1. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel Steven Verpaele 1 *, Joseph Leinders 2, Joke Van De Steene 1, Jo Bonroy 1 1 University of Ghent – Department of Soil Management and Soil Care 2 Open Universiteit Nederland - Department of Sciences * Corresponding author (steven.verpaele@telenet.be)

2. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Research questions 1.Which volatile components emanate during natural attenuation of diesel fuel? 2.Can these components be measured and quantified by passive soil gas sampling? 3.Is there a relation between volatile components concentration and the mineral oil concentration?

3. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Introduction Specific hydrocarbon constituents from diesel fuel emanating from the solid phase can: 1.volatilize or diffuse to the atmosphere;  soil gas sampling 2.solubilize in ground water;  groundwater analysis 3.be adsorbed to aquifer sediments;  soil sample analysis 4.can undergo biochemical transformations (ex. biodegradation)  oxygen and carbondioxide measurements Point 2 to 4 has been monitored on the site since 2005

4. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Description test site Soil contamination in the 1980’s with diesel fuel due to the leakage of two storage tanks of 25.000 liter (removed in 2002). Chosen method for sanitation: monitored natural attenuation in a period of 4 years starting from februari 2005.

5. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Material and Methods Analysing the VOC fraction of the soil samples taken in april 2007 with GC-MS Soil gas sampling with ORSA 5 sampling tubes during 5 months leaving the sampling device in the sampler during 2 and 4 weeks. Samplers placed on a depth of 0,5 -1 and 1,5 m below ground surface Soil samples taken every month from 0,5 – 1 – 1,5 – 2 – 2,5 – 3 and 3,5 m below ground surface to analyse the concentration of mineral oil. Analysing carbondioxide and oxygen concentrations taken by active soil gas sampling every month

6. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Results VOC screening in soil samples showed the presence of hexane, heptane, octane, nonane and decane and homologues at depths of 200 and 300 cm below ground surface. Screening of soil gas tubes showed concentrations of hexane, methylcyclopentane and methylcyclohexane. It wasn’t possible to quantify all the VOC compounds with the passive sampling technique due to temperature influence (to low temperature to have a VOC flux from 200 cm to 150 or 100 cm below ground surface) Due to very little concentrations it wasn’t possible to relate VOC concentrations with mineral oil concentrations. During winter it’s not possible to use passive soil gas samplers due to the high water table.

7. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) Conclusion & Discussion The passive sampling of soil air can only be used as a screening method to evaluate volatilization Passive soil gas monitoring can’t be used to predict the biodegradation rate of diesel fuel in soil. Further research should be done to –measure biodegradation compounds of diesel fuel by passive soil gas sampling –sample the saturated zone by passive soil gas sampling

8. Passive soil gas sampling during natural attenuation of a site contaminated with diesel fuel (Steven Verpaele) References OVAM (2005). In-situ Bioremediatie van petroleumkoolwaterstoffen. Code van goede praktijk. Openbare Afvalstoffenmaatschappij voor het Vlaamse Gewest, 125p. US EPA, United States Environment Protection Agency (1999). Monitored natural attenuation of petroleum hydrocarbons. US EPA Remedial technology fact sheet. EPA/600/F-98/021, Office of Research and Development, Washington, DC. VAN DE STEENE, J. (2004). Modelleren van diffusie en reactie van gassen in met minerale olie verontreinigde bodems. Gevalstudie van remediatie in biobedden. Doctoraat, Gent, faculteit Bio-ingenieurswetenschappen, Universiteit Gent, 267p. VERPLANCKE, H. (2004). Bodemverontreiniging en bodemsanering. Gent, Faculteit Bio-ingenieurswetenschappen, Universiteit Gent. 120p. SADLER R. & CONNEL D. (2003). Analytical Methods for the determination of Total Petroleum Hydrocarbons in Soil OVAM (2001). Code van goede praktijk voor bemonstering van grond, grondwater, bodemvocht, bodemlucht en waterbodems. Openbare Afvalstoffenmaatschappij voor het Vlaamse Gewest, 61p. SERRANO A. et al. (2005). Assessment of natural attenuation of volatile aromatic hydrocarbons in agricultural soil contaminated with diesel fuel