Physico-chemical and thermal characteristics of sandy loam soils contaminated by single and mixed pollutants (mineral and vegetable oils).

Samples of contaminated top soil (0-30 cm) and uncontaminated soil (control) from two locations in Precambrian basement complex area were analyzed to assess the effects of single and mixed oil contaminants on the physico-chemical and thermal properties of soils. Pearson's correlation and analysis of variance (ANOVA) were used to study the interrelationships of the studied parameters as well as variation of studied soil characteristics under the different oil contaminants, respectively. Results showed insignificant impact of pollutant(s) on the textural class of contaminated soils. The highest and lowest mean soil resistivity (SR) values were found in petrol-contaminated and mixed surfactants (shampoo + conditioner) -contaminated soils, respectively. The least values of mean specific heat capacity (SHC), heat capacity (HC), and soil water diffusivity (SWD) were found in soils contaminated by mixed surfactants-contaminants. However, mixed mineral oils (petrol + diesel + engine oil) and mixed vegetable oils (palm oil + groundnut oil) had mean SHC values lower than those of control soils at the two sampling locations. The mixed surfactants-polluted soil is characterized by lowest mean bulk density (BD) and highest mean gravimetric water content (GWC) while lowest mean GWC and highest mean SWD characterized engine oil-contaminated soils. The analysis of variance (ANOVA) result revealed significant variation in % sand at 5% level (p < 0.05) for petroleum-derived contaminants but no significant differences in mean values of all analyzed soil properties under vegetable oil contaminants.

Soil physicochemical and hydraulic properties of petroleum-derived and vegetable oil-contaminated Haplic Lixisol and Rhodic Nitisol in southwest Nigeria.

Various daily human activities can result in the release of pollutants of different chemical constituents and specific gravities into natural soils. Pollution of natural soils is a recurring occurrence in the environment and it contributes greatly to the alteration of soils properties. The results of an assessment of the effects of selected petroleum-derived and vegetable oils on soil physicochemical and hydraulic properties are presented in this work. Topsoil samples at a depth of 0-20 cm of the same textural class were collected from the order Lixisols and Nitisol within Ogun State, southwest Nigeria. Surface soil samples were collected and treated with petrol, diesel and palm oil at two different volumes (50 and 100 ml). Investigated soil properties include particle size distribution, soil pH, bulk density (BD), total porosity (TP), saturated hydraulic conductivity (Ksat), available water capacity (AWC), total carbon (TC), total nitrogen (TN), organic matter (OM) content, cation exchange capacity (CEC), potassium, sodium, and soil resistivity. Analysis of variance and Pearson's correlation were used to study the variations of the relationship of analyzed soil properties under different soil types and treatments. The regression analysis shows that all the generated models for predicting Ksat values under different soil treatments had R2 values ranging from 0.999 to 1.000. Results showed that treatment with either petroleum-derived or lipids has no effects on soil pH and textural class. Results further revealed that palm oil contamination at 50 ml recorded least values of Ksat in the two soil types. In all cases, BD and Ksat of the contaminated soils of the two sampling locations were reduced compared with their control values. Correlation coefficient showed expected strong negative correlation between TP and BD as well as between any two of organic parameters (TC, TN, and OM) and soil resistivity, TC, and TN at 1% level in both soil types. Two-way ANOVA showed that there were significant differences at 5% level between the two locations with respects to BD, TP, and CEC while significant differences in Ksat, pH, TC, TN, and OM occur between soils from the two locations under various treatments at 5% level.

Geostatistical analysis of uranium concentrations in North-Western part of Ogun State, Nigeria.

Several statistical techniques have been adopted in the analysis and interpretation of radiometric survey data set with little attention to the geostatistical approach. In this study, the geostatistical technique was used to analyse an airborne uranium data set in the North-western part of Ogun state to deduce the autocorrelation level of uranium with the corresponding geological composition through the geostatistical model fitting. Twelve uranium lithological (UL) units were identified and analysed using variogram and kriging. Three variogram models namely; spherical, exponential and gaussian, were utilised. The variogram results showed that the three models fit in the interpretation of uranium data in the order of Spherical < Gaussian < Exponential models for all the UL units except at UL6 which had range (R) values of 4227.3 m, 5318.2 m and 5636.4 m for Gaussian, Spherical and Exponential models, respectively. The Nugget-Sill ratios (NSR) were in the range of 3.57-18.97% for the three models across the 12 UL units. These results indicate strong spatial autocorrelation/dependency of uranium concentration on geological composition. The ordinary kriging estimator revealed that the weathered basement formation has the highest uranium concentration compared to basement and sedimentary formations across the study area. The coefficient of variation results also revealed homogeneity in the uranium source across the UL units. The geostatistics technique is a useful mathematical tool in the analysis and interpretation of uranium concentration in the North-western part of Ogun State.