Soil classification and concentration of selected heavy metals in some soils of the Niger Delta region, Nigeria
Date
2023-06
Authors
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Publisher
Federal University of Technology, Owerri
Abstract
Some physicochemical characteristics and heavy metal levels in selected spilled and unspilled soils of the Niger Delta region, Nigeria were analysed. A total of three locations were sampled and two profile pits (spilled and unspilled) were dug at each location making a total of six (6) profile pits. Samples were collected from genetic horizons starting from the lowest horizon in each pedon. Conventional analytical methods were employed for the determination of these physico-chemical properties and heavy metals. Data gotten from the laboratory analysis were subjected to simple correlation, coefficient of variability and t-test. Results showed that the consistence of the soils was very friable(Egbem-spilled and unspilled, Oguta unspilled), friable(Oguta spilled and Ugwunagbo spilled) and loose in the epipedons and friable in all subsurface horizon, while the soil structure ranged from very weak fine granular to medium subangular blocky in spilled pedons whereas unspilled pedons were predominantly very fine single grained. There were generally fine and medium roots in the studied soils. The soils were basically Sandy Loam (SL) and Sandy Clay Loam (SCL). The value of sand ranged from 740 - 810 g/Kg. Sand and Silt fractions decreased down the pedons. Low clay characterized the epipedons. The soils were well drained and all soils were deep (> 180cm). Bulk density increased with depth for all pedons and ranged from 1.17 – 1.56 gcm-3 . Spilled pedons had higher bulk densities (1.37 gcm-3 , 1.37 gcm-3 and 1.40 gcm-3 ) than the unspilled pedons (1.33 gcm-3 , 1.30 gcm-3 and 1.33 gcm-3 ).Slight variations (CV < 15%) were recorded for bulk density in all pedons. Moisture content was lower in spilled sites, it showed slight variations (CV<15%) at Ugwunagbo unspilled site and Oguta spilled site, moderate variation in Oguta unspilled and high variation in Egbema (spilled and unspilled) and Ugwunagbo spilled. The pH values in all sites ranged from 4.8 – 6.3 indicating that the studied soils were acidic. The spilled pedons in Egbema and Ugwunagbo were more acidic than their unspilled pedons. But the reverse was observed in Oguta sites where the spilled site had a higher pH than the unspilled pedon. Generally, pH in KCl was less than in water. The pH showed slight variability (CV<15%). There was a significant difference between spilled and unspilled pedons. Generally, total nitrogen was highly variable (49 – 92 %), it was higher in spilled pedons of Egbema and Oguta but the reverse was the case in Ugwunagbo. It decrease down the pedons. Available Phosphorus values ranged from low (<5mg/kg) to high (>15mg/Kg). It was highly variable (CV>35%) in most pedons. Available Phosphorus was higher in unspilled than spilled soils. Organic Carbon generally decreased with depth. Values of Calcium and Magnesium were higher in unspilled than in spilled soils. Sodium values were generally low and varied for different pedons. Exchangeable Potassium had higher values in unspilled than spilled soils. Ca:Mg ratio was below 3 in (Egbema-spilled and unspilled, Oguta unspilled and Ugwunagbo spilled and unspilled) indicating unfertile soils. Higher values were recorded for ECEC in unspilled soils than in spilled soils. Values of Base saturation were higher in unspilled than spilled soils and showed a significant difference between spilled and unspilled pedons. Aluminum saturation values were low in the studied soils. Heavy metal values decreased down the pedon and were generally higher in spilled than unspilled soils, but they were within the permissible limit for use. Generally, the magnitude of heavy metals followed Ni > Pb > Cd > Cr for spilled soils and Ni>Pb>Cr>Cd for unspilled soils. Though the detected levels of heavy metals in the studied soil were within the permissible limits, caution should be taken to avoid accumulation and toxicity. The soils of Ugwunagbo and Egbema were classified as Typic paleudult - Dystric Nitisol (FAO/WRB). While those of Oguta were classified as Typic tropudult - Orthic Acrisol (FAO/WRB).
Description
This thesis is for the award of Master of Science (MSc.) in Soil Survey and Landuse
Keywords
Soil pollution, remediation, soil classification, heavy metals, soil physico-chemical properties, Department of Soil Science and Technology
Citation
Sule, B. A. (2023). Soil classification and concentration of selected heavy metals in some soils of the Niger Delta region, Nigeria (Unpublished Master's Thesis). Federal University of Technology Owerri, Nigeria