TY - JOUR
T1 - Mathematical analysis of the whole core injection method accuracy for measuring phenanthrene biodegradation rates in undisturbed marine sediments
AU - Tang, Yinjie J.
AU - Krieger-Brockett, Barbara
N1 - Funding Information:
The authors thank J. Deming, S. Carpenter, and B. Finlayson for a fruitful collaboration and Tony Wirth for her extensive sediment property measurements. The authors also gratefully acknowledge the financial support of the WA Sea Grant program, the Navy under the University Research Initiatives Grant to the UW, the University of Washington, Department of Chemical Engineering, and the US Department of Energy, Office of Science, Office of Biological and Environmental Research, Genomics: GTL Program through contract DE-AC02-05CH11231.
PY - 2007/6
Y1 - 2007/6
N2 - Rates of 14C-phenanthrene mineralization in contaminated, undisturbed marine sediments were measured using the whole core injection method to assess microbial natural attenuation activity as a function of sediment depth. Submerged sediments were sampled from Eagle Harbor, a marine superfund site in Puget Sound. Experiments show significant biodegradation activities (0.0012-0.0036 day-1) in the sediment horizons from 0 to 10 cm. The purpose and scope of this paper is to evaluate the range of experimental conditions giving valid results; a mathematical simulation described competing contaminant 14C-phenanthrene diffusion and simultaneous biodegradation (Monod kinetics), both retarded by sorption. The effect of aging was examined with two sorption models in presumed pseudo-homogenous sediments having effective properties. The simulation predictions provide quantitative guidelines for the successful use of the whole core injection method. (1) The effective Monod constant KS′ in sediment is increased by a large partition coefficient KP between sediment and water and makes the apparent 14C-phenanthrene biodegradation approach first-order kinetics. (2) When KS′ > 1 mg- 1 l- 1, the measured 14C-phenanthrene biodegradation extent is biased by inadequately distributed injected tracer only when less than 7% of the sediment horizon is initially probed and mixed with injected tracer. (3) A short incubation time (<20 days) is necessary when a mobile indicator, e.g., gaseous 14CO2, is used. For longer incubation times, predictions show that a 14CO2 indicator diffuses to adjacent horizons, thus smearing the depth profile of biodegradation. (4) This method employing a radiolabeled tracer provides accurate biodegradation rates for freshly contaminated sediments, and represents an upper limit to the natural phenanthrene biodegradation extents if the contaminant is aged over 50 days.
AB - Rates of 14C-phenanthrene mineralization in contaminated, undisturbed marine sediments were measured using the whole core injection method to assess microbial natural attenuation activity as a function of sediment depth. Submerged sediments were sampled from Eagle Harbor, a marine superfund site in Puget Sound. Experiments show significant biodegradation activities (0.0012-0.0036 day-1) in the sediment horizons from 0 to 10 cm. The purpose and scope of this paper is to evaluate the range of experimental conditions giving valid results; a mathematical simulation described competing contaminant 14C-phenanthrene diffusion and simultaneous biodegradation (Monod kinetics), both retarded by sorption. The effect of aging was examined with two sorption models in presumed pseudo-homogenous sediments having effective properties. The simulation predictions provide quantitative guidelines for the successful use of the whole core injection method. (1) The effective Monod constant KS′ in sediment is increased by a large partition coefficient KP between sediment and water and makes the apparent 14C-phenanthrene biodegradation approach first-order kinetics. (2) When KS′ > 1 mg- 1 l- 1, the measured 14C-phenanthrene biodegradation extent is biased by inadequately distributed injected tracer only when less than 7% of the sediment horizon is initially probed and mixed with injected tracer. (3) A short incubation time (<20 days) is necessary when a mobile indicator, e.g., gaseous 14CO2, is used. For longer incubation times, predictions show that a 14CO2 indicator diffuses to adjacent horizons, thus smearing the depth profile of biodegradation. (4) This method employing a radiolabeled tracer provides accurate biodegradation rates for freshly contaminated sediments, and represents an upper limit to the natural phenanthrene biodegradation extents if the contaminant is aged over 50 days.
KW - Aged contaminant
KW - Monod biodegradation kinetics
KW - Pseudo-homogenous
KW - Sorption
KW - Undisturbed sediment
UR - http://www.scopus.com/inward/record.url?scp=34247120150&partnerID=8YFLogxK
U2 - 10.1016/j.chemosphere.2007.02.038
DO - 10.1016/j.chemosphere.2007.02.038
M3 - Article
C2 - 17412394
AN - SCOPUS:34247120150
SN - 0045-6535
VL - 68
SP - 804
EP - 813
JO - Chemosphere
JF - Chemosphere
IS - 5
ER -