Black carbon transport to a remote mountaintop in the northeastern US and relationship with other pollutants

We report Aethalometer black carbon (BC) measurements carried out at 15-min intervals over 30 months at a mountaintop site in northeastern New York, along with co-located measurements of CO, O3, and SO2, and high time resolved measurements of PM2.5 mass and aerosol sulfate (SO4) concentrations acquired near the base of the mountain. The mean BC concentration at the site was 84 ng m−3 while monthly means varied from 25 to 144 ng m−3. Correcting for the impact of “mountain meteorology” yields an estimated surface equivalent annual mean concentration of 100 ng m−3. Periods of episodic high BC concentrations (>300 ng m−3), however, occurred throughout the year but were longer and more intense during the warmer months. We observed that the concentrations of O3, SO2, SO4, and PM2.5 mass, and to a lesser degree CO were often highly correlated with BC concentrations during the episodes, even when air trajectories indicated that the air masses reaching the site had passed through widely varied geographical regions. We report details of three specific BC episodes and examine the relationship between the co-measured species and air trajectories.