Physiological responses of the tropical tree Tibouchina pulchra Cogn under the influence of combustion of crude oil and natural gas at an oil refinery

A refinery located on the slopes of a mountain range in the city of Cubatão (SE-Brazil) is the main source of sulfur dioxide (SO2) in the region. For this reason, the refinery replaced a system in which energy was produced from crude oil combustion in boilers with a system of energy and vapor co-generation in a thermoelectric power plant fueled by natural gas. The aim of this study was to investigate the responses of Tibouchina pulchra to the fuel switching. Saplings planted in pots were distributed throughout monitoring sites around the polluting source (sites I, II, III and IV) and in a site (V) far from emissions. Changes on the plants responses occur along the three fuel switching phases. During the last phase, increased carbon assimilation (Asat) and decreased stomatal conductance (gs) were observed in plants growing in sites II and III; as a consequence, intrinsic water use efficiency (iWUE) increased. However, the increase in Asat did not promote growth increase suggesting that changes at the refinery did not result in better air quality, but only in a change in the main contaminants. ► An oil refinery exchanged its fuel from oil to gas to reduce SO2 emissions. ► Fuel exchange resulted in changes on Asat and growth. ► Asat increase did not promote growth increase. ► Photoassimilates products may be used for maintenance and damage repair. ► The fuel substitution only altered the air pollution profile in the region.