CO2 flux from oil contaminated intertidal sediments to evaluate in-situ biodegradation of oil: a mesocosm study

Abstract

CO2 fluxes were measured to monitor biodegradation of oil in mesocosms of oil contaminated sediments for 71 days. Mesocosms, placed in an intertidal zone exposed to semidiurnal tides, were constructed by mixing a given amount of crude oil with sediment from the site. Experimental groups include control (native microbes NM), NM + fertilizer (F), NM + a commercial biological enzyme (ENZ), NM + a commercial nutrient based stimulant (STM), NM + activated carbon, F + effective microorganisms (EM), and F + a consortium of oil degrading microbes (ODM). Change of CO2 concentrations in a closed chamber system was measured using an infrared gas analyzer to calculate CO2 flux from the artificially contaminated sediments in each experimental group. On average, CO2 evolution was highest in the F + ODM group (0.89 g CO2/m2/hr), followed by NM + ENZ group (0.45 g CO2/m2/hr) and F + EM group (0.38 g CO2/m2/hr). Changes of CO2 evolution were not obvious in the other groups. The highest flux was noticed at 4 days after the treatment in a NM + ENZ group (1.50 g CO2/m2/hr) which was about six times higher than those from a control group (0.24 g CO2/m2/hr). Thereafter, the CO2 flux was decreased drastically and return to the level of control in 15 days after the treatment. In contrast, CO2 evolution from the F + ODM group was maintained relatively high during the whole experimental period, with a maximum CO2 evolution at day 23 (1.43 g ith sediment from the site. Experimental groups include control (native microbes NM), NM + fertilizer (F), NM + a commercial biological enzyme (ENZ), NM + a commercial nutrient based stimulant (STM), NM + activated carbon, F + effective microorganisms (EM), and F + a consortium of oil degrading microbes (ODM). Change of CO2 concentrations in a closed chamber system was measured using an infrared gas analyzer to calculate CO2 flux from the artificially contaminated sediments in each experimental group. On average, CO2 evolution was highest in the F + ODM group (0.89 g CO2/m2/hr), followed by NM + ENZ group (0.45 g CO2/m2/hr) and F + EM group (0.38 g CO2/m2/hr). Changes of CO2 evolution were not obvious in the other groups. The highest flux was noticed at 4 days after the treatment in a NM + ENZ group (1.50 g CO2/m2/hr) which was about six times higher than those from a control group (0.24 g CO2/m2/hr). Thereafter, the CO2 flux was decreased drastically and return to the level of control in 15 days after the treatment. In contrast, CO2 evolution from the F + ODM group was maintained relatively high during the whole experimental period, with a maximum CO2 evolution at day 23 (1.43 g