Indirect Nitrous Oxide Emissions from Major Rivers in the World: Integration of a Process-based Model with Observational Data
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The atmospheric concentration of nitrous oxide (N2O), one of major greenhouse gases, has increased over 121% compared with the preindustrial level, and most of the increase arises from anthropogenic activities. Previous studies suggested that indirect emissions from global rivers remains a large source of uncertainty among all the N2O sources and restricted the assessment of N2O budget at both regional and global scales. Here, we have integrated a coupled biogeochemical model (DLEM) with observational data to quantify the magnitude and spatio-temporal variation of riverine N2O emission and attribute the environmental controls of indirect N2O emission from major rivers in the world. Our preliminary results indicate that the magnitude of indirect N2O emission from rivers is closely associated with the stream orders. To include N2O emissions from headwater streams is essential for reducing uncertainty in the estimation of indirect N2O emission.?By implementing a set of factorial simulations, we have further quantified the relative contributions of climate, nitrogen deposition, nitrogen fertilizer use, and manure application to riverine N2O emission. Finally, this study has identified major knowledge gaps and uncertainties associated with model structure, parameters and input data that need to be improved in future research.