Dry deposition calculations for the clean air status and trends network

doi:10.1016/S1352-2310(97)00141-6

Atmospheric Environment

Volume 31, Issue 21, November 1997, Pages 3667-3678

https://doi.org/10.1016/S1352-2310(97)00141-6 Get rights and content

Abstract

The National Dry Deposition Network (NDDN) was established in 1986 to document the magnitude, spatial variability, and trends in dry deposition across the United States. Currently, the network operates as a component of the Clean Air Status and Trends Network (CASTNet). Dry deposition is not measured directly in CASTNet, but is determined by an inferential approach (i.e. fluxes are calculated as the product of measured ambient concentration and a modeled deposition velocity). Chemical species include ozone, sulfate, nitrate, ammonium, sulfur dioxide, and nitric acid. The temporal resolution for the ambient concentration measurements and dry deposition flux calculations is hourly for ozone and weekly for the other species. This paper describes the 50-station CASTNet dry deposition network, discusses dry deposition calculation procedures and presents dry deposition data for sulfur dioxide and nitric acid for 1991. Sources of uncertainty in dry deposition estimates are also discussed.

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Given the good performance of the EC system, longer observations are expected to constrain the annual dry deposition of this agricultural region. The inferential model method is the most common method for the quantification of site-scale reactive nitrogen deposition (Clarke et al., 1997). Using this method, Xu et al. (2015) estimated the monthly dry deposition of NH3 at the Quzhou experimental station, which is very close to our experimental field (2 km in the northwest).
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A review of quantification methods and the global data on nitrogen deposition and a systematic framework was proposed for quantifying nitrogen deposition.
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The data applied in this paper are termed the “Historical Deposition Data” and were preferred for this analysis because the data set extends back to the 1980s, necessary to evaluate long-term temporal trends. Dry deposition was calculated from measurements of HNO3, and particulate NO3− and NH4+ by applying deposition velocity estimates and the Multilayer Model as described by Clarke et al. (1997). Data from these networks are important in exploring temporal patterns because they represent samples collected using consistent field and laboratory methods over many years.
The Chesapeake Bay watershed has been the focus of pioneering studies of the role of atmospheric nitrogen (N) deposition as a nutrient source and driver of estuarine trophic status. Here, we review the history and evolution of scientific investigations of the role of atmospheric N deposition, examine trends from wet and dry deposition networks, and present century-long (1950–2050) atmospheric N deposition estimates. Early investigations demonstrated the importance of atmospheric deposition as an N source to the Bay, providing 25%–40% among all major N sources. These early studies led to the unprecedented inclusion of targeted decreases in atmospheric N deposition as part of the multi-stakeholder effort to reduce N loads to the Bay. Emissions of nitrogen oxides (NO_x) and deposition of wet nitrate, oxidized dry N, and dry ammonium (NH₄⁺) sharply and synchronously declined by 60%–73% during 1995–2019. These decreases largely resulted from implementation of Title IV of the 1990 Clean Air Act Amendments, which began in 1995. Wet NH₄⁺ deposition shows no significant trend during this period. The century-long atmospheric N deposition estimates indicate an increase in total atmospheric N deposition in the Chesapeake watershed from 1950 to a peak of ~15 kg N/ha/yr in 1979, trailed by a slight decline of <10% through the mid-1990s, and followed by a sharp decline of about 40% thereafter through 2019. An additional 21% decline in atmospheric N deposition is projected from 2015 to 2050. A comparison of the Potomac River and James River watersheds indicates higher atmospheric N deposition in the Potomac, likely resulting from greater emissions from higher proportions of agricultural and urban land in this basin. Atmospheric N deposition rose from 30% among all N sources to the Chesapeake Bay watershed in 1950 to a peak of 40% in 1973, and a decline to 28% by 2015. These data highlight the important role of atmospheric N deposition in the Chesapeake Bay watershed and present a potential opportunity for decreases in deposition to contribute to further reducing N loads and improving the trophic status of tidal waters.
Enhanced atmospheric nitrogen deposition at a rural site in northwest China from 2011 to 2018
