STUDY OF JET FUEL NATURAL ATTENUATION - BIODEGRADATION EFFECTS IN GROUNDWATER (VITANOVAC, SERBIA)

Biodegradation often plays a major role among natural attenuation processes in the reduction of groundwater contamination by petroleum hydrocarbons. The study was conducted 25 years after the accidental spill of jet fuel at the site in Vitanovac in Serbia (1993-2018). During this period, natural attenuation processes were active without any anthropogenic stimulation. The traces of groundwater contamination were analyzed using GCxGC-MS chromatography. The microbiological analysis included measurements of total chemoorganoheterotrophs (TC), hydrocarbon degrading (HD), and anaerobic bacterial (AB) content in groundwater and sediments. The following hydrochemical indicators in groundwater were measured: O₂, NO₃⁻, Mn, Fe, SO₄²⁻, HCO₃⁻. Due to the long-term hydrocarbon contamination and exposure to different biodegradation mechanisms, the lowest concentrations of electron acceptors and the highest concentrations of microbial metabolic activity products overlap. Based on the analysis of redox-sensitive compounds in groundwater samples, the terminal electron accepting processes ranged from mixed oxic-anoxic (O₂-Fe(III)/SO₄) to oxic (O₂). The most anoxic conditions were registered in monitoring wells closest to the former source of contamination, as also confirmed by redox potential (Eh) in situ measurements. Overall, the study provides clear evidence of the activity and effects of biodegradation mechanisms under natural attenuation processes in groundwater contaminated by jet fuel.