Estimating In Situ Biodegradation Rates of Petroleum Hydrocarbons and Microbial Population Dynamics by Performing Single-Well Push–Pull Tests in a Fractured Bedrock Aquifer
2013
Cho, Yunchul | Han, Kyungjin | Kim, Namhee | Park, Sunhwa | Kim, Young
The single-well push–pull test (SWPPT) was adapted to quantify in situ aerobic respiration and denitrification rates and to assess microbial population dynamics in a petroleum-contaminated fractured bedrock aquifer. Among three test wells, significant dissolved oxygen (DO) consumption was observed only in one well, with average zero- and first-order rate coefficients of 0.32 ± 0.63 and 7.07 ± 13.85 mmol L⁻¹ day⁻¹, respectively. Of the four test wells, significant NO₃ ⁻ consumption was noted in three wells. The average zero- and first-order rate coefficients were 2.87 ± 2.21 and 11.83 ± 7.99 mmol L⁻¹ day⁻¹, respectively. These results indicate that NO₃ ⁻ was more effectively consumed within this fractured bedrock aquifer. Significant DO or NO₃ ⁻ (electron acceptors (EAs)) consumption, the limited contribution of Fe(II) to overall EAs consumption, the production of dissolved CO₂ during aerobic respiration and denitrification tests, and N₂O production strongly suggest that the EAs consumption was largely due to microbial activity. Detection of Variovorax paradox, benzene-degrading culture, and 28 novel microbial species after the addition of O₂ or NO₃ ⁻ suggests that EA injection into a fractured rock aquifer may stimulate aerobic or denitrifying petroleum-degrading microbes. Therefore, SWPPT may be useful for quantifying in situ aerobic respiration and denitrification rates and for assessing microbial population dynamics in petroleum-contaminated fractured bedrock aquifers.
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