Biodegradation rates of crude oil in seawater

Abstract

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Measurements of the rate of biodegradation of crude oil in seawater in laboratory, mesocosm, and field systems from 16 published reports were reviewed and compared. Volumetric biodegradation rates range widely from approximately 0.01 to 1 000 gC/m 3 -d. Laboratory studies report rates at the higher end of this range, while field and mesocosm studies, of which there are fewer, suggest much lower rates ranging from 0.01 to 0.3 gC/m 3 -d. Possible explanations for the discrepancy between measurements made at different scales are differences in oil concentration and in mixing energy. When temperature-scaled degradation rates from all systems are plotted versus initial oil concentration on a log-log scale, the data are approximately linearzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (r 2 = 0.86) over several orders of magnitude. The slope of the regressed line is near 1, indicating that the process can be interpreted as first order with respect to oil concentration. The half-life for biodegradation is estimated to be approximately two months at 20°C. This analysis suggests that crude oil biodegradation in seawater is relatively slow and indicates that further research is required to bridge the gap between laboratory and field systems. Water Environ. Res., 65, 845 (1993).

Biodegradation of Crude Oil and Corexit 9500 in Arctic Seawater

“…Abiotic losses were measured in killed (autoclaved seawater) controls and were subtracted from all time points to calculate biodegradation. Using first-order kinetics ( Mihelcic, 1999 ), we used the rate law for a first order reaction ([C] = [C 0 ]e - k t ) to calculate the biodegradation rate constant ( k ) ( Stewart et al, 1993 ; Venosa and Holder, 2007 ; Brakstad et al, 2008 ).…”

A tradeoff between physical encounters and consumption determines an optimal droplet size for microbial degradation of dispersed oil

“…In the encounter stage, we consider the droplet—assumed neutrally buoyant and initially free of oil-degrading bacteria—and a single species of non-motile, oil-degrading bacteria, suspended in a quiescent fluid environment. For simplicity, we assume that the droplet-phase oil is composed of two components: one metabolizable by the modeled bacteria and one non-metabolizable 34 . During this first stage, the droplet radius and mass do not change, as there is no biodegradation.…”

“…We also refer to the growth and saturation stages taken together as the consumption phase. In the final stage, the residual stage, biodegradation of the oil droplet ceases, leaving a (non-metabolizable) fraction of the original oil mass and the colonizing cells in a small pellet 34 . We implement these four stages in a new, microscale oil degradation model (MODEM), which we use to predict large-scale oil degradation dynamics under different environmental conditions.…”

“…In marine environments it is challenging to distinguish between biodegradation and dilution and to differentiate the degradation of insoluble hydrocarbons from their dissolved counterparts. Often, the assertion of rapid biodegradation of droplets in the field has been based on comparisons to laboratory studies 18 , 20 , 34 , 46 , 48 . In light of the long biodegradation timescales predicted by our physically-based microscale model, alternative factors may be playing a larger role in the ultimate fate of suspended oil.…”

Modeling the Impact of Dilution on the Microbial Degradation of Dispersed Oil in Marine Environments

“…A consequence o the xed number o attached bacteria once capacity is reached is that the mass o metabolizable oil decreases linearly with time during this nal portion o the degradation process: a constant number o bacteria grow at a constant rate, resulting in a steady utilization o the available carbon. This proceeds until all the metabolizable carbon (assumed to be 85% o the initial oil volume (Stewart et al, 1993)) is used. Note that a loss o 85% o the volume would result in a reduction o only approximately 50% in the diameter o the droplet (see Figure 13.1).…”