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Soil sorption and biodegradation of PAH: model-based analysis of kinetics and the influence of soil amendments

Arno Rein1, Geoffrey Marchal2, Kilian E.C. Smith3, Stefan Trapp4, Ulrich G. Karlson5
1 Lehrstuhl für Hydrogeologie, Technische Universität München (TUM)
2 Center for Energy Resources Engineering, Technical University of Denmark, Lyngby, Denmark
3 Korean Institute of Science and Technology Europe, Saarbrücken, Germany
4 Department of Environmental Engineering, Technical University of Denmark
5 Department of Environmental Science, Aarhus University, Roskilde, Denmark

O 9.4 in Urbane Hydrogeologie

29.05.2014, 16:20-16:40, H17, NW II

Soils contaminated by hazardous compounds such as polyaromatic hydrocarbons (PAH) can impact groundwater quality and pose environmental risks when uptake by animals and plants leads to toxicity. Sorption of PAH to soil and soil amendments reduces dissolved concentrations, thereby limiting toxicity but also potentially biodegradation. In order to analyze the kinetics of sorption and microbial degradation, experiments with soil suspensions were done, and mathematical modeling was conducted aiming at analyzing key processes and estimating kinetic parameters (Marchal et al. 2013).

 

The experiments were conducted with the degrader strain Sphingomonas sp. 10-1 in soil suspensions spiked with 14C-labeled phenanthrene. Three different soils were tested, and the influence of activated carbon (AC), charcoal and compost amendments on the biodegradation of PAH was assessed. Desorption kinetics was determined from abiotic experiments (desorption of PAH from spiked soil into solution). The extent and kinetics of biodegradation was examined in biotic experiments with soil suspension. A five-compartment model considering abiotic desorption from soil, desorption and biodegradation was set up to describe and simulate the experimental observations.

 

Desorption kinetics could be described by combining a rapid and a slow first-order process, reflecting chemical adsorption to soil particle surface followed by subsequent diffusion into particle interior (Cornelissen et al. (1998) and Johnson et al. (2001)). The rate constants were fitted and used for simulation of the biotic desorption experiments. Microbial growth and biodegradation was simulated using Monod and Michaelis-Menten kinetics. Observations from biodegradation experiments could be explained by assuming co-metabolism (microbial growth supported by soil organic carbon).

 

Complete desorption was observed both in un-amended and compost-amended soils. Contrary, desorption was strongly inhibited by biochar and in particular activated charcoal. The reduction of desorption by the soil amendments subsequently affected mineralization. The model kinetics strongly suggest that with AC and charcoal treatments, desorption into dissolved phase was slow and limited mineralization. In studies with pure AC and biochar amendments, this effect was not observed. This suggests that the mix of soil and amendments leads to reduced bioavailability, but there is no definitive conclusion allowed from the present observations. The calibrated model can be applied to simulations of ad/desorption of PAH and other non-soluble contaminants, and the effect of bioavailability on biodegradation kinetics.



Marchal, G., Smith, K.E., Rein, A., Winding, A., Wollensen de Jonge, L., Trapp, S., Karlson, U.G. (2013): Impact of activated carbon, biochar and compost on the desorption and mineralization of phenanthrene in soil. Environmental Pollution 181, 200-210.

Cornelissen, G., Rigterink, H., Ferdinandy, M.M.A., van Noort, P.C.M. (1998): Rapidly desorbing fractions of PAHs in contaminated sediments as a predictor of the extent of bioremediation. Environmental Science & Technology 32, 966-970.

Johnson, M.D., Keinath, T.M., Weber, W.J. (2001): A distributed reactivity model for sorption by soils and sediments. 14. Characterization and modeling of phenanthrene desorption rates. Environmental Science & Technology 35, 1688-1695.



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Letzte Änderung 31.10.2013