Chemical composition of rainwater and anthropogenic influences in the Piracicaba River Basin, Southeast Brazil

The influences of different kinds of anthropogenic activities on rainwater chemistry in a tropical area were studied during one uninterrupted year at Piracicaba River Basin (Southeast Brazil). A total of 272 rainwater samples collected continuously from August 1997 to July 1998 at four different sit es were analyzed for F-, CH3COO-, HCOO-, MSA, Cl-, NO2-, Br-, NO3-, SO42-, C2O42-, PO43-, Na+, NH4+, K+, Mg2+, Ca2+, DOC (dissolved organic carbon), D IC (dissolved inorganic carbon), pH and conductivity. The most abundant ion was H+ and rain acidity was significant at all sampling sites (average pH of 4.4-4.5). The sources of this free acidity differ among sites and appear to be correlated to the different land-uses. The composition of rainwater appeared to be controlled mostly by three sources: soil dust, sugar cane bu rning and industrial emissions. (C) 2001 Elsevier Science Ltd. All rights r eserved.