Integrated and sequential bulk and wet-only samplings of atmospheric precipitation in Londrina, South Brazil (1998–2002)

The present study investigated the chemical composition of bulk and wet atmospheric precipitation samples in Londrina city, in south Brazil. The samples were collected from April 1998 to November 2002. A total of 350 rainwater samples were collected on an event basis, integrated for 24 h, and analyzed for pH, conductivity, Na+, K+, NH4+, Cl-Cl-, NO3-, and SO42-. The concentration variability of rainwater was evaluated through sequential analysis of fractionated rainwater samples during three rainfall events. The comparison of bulk and wet-only sample results revealed that there are differences between collectors as to ionic composition and conductivity. Acid rain was characterized in 34% (bulk collector) and 35% (wet-only collector) of the samples. The correlation (>0.5) of NH4+with Cl-Cl-, NO3- and SO42- suggests that NH4+ is the neutralizing constituent. Below cloud scavenging processes were observed due to the decline in the concentrations of all chemical species analyzed in the fractions along event. The total wet deposition rate of NH+, NO3- and SO42- were, respectively, 18.3, 17.1 and 13.4 meq m−2 yr−1. The composition of the rainwater collected appeared to be controlled by the following potential sources: crustal, agricultural activity (animal/fertilizer), and biomass and fossil fuel combustion. The precipitation chemistry in Londrina seems to be controlled by man-made emissions of S and N gases.