Spatial Patterns in Wet and Dry Deposition of Atmospheric Mercury to Illinois Watersheds

Abstract

An intensive one month atmospheric mercury monitoring campaign was carried out at 8 sites in central Illinois, USA, during summer of 2011 to assess spatial patterns in wet and dry deposition. Daily precipitation samples, turf surrogate surfaces, and throughfall samples were collected concurrently to measure both wet and dry deposition of mercury, trace metals and major ions. Average deposition values observed for the study period (June 9 to July 3, 2011) for total wet deposition and total dry deposition were 4.0 ± 0.8 µg/m 2 and 1.2 ± 0.4 µg/m 2 , respectively. Based on previous findings, the summer 2011 wet deposition rates were higher compared to summers of 2008 and 2009 at the Nilwood and Peoria sites, and wet deposition during this period represented 20-30% of the annual deposition previously measured. Dry deposition ranged from 17 - 31% of total deposition across sites during the study period. Nilwood and its surrounding monitoring sites had slightly higher wet deposition compared to the more northerly Peoria and surrounding sites.