in Nigeria. In Nigeria, this practice had not been perceived as having a significant potential contaminant effect in the environment and especially the groundwater component as search of literature attracted no such study to the country. In Benin City and Nigeria in general, the major cemeteries and dumpsites are located close to human residential areas and virtually all the populace within this locality depends on groundwater as the primary water source for various domestic purposes. Res2Dinv was employed in both sites as the geophysical method. The investigation of cemeteries is always difficult and challenging task in geoforensic prospective. Most researchers assess the impact of interment on the environment by comparing study results from cemeteries with data from reference sites. This study is based on this premise. The 2-D Geological Models showed that both Third Cemetery and Costain Dumpsite contained leachate plumes of various degrees as indicated by the low resistivity values, which infiltrated into the groundwater. The values of Water Quality Index (WQI) of groundwater samples in Third Cemetery and Costain Dumpsite were found to be 13.40 and 21.58 respectively which indicated that the quality of water at both Third Cemetery and Costain Dumpsite were good for drinking and other domestic purposes though with some degrees of contamination.

Leachate Quality Characteristics: A Case Study of Two Industrial Solid Waste Dumpsites

The study evaluates the associated environmental risk of two industrial solid waste dumpsites. The Toxicity Characteristic Leaching Procedure (TCLP) and American Society for Testing and Materials (ASTM) extraction test were used to characterize leachate quality on six solid waste samples obtained in July 2005, March 2006 and July 2006. Solid waste compositions varied with 58% metal scraps, 30% vegetation matter, 10% plastics and 2% paper materials. Statistical T-test (95% confidence limit) showed no significance difference in physico-chemical quality of the leachates obtained by both methods from both sites. Leachates obtained by the TCLP extraction accounted for a total of 92.4% of the overall metal load as against 6.01% for the ASTM method. This disparity is due to the acidic nature of the TCLP procedure which enhances more efficient extraction of metals than the ASTM method. Solid waste deposits at SITE-1 were considered hazardous to the environment, given that the upper 90% UCL values for lead exceeded the TCLP characteristic regulatory levels. These may pose a risk to vegetations and ground water reserve within the vicinity of the dumpsite on the long run. The risk may be such as bioaccumulation of lead in the food chain. Therefore, constant monitoring and possible remediation measures should be carried out to contained contamination.

Assessment of Potential Ecological Risk of Heavy Metals in Soils from Waste Dumpsites in Military Formations in Makurdi, Nigeria

Chemical fractionation of toxic metals (As, Cd and Zn) along the soil profile at waste dumpsites in military formations for dry and wet seasons using Tessier’s sequential extraction procedure was determined using AAS techniques. The order of yield across the fractions was mainly: exchangeable (F1) 2) 3) 4) 5). Statistical analysis (p < 0.05) indicated that there was no significant variation between the values of results obtained from dumpsites A and B of each sampling station. However, the variation between the dumpsites and control was significant (p > 0.05) in most stations. The pollution index was assessed using the degree of contamination (Cd), the modified degree of contamination (mCd), potential ecological risk and mobility factor. The Cd indicated that NFB top soil was considerably contaminated (16.3) while the soils (20 - 40 and 40 - 80 cm) recorded moderate (13.6) and low (5.60) contaminations respectively. Top soil of NSM was moderately contaminated while the contamination status of NPS, NFB and SFB waste dump soils across the depths was “low”. The mCd index for NFB dump soil was “moderate” (2.33) and subsoils (20 - 40 and 40 - 80 cm) were “low” (1.94) and “Nil to very low” (0.800) respectively. The mCd for the other three dumpsites was “Nil to very low” except the top soil of NSM which was “low”. The order of the toxic metals mobility in the studied soils using the Mobility factor (Mf) for dry and wet seasons was Cd > As > Zn and Zn > Cd > As respectively.

