car emissions lab
What do you do while driving? It may be more harmful than you think. Transportation devices as a whole still contribute almost half of the nitrogen oxides (NOx) introduced into the atmosphere today. Nitrogen oxides contribute to acid rain, the greenhouse effect, deterioration of the ozone layer and smog. The catalytic converter present in most modern cars changes nitrogen oxides back into nitrogen and oxygen using unburned gasoline. One downfall to these catalytic converters is that they only work on warm/hot engines. This means that, once a car is started, until the time the engine is “warm”, the tailpipe is essentially, emitting high levels of pollutants to the environment.
In this lab, vehicle exhaust is tested for both nitrogen oxides and particulates when the car is cool and when the car is warmed up. Since NO2 absorbs visible light, standard calibration curves for NO2 and nitrogen absorbing solutions were made. Also, using a SMPS system, that measures particulates in the air, particulate output and NOx output were assessed for seven different vehicles.
The results are as follows. From our results of hot vs. cold starts, we were expecting to find higher concentrations of NO2 on “cold starts” for each car, and lower concentrations for “hot engines”. It is interesting to note that the cars do not all exhibit the same behavior over time (the cool exhaust contains less NOx, or vice versa). While on day two of collecting data from cars, 3 of the 4 cars tested did follow our predictions (the 4th car however was the extremely old corolla, most likely not having a catalytic converter), almost the entire opposite trend happened on the first day of car sampling. Therefore according to our data, no exact conclusion could be drawn regarding the catalytic converter assumption that lower emissions of NO2 would result from a warm engine. In order of highest to lowest cold start NOx emissions the cars are as follows: Jetta, Corolla, Civic, Villager, Saab, Alero, and Echo. As for the hot, the cars rank Corolla, Saab, Villager, Alero, Civic, Echo, and Jetta. The Villager, Jetta and Civic produce much lower concentrations once they have warmed up, while the Corolla almost appears to have a malfunctioning catalytic converter.
The data from the SMPS was also analyzed and graphed, showing total particle numbers and particle volumes.
All the cars except the Jetta and Civic have greatly reduced particulate emissions once they are warm.
In conclusion, it seems that the production of nitrogen oxides in vehicle emissions is very unpredictable. However, once cars are warm they tend to greatly reduce their particulate emissions.