RESEARCH ARTICLE Urbanization in China changes the composition and main sources of wet inorganic nitrogen deposition

Abstract Nowadays, nitrogen (N) deposition has become a growing global concern due to urbanization activities increas-ing the large amount of reactive N in the atmosphere. However, it remains unclear whether urbanization affects the composition and main sources of N deposition in rapidly urbanizing areas such as in China. One-year measurement of wet inorganic N deposition was conducted using ion-exchange resin (IER) columns in the range of 260 km from urban to rural areas in the Pearl River Delta (PRD) region, south China. An increasing pattern of wet inorganic deposi-tion along the urbanization gradient was observed and it increased in the order: rural (15.26±0.20 kg N ha−1 year−1) <suburban/rural (21.45±3.73 kg N ha−1 year−1)<urban (31.16±0.44 kg N ha−1 year−1)<urban/suburban sites (34.15 ±5.73 kg N ha−1 year−1). Nitrate N (NO3 −–N) accounted for 53.5–79.1 % of total wet inorganic N deposition, indicating a significant negative correlation with distance from the urban core. Based on moss δ15N-values the main source of NO3 −–N was considered to be emitted from vehicles. Our results dem-onstrate that urbanization has large impacts on the regional pattern of wet inorganic N deposition. Thus, controlling NOx emission, especially vehicle emissionwill become an effective strategy for N pollution abatement in China