The use of lipid-containing semipermeable membrane
devices (SPMDs) is becoming commonplace, but very little
sampling rate data are available for the estimation of
ambient contaminant concentrations from analyte levels
in exposed SPMDs. We determined the aqueous sampling
rates (R
ss; expressed as effective volumes of water
extracted daily) of the standard (commercially available
design) 1-g triolein SPMD for 15 of the priority pollutant (PP)
polycyclic aromatic hydrocarbons (PAHs) at multiple
temperatures and concentrations. Under the experimental
conditions of this study, recovery-corrected R
s values
for PP PAHs ranged from ≈1.0 to 8.0 L/d. These values
would be expected to be influenced by significant changes
(relative to this study) in water temperature, degree of
biofouling, and current velocity-turbulence. Included in this
paper is a discussion of the effects of temperature and
octanol−water partition coefficient (K
ow); the impacts of
biofouling and hydrodynamics are reported separately. Overall,
SPMDs responded proportionally to aqueous PAH
concentrations; i.e., SPMD R
s values and SPMD-water
concentration factors were independent of aqueous
concentrations. Temperature effects (10, 18, and 26 °C)
on R
s values appeared to be complex but were relatively
small.
We present a first comprehensive set of experiments that demonstrate the performance of activated carbon (AC) to reduce the availability of polycyclic aromatic hydrocarbons (PAHs) including alkylated-PAHs in petroleum-impacted sediments. The uptake in polyethylene samplers for total PAHs in a well-mixed sediment slurry was reduced up to 99% and 98% for petroleum-impacted sediments with oil contents of 1% and 2%, respectively, by treatment with 5% AC. The AC showed similar efficiency for parent-PAHs and a suite of alkylated-PAHs, which predominate over parent-PAHs in petroleum-impacted sediments. A mass transfer model was used to simulate the AC performance in a slurry phase with site-specific mass transfer parameters determined in this study. Comparison between the experimental data and simulation results suggested that dissolved organic matter and/or oil phase may have attenuated the AC performance by a factor of 5-6 for 75-300 μm AC with 5% dose at one month. The attenuation in AC performance became negligible with increase in AC-sediment slurry contact time to 12 months and with decrease in AC particle size. The results show the potential for AC amendment to sequester PAHs in petroleum-impacted sediments and the effect of contact time and AC particle size on the efficiency of the treatment.
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