Heavy Metals Contents of Municipal Solid Waste Dumpsites in Potiskum, Yobe State Nigeria

The concentrations of As, Cd, Cr, Cu, Ni, Pb, Fe and Zn in selected dumpsites in Potiskum were determined with Buck Scientific 210VGB Atomic Absorption Spectrometer (AAS) AVG 210. One-way ANOVA was deployed at p < 0.05 level of significance for obtained triplicate values. It was found that the concentration (mg·kg-1) of studied heavy metals in Potiskum dumpsites ranged from 0.108 ± 0.02 - 262.536 ± 0.68 with pattern of accumulation Pb (262.536 ± 0.02) > Zn (183.369 ± 0.58) > Fe (159.453 ± 0.50) > Cu (111.382 ± 0.62) > Cr (43.523 ± 0.36) > Ni (6.419 ± 0.26) > Cd (0.679 ± 0.01) > As (0.108 ± 0.02) mg·kg-1. The concentrations of As, Cr, Ni, Fe and Zn fell below the WHO standards while those of Pb, Cd and Cu were above set limits by WHO. High acidity corresponds markedly with high levels of Cd, Cu, Cr and Zn and requires urgent attention as this trend is capable of groundwater contamination that will cause public health concern in affected areas.

Characterization of Dumpsite Leachate: Case Study of Ogbomosoland, South-Western Nigeria

Leachates contain varying complex characteristics. The 5 Local Government Areas (LGAs) under this study that characterized leachate are no exceptions. Five aged dumpsites, one per LGA were selected and leachates extracted from them through BS 1377 standard method. Samples were taken seasonally over 2 years and subjected to Laboratory analyses for physical, inorganic, metallic and microbial characteristics. The key leachate contents mean, (pollution indices) included Nickel (0.2 mg/l), Manganese (1.8 mg/l), Dissolved Oxygen (11.5 mg/l) and Total Coliform (24.3 cfu/ml). Results obtained were compared with the Nigerian Federal Environmental Protection Agency (FEPA) standards. The leachate of the area is found to be stable, objectionably coloured, odoured, alkaline, turbid, hard, with moderate recalcitrant organic and biological matters. The study recommends leachate treatment to minimize groundwater pollution.

Electrical Resistivity Survey on Two Waste Dumpsites at Nguru,Potiskum,Yobe State,Nigeria to Determine the Effect of Leachates on Ground Water Aquifer

The research intends to bring out the contribution of leachate on groundwater in two dumpsites in Nguru and Potiskum all in Yobe state,Nigeria.A total of seven(7)and eight(8)VES by Schlumberger electrode with the use of Wenner electrode configuration.The results were interpreted by the use of WinRESIST for VES and IPWIN2INV for ERT.The study pointed out that,the area in question is comprised of four layers of geoelectric such as the topsoil,clay,sand,sandy clay and sand.The range of the first resistivity layer was from 6.16Ωm to 332Ωm in the first geo-electric layer and its thickness range from 2.77 m to 37.7 m and a depth range of 2.77 m to 37.7 m.the range of the second resistivity layer was from 16.5Ωm to 37.9Ωm which has the range of its thickness from 4.1 m to 10.7 m.The range of the third resistivity layer was from 101.2Ωm to 288.2Ωm which has the range of its thickness from 38.9 m to 99.7 m,and the first aquifer in the area.The range of the first resistivity layer was from 100.7Ωm to 214.3Ωm which has the range of its thickness from 28.5 m to 94 m.The fifth layer which is the second aquifer and has resistivity from 254Ωm to 350Ωm with a very large thickness.The range of the first resistivity aquifer is from 101.2Ωm to 288.2Ωm and the range of the second resistivity aquifer is from 253.8Ωm to 350.1Ωm.The 2D ERT profiles unveiled areas with low resistant zones and later discussed as zones penetrated by contaminants originated from dumpsites whereas high resistant zones represent areas of low or non-conductive materials in the area.Data obtained from four dumpsites indicated that leachate of the waste dumpsites penetrated into aquifers and polluted the groundwater.The existence of contaminants in the water was noted by a decrease in the formation resistant values.It is seen,from the results of the survey(geophysical)that the water in the area is polluted and it accounts for the prevalence of any disease related to water that are common in the area.

