A framework to quantify riverine dissolved inorganic nitrogen exports
under changing land use pattern and hydrologic regime
Abstract
Riverine dissolved inorganic nitrogen (DIN), when elevated by human
activities (e.g., land-use change), can accelerate the nitrogen cycle
and downstream dispersal. However, estimating DIN export coefficients
for individual land-use types can be complex due to mosaic land-use
patterns and interactions between fertilizers and hydrological
processes. We propose a framework that integrates an empirical model, a
moving-window method with an elasticity method to quantify seasonal DIN
export coefficients for each land use in the Shixi Creek catchment,
southeast China. Our model showed good agreement with field observations
according to root mean square error and a normalized objective function.
The DIN export coefficients of farmland and forest were the highest
(9.16 mg/L) and lowest (2.91 mg/L), respectively, resulting in DIN
exports for farmland and forest of 1,951 kg km-2 yr-1 and 619 kg km-2
yr-1, respectively. Urbanization was a dominant factor influencing DIN
export represented by the export coefficient of built-up areas with the
highest elasticity and highest uncertainty. This study can shed light on
how to improve riverine N management in a catchment by considering the
interactive effects of climate and land use changes.