Preliminary Evaluation of In Situ Chemical Oxidation Effects on Soil Carbon Dioxide Emission in a Soil Slurry System

ABSTRACT In situ chemical oxidation (ISCO), a remediation technology for soil and groundwater contamination, utilizes oxidants that can impact the soil environment and indirectly influence soil CO 2 emissions. Understanding these emissions may support more sustainable ISCO applications by enabling adjustments to treatment conditions that limit unnecessary CO 2 release. This study assessed the effects of ISCO on soil CO 2 emission rates and total bacterial counts by evaluating three common ISCO oxidants: hydrogen peroxide (HP), sodium persulfate (SPS), and potassium permanganate (PM), also in combination with various activation methods. CO 2 emission rates from the soil slurry system were measured using a closed static chamber method and expressed in nanograms of CO 2 per gram of dry soil per hour (ng CO 2 g ds –1 h –1 ). Under stable conditions, soil CO₂ emission rates were ranked as follows: SPS groups (2.0~4.0) > PM group (1.9–3.1) > HP groups (0.6–1.8) ≈ original soil (0.4–1.0), while total soil bacterial counts (CFU g ds −1 ) ranked as: PM group (~10 7 ) > HP groups (~10 6 ) > original soil (~5.0 × 10 6 ) > SPS groups (~10 4 –10 6 ). Most oxidant activation treatments led to higher CO 2 emission rates and soil bacterial counts, except under alkaline activation. These findings demonstrate the influence of different ISCO processes on soil CO 2 emissions and offer a baseline for emission rates during ISCO remediation.