Atmospheric nitrogen deposition to forest and estuary environments in the Pearl River Delta region, southern China

Abstract

Due to its significant ecological and climate consequences, atmospheric nitrogen (N) deposition is a growing global concern, especially in the severely N-polluted regions such as the Pearl River Delta (PRD) region of southern China. One-year measurements of reactive N species, including ammonium nitrogen ( -N), nitrate nitrogen (-N) and total organic nitrogen (ON) in dry and wet deposition, were conducted using an automated wet–dry sampler incorporated with a DDAS (dry deposition on aqueous surface) sampling device at Dinghushan (DHS), a natural forest site in the northwest of PRD and at Hengmen (HM), an estuary site in the south of PRD during 2006–2007. Total deposition fluxes of N at DHS and HM were up to 48.2 and 37.8 kg ha−1 yr−1, respectively, with most of the deposition occurring in the rainy season. Wet deposition was the dominant form, contributing 65–70% to the total deposition. -N was the largest contributor to the total N deposition at DHS (47%) due to significant influence of agriculture emissions. ON was the most important N component at HM (41%), which is probably attributed to the marine sources. However, -N deposition is increasing rapidly recently and is expected to be more important in the near future. The current N deposition level in PRD is much higher than those in Europe and North America. Great challenges exist in reducing reactive N emission in this region. Thus, a scenario of rising N deposition in PRD in the near future cannot be ruled out. The environmental consequences due to elevated N deposition should therefore be paid more attention in the future

Wet and Dry Nitrogen Depositions in the Pearl River Delta, South China: Observations at Three Typical Sites With an Emphasis on Water‐Soluble Organic Nitrogen

“…The seasonal pattern of wet WSON deposition in the PRD was different from those observed in the Eastern China, North China, and Sichuan Basin (Song et al, ; Yang et al, ; Zhang et al, ). Although Wang, Wu, et al () measured high ON concentrations in rainwater at DHS during fall of 2007, their result was not highlighted and fully discussed. Considering that biomass burning could be substantially enhanced during dry season in the PRD (Ding et al, ; Yu et al, ; Yu et al, ) and that biomass burning has been recognized as an important source of WSON species (Mace, Artaxo, & Duce, ; Zamora et al, ; Yu et al, ), we propose that the enhanced concentration and proportion of WSON in wet deposition during fall were attributed to biomass burning (discussed below).…”

“…Our results indicate that during harvest season, open biomass (straw) burning should be the significant source of WSON in wet deposition. In particular, the volume‐weighted concentrations of WSON and K + were both higher at the DHS site than the other two sites, indicating a more pronounced biomass burning contribution at the forest site, which was surrounded by intensive agricultural activities (Wang, Wu, et al, ). Previous studies argued that agricultural fertilization might be a source of WSON in wet/bulk deposition due to higher WSON deposition at agricultural sites than urban sites (Song et al, ; Zhang et al, ).…”

“…TDN rate at the forest DHS was as high as 52 kg N ha −1 year −1 , with 35.2 and 16.8 kg N ha −1 year −1 for IN and WSON depositions, respectively, which were substantially higher than those at other forest sites (Song et al, 2017;Zhang et al, 2012). Similarly, Fang et al (2008) and Wang, Wu, et al (2013) reported that at DHS total rates of N deposition were 49.4 and 48.2 kg N ha −1 year −1 , respectively, in 10 years ago. Overall, on a spatial scale, IN deposition rate in the PRD was in the range of IN deposition across China, while WSON deposition rate in the PRD could be among the highest level in developed regions in China and the world.…”

Reply to “Comments on ‘Half-century nitrogen deposition increase across China: A gridded time-series dataset for regional environmental assessments’”

“…A recent study in Southern China (Wang et al, 2013) revealed that wet deposition contributed 65e70% to the total deposition. Humid area is likely to receive more nitrogen input through wet deposition due to lengthy rainy season and large precipitation amount.…”

Responses of Inorganic Nitrogen of Forest Soils to Urbanization in Pearl River Delta, South China

“…Urbanization producing important sources for reactive N compounds, in particular from meat consumption, sewage from huge urban residents and from fossil fuel combustion in automobile engines [4,5], and greatly increases atmospheric N deposition levels [6,7]. Higher N deposition with nitrate dominance was observed in urban than in rural areas [7,8].…”