Air quality and atmospheric deposition in the eastern US: 20 years of change

Sickles, J.E.; Shadwick, Douglas S.

doi:10.5194/acp-15-173-2015

Cited by 101 publications

(101 citation statements)

References 42 publications

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“…In the United States, the National Atmospheric Deposition Program/National Trends Network (NADP/NTN; https://nadp.slh.wisc.edu/ntn) provides the nation's primary WD data. These observed WD values are often used to estimate past and current loads of acidic (S + N) and nutrient (N) deposition on sensitive ecosystems for critical loads exceedance studies in the United States (Nanus et al, ; Sickles & Shadwick, , ). Using NADP/NTN data from 1985 to 2012, Du et al () found a positive trend in ammonium WD at the national scale and a significant negative trend in nitrate WD, especially in the Northeast.…”

Section: Introductionmentioning

confidence: 99%

A Measurement‐Model Fusion Approach for Improved Wet Deposition Maps and Trends

et al. 2019

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Air quality models provide spatial fields of wet deposition (WD) and dry deposition that explicitly account for the transport and transformation of emissions from thousands of sources. However, many sources of uncertainty in the air quality model including errors in emissions and meteorological inputs (particularly precipitation) and incomplete descriptions of the chemical and physical processes governing deposition can lead to bias and error in the simulation of WD. We present an approach to bias correct Community Multiscale Air Quality model output over the contiguous United States using observation‐based gridded precipitation data generated by the Parameter‐elevation Regressions on Independent Slopes Model and WD observations at the National Atmospheric Deposition Program National Trends Network sites. A cross‐validation analysis shows that the adjusted annual accumulated WD for NO 3 − , NH 4 + , and SO 4 2− from 2002 to 2012 has less bias and higher correlation with observed values than the base model output without adjustment. Temporal trends in observed WD are captured well by the adjusted model simulations across the entire contiguous United States. Consistent with previous trend analyses, WD NO 3 − and SO 4 2− are shown to decrease during this period in the eastern half of the United States, particularly in the Northeast, while remaining nearly constant in the West. Trends in WD of NH 4 + are more spatially and temporally heterogeneous, with some positive trends in the Great Plains and Central Valley of CA and slightly negative trends in the south.

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Section: Introductionmentioning

confidence: 99%

A Measurement‐Model Fusion Approach for Improved Wet Deposition Maps and Trends

et al. 2019

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“…A recent analysis of US National Atmospheric Deposition Program (NADP) observations (24) illustrates decreases in US wet nitrate deposition and increases in wet ammonium deposition in many regions. Focusing on the Midwest and Eastern United States, Sickles and Shadwick (25) reported that reductions in NO x emissions have decreased oxidized nitrogen dry and wet deposition and that particulate ammonium concentrations now exceed concentrations of particulate nitrate plus gaseous nitric acid in the region. Ammonia gas was not considered in their study.…”

Section: Significancementioning

confidence: 99%

Increasing importance of deposition of reduced nitrogen in the United States

Schichtel

Walker

et al. 2016

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

355

253

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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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“…The decline in SO 4 concentrations vs. emissions or ambient SO 2 tends to be linear, but less than 1:1 (e.g. Hidy et al, 2014;Sickles and Shadwick, 2015). As discussed later, the difference between the responses of ambient SO 2 and SO 4 is identified with the atmospheric production of SO 4 during dispersal from primary SO 2 sources.…”

Section: Us National Ambient Sulfur Oxide Trendsmentioning

confidence: 99%

“…Dry deposition rates have been estimated typically for relatively smooth surfaces sometimes covered with low vegetation; forested, hilly and mountainous terrain have not been characterized with the same certainty. (e.g., Sickles and Shadwick, 2015). Trends in dry deposition have been found to follow trends in ambient concentrations of SO x , accounting for surface inhomogeneities in spatially differentiated models.…”

Section: Us National Ambient Sulfur Oxide Trendsmentioning

confidence: 99%

The changing face of lower tropospheric sulfur oxides in the United States

Hidy¹,

Blanchard²

2016

Elementa: Science of the Anthropocene

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Sulfur oxides, sulfur dioxide and airborne sulfate, SO x , are short-lived species in the troposphere whose concentrations in air and precipitation have changed dramatically in association with fossil fuel combustion. The historic rise in concentration is coincident with the era of the so-called "Anthropocene." Unlike concentrations of long-lived species such as carbon dioxide, atmospheric SO x in the United States (US) peaked between 1970 and 2005 then declined. The rise and fall of SO x is traced by comparing national data on emission changes, ambient concentrations, and precipitation sulfate from prior to World War II to the present. Surface SO x concentrations and precipitation sulfate have decreased with emissions in most parts of the US after the late 1970s. Continued reduction toward a natural "background" condition has depended on aggressive management of anthropogenic emission sources. Annual average ambient concentrations of SO 2 and SO 4 have become more uniform across the US at levels of 1-3 ppbv and 0.3-3 µg/m 3 , respectively. Precipitation SO 4 has a nominal concentration generally less than 0.5 mg/L. The effective lifetime of SO x in the troposphere is a few days. This duration limits the spatial extent of emission source influence of SO x to regional scales, wherein spatial gradients in species concentrations lead to variations in human exposure and impacts on vulnerable terrestrial and aquatic ecosystems. The effects of domestic emission reductions on SO x levels are moderated by intra-and intercontinental transport of SO x from Canada, Mexico, Asia and elsewhere. The trends in tropospheric SO x concentrations illustrate the results of more than a century of rising public awareness and action to progressively reduce a US environmental risk, accomplished with advances in energy production technology that have maintained economic well-being.

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Air quality and atmospheric deposition in the eastern US: 20 years of change

Cited by 101 publications

References 42 publications

A Measurement‐Model Fusion Approach for Improved Wet Deposition Maps and Trends

A Measurement‐Model Fusion Approach for Improved Wet Deposition Maps and Trends

Increasing importance of deposition of reduced nitrogen in the United States

The changing face of lower tropospheric sulfur oxides in the United States

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