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Seasonal and air-mass trajectory effects on rainwater quality at the south-western european border

1991; Elsevier BV; Volume: 25; Issue: 10 Linguagem: Inglês

10.1016/0960-1686(91)90101-c

1878-2124

Casimiro Pio, Maria L. Salgueiro, Teresa Nunes,

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Rainwater was collected daily, at the Portuguese west coast, between April 1985 and October 1989 and analysed for pH, conductivity, Cl−, NO3−, SO22− and NH4+ concentrations. A seasonal variation was observed for sulphates and nitrates, with minimum concentrations during autumn and maximum during winter and spring. No seasonal pattern could be detected for acidity. The level of acidity in rainwater is highly dependent on the history of the air mass. Levels of acidity 10 × higher than average were found in rain events associated with air masses proceeding from industrialized countries in Europe and transported over the ocean. However, as these rain events constitute only a small fraction of total wet deposition, and approximately 80% of total precipitation is associated with transport from the Atlantic Ocean, the average pH is 5.3.