Assessment on Radiation Hazard Indices from Selected Dumpsites in Lafia Metropolis,Nasarawa State,Nigeria

This research reports an assessment of ionizing radiation in some chosen Dumpsites in Lafia Local government area of Nasarawa State.Ionizing radiation measurement was conducted at four Dump sites.The survey was done using a radiation survey meter(Radex one Outdoor 55130719 NA).Radiation exposure rate in micro sievert per hour(μSvhr^(-1))was measured.Readings were taken by placing the detector at gonad level about 1 meter above the ground.Result showed that the average annual effective dose rate in the selected dumpsites were 0.22 mSv/yr for Lafia modern market,0.17 mSv/yr for dumpsite opposite governor Isa house,0.15 mSv/yr for Timber shade Lafia and 0.20 mSv/yrfor Science School Lafia respectively with a mean value of 0.19 mSv/yr for all location,while the mean calculated excess life cancer risk(ELCR)is 0.65×10^(-3).Dumpsites yearly absorbed dose rate and their corresponding ELCR values did not exceed the 1.0 mSv/y Basic Safety Standard set for the masses by International Council on Radiation Protection(ICRP,1999)and mean world average ECLR value of 1.16×10^(-3).Based on these results there are no radiation consequence to the scavengers,dumpsite workers and residents living around the dumpsites.

Migration of Biodegradable Organic Matter in Underlying Soils of Household Waste Dumpsites: A Case Study in Abomey-Calavi, Benin

This paper presented the first part of the studies about the development of a tool for groundwater contamination prediction, conducted by the Laboratory of Sciences and Technology of Water (UAC/Benin). The investigation made consisted in estimating the combined effect of retardation factor and biodegradation on migration processes of leachate, in the underlying soils of household waste dumpsites, without active safety barrier. Leachate infiltration tests for different initial conditions were made on soil columns and the breakthrough curves were traced for electrical conductivity, the 5 day biochemical oxygen demand (BOD5) and total kjeldahl nitrogen TKN. A mathematical migration model was developed and solved numerically by finite difference method and implemented with Matlab R2013a. Thus, the calibration of the model was made with electric conductivity data by determining the dispersion coefficient of the studied soils (D = 0.96 cm2/min). Simulations for model verification showed that the established model can perfectly predict the migration of biodegradable organic pollution (BOD5) but did not give conclusive results for the monitoring of nitrogenous organic matter (TKN). The influence of the retardation factor on the migration of biodegradable organic pollutants in soils was linear, while the biodegradation rate of the organic material on migration showed an exponential pattern.

Recovery of plastics from dumpsites and landfills to prevent marine plastic pollution in Thailand

Marine plastic pollution has become a major threat to the ecosystem.The increasing production and use of plastic,combined with limitations of waste management practices,mean the leakage of plastic waste into the environment is bound to increase.This study focuses on the determination of plastic recovery potential from dumpsites and landfills in Thailand,to potentially prevent marine plastic pollution.In this study,two dumpsites were analysed wherein an average of 42% of plastic was found to be present.This value,when extrapolated for Thailand,is equivalent to 187.9 million tonnes of plastic waste in dumpsites and landfills.While there are 2380 dumpsites in the country,this study suggests that 973 of these spread over 42 provinces are located near water bodies or coastline,which should be considered as a priority.The plastic waste recovered from these dumpsites can be treated by co-fuelling in cement industries.Cement kilns can valorise plastic waste as they can reach up to 75%energy recovery from waste,which is much higher compared to traditional waste-to-energy plants.With adequate incentives and sound regulations,cement industries could help in the reduction of marine plastic pollution with controlled emissions and a very large capacity to co-fuel cement production,there is a readily available solution to manage the large volumes of solid waste generated.

Monitoring Groundwater Contamination Using Surface Electrical Resistivity and Geochemical Methods

Surface electrical resistivity has been used as a tool in the detection of groundwater contamination. In this work, five geoelectric soundings with two at waste dumpsites have been carried out in Uyo, Southwestern Nigeria to map the gross layered structure of the refuse as well as the extent of groundwater contamination. The geology of the area (Benin Formation) mainly consists of fine-medium-coarse grained sands. The data of five Schlumberger Vertical Electrical Soundings (VES), with a maximum of AB/2=500 m, were analyzed using Hemkler computer program. In general, there exists a common feature in the resistivity variation pattern of high-low-high-low-high in the area. The result shows a wide range of resistivity variation ranging from 2.0 to 60700 ?m. Based on the survey results, the resistivity values less than 75 ?m shows contamination due to waste at Eka street and Udo street. Also, the high resistivity value at mechanic village (60700 ?m) may be related to the waste oil deposit due to the automobile repair activities. A comparison of the resistivity values and the curve types at the dumpsites (Eka street and Udo street) and other locations show that the two dumpsites have an H curve type indicating contaminated zones, while other locations have a K curve type indicating non contaminated zones. Hydrochemical analysis of groundwater samples collected in the area was also carried out for some physico-chemical parameters. The results produced higher concentration of conductivity, total dissolved solids and chloride values for water collected at close locations to dumpsites than those far away from the dumpsites: an evidence for a quantitative assessment of groundwater contamination.

