Our previous research on atmospheric samples suggested that Lake Ontario might receive significant amounts of Dechlorane Plus (DP), a highly chlorinated flame retardant, from the atmosphere and from inputs from DP's manufacturing facility in Niagara Falls, New York. To confirm this suspicion, a sediment core from the central basin of Lake Ontario was analyzed for the two isomers of DP, for polybrominated diphenyl ethers (PBDEs), and for 1,2-bis(2,4,6-tribromophenoxy)ethane (TBE). The results showed that the concentration of DP in sediment increased rapidly starting in the mid-1970s and reached its peak concentration (310 ng g(-1) dry weight) in the mid-1990s. The peak flux and total inventory of DP were estimated to be 9.3 ng cm(-2) yr(-1) and 120 ng cm(-2), respectively. These values suggest that the total burden of DP in Lake Ontario is similar to 20 tons and that the maximum load rate was similar to 2 tons per year. The highest concentrations of PBDEs and TBE were found in the surficial sediment, with average concentrations of 2.8, 14, and 6.7 ng g(-1) d.w. for PBDE3-7 (tri- through hepta-BDEs), BDE-209, and TBE, respectively. The surface fluxes were 0.08, 0.43, and 0.20 ng cm(-2) yr(-1), and the inventories were 0.87, 3.9, and 1.8 ng cm(-2) for PBDE3-7, BDE-209, and TBE, respectively. The concentration of DP in Lake Ontario sediment exceeds that of the brominated flame retardants combined.
The direct polymerization of isoprene and alpha-pinene on acidic sulfate aerosols has been studied in a reaction chamber utilizing aerosol mass spectrometry. Results indicated that both species can be directly taken up into acidic aerosols to a significant extent, forming polymers that contain at least 4 isoprene or 2 alpha-pinene repeating units. Aerosol mass spectra indicate that double bonds in the polymers hydrate under acid catalysis, leading to partial oxygenation of the polymers. This reactive uptake depends highly upon relative humidity and particle acidity. This process is rapid and reaches equilibrium in less than 50 minutes, with effective partition coefficients (K-p,K-eff) between 1.2-14.1 x 10(-6) m(3) mu g(-1), from which it is estimated <0.5-5 ng m(-3) of polymers may be present from both species in acidic aerosols. The formation of biogenic polymers is an important mechanism for incorporating hydrophobic, unsaturated species into polar aerosols and enhanced SOA formation.