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Air pollutant emissions from the industrial complex of Cubatao, SE-Brazil, have caused a severe decline of the Atlantic Forest in that region. In order to test the influenceof air pollution on the mineral nutrition of trees, leaves of the native species Tibouchina pulchra Cogn. (Melastomataceae), Miconia pyrifolia Naud. (Melastomataceae) and Cecropia glazioui Snethl. (Cecropiaceae) were sampled during winter and summer seasons at four sites with different pollution characteristics. Additionally, saplings of T. pulchra were cultivated in uniform soil and exposed to ambient air at the same experimentalsites for periods of 16 weeks. In both kinds of leaf samples, the concentrations of macro-nutrients were determined and nutrient ratios calculated. In leaves of mature T. pulchraand C. glazioui growing at polluted sites N, P and S levels were significantly higher than in trees from the reference area. With respect to K contents, C. glaziouishowed an increase, T. pulchra a decrease when compared to reference trees. Mg and Ca concentrations generally did not exhibit great variations. As a consequence of the changes in mineral contents nutrient ratios (N/K, N/Ca, S/K, S/Ca) shifted to higher values. The results of the exposure experiments together with data on pollutant concentrations inambient air and rain water demonstrated that atmosphericdeposition to the plants and pollution effects on the soilchemistry are the main reasons for the observed alterations inmineral nutrition of trees.