Estimation of total dissolved solid in groundwater using multiple linear regression analysis around Igando dumpsites in Lagos, South-West, Nigeria

This study presents a multiple linear regression (MLR) TDS model that relates the TDS data obtained from groundwater samples to the geophysical data obtained from Electromagnetic (EM) data, as an alternative approach to mapping and monitoring the impact of TDS in groundwater. The predictive power of the developed MLR TDS model was appraised to determine the feasibility of using the TDS model to predict groundwater TDS around the study area. Although, the accuracy of the developed TDS model is site specific, the EM data around the area can be applied to the model to determine TDS concentration in groundwater, thus reducing the time and cost of acquiring and monitoring both parameters separately. The utilisation of the proposed MLR TDS model could assist in the implementation of seasonal groundwater quality monitoring programmes around the dumpsites. From the results also, association between TDS and EC and between TDS and N03 are 0.93 and 0.67 respectively, while that between TDS and hardness is 0.81, suggesting common source of contamination around the sites. Generally, there are relatively higher values of the measured physicochemical properties of water around the North-western part of Solous 1, North-western and South-western part of Solous 2, South-western and Southeastern part of Solous 3 dumpsite when compared with other parts investigated. Therefore, groundwater within the study area may have been impacted by the leachates from the decomposed refuse, and boreholes located at positions other than these zones are likely to yield uncontaminated wate

Time dependent electrical resistivity tomography and seasonal variation assessment of groundwater around the Olushosun dumpsite Lagos, South-west, Nigeria

Time-lapse electrical resistivity tomography (ERT) and seasonal variation studies of the physicochemical properties of groundwater were carried out on the Olushosun dumpsite in Lagos South-western Nigeria, to monitor, track the depth of leachate contamination, and to investigate the impact of seasonal variation on groundwater quality around the dumpsite. Six 2-D resistivity imaging lines were investigated. The independent inversion of the dipole–dipole and pole-dipole resistivity data indicated that contaminated zones are characterised by resistivity values ranging from 0.63 to 12.5 Ωm, and a maximum depth of 141m was investigated. The pole-dipole models show clear evidence of vertical migration of contaminant with time, as depth of contamination increased from 106m in May 2014 to about 120m in December 2015 around the investigated portion of the dumpsite. Analysis of the seasonal variation of the examined physicochemical properties of the water samples taken from wells and boreholes within and around the site showed that there is increase in concentration of TDS and EC in the dry season study and a corresponding increase in the mean concentration of pH, Ca, Mg, hardness, Cu, Cr, NO3, SO4 and Na from the dry season results. Also, there is reduction in the mean concentration of Fe, Zn, Mn, PO4, Cl, and Ni in the dry season when compared with the wet season analysis. Generally, there is a strong correlation between the ERT results and the physicochemical parameters of ground water quality viz-a-viz the contamination status of the Olushosun dumpsite. This increased trend in the dry season period could be attributed to the increase in concentration of the dissolved metals due to evaporation, and on the other hand, dilution effect of the rainfall during the wet season. South East direction of contaminant flow was established from the water table contour lines produced for the area. The research has clearly shown that the groundwater within the study area has been impacted by the leachate from the decomposed refuse at the dumpsite and may constitute danger to the life of residents living around the dumpsit

Geophysical assessment for vertical leachate migration profile and physicochemical study of groundwater around the Olusosun dumpsite Lagos, south‑west Nigeria

