Strong similarities in seasonal concentration ratios of SO42-, NO3- and NH4+ in precipitation between Sweden and the northeastern US*

Abstract

We analyzed 21-year long records of precipitation chemistry from central Scandinavia and the north-eastern US to compare seasonal variations of three major pollutant ions, SO 4 2- , NO 3 - and NH 4 + . Seasonal variations in concentrations of the individual ions were distinctly different between the two regions. However, despite these differences, we found strong and unexpected similarities between the two regions in seasonal variations of the concentration ratios NO 3 - /SO 4 2- , NH 4 + /NO 3 - and NH 4 + /SO 4 2- . A preliminary analysis suggests that these similarities are due to similarities between the two regions in chemical transformation and removal processes affecting SO 4 2- and NO 3 − in the atmosphere, and to a coupling between NH 4 + and SO 4 2- aerosol in long-range transport. Ion ratios appear to be less sensitive to seasonal variations in SO 2 and NO x emissions compared to individual ion concentrations. DOI: 10.1034/j.1600-0889.1990.t01-4-00005.x