Physiological response and sulphur accumulation in the biomonitor Ramalina celastri in relation to the concentrations of SO2 and NO2 in urban environments

Abstract

This study extends the current knowledge regarding the use of different tools for monitoring atmospheric pollution. The chemical response of the lichen Ramalina celastri was evaluated through physiological parameters and sulphur accumulation in relation to the SO2 and NO2 concentrations present in the air at the monitoring sites with different emission sources, in order to assess the atmospheric pollution in urban environments. In this way, it was possible to establish different levels of air quality using simultaneous measurements of gaseous pollutants in the air and of parameters for the exposed biomonitor, as well as to determine the relationship among them and their association with the different emission sources present. Thalli of Ramalina celastri were transplanted at sites with different pollutant emission sources within the city of Córdoba, and simultaneously the concentrations of SO2 and NO2 were measured at the same sampling sites. Pigment content, hydroperoxy conjugated dienes, malondialdehyde and sulphur accumulation were quantified in the lichen and the pollution index was calculated. The results showed that high concentrations of atmospheric SO2 in urban environments can be detected with certainty by measuring sulphur accumulation on the biomonitor. Although this relationship has often been assumed, it has not been confirmed by using simultaneous measurements. This biomonitor allowed different air quality levels to be identified in relation to the concentrations of NO2 and SO2 in Córdoba city. The biomarkers that best reflected the damage caused by pollutants on the lichen were pollution index, hydroperoxy conjugated dienes and malondialdehyde, which revealed a strong association with the most polluted areas in the city (industrial and heavy traffic sites).