Nr emissions (including NH 3 , NO x (NO x ¼ NO + NO 2 ), and N 2 O) to the air both on
temporal (from 1980 to 2015) and spatial (provincial and 1 Â 1 km land use) scales
and their drivers by integrating both natural and human factors.
5.2.1 CHANS Boundary
The framework used for calculation is shown in Fig. 5.1. It quantifies and tracks the
fluxes of all N flows in the CHANS model. It is a comprehensive approach to analyse
the N budget and their human and natural driving factors. The study area only includes
the mainland of China, and Taiwan, Hong Kong, and Macao were excluded due to
data limitations. The N cycling within the CHANS framework starts from the entry of
Fig. 5.1 Coupled human and natural systems (CHANS). Arrows represent N fluxes; solid rectangle
boxes represent subsystems (cropland, grassland, forest, livestock, aquaculture, industry, humans,
pets, urban green land, wastewater treatment, solid waste treatment, atmosphere, surface water, and
groundwater) and system; solid colourful lines represent boundaries of functional groups, of which
green represents the processor, red represents the consumer, cyan represents the remover, and blue
represents the life-supporter. (See more details in Gu et al. 2015)
5 Reactive Nitrogen Budgets in China
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