RELATIONSHIP BETWEEN THE ATMOSPHERIC PARTICULATE FRACTION AND THE IONIC CONTENT OF PRECIPITATION IN AN AREA UNDER INFLUENCE OF A WASTE INCINERATOR LOCATED IN THE BASQUE COUNTRY (SPAIN)

During the period between April 1988 and April 1991, the relationship between the ionic content of the atmospheric particulate fraction and the rainwater collected at Olaeta, a cattle raising and forested area in the Basque Country, has been studied. The site is affected by the e missions from a waste incinerator located 11 km away in a north-easter ly direction. SO42- and NH4+ ions are the most important species in th e particulate fraction with 4.6 mu g m(-3) for each of them. The preci pitation is characterized by very high concentrations of Cl- ion with 173.4 mu eq l(-1) (Cl-/Na+ ratio = 3), the next important ions are NH4 +, Ca2+ and SO42- with 95.9, 91 and 69.2 mu eq l(-1) respectively. The average H+ concentration is 47.9 mu eg l(-1) (pH = 4.3). The contribu tions of both soluble particulate fraction and gases to the ionic conc entrations recorded in the precipitation differ widely from one type o f ion to another, the contribution of HCl gas being the most important one. Approximately, 95% of Cl- ion present in the rainwater come from the gaseous phase. The contribution of the particulate fraction tb th e rainwater concentrations varies between 100% (for SO42- and NH4+ ion s) and 22% (for Ca2+ ion). The scavenging ratio for Cl- ion (W = 40,00 0) is very high as it is mainly in the gaseous phase in the atmosphere . The scavenging ratios of NH4+ and SO42- ions are the lowest (W = 600 and 1000 respectively), probably because these species are in the fin e particle range of the aerosol.