Year of Award
Master of Science (MS)
Department or School/College
Department of Geosciences
James Sears, Ylva Lekberg
elemental sulfur, remediation, biodegradable, trap, skeet, shooting range
University of Montana
Soil contamination that results from elemental sulfur (S0) deposition is a new occurrence. Elemental sulfur is stockpiled as a byproduct from the oil and gas industry and is deposited by biodegradable trap and skeet targets at shooting ranges. Chemolithotrophs and mixotrophs can oxidize S0 to H2SO4. Consequently, in areas where excess S0 is deposited or stockpiled, soils can acidify to pH values observed with acid mine drainage.
I studied S0 contamination at a former sporting clay range. For seven years, the range used biodegradable trap and skeet targets that contained S0. I analyzed the chemistry of the targets and sampled and analyzed range soils. We then conducted batch experiments to investigate whether amendments restore contaminated soils. Amendments included CaCO3 by itself and in combination with: fertilizer, compost, biochar, chitin, or biochar and fertilizer. I paired the batch experiments with a similar study that tested the ability of the amendments to restore vegetative cover.
Targets were composed of approximately 53% CaCO3, 41% S0,and 6% modifiers, and on a molar basis, there was 2.3 times more S0 than CaCO3. From field data, I observed a positive correlation between target cover and SO42- (ρ = 0.82, P < 0.001),which indicated the oxidation of S0 to H2SO4. Sulfatewas negatively correlated with pH (ρ = -0.93, P < 0.001) because insufficient CaCO3 existed in the targets to neutralize all the acid produced from S0 oxidation. Plant cover decreased with decreasing soil pH (ρ = 0.62, P = 0.006).
The addition of CaCO3 in the batch experiments raised contaminated soil pH from 3.3 to 6.3, which equaled the pH in uncontaminated soils. Total plant biomass was the greatest for “CaCO3”, “CaCO3 + Fertilizer” and “CaCO3 + Biochar + Fertilizer” amended soils. The oxidation of S0 to H2SO4 was likely responsible for the decrease in soil pH over time. The experiments demonstrated that techniques to restore acidic soils may be used for acidic soils contaminated with S0, but in the long term, the acid generating potential of S0 must be considered to avoid future acidification.
McTee, Michael Ryan, "The biogeochemistry of elemental sulfur contaminated soils: insights into effective remediation" (2015). Graduate Student Theses, Dissertations, & Professional Papers. 4446.
© Copyright 2015 Michael Ryan McTee