The study was aimed at assessing the vertical movement of leachate from 2001 through 2015, and groundwater physicochemical parameters analysis around the Olusosun dumpsite, through a time-lapse study.Tracking the leachate vertical migration profile was achieved through analysis of VES time-lapse data obtained from previous investigations on the dumpsite between 2001 and 2006, and 2D resistivity data acquired from this study in 2014 and 2015. Seventeen borehole and hand-dug well water samples were obtained randomly from 17 sampling locations around the dumpsite, first, in August 2014 (wet season) and then a repeat in December 2015 (dry season). The results of the VES data and 2D resistivity analysis showed that there is a constant and progressive increase in the depth of migration of the contaminants generated on this site into the subsurface environment over the years. It also showed that the contaminated zones are characterised by resistivity values ranging from 0.63 to 12.5 Ωm, and a maximum depth of 120 m has been impacted by the contaminants. The results of the water sample analysis showed clear variations for the various elemental constituents analysed for. Most of the physicochemical parameters analysed fell within the World Health Organisation (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ) standard limit. Comparing the wet and dry season results, there was generally an increase in the mean concentrations of TDS, EC, temperature, hardness, Ca2+, Mg2+, K+, Na+, Cl−,NO− 3 , Zn, Cu, Pb and Cr from the dry season study, particularly the samples with close proximity to the dumpsite. On the other hand, there was reduction in the mean concentrations of SO2− 4 ,PO3− 4 , Fe, pH, and Ni from the dry season study when compared with the wet season. This trend could be attributed to the fact that in the absence of rainfall during the dry season period, contaminant accumulation in groundwater continued undiluted due to continuous breakdown of the biodegradables units with time, and this led to the generally high concentration of the physicochemical properties during the dry season. The implication is that the water around the study area has lower quality in the drier season when compared to the quality of water during the wet season, and so water treatment should be given more priority during the dry season before consumption and usage for other domestic purposes to avoid waterborne diseases. Generally, the information obtained from the geophysical study will facilitate decisions on improving protection for groundwater resources around the study area

Geophysical and hydrophysical evaluation of groundwater around the Igbenre Ekotedo dumpsite Ota, Southwest Nigeria, using correlation and regression analysis

A study involving geophysical survey and groundwater analysis was carried out at the Igbenre Ekotedo dumpsite in Ota, Southwest Nigeria. The aim was to monitor and track the depth of leachate contamination around the dumpsite. A proposed simple multiple linear regression (MLR) model of groundwater total dissolved solids (TDS) was also developed. This was achieved by correlating the observed TDS of groundwater samples collected within and around the vicinity of the dumpsites with multiple terrain conductivity data derived from a geophysical method. The results of the electrical resistivity tomography (ERT) obtained along four profile lines in August 2014, and a time‐lapse survey in December 2015 delineated leachate plumes as low‐resistivity zones ranging between 0.54 and 12.5 Ω m around the dumpsite, with good correlation between the wet and dry season models. The results also showed that leachate from the decomposed refuse materials has polluted the subsurface under the dumpsite from the surface to a depth of about 45 m, and by extension contaminating groundwater aquifer around the area. Results from the electromagnetic (EM‐34) experiment and groundwater TDS parameters from seven (7) boreholes around the vicinity of the EM profiles showed a strong positive correlation. Therefore, a simple multiple linear regression (MLR) TDS model that relates the TDS data obtained from boreholes to the geophysical parameters obtained from the EM‐34 data (HD 20, HD 40, and VD 40) was developed for the purpose of efficient groundwater resources monitoring and management around the dumpsite and their communities. The predictive power of the developed MLR TDS model was also apprised to determine the feasibility of using the TDS model to predict and estimate groundwater TDS around the study area. The developed TDS model can be reliably deployed for groundwater TDS estimation and monitoring around the study area where there are no boreholes, but with only terrain conductivity data. However, where there are borehole and hand‐dug wells, terrain conductivity data around the area alone can be applied to the model to determine TDS concentration in groundwater, thus reducing the time and cost of determining and monitoring both parameters independently

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 tomo- graphy (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 ground- water. 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 ele- ments and physicals properties) in NW-SE direction which agrees with similar flow pattern deduced from ERT results

Groundwater Quality and Identification of Hydrogeochemical Processes within University of Lagos, Nigeria