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Few related studies have been carried out for northwest China's the inland, although the increasing inorganic reactive nitrogen (Nr) deposition and severe air pollution in China have attracted considerable attention. Based on eight-year measurements of the concentrations of NH₃, HNO₃, particulate (p) NH₄⁺, pNO₃⁻, and NO₂ in the air and inorganic nitrogen (NH₄⁺, NO₃⁻) in the precipitation at a rural site in Wuwei, Gansu Province, we quantified the dry and bulk/wet Nr deposition fluxes and analyzed their temporal trends in combination with air pollution data (2015–2018). The concentrations of the single Nr species in the air did not exhibit significant seasonal variations, except for that of pNO₃⁻ which were the highest in summer and the lowest in winter. The average annual total Nr (dry + bulk) deposition was 27.2 ± 6.7 kg N ha⁻¹ with a significant (p < .05) annual increase rate of 10%, which was dominated by the dry deposition flux (20.8 ± 7.1 kg N ha⁻¹ yr⁻¹) during the entire period. The NH₄⁺-N and NO₃⁻-N deposition fluxes in the precipitation were significantly (p < .05) higher in the summer than in the other three seasons owing to the heavy rainfall. The reduced N (NH₃, pNH₄⁺, and NH₄⁺) deposition flux was 4.7 times that of the oxidized N (HNO₃, pNO₃⁻, NO₂, and NO₃⁻), which increased with a high annual rate (25%). The annual mean concentrations of the main air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, and CO) significantly decreased by 15%–76%; in contrast, increasing trends of the O₃ and NH₃ concentrations were observed. Our results highlight the importance of the control of NH₃ emissions and O₃ pollution to comprehensively mitigate N deposition and improve air quality in the considered region.
A review of measurements of air-surface exchange of reactive nitrogen in natural ecosystems across North America
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Citation Excerpt :
However, these networks do not provide measurements of dry deposition. Rather, the measured air concentrations are used to estimate dry deposition using inferential modeling approaches (Clarke et al., 1997; Sickles and Shadwick, 2015; Zhang et al., 2009; Li et al., 2016) or by applying deposition velocities output from chemical transport models (CTMs) (Bowker et al., 2011; Schwede and Lear, 2014). These networks also do not provide information on organic forms of N (ON), which contribute significantly to total Nr deposition (Jickells et al., 2013).
This review summarizes the state of the science of measurements of dry deposition of reactive nitrogen (Nr) compounds in North America, beginning with current understanding of the importance of dry deposition at the U.S. continental scale followed by a review of micrometeorological flux measurement methods. Measurements of Nr air-surface exchange in natural ecosystems of North America are then summarized, focusing on the U.S. and Canada. Drawing on this synthesis, research needed to address the incompleteness of dry deposition budgets, more fully characterize temporal and geographical variability of fluxes, and better understand air-surface exchange processes is identified.
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Changes in United States deposition of nitrogen and sulfur compounds over five decades from 1970 to 2020
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Evaluating long-term air quality and deposition trends can demonstrate effectiveness of control strategies and guide future air quality management planning. Observations show a reduction of atmospheric concentrations of NO_x and SO_x species and their wet and dry deposition since monitoring began in 1978 and 1987, respectively, although deposition observations are sparse. This study used a regional model (CAMx) nested within a global model (GEOS-Chem) to characterize regional changes in sulfur and nitrogen deposition due to intercontinental transport and local/regional anthropogenic emissions representing six modeling years spanning five decades (1970–2020). The meteorological year and the natural emissions were fixed at 2005 to isolate the effects of changing anthropogenic emissions. The downward trend from 1970 to 2020 of mean atmospheric SO₂ concentration is 1.5–1.8%; of total S deposition is 1.0–1.7%; and of SO₂ emissions is 1.4–1.8% per year. The rate of decline in NO_y deposition of 0.6–1.4% per year is similar to the 0.5–1.6% per year reduction in NO_x emissions, thus showing that the changes in deposition have tracked changes in emissions of SO₂ and NO_x emissions quite well. Further reducing N deposition could face some challenges due to increasing NH_x contribution from NH₃ emissions and the expectation of these to increase globally. Our study also examined the transference ratios of NO_y and SO_x in the context of the secondary NAAQS for NO_x and SO_x and found them to be sensitive to emission reductions over the study period.

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^†: On assignment tc National Exposure Research Laboratory, U.S. Environmental Protection Agency.

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Dry deposition calculations for the clean air status and trends network

Abstract

Atmospheric Environment

Atmospheric Environment

Atmospheric Environment

Deposition of airborne radioiodine vapor

Nucleonics

Dry deposition flux calculations for the National Dry Deposition Network

Design and implementation of a transportable system for direct measurement of dry deposition fluxes

National Dry Deposition Network (CASTNet) Data Management Manual

National Dry Deposition Network (CASTNet) Laboratory Operations Manual

On the use of monitored air concentrations to infer dry deposition

NOAA Tech. Memo. ERLARL-141