Comparison of Ammonium Deposition Flux at Roadside and at an Agricultural Area for Long-Term Monitoring: Emission of Ammonia from Vehicles

To understand the effect of the NH₃ emissions from vehicles, the NH₄ ⁺ bulk deposition and concentrations of gaseous NH₃ and particulate NH₄ ⁺ were measured at two sites in Saitama prefecture, Japan, one at the roadside of an arterial road (Kounosu), and the other in an agricultural area (Kisai). We observed that the NH₄ ⁺ bulk deposition and NH₃ concentration were significantly increased in Kounosu; the effect of NH₃ emissions from vehicles was confirmed. NOx was a primary pollutant mainly emitted by vehicle exhaust in the vicinity of arterial roads, and the relationship between NO _x and sum of gaseous NH₃ and particulate NH₄ ⁺ (T-NH₄ ⁺) was examined. The [T-NH₄ ⁺/NO _x ] ratios in Kounosu ranged from 0.08 to 0.23 (average 0.15), and in Kisai they ranged from 0.16 to 0.67 (average 0.39). In Kounosu, the effect of vehicle exhaust was great, but seasonal variation was small. The contribution ratio of NH₃ from vehicle emissions increased at low temperatures, while that from the non-vehicle emissions increased at high temperatures.