The guava tree as bioindicator during the process of fuel replacement of an oil refinery

This study was performed to verify whether the exchange of the fuel used in the boilers of a crude oil refinery located in Cubatao (SE Brazil) would result in alterations on gas exchange, growth and leaf injuries in saplings of Psidium guajava `Paluma'. The purpose of the refinery was to reduce the SO2 emission, but using natural gas as fuel could increase the concentrations of O-3 precursors in the atmosphere. Thus a biomonitoring was performed with a native species sensitive to O-3. The plants were exposed in five areas (CM1, CM5, CEPEMA, Centro, and RP) at different distances to the refinery, both before and after the fuel exchange. We performed six exposures under environmental conditions, with length of ca. 90 days each. With the utilization of natural gas, the saplings presented reductions in carbon assimilation rate under saturating light conditions (Asat, mu mol CO2 m(-2) s(-1)) and the stomatal conductance (gs, mol H2O m(-2) s(-1)), and increase in height, number of leaves, and dry mass of leaves and shoots. There were also reductions in root dry mass and in the root/shoot ratio. The saplings also presented O-3-induced leaf injuries. The responses of P. guajava `Paluma' were altered after the fuel exchange as a result of a new combination of pollutants in the atmosphere. The fuel exchange has not resulted in environmental benefit to the surrounding forest; it has only altered the contamination profile of the region. (c) 2013 Elsevier Inc. All rights reserved. (AU)