Quantitative human risk analysis of 2015 Shenzhen dump failure considering influence of urbanization

With the rapid development of urbanization, a large amount of construction spoil was stockpiled around cities and formed extensive dumps. Construction spoil is one of the main construction and demolition(C&D) waste and municipal solid waste(MSW). Once the construction spoil dump becomes unstable, it will bring great risks to the surrounding residents. A catastrophic dump failure occurred on 20 December 2015 in Guangming New Strict, Shenzhen, China. Approximately 2.51×10^(6) m^(3) of construction waste slid out from the dumpsite, destroying 33 houses and causing total 77 casualties. This paper attempts to analyze the failure probability of the construction spoil dump using Monte Carlo simulation considering the spatial variability of soil properties, and to quantify the dynamic human risk considering the increasing urbanization. Influence of urbanization on the human element at risk is analyzed by referring to multi-temporal remote sensing images. A quantitative human risk assessment model is employed to determine the landslide human risk referring an assessment criteria curve between frequency of number fatalities and number of fatalities(F-N curve). It is found that the societal risk at daytime was 0.078, 0.088, and 1.432 in 2002, 2014, and 2015, respectively. Meanwhile, the societal risk at night was 0.034, 0.037, and 0.611 in 2002, 2014, and 2015, respectively. The quantitative method was benchmarked by the other landfill failure. It implies that the human risk increased with the development of urbanization and its value at daytime was approximately twice as much as at night. The new approach for the human risk assessment provides guidance for modern MSW landfills and highlights the obvious influence of urbanization on the human risk in other areas.

Geological environment impact analysis of a landfill by the Yangtze River

In order to assess the geological environment impact of a city landfill by the Yangtze River, soils from different depths in the dumpsite were sampled and analyzed. It was found that pollutants content at the site was distinctly higher than that in nearby environments. The content of heavy metals, such as Cd, Hg, As, Pb and Cu, reduces as depth increases; the content of elements F, Cl and N is the contrary. Pollutants migration driven by underground water flow was analyzed, considering the hydro-geological conditions of the site. It is believed that, due to leaching after rainfall infiltration, pollutants in the garbage layer migrates deeper, the cohesive soil in the underlying surface prevents them from spreading to the deeper aquifer; additionally, the high pressure tolerance of the deep groundwater is a key factor in preventing pollutants from entering the aquifer. Furthermore, human control has reduced the annual fluctuation range of water level in nearby rivers, weakening the hydrodynamic relations with phreatic water, and thus reducing the spreading of pollutants to nearby surface waters.

Heavy Metal Pollution of Topsoil in the Vicinity of an Industrial Estate Co-Located with a Housing Estate in Southwestern Nigeria

Heavy metals were determined in topsoils around a major industrial estate co-located with a housing estate in the southwestern region of Nigerian. Samples were collected on three-monthly basis for 18 months, from the industrial waste dumpsites, industrial area, residential area, around an effluent channel, outskirts of the estate and control sites. Average levels of Cu (2850 ± 3340 mg/kg), Pb (768 ± 450 mg/kg) and Ni (105 ± 30 mg/kg) at the dumpsites were significantly higher than other locations. At the industrial area and effluent channels, Pb and Cr levels were slightly elevated compared with other metals. Metal levels at the residential area and outskirts of the estate were about the levels in the control. Generally, the degree of contamination within the vicinity of the estate was of the order Cu>Pb>Ni>Cd>Co>Cr. Average total bioavailable (non-residual) fraction of the metals consisted of 52.0% of the metal load, with this fraction for Cd and Pb being 73.9% and 60.7% respectively. Topsoils around the dumpsite were evidently polluted with high levels of copper and lead. Seepage of leachate from the dumpsite has the potential of contaminating ground water reserves. Improper disposal of industrial solid wastes appears to be the likely source of metal pollution in the industrial estate. Heavy metal pollution in the estate can therefore be significantly reduced by prompt and proper disposal of generated solid wastes, and the application of particulate scrubbers in the industries.