Measuring Ammonia Concentration Distributions with Passive Samplers to Evaluate the Impact of Vehicle Exhaust on a Roadside Environment in Tokyo, Japan

Evaluating the impact on roadside environments of NH3 from vehicle emissions is important for protecting the ecosystem from air pollution by fine particulate matter and nitrogen deposition. This study used passive samplers to measure NH3 and NOX at multiple points near a major road to observe the distribution of these gases in the area. The impact of NH3 emitted from vehicles on a major road on the environmental concentration of NH3 at different distances from the roadside was found to be similar to that of NOX and NO2. The concentration of NH3 rapidly decreased due to dilution and diffusion within approximately 50 m of the road, and after 100 m the concentration remained almost the same or decreased slowly. Furthermore, CO2 observations taken in the same period along the roadside and in the background yielded a vehicular emission factor of 4–50 mg/km for NH3, which is comparable with previous research. This emission factor level contributes 4–11 ppb to the NH3 concentrations in roadside air through the dilution and diffusion process. A correlation was found between the emission factors of NH3 and NOX that is different from the trade-off relationship seen when single-vehicle exhaust is measured