Reactive nitrogen (N) is essential to life, making up compounds such as proteins and nucleic acids....
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Transcript of Reactive nitrogen (N) is essential to life, making up compounds such as proteins and nucleic acids....
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Reactive nitrogen (N) is essential to life, making up compounds such as proteins and nucleic acids.
Technology now allows us to create N fertilizers, increasing food production. Currently, 50% of N in the human body is synthetic N fertilizer. N also is an important component of many industrial products.
Human-created N is critical for our modern society and economy. However, its overabundance in the environment harms human health, alters ecosystem function, and contributes to climate change.
Projected changes in climate for the 21st century may dampen or exacerbate human health and ecosystem effects of overabundant, human-created N. Understanding the interactions between reactive N and climate change is critical.
Estimate reactive N inputs across the conterminous United States (US).
Identify important reactive N sources across conterminous US watersheds.
Project mid-century shifts in riverine N export due to climate change.
CC-26: Mapping Loading Rates and Sources of Reactive Nitrogen across the United States suggests Regional Interactions with Climate ChangeDaniel J. Sobotaa,b, Jana E. Comptona,c, Shweta Singha,d, and Douglas J. Nortone aWestern Ecology Division, US Environmental Protection Agency, Corvallis, OR: bOak Ridge Institute for Science and Education; cNational Health and Environmental Effects Research Laboratory; dNational Research CouncileOffice of Water, US Environmental Protection Agency, Washington, DC
ObjectivesReactive nitrogen is a wicked problemShifts in riverine N exports due to climate changeReactive nitrogen inputs and sources, circa 2000Acknowledgements: Funding was provided by Oak Ridge Institute for Science and Education, the National Research Council, and the US Environmental Protection [email protected]@epa.gov
www.whoi.edu Harmful Algal Blooms & HypoxiaColin Bishop
Products & [email protected]@epa.gov
Colin BishopEnhanced crop productionEnergy &productsWater pollutionAir pollution Source data for reactive N inputs
Changes in riverine N exports due to climate change
Methods
Air
LandWaterHuman consumptionAgriculturalproduction
Energy consumption
BiologicalN fixation
The Nitrogen CascadeGalloway JN, Aber JD, Erisman JW, et al. 2003. The nitrogen cascade. Biosci 53:341-356.
New human-created reactive N inputs8-digit USGS Hydrologic UnitsNational reactive N inputsHuman activities currently put 7.5 times more new reactive N into the US annually than do natural processes alone.
Synthetic fertilizer is clearly the largest national reactive N source. However, atmospheric deposition is important in the East and Southwest, while legumes are important in the West.Largest human-created reactive N sources8-digit USGS Hydrologic Units
National reactive N sourcesReactive N sourceSpatial resolutionTime scaleSynthetic fertilizerCounty1997-2001LegumesCounty1997, 2001Atmospheric deposition36 km grid2002Industrial productsNational2002 - 2009ManureCounty1997SewageCounty2000Trade exportNational2002Riverine N export data
Changes in annual temperature and precipitation regimes may reduce or increase riverine N export depending on region.For data references, see: Sobota DJ, Compton JE, Harrison JA. 2013. Reactive nitrogen in US lands and waterways: How certain are we about sources and fluxes? Fron Ecol Environ 11:82-90.Spatial data were reformatted to 8-digit USGS Hydrologic Unit Codes (HUC8s) using the Zonal Statistics Tool in ArcMap 10.0 (ESRI Inc., Redlands, CA).We compiled data from 71 watersheds in the US that described riverine export of annual watershed N inputs (fractional N export):Boyer, EW, Goodale CL, Jaworski NA, Howarth RW. 2002. Anthropogenic nitrogen sources and relationships to riverine nitrogen export in the northeastern USA. Biogeochem 57/58: 137-169Schafer SC, Alber M. 2007. Temperature controls a latitudinal gradient in the proportion of watershed nitrogen exported to coastal ecosystems. Biogeochem 85:333-346.Schafer SC, Hollibaugh JT, Alber M. 2009. Watershed nitrogen input and riverine export on the west coast of the US. Biogeochem 93:219-233.Sobota DJ, Harrison JA, Dahlgren RA. 2009. Influences of climate, hydrology, and land use on input and export of nitrogen in California watersheds. Biogeochem 94:43-62.
Mean annual temperature and precipitation were used to predict fractional N export (see equation in climate change panel).
Ensemble average data (4.5 km grids) for mean annual temperature and precipitation changes for 2040 2059 were downloaded from the National Center for Atmospheric Research (https://gisclimatechange.ucar.edu).
Ensemble temperature and precipitation data were scaled to HUC8s using ArcMap 10.0.
Coefficients for the fractional N export~precipitation and temperature regression equation presented in the climate change panel were applied to HUC8 climate change data.ln(annual riverine export of watershed N inputs) =1.83+0.0018*Mean Annual Temperature - 0.11*Mean Annual Precipitationn=71; p