MICROCOSM STUDY OF EFFECT OF DIFFERENT NUTRIENT ADDITION ON BIOREMEDIATION OF FUEL OIL NO. 2 IN SOIL FROM NOVA SCOTIA COASTAL MARSHES

摘要

Biostimulation has been shown to be an effective tool for the treatment of oil spills in medium to low-energy marine environments. Little information is available on the bioremediation of oil spills in low-energy coastal wetlands. Most of the previous laboratory studies have been carried out under total flooding conditions. In this study, a tidal salt marsh was simulated in laboratory microcosms. The study was carried out in glass columns filled to a depth of 10 cm with sediment. Each microcosm was operated on a 24 hours square tidal cycle with a 12-hour submergence period. The entire sediment was mixed with weathered fuel oil No 2 (FO2) to a concentration of 20 g/kg of wet sediment. Two biomarkers, 5 α-cholestane and heptamethylnonane were added to the oil for data normalization. Nutrients were premixed with the soil in an amount equivalent to 1 gram as nitrogen and 0.2 grams as phosphorus per column. The experiment was conducted with a no fertilizer control and three types of fertilizer: a slow-release, inorganic, granular fertilizer, prilled ammonium nitrate; sodium nitrate; and ammonium chloride. The source of phosphorus was sodium tripolyphosphate. Duplicate columns were sacrificed at 15, 30, 60 and 120 days after FO2 addition. Sediments were divided into two layers from the top and bottom of the columns, extracted with dichloromethane (DCM) by Soxhlet extraction and analyzed for oil components by GC/MS. Nitrate, ammonia, and pH were monitored in the water samples on a weekly basis. Soil samples were also extracted for nutrients to perform a mass balance. Phospholipids analysis and Most Probable Number (MPN) were performed on the sediment samples to establish a measurement of biological growth. Results indicated that: (1) oil degradation was slightly higher for all treatments in the top 5 cm layer and it occurred mostly during the first 15 days of the experiment; (2) microbial growth of 2 orders of magnitude was detected in the top layer; (3) no significant differences were observed among treatments; (4) degradation was probably limited by oxygen availability.