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Controls and Rates of Acid Production in Commercial‐Scale Sulfur Blocks
Author(s) -
Birkham T. K.,
Hendry M. J.,
Barbour S. L.,
Lawrence J. R.
Publication year - 2010
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2009.0253
Subject(s) - sulfur , oxidizing agent , chemistry , relative humidity , drainage , environmental chemistry , zoology , ecology , biology , physics , organic chemistry , thermodynamics
Acidic drainage (pH 0.4–1.0) from oxidizing elemental sulfur (S 0 ) blocks is an environmental concern in regions where S 0 is stockpiled. In this study, the locations, controls, and rates of H 2 SO 4 production in commercial‐scale S 0 blocks (∼1–2 × 10 6 m 3 ) in northern Alberta, Canada, were estimated. In situ modeling of O 2 concentrations ([O 2 ]) suggest that 70 to >97% of the annual H 2 SO 4 production occurs in the upper 1 m of the blocks where temperatures increase to >15°C during the summer. Laboratory experiments show that S 0 oxidation rates are sensitive to temperature (Q 10 = 4.3) and dependent on the activity of autotrophic S 0 –oxidizing microbes. The annual efflux of SO 4 in drainage water from a S 0 block (5.5 × 10 5 kg) was within the estimated range of SO 4 production within the block (2.7 × 10 5 to 1.2 × 10 6 kg), suggesting that H 2 SO 4 production and removal rates were approximately equal during the study period. The low mean relative humidity within the block (68%; SD = 17%; n = 21) was attributed to osmotic suction from elevated H 2 SO 4 concentrations and suggests a mean in situ pH of approximately −2.1. The low pH of drainage waters was attributed to the mixing of fresh infiltrating water and low‐pH in situ water. Heat generation during S 0 oxidation was an important factor in maintaining elevated temperatures (mean, 11.1°C) within the block. The implications of this research are relevant globally because construction methods and the physical properties of S 0 blocks are similar worldwide.