Emission of Volatile Organic Compounds and Greenhouse Gases from the Aerobic Bioremediation of Soils Contaminated with Diesel

Abstract

Bioremediation processes have been credited for reducing high levels of organic contaminants from soils. However, during the bioremediation of soils contaminated with diesel, the conversion of heavy molecules to volatile organic compounds (VOCs) and greenhouse gases (GHGs) and the volatilization of light molecules can occur. The ongoing construction of a large petrochemical complex in Rio de Janeiro (COMPERJ) and the transportation of large volumes of oil by-products have raised serious concerns regarding accidents that may result in soil contamination. Bioremediation is a potential technique that can be applied to minimize damage from such contamination. The objective of this study was to characterize the emission of GHGs and VOCs during the bioremediation of soils contaminated with diesel oil. Soil samples contaminated with 0.5, 2.0, and 4.0 w/w% diesel oil were kept in glass rectors (2 L internal volume) for 3 months under anaerobic/anoxic conditions. The soil moisture was kept at 80 % of the field capacity. Bioremediation processes were investigated in regard to nutrient adjustment (biostimulation), no adjustment (natural attenuation), and sterilized soil (abiotic process). The gases emitted from various reactors were collected with coconut shell charcoal cartridges, and the GHGs were collected in Tedlar bags. The chemical analyses of GHGs and VOCs were performed using gas chromatography. The results indicated that air samples contained high concentrations of CO2, but low concentrations of CH4. Differences in the composition of the gas emitted, regarding CO2, were not statistically significant. Regarding VOC emissions, such as alkanes and alkenes (both branched), cycloalkanes, and aromatic-substituted compounds, the compounds with higher emissions were cycloalkanes and branched alkanes.