Anthropogenic modification of the nitrogen cycling within the Greater Hangzhou Area system, China

Abstract

Based on the mass balance approach, a detailed quantification of nitrogen (N) cycling was constructed for an urban-rural complex system, named the Greater Hangzhou Area (GHA) system, for this paper. The GHA is located in the humid climatic region on the southeastern coast of China, one of the earliest regions in the Yangtze Delta to experience economic development. Total N input into the GHA was calculated at 274.66 Gg/yr (1 Gg = 10(9) g), and total output was calculated at 227.33 Gg/yr, while N accumulation was assessed at 47.33 Gg/yr (17.2% of the total N input). Human activity resulted in 73%of N input by means of synthetic fertilizers, human food, animal feed, imported N containing chemicals, fossil fuel combustion, and other items. More than 69.3% of N was released into the atmosphere, and riverine N export accounted for 22.2% of total N output. N input and output to and from the GHA in 1980 were estimated at 119.53 Gg/yr and 98.30 Gg/yr, respectively, with an increase of 130% and 131%, respectively, during a 24-year period (from 1980 to 2004). The N input increase was influenced by synthetic fertilizers (138%), animal feed (225%), N-containing chemicals (371%), riverine input (311%), and N deposition (441%). Compared to the N balance seen in the arid Central Arizona-Phoenix (CAP) system in the United States, the proportion of N transferred to water bodies in the humid GHA system was found to be 36 times higher than the CAP system. Anthropogenic activity, as it typically does, enhanced the flux of N biogeochemistry in the GHA; however, a lack of an N remover (N pollutant treatment facilities) causes excess reactive N (Nr; such as NH3, N2O, NOx), polluting water bodies and the atmosphere within the GHA. Therefore many challenges remain ahead in order to achieve sustainable development in the rapidly developing GHA system.

The long-term impact of urbanization on nitrogen patterns and dynamics in Shanghai, China

“…1). The vertical boundary definition follows Gu et al (2009); the upper boundary is defined as 1000 m above the ground surface taking into account nitrogen deposition; the lower boundaries consider the thin soils in mountainous regions, deep groundwater in lowlands, and other ground media above the bedrock.…”

“…The expanded urban area is mainly converted from cropland in the GSA (Zhao et al, 2006). It intensively alters the regional nitrogen cycle since both the urban area and cropland are hotspots of nitrogen fluxes but have different effects on nitrogen cycle (Gu et al, 2009;SvirejevaHopkins et al, 2011). This rapid urbanization process in the GSA has resulted in a series of consequences on regional even global environment and human health.…”

Quantitative evaluation of reactive nitrogen emissions with urbanization: a case study in Beijing megacity, China

“…We obtained environmental and economic data mainly from yearbooks published by Beijing Municipal Bureau of Statistics and National Bureau of Statistics of China (2000-2013a, b, c), which, in recent years, have supplied the best available data for the calculation of anthropogenic N fluxes in China (Gu et al 2009). In this study, the official statistical data from 2000 to 2012 were used, a time period in which an improved system of up-to-date data collection was in place.…”

“…Although the number of such treatment plants in Beijing is increasing, from 4 in 2000 to 24 in 2012, with average sewage treatment rates as high as 80 %, the increased facilities are unable to treat all the wastewater from the city, which results in the discharge of raw and even treated sewage directly into the rivers. The direct and indirect discharge of sewage are assumed to be the main sources of dissolved Nr release and significantly contribute to the N pollution of urban rivers in Beijing (Gu et al 2009;Ren et al 2014).…”

“…The improvement in inhabitants' livelihoods and industrialization are the main factors driving the increased demand for N consumption, resulting in increased N emissions to the environment (Liu et al 2015). Especially in the megacity ecosystem, where the urban core strongly affects its periphery areas including suburban and rural regions (Gu et al 2009), the magnitude of this increase is larger than that driven by natural processing (Duh et al 2008). For instances, in terms of domestic food consumption, the N embedded in proteins from food for human consumption accounts for approximately 20 % of the total N input for food production (Galloway and Cowling 2002).…”