Comparative field study on precipitation, throughfall, stemflow, fog water, and atmospheric aerosol and gases at urban and rural sites in Japan

Precipitation collected by a wet-only sampler (WP), precipitation collected by a filtering-type bulk sampler (BP), throughfall (TF), stemflow (SF), fog water (FW), and atmospheric aerosol and gases were collected at two sites with different site classifications: an urban site (Mt. Rokko) and a rural site (Mt. Awaga) to investigate canopy–atmosphere interactions and to study the chemistry of precipitation in forested areas located in different atmospheric conditions. Compared to those at the rural site, the monthly volume-weighted pH values at the urban site were not significantly (p > 0.05) different for WP, higher (p < 0.05) for BP, not significantly (p >  0.05) different for TF, lower (p < 0.01) for SF, and lower (p < 0.01) for FW. The order of mean pH values at the urban site was FW < SF < WP < TF < BP. In contrast, the order at the rural site was FW < SF < BP < WP < TF. Concentrations of chemical species at the urban site were higher than those at the rural site in all samples and all chemical species. In particular, higher NO3− concentrations at the urban site were observed in all samples. The amount of dry deposition on leaves at the urban site was approximately 1.17 times larger than that at the rural site. The monthly net TF (= TF − BP) in autumn seemed to be larger than that in summer; this trend was remarkable in K+. The monthly NO3− deposition in the net TF was larger at the urban site than at other parameters and at the rural site. The concentrations of chemical species in aerosol and gases that were measured near the central part of Kobe City were ca. 3.4 times higher than those in the rural area. Mt. Rokko borders the central part of the city, which caused the concentrations at Mt. Rokko to be higher than those at Mt. Awaga. The deposition amounts at Mt. Rokko were larger than those at Mt. Awaga, which probably can be attributed to the higher concentrations of chemical species in atmospheric aerosol and gases.