Water samples from twenty one boreholes were col lected within University of Lagos and analyzed for physical properties. trace elements and cations using inductively coupled plasma optical emission spectrometry (ICP-OES). Physical analysis of the samples shows slight acidity and alkalinity with 78% of the samples exceeded recommended standards. They can be classified as fresh water based on TDS and EC. Chloride concentrations fall within water standards in most s<1mples while AI, Na, Pb and Br exceeded·recommended standards in most samples. Gibbs plot, rel ationship between total c<1tions. Na + K . Ca .,. Mg and Cl showed that all the groundwater samples fall in the water-rock interaction field which suggests that the weathering of rocks and influence of sea water primarily controls the major chemistry of groundwater in the area. Sodium Absorpti on Ratio (SAR) for all the water samples was less than 10 and excel lent for irrigntion purpose. Only 33% of water samples were su itable for irrigation based on Soluble Sodium Percentage (SSP) and Magnesium A dsorption Ratio (MAR), whereas based on Kellys Ratios (KR) all the water samples were not good for irri.gation purpose having KR greater than I. Fifty percent of the water samples showed pollution index (PI) above I with highest contribution (37.8%) from lead (Pb). Mn, AI, N i, Fe and As contributed 29.3%, 19.13%, 8.66%, 4.25% and 0.8:2% respectivel

Radiometric and electromagnetic investigations of the Olushosun dumpsite Lagos, Southwest, Nigeria

The Olushosun dumpsite is one of the largest dumpsites in Nigeria, and variety of waste materials are often deposited on the dumpsite. Therefore, radiometric and electromagnetic (EM) investigation of the dumpsite was embarked upon to assess the radioactive status and the extent of leachate contamination. A well calibrated portable radiometric spectrom- eter nuclear radiation monitoring metre (Model BG0-Super-SPEC RS 230) and the Geonics EM 34 measuring instruments were used to achieve this objective. The mean activity con- centration of 40 K measured along all the profile lines ranged from 0.22% to 1.19% (68.86–372.47 Bq/kg), while that of 238 U and 232 Th ranged from 0.88 ppm to 2.02 ppm (10.87–24.95 Bq/kg) and from 4.87 ppm to 15.61 ppm (19.65–63.38 Bq/kg) respectively. The results of the radiation dose rate measurement showed that the overall mean absorbed dose rate measured in the study area were comparable to those reported around some cities in Nige- ria. The radiation level along some points on the profile lines, even though high, did not exceed the safe limit of 70 μSvyr −1 as recommended by UNESCO on effect of Atomic Ra- diation. This implies that the inhabitants around this area are not exposed to radiological risk, and the dumpsite when reclaimed in future, could be used for the construction of buildings without any form of restrictions. However, continuous exposure to these radia- tions may have long term consequences on human health. Results from the EM data set along traverses on the dumpsite show that the subsurface is characterised by high conduc- tivity (60–680 mS/m) up to a depth of 60 m. The high terrain conductivity signature here may be attributed to leached contaminats migrating into the subsurface and contaminating shallow aquifers. The descriptive statistical analysis of the measured EM data sets showed higher level of correlation among parameters measured along control lines outside of the dumpsite. Generally, correlation between the entire EM data on the dumpsite was poor, but reasonably better for the control data. This could be attributed to the heterogeneous properties of waste materials deposited on the dumpsite

Modeling groundwater total dissolved solid from derived electromagnetic data using multiple linear regression analysis: a case study of groundwater contamination

