Two sampling points were chosen and forty samples were collected between January and
December 2006 at Alto Sorocaba basin. The rainwater pH varied from 5.46 to 6.36 (Ibiúna)
and 5.26 to 6.81 (Itupararanga), being Ca2+ the main ion responsible for controlling
the rainwater pH. The ionic concentrations decreased in the following order: Ca2 +>Na+>
Mg2+>K+ for cations and SO4(2-)>HCO3->NO 3->Cl- >PO4(3-) for anions. The annual atmospheric
deposition appeared to be controlled mostly by following sources: mining activities
and cement factories (Ca2+ and HCO3-), natural soil dust (Na+, Mg2+ and HCO3-), fossil
fuel burning (SO4(2-)) and agriculture activities (K+, NO3- and PO4(3-)).