A novel hybrid approach for estimating total deposition in the United States

Schwede, Donna; Lear, Gary

doi:10.1016/j.atmosenv.2014.04.008

Cited by 180 publications

(137 citation statements)

References 28 publications

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“…The maximum regional average inorganic N deposition flux (12.1 kg N/ha per year) was observed in the Upper Midwest region (IV); relatively large deposition fluxes were also observed for California and the eastern United States. These spatial patterns are similar to those identified in recent model simulations (43).…”

Section: Fractional Reduced N Contributions To the Total Inorganic N supporting

confidence: 76%

Increasing importance of deposition of reduced nitrogen in the United States

Schichtel

Walker

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Rapid development of agriculture and fossil fuel combustion greatly increased US reactive nitrogen emissions to the atmosphere in the second half of the 20th century, resulting in excess nitrogen deposition to natural ecosystems. Recent efforts to lower nitrogen oxides emissions have substantially decreased nitrate wet deposition. Levels of wet ammonium deposition, by contrast, have increased in many regions. Together these changes have altered the balance between oxidized and reduced nitrogen deposition. Across most of the United States, wet deposition has transitioned from being nitrate-dominated in the 1980s to ammonium-dominated in recent years. Ammonia has historically not been routinely measured because there are no specific regulatory requirements for its measurement. Recent expansion in ammonia observations, however, along with ongoing measurements of nitric acid and fine particle ammonium and nitrate, permit new insight into the balance of oxidized and reduced nitrogen in the total (wet + dry) US nitrogen deposition budget. Observations from 37 sites reveal that reduced nitrogen contributes, on average, ∼65% of the total inorganic nitrogen deposition budget. Dry deposition of ammonia plays an especially key role in nitrogen deposition, contributing from 19% to 65% in different regions. Future progress toward reducing US nitrogen deposition will be increasingly difficult without a reduction in ammonia emissions.ammonia | dry deposition | wet deposition | nitrogen oxides | agriculture

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Section: Fractional Reduced N Contributions To the Total Inorganic N supporting

confidence: 76%

Increasing importance of deposition of reduced nitrogen in the United States

Schichtel

Walker

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

354

253

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“…The spatial distribution of reduced and oxidized Nr deposition is comparable with other studies (Zhang et al, 2012;Du et al, 2014;Schwede and Lear, 2014) yet a few differences and uncertainties are worth considering. Du et al (2014) found greater wet deposition of NH + 4 compared to wet deposition of NO − 3 over the contiguous US except in the Northeast region.…”

Section: Evaluation Of Simulated Nr Depositionsupporting

confidence: 70%

“…This suggests that oxidized Nr may be overestimated in our study. Schwede and Lear (2014) generated maps of Nr deposition for multiple years, including 2010. These maps display localized hotspots in parts of Colorado and Idaho that are not evident in our results.…”

