Journal article
Factors influencing export of dissolved inorganic nitrogen by major rivers: A new, seasonal, spatially explicit, global model
Global biogeochemical cycles, Vol.28(3), pp.269-285
03/01/2014
Handle:
https://hdl.handle.net/2376/124310
Abstract
Substantial effort has focused on understanding spatial variation in dissolved inorganic nitrogen (DIN) export to the coastal zone and specific basins have been studied in depth. Much less is known, however, about seasonal patterns and controls of coastal DIN delivery across large spatial scales. Understanding seasonal patterns of DIN export is critical to efforts to predict impacts of coastal eutrophication, such as algal blooms and hypoxic areas, which are often seasonal phenomena. Here we describe, test, and apply a global model that predicts seasonal DIN export to coastal regions for >6000 rivers using the Nutrient Export from Watersheds (NEWS2) model. NEWS2-DIN-S used spatially explicit, seasonal N inputs and was calibrated with measured DIN yield (kgNkm(-2) season(-1)) for 77 rivers, distributed globally. Of the characteristics considered, DIN-transport efficiency was positively related to runoff and negatively related to temperature (r(2)=0.34-0.60, depending on season p<0.0001), likely due to flushing effects and increased retention by plants and soils, respectively. NEWS2-DIN-S incorporated these insights and performed well in predicting DIN yield (Nash-Sutcliffe Efficiency=0.54-0.65, depending on season). Catchments were effective in retaining DIN and average export rates were lower during the growing season (3-5% of total nitrogen inputs) compared to other seasons (6-10%) for major latitude bands. Model output was insensitive to changes in the magnitude of N inputs, suggesting that refinement of seasonal N input budgets will not substantially improve model performance. Rather, better representation of land-to-river N transfers could improve future models because of strong landscape N attenuation.
Key Points
Catchment DIN attenuation is greater in summer compared to other seasons Both runoff and temperature influence seasonal DIN-transport efficiency Depending on season and latitude, 3-10% of TN inputs are exported as DIN
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Details
- Title
- Factors influencing export of dissolved inorganic nitrogen by major rivers: A new, seasonal, spatially explicit, global model
- Creators
- Michelle L McCrackin - Washington State University VancouverJohn A Harrison - Washington State University VancouverJana E Compton - Environmental Protection Agency
- Publication Details
- Global biogeochemical cycles, Vol.28(3), pp.269-285
- Academic Unit
- Environment, School of the (CAS); Harrison Research Group: Global Change and Watershed Biochemistry
- Publisher
- AMER GEOPHYSICAL UNION
- Number of pages
- 17
- Grant note
- National Academies of Science Research Associateship Program U.S. Environmental Protection Agency; United States Environmental Protection Agency UNESCO-IOC
- Identifiers
- 99900668018601842
- Language
- English
- Resource Type
- Journal article