potential of natural attenuation processes IN Environmental contamination by petroleum hydrocarbons Nenad Marić, Zoran Nikić University of Belgrade, Faculty of Forestry Department of Ecological Engineering for Soil and Water Resources Protection

INTRODUCTION About 39-50% of the land surface of Earth has been modified due to human activities such (Alvarez and Illman, 2006). Petroleum hydrocarbons are among the most common soil and water contaminants (e.g. U.S. NRC, 1993; Yadav and Hassanizadeh, 2011) Application of conventional methods for remediation of sites contaminated by petroleum hydrocarbons has proven to be less practical and reliable than first envisioned (Mackay and Cherry, 1989; Travis and Doty, 1990) Soil and shallow sediments contain a, ranging from simple prokaryotic bacteria and cyanobacteria to more complex eukaryotic algae, fungi and protozoa (McNabb and Dunlap, 1995; Ghiorse and Wilsson, 1998) Natural attenuation of petroleum hydrocarbons in soil and groundwater includes a number of naturally occurring processes such as biodegradation, sorption and dispersion

electron acceptor utilization: O2→ NO3-→ Mn4+→ Fe3+→ SO42-→ HCO3- Biodegradation of petroleum hydrocarbons can be defined as a process where microorganisms are capable, under favorable conditions, of utilizing these compounds as a metabolic carbon source (Mearns, 1997; Atlas, 1991) Microorganisms obtain energy by treansfer of electrons from donor (contaminant molecule) to an electron acceptor (inorganic compounds) (Alvarez and Illman, 2006) electron acceptor utilization: O2→ NO3-→ Mn4+→ Fe3+→ SO42-→ HCO3- biodegradation mechanisms: aerobic respiration → nitrate reduction → manganese (IV) reduction → iron (III) reduction → sulfate reduction → methanogenesis

STUDY AREA AQUIFER The site of historical contamination by kerosene (JET fuel) in Vitanovac, Municipality of Kraljevo, Serbia Neogene: dacites, andesites Miocene-Pliocene:clastic deposits Quaternary: - terrace deposits (fine sands, clays) - alluvial deposits (sands, gravels) AQUIFER intergranular porosity unconfined (phreatic) Kf=8.4 x 10-5 to 4.6 x 10-3 m/s GWT average depth: 3.5 to 4.3 m Discharge zone: Zapadna Morava

Accident: 540 tons of kerosene leaked through the storage tank’s drainage system into the subsurface (Matić, 1994) The free-phase kerosene plume was located in the zone of the road and railway Dissolved kerosene components in groundwater were found within the entire study area Remediation activities : pumping of the free-phase kerosene from the subsurface During remediation treatment (10.02.1994 to 29.09.1995) about 300 tons of kerosene were extracted from the subsurface (Kaćanski, 1995). An unknown amount of kerosene was left in the subsurface as a long term source of contamination.

MATERIALS AND METHODS Chemical parameters: - Total petroleum hydrocarbons (TPH) (method 9377-2:09, ISO 2009) - NO3- (EPA 300.1, 1997) - Mn (EPA 200.7, 1998) - Fe (EPA 200.7, 1998) - SO42- (EPA 300.1, 1997) Microbiological parameters: - Total number of chemoorganoheterotrophs (TC) (serial dillutions - nutrient agar) - Total number of hydrocarbon degraders (HD) (serial dillutions - mineral base with 2 g/l D2) In situ measurements: O2 (WTW 330i/SET 2B20-0011) Water table depth (Eijkelkamp 11.08.07 device) Preliminary research activities : July 2011 Monitoring of natural attenuation- biodegradation effects in groundwater : May – July 2013

RESULTS AND DISCUSSION Preliminary research activities 18 years after the accidental spill (July 2011) former free-phase kerosene zone TPH (mg/l) groundwater MAC (mg/l) TPH (mg/kg) sediments (mg/kg) Total number of chemoorganoheterotrophs (CFU/g) Total number of hydrocarbon degraders (CFU/g) 0.61 0.6 350-1200 5000 2.7 x 106 - 4.5 x 107 2.3 x 105 - 1.2 x 106

Natural attenuation – biodegradation effects in groundwater (May-July 2013) 20 years after the accidental spill TPH concentration decrease allong profile AB direct impact of groundwater from P-1 on downgradient piezometers Piezometer TPH (mg/l) O2 NO3- Mn Fe SO42- P-1 0.22 0.95 1.0 6.2 51.2 3.0 P-2 0.14 1.25 0.9 1.73 12.7 36.1 P-3 0.11 1.92 2.6 0.039 0.287 55.0

A B aerobic respiration nitrate reduction O2 0.95 mg/l NO3- 1.0 mg/l Mn 6.2 mg/l Fe 51.2 mg/l SO42- 3.0 mg/l manganese (IV) reduction Groundwater flow movement TPH concentration decline iron (III) reduction O2 1.92 mg/l NO3- 2.6 mg/l Mn 0.039 mg/l Fe 0.287 mg/l SO42- 55.0 mg/l sulfate reduction B

CONCLUSION traces of contamination at the site in Vitanovac were registered 20 years after the accidental spill of kerosene the highest concentrations of TPH correspond to the lowest concentrations of electron acceptors (O2, NO3-, SO42-) and the highest concentrations of metabolic products of biodegradation (Mn, Fe), proving the occurence of different biodegradation mechanisms in groundwater: aerobic respiration → NO3 reduction → Mn (IV) reduction → Fe (III) → SO4 reduction and biodegradability of kerosene components in field conditions depending on their capacity to ensure protection of public health, safety and the environment, natural attenuation processes can provide significant economic benefits in remediation of hydrocarbon-contaminated sites Acknowledgments: This study was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia under Grant No. III 43004 and Grant No. OI 176018

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