Scavenging ratios in an urban area in the Spanish Basque Country

Abstract

For a period of six years (1995-2000) the scavenging ratio, which is the ratio of a pollutant's concentration in water to its concentration in air, collected at an urban site in the Spanish Basque Country was studied. The aerosol is characterized by SO42- and NO3- with 1.79 and 1.61 μg m-3, respectively. Greater fractions of SO42-, NO3-, and NH4+ ions were present in the fine particle range, while greater fractions of other ions appeared in the coarse range. The most important species found in the precipitation is SO42- with 3.0 mg l-1. NO3-, Ca2+, and Cl- are the second most important ions. The volume-weighted mean concentration of H+ is 4.6 μg l-1 (pH = 5.3). The concentration of all analyzed ions (except H+) decreases throughout the rain event, showing the washout phenomenon of the rainwater. The scavenging ratio for the anthropogenic ions NO3-, SO42-, NR4+, and K+ is lower than the scavenging ratio for the marine-terrigenous ions, Cl-, Na+, and Ca 2+.