Section: Evaluation Of Simulated Nr Depositionmentioning

confidence: 99%

Sources of nitrogen deposition in Federal Class I areas in the US

et al. 2016

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Abstract. It is desired to control excessive reactive nitrogen (Nr) deposition due to its detrimental impact on ecosystems. Using a three-dimensional atmospheric chemical transport model, GEOS-Chem, Nr deposition in the contiguous US and eight selected Class I areas (Voyageurs (VY), Smoky Mountain (SM), Shenandoah (SD), Big Bend (BB), Rocky Mountain (RM), Grand Teton (GT), Joshua Tree (JT), and Sequoia (SQ)) is investigated. First, modeled Nr deposition is compared with National Trends Network (NTN) and Clean Air Status and Trends Network (CASTNET) deposition values. The seasonality of measured species is generally well represented by the model (R 2 > 0.6), except in JT. While modeled Nr is generally within the range of seasonal observations, large overestimates are present in sites such as SM and SD in the spring and summer (up to 0.6 kg N ha month −1 ), likely owing to model high-biases in surface HNO 3 . The contribution of non-measured species (mostly dry deposition of NH 3 ) to total modeled Nr deposition ranges from 1 to 55 %. The spatial distribution of the origin of Nr deposited in each Class I area and the contributions of individual emission sectors are estimated using the GEOS-Chem adjoint model. We find the largest role of long-range transport for VY, where 50 % (90 %) of annual Nr deposition originates within 670 (1670) km of the park. In contrast, the Nr emission footprint is most localized for SQ, where 50 % (90 %) of the deposition originates from within 130 (370) km. Emissions from California contribute to the Nr deposition in remote areas in the western US (RM, GT). Mobile NO x and livestock NH 3 are found to be the major sources of Nr deposition in all sites except BB, where contributions of NO x from lightning and soils to natural levels of Nr deposition are significant (∼ 40 %). The efficiency in terms of Nr deposition per kg emissions of NH 3 -N, NO x -N, and SO 2 -S are also estimated. Unique seasonal features are found in JT (opposing efficiency distributions for winter and summer), RM (large fluctuations in the range of effective regions), and SD (upwind NH 3 emissions hindering Nr deposition). We also evaluate the contributions of emissions to the total area of Class I regions in critical load exceedance, and to the total magnitude of exceedance. We find that while it is effective to control emissions in the western US to reduce the area of regions in CL exceedance, it can be more effective to control emissions in the eastern US to reduce the magnitude of Nr deposition above the CL. Finally, uncertainty in the nitrogen deposition caused by uncertainty in the NH 3 emission inventory is explored by comparing results based on two different NH 3 inventories; noticeable differences in the emission inventories and thus sensitivities of up to a factor of four found in individual locations.

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“…Each study reports 2 years of locally measured annual averages for a total of 8 data points. For reference, we compared these local data with estimates for Lake Mattamuskeet in 2012 (the most recent year of available data) using a hybrid method that incorporates both wet and dry deposition (Schwede and Lear 2014). We found that the mean of local measurements (5.1 kg N ha…”

Section: Atmospheric Depositionmentioning

confidence: 99%

Waterfowl Impoundments as Sources of Nitrogen Pollution

Winton

Moorman

Richardson

2016

Water Air Soil Pollut

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Hydrologically controlled moist-soil impoundment wetlands provide critical habitat for high densities of migratory bird populations. Nutrients exported from heavily used impoundments by prescribed seasonal drawdown of surface water may contribute to the eutrophication of aquatic ecosystems. To investigate the relative importance of nutrient export from managed impoundment habitats, we conducted a field study at Mattamuskeet National Wildlife Refuge in North Carolina, USA, which contains 1545 ha of impoundments that drain into hypereutrophic Lake Mattamuskeet. We found that prescribed hydrologic drawdowns of an impoundment exported roughly the same amount of nitrogen (N) as adjacent fertilized agricultural fields on a per-area basis and contributed approximately one fifth of total N load to Lake Mattamuskeet. The prescribed drawdown regime, designed to maximize waterfowl production in impoundments, may be exacerbating the degradation of habitat quality in the downstream lake as an unintended consequence. Few studies of wetland N dynamics have targeted impoundments managed to provide wildlife habitat, but a similar phenomenon may occur in some of the 36,000 ha of similarly managed moist-soil impoundments on National Wildlife Refuges in the southeastern USA, especially those hosting dense concentrations of waterfowl. We suggest an earlier seasonal drawdown could potentially mitigate impoundment N pollution and estimate it could reduce N export from our study impoundment by more than 70 %.

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A novel hybrid approach for estimating total deposition in the United States

Cited by 180 publications

References 28 publications

Increasing importance of deposition of reduced nitrogen in the United States

Increasing importance of deposition of reduced nitrogen in the United States

Sources of nitrogen deposition in Federal Class I areas in the US

Waterfowl Impoundments as Sources of Nitrogen Pollution

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