Estimating In Situ Biodegradation Rates of Petroleum Hydrocarbons and Microbial Population Dynamics by Performing Single-Well Push-Pull Tests in a Fractured Bedrock Aquifer

摘要

The single-well push-pull test (SWPPT) was adapted to quantify in situ aerobic respiration and deni-trification 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 mmolL~(-1) day~(-1), respectively. Of the four test wells, significant NO_3~- consumption was noted in three wells. The average zero- and first-order rate coefficients were 2.87±2.21 and 11.83± 7.99 mmolL~(-1) day~(-1), respectively. These results indicate that NO_3~- was more effectively consumed within this fractured bedrock aquifer. Significant DO or NO_3~- (electron acceptors (EAs)) consumption, the limited contribution of Fe(Ⅱ) to overall EAs consumption, the production of dissolved CO_2 during aerobic respiration and denitri-fication tests, and N_2O production strongly suggest that the EAs consumption was largely due to microbial ac-rfvity. Detection of Variovorax paradox, benzene-degrading culture, and 28 novel microbial species after the addition of O_2 or NO_3~- 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.