The high concentration of total dissolved solids (TDS) and other physicochemical parameters in groundwater around dumpsites have been used to implicate contamination from decomposed waste materials. A simple multiple linear regression (MLR) TDS model that integrates the TDS data derived from boreholes and hand-dug wells to the geophysical parameters obtained from the frequency-domain electromagnetic (EM) data was developed in this research. This is with a view to efficiently monitor groundwater resources and exploration around the Olusosun dumpsite and its communities. With the aid of the MLR equation, the observed TDS concentration of water samples collected from boreholes and hand-dug wells, and the corresponding estimated ground conductivity data in the vertical dipole mode (VD 40) and horizontal dipole modes (HD 40 and HD 20), obtained from geophysical surveys were regressed in Microsoft Excel software to generate a MLR TDS model. The integrity of the derived TDS model was appraised to examine the possibility of deploying it to investigate the TDS content of groundwater around the study area. The EM data and the resistivity models obtained around the study area confirmed contamination going on around the dumpsite. The developed TDS model can be put to use with high confidence, for groundwater TDS prediction around the study area where there are only terrain conductivity data but with no boreholes parameters. Also, terrain conductivity data alone can be applied to the model to predict the concentration of TDS in groundwater where there are no boreholes and hand-dug wells, therefore reducing the cost and time of determining and monitoring both parameters independently. With the aid of the ArcGIS software, the TDS model was used to generate TDS estimate map for the area. The knowledge of the TDS variability in such a map could give a clue about the integrity of the underground water around the site

Seasonal Evaluation of Groundwater Quality and Radiometric Parameters Around the Igbenre-Ekotedo Dumpsite in Ota, South-West, Nigeria

This study was carried out in response to public concerns on the status of groundwater tapped from boreholes by some residents around the study area. The area was also assessed for its radiometric status. Water samples were obtained from nine (9) sampling points around the dumpsite to determine their physicochemical parameters. Analysis of the water samples carried out in May 2018, and March 2019 indicated that TDS, EC, hardness, Ca2+, Mg2+, pH, Fe, Mn, Cl- , NO - around the western part of the dumpsite were higher when compared with WHO, 2007 benchmark. Leachates 3 from the dumpsite could have been responsible for these high values. In terms of seasonal variation of the measured parameters, the values obtained for the dry season were relatively higher than those obtained during the rainy season. The depths of boreholes around the western part where contamination was inferred are within 30 m to 40 m. Therefore, borehole location for water in the future should target deeper aquifers to avoid being contaminated, and attention must be given to water treatment during the dry season. The mean annual radiation level for all the profiles were41.11 μSvyr-1, 44.73 μSvyr-1, 36.81 μSvy-1, 45.00 μSvyr-1, 16.16 μSvyr-1 and 19.69 μSvyr-1 respectively. The results of the radiation emission study showed that the general average absorbed dose rate measured on the dumpsite did not surpass the minimum radiation level of 70 μSvyr-1 as prescribed by UNESCO on the effect of Atomic Radiation. Therefore, the dumpsite does not pose any radiometric threat to the inhabitants of the community

Hydrogeophysical mapping of aquifer in new foursquare camp, ajebo, southwestern nigeria

Abstract: Groundwater mapping using vertical electrical resistivity sounding (VES) with Schlumberger electrode array in rugged basement terrain of the new site of Foursquare campground, Ajebo was carried out. The camp already has about five water boreholes with only one fully functioning and about three completely failed. This resulted to scarcity of the commodity within the camp largely patronized by mammoth crowd drawn from across and outside Nigeria. Twenty-seven (27) VES points were established, five out of which were located beside existing boreholes for post-drilling assessments and comparison. The result shows four geoelectric layers -top soil, clay/lateritic clay, weathered/fractured layers and fresh basement. The Dar-Zarrouk parameters evaluated are total longitudinal conductance (S), total transverse resistance (T), average longitudinal resistivity (ρ L ), average transverse resistivity (ρ t ), electric anisotropy (l), root mean square resistivity (ρ m ) with values ranging from 0.02 -0.46 -1 , 315 -15039 m 2 , 22 -439 m, 46 -655 m and 1.02 -1.63 dimensionless, 36 -356 m respectively. These gave clue to aquifer potential of the study area. In addition, combination of sounding results, borehole history and geoelectric parameters of five VES points beside the pre-existing drilled holes were also employed to achieve optimum result. These reveal that most of the failed pre-existing water boreholes in the area were located on clay/clayey sand or thin weathered layer horizons while the one sited beside the functioning borehole was located on fractured layer having resistivity of 290 m and 22.37m thickness. Thus, this was then used as reference point to recommend additional locations for siting water-supply wells in the area