Will the shift from crude oil to natural gas burning for power generation at an oil refinery increase ozone concentrations in the region of Cubatão (SE-Brazil)?

The ozone (O3) hypersensitive species Nicotiana tabacum Bel W3 was used to assess the impact on O3 contamination profile by a natural gas-powered thermoelectric plant (TP) that provides power to an oil refinery at Cubatão (SE-Brazil). An increase in O3 levels would represent an even more harmful effect to the Atlantic Rainforest present in the region. The biomonitoring study was performed along TP pre-operation, transition and TP post-operation phases. Tobacco plants were biweekly exposed at urban, industrial and forest areas at different altitudes. O3-induced leaf injuries were evaluated at the end of each exposure. N. tabacum plants at forest sites at mountain slope were usually more affected by O3, especially at higher layers. As TP started operating, nitrogen dioxide (O3 precursor) mean concentrations increased considerably (6 ppb to 16 ppb). The contamination of the Atlantic Rainforest by high levels of N created a favourable scenario for an increase in O3 concentrations. In fact, F200, F300 and F350 sites (forest sites at 200, 300 and 350 m.a.s.l.) had plants showing a significant increase in O3-induced leaf injuries. Phytotoxic levels were similar to those found at F700 site (forest site at 700 m.a.s.l.), which were high for the whole study period. The new O3 contamination profile persisted for F200 and F300 sites during TP post-operation phase. Although slightly lower levels than those seen on transition phase, the intensity of O3-injuries remained higher compared to the original conditions. The use of Nicotiana tabacum Bel W3 allowed to see the negative impact on the air quality after TP started operating, contributing to an increase in O3 concentrations and phytotoxic levels at forest sites at mountain slope. Plant community were then exposed to an even higher harmful effect compared to the first phase. The stability and fitness of the Atlantic Rainforest influenced by the pollution coming from Cubatão are still under potential risk. However, how the vegetation will behave at this new scenario is unknown and requires time.