Quality Of Soil Samples Research Articles

Pollution indices and microbiological assessment of soil samples from motor parks around New Benin Market, Benin City, Nigeria

This study was designed to assess the physicochemical, pollution level and microbiological quality of soil samples collected from motor parks around the busy New Benin Market. Four different motor parks were selected for the study including a control location. Atomic Absorbance Spectrophotometry, pour plate method were adopted in analyzing the physico-chemical, heavy metals and microbial flora of the top soils Result obtained for physiochemical analysis revealed pH and electrical conductivity of the soils ranged from 6.68±0.09 - 7.39±0.12 and 314.5±34.50 – 1598.5±157.50μS/cm respectively. Soil particle analysis revealed percentage composition of sand and silt ranged from 92.92±0.91 – 95.585±0.12 %. And 2.32±0.17 – 4.33±0.05 % respectively. The levels of Lead, Cadmium and Chromium 0.01±0.01 – 0.06±0.04 mg/g, 0.02±0.02 – 0.14±0.11 mg/g and 0.02±0.01 – 0.14±0.11 mg/g respectively. The ecological risk index in soil samples revealed that lead, cadmium and chromium concentrations in soil samples had no ecological risk (ERI<40). Pollution Load Index of soils ranged from 0.00229-0.00607. Potential ecological risk index (PERI) of soils ranged from 0.007-2.41. The Total heterotrophic bacterial counts and Total fungal counts of the soil samples ranged from 60.50±2.50 – 114.00±3.00 (×104 cfu/g) and 50.50±5.50 – 70.50±4.50 (×104 cfu/g) respectively. Identified bacteria were Klebsiella sp., E. coli, Enterobacter aerogenes, Aerobacter sp., P. mirabilis, Serratia sp., Bacillus sp. And Micrococcus sp. Predominant fungal isolates were species of Aspergillus, Trichoderma, Mucor and Penicillium. The contamination levels from the studied soil samples indicate relative low pollution; however, there is a call for environmental attention to avoid any possible escalation of pollution levels.

Optimization of the sampling scheme for maps of physical and chemical properties estimated by kriging

The sampling scheme is essential in the investigation of the spatial variability of soil properties in Soil Science studies. The high costs of sampling schemes optimized with additional sampling points for each physical and chemical soil property, prevent their use in precision agriculture. The purpose of this study was to obtain an optimal sampling scheme for physical and chemical property sets and investigate its effect on the quality of soil sampling. Soil was sampled on a 42-ha area, with 206 geo-referenced points arranged in a regular grid spaced 50 m from each other, in a depth range of 0.00-0.20 m. In order to obtain an optimal sampling scheme for every physical and chemical property, a sample grid, a medium-scale variogram and the extended Spatial Simulated Annealing (SSA) method were used to minimize kriging variance. The optimization procedure was validated by constructing maps of relative improvement comparing the sample configuration before and after the process. A greater concentration of recommended points in specific areas (NW-SE direction) was observed, which also reflects a greater estimate variance at these locations. The addition of optimal samples, for specific regions, increased the accuracy up to 2 % for chemical and 1 % for physical properties. The use of a sample grid and medium-scale variogram, as previous information for the conception of additional sampling schemes, was very promising to determine the locations of these additional points for all physical and chemical soil properties, enhancing the accuracy of kriging estimates of the physical-chemical properties.

Micro-morphological analysis of the effect of sampling by the volumetric ring method on soil structure

This report investigates the effect of sampling by the volumetric ring method on pore size number and shape distributions. Soil porosity was analyzed using the micromorphological image analysis technique, which helped to explain soil structure changes near the border of samples collected in cylinders and provided detailed information about pore shape, number, and size distribution variations along the samples. Compaction due to sampling affects mainly large irregular and rounded pores of the soils utilized in this study. When evaluating inaccuracies in density measurements due to the compacted regions caused by the sampling device the average soil bulk density for each soil resulted in the ranges of 1.72 ± 0.05 g.cm −3 for Geric Ferralsol soil, 1.66 ± 0.03 g.cm −3 for Eutric Nitosol soil and 1.33 ± 0.05 g.cm −3 for Rhodic Ferralsol soil, respectively. When calculating the average soil bulk density over smaller regions, e.g. in the center of each sample (area of 17.14 mm 2 ) results reduced to 1.64 ± 0.05 g.cm −3 with Geric Ferralsol soil, 1.56 ± 0.03 g.cm −3 with Eutric Nitosol soil and 1.29 ± 0.10 g.cm −3 with Rhodic Ferralsol soil, respectively. These results clearly indicate the effect of sampling by the volumetric ring method. The use of image analysis was essential to explain compaction differences close to the border of the samples collected using cylinders (volumetric ring method) and provided detailed information about pore shape and size distribution variations within soil samples. The results are useful as indicators of the consequences of sampling on the quality of soil samples.

Automation and Standardisation of Site Specific Soil Sampling

The quality of soil sampling has a significant effect on the accuracy of site specific fertiliser application. Soil sampling depth, number of cores and their distribution within a field or field section are important criteria for achieving a high quality sample. Considering the increased number of soil samples required for site specific fertiliser application, the chosen method of sampling needs to be fast, cost effective and accurate to provide reliable information. Soil sampling systems currently in use do not allow an automatic control of the precise soil sampling depth and the number of cores taken. The system described here uses a newly designed hydraulic auger, that samples the soil at a constant depth under varying field and soil conditions. This has been achieved by a specific shape and angle of the auger turns. The number of cores taken and their depth are controlled automatically by a sensor linked to an on-board computer. Furthermore, diagnostic tools identify errors and prevent any malfunction. The soil sampling system allows a fully automated and standardised sampling procedure, providing the required reliability for site specific fertiliser application.

Numerical analysis of sampling disturbances in clay soils

AbstractIn this paper, an insight is provided into the quality of soil samples during the penetration of soil samplers. An updated Lagrangian finite element formulation with the second Piola–Kirchhoff stress rate (the Truesdell stress increment) to account for the large deformation behaviour near the sampling tube is used to determine the mechanical disturbances to a soft clay. The penetration of the sampler is simulated by splitting a group of nodes ahead of the penetration route up to a sufficient depth and applying incremental displacements to match the geometric configuration of the sampling tube. Consolidation effect is included to account for the rate of penetration. Thin‐layer elements are added at the inside wall of the sampling tube to model the soil–sampler interface.The numerical results show that the central core of the sample is subjected to three distinct stages of vertical strain history, compression–extension–recompression, with the primary irrecoverable disturbances due to the compression stage ahead of the sampler. The degree of disturbance for a frictionless sampler was found to be constant after a penetration depth of 75 per cent of the sample tube diameter, while for a frictional sampler the degree of disturbances keeps increasing as the penetration proceeds. The results of a parametric study to determine the influence on sampling disturbances due to the rate of penetration, the thickness and the tip angle of the sample tube and sampler type are also presented.

Liquefaction potential of fine cohesionless Soils using the CPT

This paper describes an approach for interpreting cone penetration test (CPT) results to pro-vide a direct measure for assessing soil liquefaction potential of fine granular soil deposits. The use of CPT is justified when the cost of conventional testing techniques is high or the quality of soil samples is not satisfactory. The results of a field investigation program conducted in the Mexicali Valley in the north of Mexico were used to develop correlations between, over-burden pressure, σ υ ′ , maximum surface acceleration, a max , and liquefaction potential. The method developed here suggests that CPT data can provide a measure for assessing soil liquefaction potential.