Passage III
Motor vehicle exhaust is a significant source of several air pollutants, including the nitrogen oxides, NO2 and NO. Scientists performed two experiments to investigate the levels and behavior of these pollutants and naturally occurring gases in the atmosphere near busy roadways.
Experiment 1
Scientists studied how NO2, levels vary with vehicle use. They measured NO2 levels hourly for a 24-hour period, 10 meters (m) downwind from six roadways. Each roadway had a combination of a different speed limit and vehicle usage (approximate number of vehicles per day). An average NO2 value for each roadway was calculated in parts per billion (ppb). The results are in Table 1.
Experiment 2
Next, levels of NO2 and NO were measured at 0, and 100 m downwind from the 100 km/hr roadway which averaged 30,000 vehicles per day. The level of NO2 decreased from 30 ppb at 0 m to 17 ppb at 100 m. The level of NO decreased from 150 ppb at 0 m to 42 ppb at 100 m.
(Note: The levels of NO2 and NO that would be found far from pollution sources are 15 ppb and 35 ppb, respectively.)
Experiment 3
Ozone (O3) is a naturally occurring gas in the atmosphere. Levels of ozone, in parts per million (ppm) were taken at various distances downwind from the 100 km/hr roadway which averaged 30,000 vehicles per day. The results are in Table 2.
(Note:The naturally occurring ozone concentration is 0.12 ppm.)
13. According to the experimental results, one way to reduce levels of NO2 in an area would be to:
Your Answer is
Correct Answer is B
Explanation
It can be seen from table 1 that when the speed limit is lower, the same number of vehicles will emit less NO2