Assessment of diesel exhaust pollutants effects in Tillandsia capillaris and Ramalina celastri by laboratory trials

Traffic-related air pollution is one of the most relevant environmental problems in urban areas. Several cryptogams (i.e., lichens and mosses) and vascular species have been employed to monitor urban air pollution since they allow the assessment of air quality in a large number of sampling sites simultaneously at low cost. In large urban cities, vehicle emissions are frequently the major source of air pollution along with residential energy (for cooking and heating), industry, power generation, and waste incineration. Biomonitors in these urban environments are exposed to a mixture of pollutants making it difficult to identify which pollutant causes the greatest damage to organisms. However, studies that analyze the effect of pollutants emitted by vehicle exhaust are scarce and in the particular case of the most used biomonitor species in Argentina, no analysis of how they are affected by vehicle emissions has been carried out so far. So, the aim of this work was to analyze changes in physiochemical parameters (pigment content, pro-oxidant products, and sulfur accumulation) in Ramalina celastri, and heavy metal accumulation in Tillandsia capillaris, exposed to diesel exhausts under laboratory conditions. A strong damage in the photosynthetic apparatus of R. celastri was observed as well as metal concentration in T. capillaris after 20 min of exposure and 48 h of permanence in the exposure chambers. The results indicate that not only the particles and metals cause damage to these two well-known biomonitors, but the interaction of these pollutants with other components of the atmosphere that form different secondary pollutants, together with a longer exposure time, could cause the highest level of damage in them.