Statistical Analysis of Arsenic Concentrations in Subsurface Soils at the University of Mississippi Field Station

Webb, David Thomas (2016) Statistical Analysis of Arsenic Concentrations in Subsurface Soils at the University of Mississippi Field Station. Undergraduate thesis, under the direction of Robert M Holt from Geology and Geological Engineering , University of Mississippi .

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The purpose of this investigation is to determine how arsenic concentration varies in soils with respect to soil structures, grain size, soil type, and depth. The investigation was conducted at the University of Mississippi Field Station (UMFS). The UMFS is located in Abbeville, MS and is roughly 700 acres in size. It includes ponds and former agricultural fields, and lies within an internally draining basin. Seven boreholes were drilled using a direct push geoprobe and sampled. The cores obtained from the borings were then cut at one foot intervals, producing a total of 90 soil samples. Each sample was observed and described in boring logs. Then the samples were split in half, one half was sent for laboratory testing to determine arsenic concentration present in each sample, sieve analysis was conducted on the other half at the University of Mississippi. Each sample was sieved twice. The first time the samples were loosely broken apart in order to maintain natural soil structures, the second time the samples were crushed. In addition, the weight wet and dry weight of each sample was recorded and used to calculate moisture content. Statistical analysis was conducted on the data obtained in order to quantify the relationship of each variable in relation to arsenic concentration. The analysis revealed that arsenic concentrations decreased with depth, with the highest arsenic concentration found at the surface, and had a weak, positive correlation with moisture content. Arsenic showed the strongest correlation with peds (soil structures larger than 1 mm) in uncrushed samples, correlation coefficients ranging from 0.81 to 0.84. In the crushed samples, arsenic showed the strongest correlation to materials less than 0.062 mm, correlation coefficient of 0.78. This relationship is due to the crushing of the peds, which frees clay- and silt-sized particles. The highest arsenic concentrations are found in materials containing peds, within one foot of ground surface in the top soil and at an elevation of 466 to 464 feet which corresponds to the B horizon of the Lexington Silt loam. Our results suggest that natural soil arsenic is concentrated by soil forming processes.

Item Type: Thesis (Undergraduate)
Creators: Webb, David Thomas
Student's Degree Program(s): B.S. Geological Engineering
Thesis Advisor: Robert M Holt
Thesis Advisor's Department: Geology and Geological Engineering
Institution: University of Mississippi
Subjects: Q Science > QE Geology
T Technology > TA Engineering (General). Civil engineering (General)
Depositing User: David David Thomas Webb IV Webb
Date Deposited: 13 May 2016 13:19
Last Modified: 13 May 2016 13:19

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