PNNL

Abstract

The bioremediation of organic contaminants such as polynuclear aromatic hydrocarbons (PAHs) in marine or estuarine sediments is seriously complicated by the anaerobic conditions that prevail in these environments. One possibility to overcome the oxygen transport limitations is to use rooted marine plants such as sea-grasses for increasing the flux of oxygen into water-logged sediments. An experimental study was conducted in seawater aquaria with greenhouse and artificial lighting to evaluate whether eelgrass (Zostera marina) enhances the biodegradation of PAHs in crude oil contaminated marine sediments. After 5 months, total PAH removal from the eelgrass planted sediment (top 3 cm layer) was ca. 59% while it was only ca. 24% in the unplanted controls, indicating that the presence of eelgrass significantly enhances PAH biodegradation in contaminated marine sediments. Most PAHs that were removed in treatment and control sediments consisted of 2 and 3 ring parent and alkylated PAHs; however at least one four-ring PAH (fluoranthene) was partially biodegraded in the presence of plants while this aromatic was completely recalcitrant in the unplanted controls. Given that the root-zone aeration potential of the eelgrass was experimentally confirmed by measuring the increase in dissolved oxygen concentrations in the water surrounding roots of illuminated plants, it can be concluded that oxygen release by eelgrass roots was most likely responsible for the enhanced biodegradation of PAHs in crude oil contaminated marine sediments.