You are here:
ASSESSING THE BIOAVAILABILITY OF PAHS IN FIELD-CONTAMINATED SEDIMENT USING XAD-2 ASSISTED DESORPTION
Citation:
Lei, L., M. T. Suidan, A. P. Khodadoust, AND H H. Tabak*. ASSESSING THE BIOAVAILABILITY OF PAHS IN FIELD-CONTAMINATED SEDIMENT USING XAD-2 ASSISTED DESORPTION. DOI: 10.1021/es03064, J. Schnoor (ed.), ENVIRONMENTAL SCIENCE AND TECHNOLOGY. American Chemical Society, Washington, DC, 38(6):1786-1793, (2004).
Impact/Purpose:
to publish information
Description:
In the bioremediation of soils/sediments contaminated with polycyclic aromatic hydrocarbons (PAHs) it is imperative to determine the fraction of the PAHs that is amenable to remediation. For example, what fraction of the PAHs is available to the indigenous microorganisms, i.e. bioavailable? The bioavailability of PAHs varies with the contamination history and the characteristics of soils/sediments. Research was undertaken to examine the feasibility of using adsorbent-assisted desorption of PAHs for assessing their bioavailability in contaminated sediments containing aged PAHs. The sediment was collected from East River, NY, near Rikers's Island and contaminated with 2-ring to 6-ring PAHs. The kinetics of desorption of PAHs from sediment were studied using abiotic sediment-seawater slurry systems, where the nonionic polymeric adsorbent XAD-2 was added om various concentrations to the sediment/water slurry to ensure that sufficient adsorption capacity of the XAD is provided to effect the maximum rate and extent of desorption of PAHs from the sediment. By acting as an infinite PAH sink and by maintaining a constantly low PAH concentration in the aqueous phase, XAD is used to maximize the driving force for the PAHs to desorb from sediment particles without changing the sediment-aqueous phase partitioning coefficient. Batch studies on the microbial activity in the sediment slurry systems were also undertaken under aerobic conditions to investigate the potential for PAH biodegradation by the indigenous microbial consortia. The experiments were considered complete when PAH concentration levels in the sediment ceased to decrease.
A considerable residual level of PAHs was detected at the end to the experiments in both the biodegradation and XAD assisted desorption studies. This is attributed to the fact that a substantial fraction of PAHs is irreversibly sorbed onto the sediment and thus unavailable for either biodegradation or desorption activity. All 2-ring, 3-ring, and 4-ring PAHs exhibited significant biodegradation under aerobic conditions, with their residual levels in two studies closely related to each other (the correlation coefficient was 0.94). 5-ring and 6-ring PAHs showed either marginal or no biodegradation activity at all. This trend suggests that these higher ring PAHs might become available but their recalcitrance to biodegradation by the indigenous microbiota limited the biodegradation activity under the experimental conditions used. The adsorption of the desorbed PAHs onto XAD resin was a much faster process than microbial degradation, since the desorption equilibrium was attainable in just 2 weeks, while it took 24 weeks for all PAHs to attain maximum biodegradation. Overall, the results indicate that XAD-assisted desorption could be used to assess the bioavailability and the biodegradation potential of most PAHs in a timely manner, as long as the recalcitrance of PAHs is not the limiting factor in bioremediation of the contaminated sediments. Because XAD-assisted desorption does not change the sediment-aqueous phase distribution coefficients of the contaminants, this process could evaluate the bioavailability of aged PAHs representatively in the contaminated sediments and it can also be applied to other contaminant-matrix circumstances. To our knowledge, this is the first reported representative chemical measurement of bioavailability which does not require exhaustive search or extraction parameters for every specific contaminant-matrix pair.
URLs/Downloads:
ASSESSING THE BIOAVAILABILITY OF PAHS IN FIELD-CONTAMINATED SEDIMENT USING XAD-2 ASSISTED DESORPTION
TOC.PAGE?INCODEN=ESTHAG&INDECADE=0&INVOLUME=38&INISSUE=6