Bioremediation of oil-contaminated coastal freshwater and saltwater wetlands

Abstract

Two field studies involving intentional releases of crude oil onto a freshwater wetland and a salt marsh were conducted in Canada in the summers of 1999and 2000, respectively. The objective of both studies was to determine the role of nutrients in enhancing wetland restoration in the presence and absence of wetland plants, The experiments involved several replications of the following oiled treatments: (1) natural attenuation, (2) ammonium nitrate addition with intact plants, (3) ammonium nitrate addition with plants cut back to suppress plant activity, and (4) sodium nitrate addition to separate the effects of ammonium-N from nitrate-N. A fertilized, unoiled treatment was also included. For the salt marsh study, tilling was added as another treatment. Time series data from both studies were analyzed by GC/MS to monitor oil degradation. Results from both field experiments indicate that significant alkane and PAH biodegradation occurred (more so in the salt marsh). Biodegradation rates were not enhanced by any of the amendments in the freshwater wetland experiment, but substantial restoration of the wetland ecosystem was accelerated in the amended treatments. Significant treatment effects were observed in the salt marsh study in regards to alkane but not PAH degradation, and levels of restoration similar to those observed in the freshwater wetland were not evident in the salt marsh ecosystem.