Abstract
Passive samplers can be useful tools for determining truly dissolved concentrations of organic contaminants in the water. Polyethylene (PE) samplers were validated for measuring polycyclic aromatic hydrocarbons (PAHs), with a focus on alkylated PAHs that can dominate in an oil spill. Equilibrium partition coefficients between water and PE passive samplers (KPEw) were measured for 41 PAHs both at ambient conditions (20 °C, no salt) and down to -15 °C with up to 245 psu present in ice brine. For each additional alkylated carbon, logKPEw increased by an average of 0.40 (±0.20) log units, close to predictions. The increase per aromatic carbon was only 0.33 (±0.02) log units. Apparent PE-water distributions of pyrene and deuterated pyrene (performance reference compound) were within 0.1 log unit for all experiments at 20 and 2 °C but started to diverge by 0.8 log units at -4 °C (100 psu) and by 3.1 log units at -15 °C (245 psu). The delay in equilibrating PAHs in these experiments was dominated by increases in the water viscosity, which, in turn, affected both the aqueous diffusivities of the PAHs and the thickness of the water boundary layer. In a simulated marine oil spill in the laboratory, PE-based results were within a factor of 2 of conventional sampling results for the most abundant PAHs.
Highlights
The dangers of drilling for oil in the marine environment were recently realized in April when 4.9 billion barrels of oil were released into the Gulf of Mexico
In the case of the alkylated polycyclic aromatic hydrocarbons (PAHs), appropriate Kow literature values were difficult to find; calculations had at times to rely on relationships developed for parent PAHs (e.g., Ma et al, 2010)22
The deuterated PAHs used as PRCs, showed good agreement with the non-deuterated PAHs, indicating equilibrium had been reached in the 20 °C at 0 psu experiments (Table S3)
Summary
The dangers of drilling for oil in the marine environment were recently realized in April when 4.9 billion barrels of oil were released into the Gulf of Mexico. We (i) determined the KPEw values of a wide range of alkylated and parent PAHs; (ii) investigated the effect of varying salinities and temperatures on equilibration and partitioning, simulating Arctic conditions; (iii) performed a mock oil spill in the laboratory to evaluate their effectiveness; and (iv) deployed passive samplers in Narragansett The concentrations of the PAHs in the passive samplers (Table S5) and the water were determined and the KPEw calculated for each compound in each experiment.
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