The Correlation between Mercury, Ions, and Weather Conditions at PA-47

Research conducted in the 1970s found that the emissions of SO₂ and NO_x proved to be a widespread problem through the formation of acid rain. In 2002, PA-47 was established to close an NTN/MDN measurement gap in south-central Pennsylvania, and sample collection conducted by Millersville University (MU) meteorology students has continued uninterrupted ever since. PA-47 is located approximately three kilometers from the MU Weather Information Center where a full suite of meteorological variables are recorded and archived. This research uses ion/mercury analyses and meteorological data from 2006 through 2011 to understand the correlation between the variability observed in the NADP record and the weather conditions that could have contributed to the variability. This period corresponds to the availability of trajectory analyses using the HYSPLIT – Hybrid Single Particle Lagrangian Integrated Trajectory Mode, which will be employed in this study.

Anomalies were found as deviations from the mean concentrations of mercury, sulfate, potassium, calcium, magnesium, sodium, ammonium, and chlorine. This resulted in the isolation of those weeks that exhibited anomalies that were one and two standard deviations outside the mean. The meteorological conditions were found for the anomalies and categorized according to wind direction and time of year, and HYSPLIT was used to obtain back trajectories to determine source regions for this air. Results suggest that weather conditions are well correlated with variability in the weekly ion and mercury data. Our preliminary data shows that highest concentrations are found when the wind direction is from the southwest in the summer seasons in moderate precipitation events that occur after an extended period of dry conditions.