Atmospheric transport of elemental carbon

Frequent pollution episodes, defined by high SO4 (> 10 mu g/m(3)) and trace element concentrations, occur concurrently across the northeastern United States. Ten such episodes that occurred at Mayville and Whiteface Mountain in New York State (NYS) from 1983 to 2002 were chosen to investigate transport of elemental carbon (EC) from upwind emissions. The peak SO4 concentrations during these episodes at Mayville ranged from 23 to 60 mu g/m(3), and at Whiteface Mountain they ranged from 17.5 to 49 mu g/m(3). Similarly, the peak EC concentrations at Mayville ranged from 0.74 to 1.63 mu g/m(3), and they ranged from 0.26 to 0.89 mu g/m(3) at Whiteface Mountain. The HYSPLIT4 air trajectories and elemental signatures showed that the high concentrations were associated with the air masses reaching the sampling sites after traveling through the Midwest. The concentrations of EC, SO4, and Se were highly correlated during the episodes. The sector analysis using EC concentrations in 104 samples at Mayville and 162 at Whiteface Mountain showed that similar to 77% of the total EC at Mayville and similar to 87% at Whiteface Mountain was contributed by the upwind sources in the Midwestern United States. When airflow was from the north, the mean concentrations at Whiteface Mountain were very low, < 0.03 mu g EC/m(3) and 0.32 mu g SO4/m(3). The sources close to Whiteface Mountain contributed little EC. The EC data from this site should be considered as representative of the regional EC emissions. Measurements of EC in the samples collected over two decades at Whiteface Mountain should be useful in calculating radiative forcing and testing models predicting atmospheric EC burden on the basis of emissions.