EFFECT OF OIL CLEANUP METHODS ONECOLOGICAL RECOVERY AND OIL DEGRADATIONOF PHRAGMITES MARSHES

摘要

Oil spill cleanup operations in wetlands remain a criticalissue. Oil spills in four Phragmites marshes provided anexcellent opportunity to document the effect of spilled oiland different intensities of cleanup activity on ecologicalrecovery and oil degradation in wetlands. Our resultsshowed that the intensity of oil spill cleanup and initialoiling differentially affected marsh vegetation and oilremoval. Neither intensive nor light cleanup adverselyaffected the plant stem density, shoot height andaboveground biomass of the dominant marsh plant,Phragmites australis. In contrast, these parameters in theoiled marsh that did not receive cleanup were significantlylower than that for the reference marshes and the intensiveand light cleanup sites. A thick floating oil layer on thesurface was most likely the primary cause of mortality ofthe marsh vegetation at the no cleanup site. Soilpetroleum hydrocarbon concentrations were a function ofthe initial volume of oil spilled and the intensity of thecleanup. Although the intensive cleanup obviouslyremoved floating and surface oil as evidenced by thevisual absence of surface oil at the beginning of thisinvestigation, this cleanup activity may initially increasethe oil incorporated into the sediment. Overall, oilconcentration in the sediment of the intensive cleanup sitedecreased with time. However, sediment oil concentrationincreased slightly at light cleanup sites and increasedsubstantially at the no cleanup site. Containment ofspilled oil within booms at the light and no cleanup sitesappeared to be the primary cause for increased oilincorporation into the sediment because the floating oilinside the boom likely served as an oil source forincorporation into the sediment. We conclude that a noresponseoption in heavily oiled Phragmites wetlandswhere oil pools or can not naturally dissipate is not asatisfactory option.