Mark J. Potosnak
Tropospheric ozone is a ground-level pollutant and is produced from primary air pollutants like nitrogen oxides and volatile organic compounds (VOCs). While many VOCs are anthropogenic, isoprene is emitted from certain species of plants and reacts with nitrogen oxides to form ozone. Previous studies have found that isoprene can be suppressed by CO2, but such suppression can be reduced under conditions of increased temperature. However, this pattern is not seen in all plants capable of emitting isoprene. The focus of this is study is to determine if similar patterns are present in the invasive tree species of buckthorn (Rhamnus cathartica) and two oak species – red oak (Quercus rubra) and swamp chestnut oak (Quercus michauxii) – that are native in Chicago, Illinois. Two hypotheses being tested are patterns of isoprene suppression by CO2 at ambient temperature in Q. michauxii will be the same as the patterns seen in Q. rubra (H1) and patterns of isoprene suppression by CO2 at ambient temperature in R. cathartica will be the same as the patterns seen in Q. rubra. (H2). This study also tests the hypothesis that isoprene suppression by CO2 at elevated temperature will be reduced in R. cathartica, leading to poorer air quality in Chicago, IL. (H3). To test these hypotheses, individuals of the native species were grown in a greenhouse and the buckthorn species was sampled from a field and brought into the greenhouse. CO2 concentrations (400 ppm and 800 ppm) and temperatures (30 °C and 35 °C) were adjusted for the leaves using a leaf gas exchange system; isoprene was collected and measured concurrently with a gas chromatograph. Results show that patterns of isoprene suppression were not the same as those seen in Q. rubra for R. cathartica nor Q.michauxii, thus rejecting H1 and H2. Isoprene suppression was not observed for R. cathartica, even when CO2 was increased. Thus, even in conditions where CO2 emissions increase, isoprene will also increase and thus support H3. These findings will help further understand the potential effects that different plant species, whether invasive or native, can have on air quality.
Núñez, Janet G.
"Effects of Elevated CO2 Concentrations and Elevated Temperatures on Isoprene Emissions of Rhamnus cathartica (European buckthorn), Quercus rubra (red oak) and Quercus michauxii (swamp chestnut oak),"
DePaul Discoveries: Vol. 11:
1, Article 5.
Available at: https://via.library.depaul.edu/depaul-disc/vol11/iss1/5