Quantitative Assessment of Organic Mass Fluxes and Natural Attenuation Processes in a Petroleum-Contaminated Subsurface Environment

Abstract

We perceived a trend in the study and practice of petroleum-contaminate sites. Monitored natural attenuation (MNA) can reduce the contaminant concentrations in the soil and groundwater, and it is a method that can remediate the petroleum-contaminated site effectively. MNA is becoming a research focus. This study evaluated MNA using a series of lab-based bench-scale experiments and a large amount of monitoring data from field samplings. Based on the in-site total petroleum hydrocarbon (TPH) results, we used statistical methods, the Mann-Kendall test, and mass fluxes in order to evaluate the MNA of petroleum-contaminated sites in groundwater. The results showed that the TPH concentrations were decreasing, and the plume became smaller. The attenuation rate was from 0.00876 mg/d to 0.10095 mg/d; remediating the petroleum contamination site would cost 1.3 years to 10.6 years. The plume reached a quasi-steady state, and mass flux declined. The most essential process of MNA was biodegradation, and the second was sorption. During the monitoring period, 393 g of TPH was attenuated, including 355 g of TPH gradated by microbes. Biodegradation upstream of the plume was more serious. Iron(Ⅲ) and manganese were the main electron acceptors utilized by microbes during the monitored period. MNA was in progress, and it can be an effective method to remediate the petroleum-contaminated site. Lab-based bench-scale experiments were performed with much monitoring data from the field samplings in order to understand the fate and transport mechanism of the petroleum contamination from the land surface to shallow groundwater according to site conditions.