Evaluation of automated streamwater sampling during storm events for total mercury analysis.

Understanding the processes by which mercury is mobilized from soil to stream is currently limited by a lack of observations during high-flow events, when the majority of this transport occurs. An automated technique to collect stream water for unfiltered total mercury (HgT) analysis was systematically evaluated in a series of laboratory experiments. Potential sources of error investigated were 1) carry-over effects associated with sequential sampling, 2) deposition of HgT into empty bottles prior to sampling, and 3) deposition to or evasion from samples prior to retrieval.

Quantum chemical and master equation studies of the methyl vinyl carbonyl oxides formed in isoprene ozonolysis.

Methyl vinyl carbonyl oxide is an important intermediate in the reaction of isoprene and ozone and may be responsible for most of the (*)OH formed in isoprene ozonolysis. We use CBS-QB3 calculations and RRKM/master equation simulations to characterize all the pathways leading to the formation of this species, all the interconversions among its four possible conformers, and all of its irreversible isomerizations. Our calculations, like previous studies, predict (*)OH yields consistent with experiment if thermalized syn-methyl carbonyl oxides form (*)OH quantitatively.