@article{d0629ac5bbdb412897fcff73c82e8903,
title = "Ammonia dry deposition in an alpine ecosystem traced to agricultural emission hotpots",
abstract = "Elevated reactive nitrogen (Nr) deposition is a concern for alpine ecosystems, and dry NH3 deposition is a key contributor. Understanding how emission hotspots impact downwind ecosystems through dry NH3 deposition provides opportunities for effective mitigation. However, direct NH3 flux measurements with sufficient temporal resolution to quantify such events are rare. Here, we measured NH3 fluxes at Rocky Mountain National Park (RMNP) during two summers and analyzed transport events from upwind agricultural and urban sources in northeastern Colorado. We deployed open-path NH3 sensors on a mobile laboratory and an eddy covariance tower to measure NH3 concentrations and fluxes. Our spatial sampling illustrated an upslope event that transported NH3 emissions from the hotspot to RMNP. Observed NH3 deposition was significantly higher when backtrajectories passed through only the agricultural region (7.9 ng m−2 s−1) versus only the urban area (1.0 ng m−2 s−1) and both urban and agricultural areas (2.7 ng m−2 s−1). Cumulative NH3 fluxes were calculated using observed, bidirectional modeled, and gap-filled fluxes. More than 40% of the total dry NH3 deposition occurred when air masses were traced back to agricultural source regions. More generally, we identified that 10 (25) more national parks in the U.S. are within 100 (200) km of an NH3 hotspot, and more observations are needed to quantify the impacts of these hotspots on dry NH3 deposition in these regions.",
author = "Zondlo, {Mark A.} and Da Pan and Benedict, {Katherine B.} and Golston, {Levi M.} and Rui Wang and Collett, {Jeffrey L.} and Lei Tao and Kang Sun and Xuehui Guo and Jay Ham and Prenni, {Anthony J.} and Schichtel, {Bret A.} and Tomas Mikoviny and Markus M{\"u}ller and Armin Wisthaler",
note = "Funding Information: D.P. and L.M.G. acknowledge support for the DISCOVER-AQ field measurements from NASA NNX14AT36G/NNX14AT32G. X.G. acknowledges support from a NASA Earth and Space Science Fellowship NASA 80NSSC17K0377. Satellite analyses were supported by NASA NNX16AQ90G. The authors acknowledge Lars Wendt, Victor Fu, Naomi Pohl, and Levi Stanton for their assistance with the Princeton field data collection in Colorado. The authors appreciate the NASA DISCOVER-AQ science team and aircraft and technical crews. PTR-MS measurements during DISCOVER-AQ were supported by the Austrian Federal Ministry for Transport, Innovation and Technology (BMVIT) through the Austrian Space Applications Programme (ASAP 8, #833451 and #840086) of the Austrian Research Promotion Agency (FFG). Measurements in RMNP were supported by the National Park Service and USEPA. The assumptions, findings, conclusions, judgments, and views presented herein are those of the authors and should not be interpreted as necessarily representing the National Park Service. Funding Information: D.P. and L.M.G. acknowledge support for the DISCOVER-AQ field measurements from NASA NNX14AT36G/ NNX14AT32G. X.G. acknowledges support from a NASA Earth and Space Science Fellowship NASA 80NSSC17K0377. Satellite analyses were supported by NASA NNX16AQ90G. The authors acknowledge Lars Wendt, Victor Fu, Naomi Pohl, and Levi Stanton for their assistance with the Princeton field data collection in Colorado. The authors appreciate the NASA DISCOVER-AQ science team and aircraft and technical crews. PTR-MS measurements during DISCOVER-AQ were supported by the Austrian Federal Ministry for Transport, Innovation and Technology (BMVIT) through the Austrian Space Applications Programme (ASAP 8, #833451 and #840086) of the Austrian Research Promotion Agency (FFG). Measurements in RMNP were supported by the National Park Service and USEPA. The assumptions, findings, conclusions, judgments, and views presented herein are those of the authors and should not be interpreted as necessarily representing the National Park Service. Publisher Copyright: {\textcopyright} 2021 The Authors. Published by American Chemical Society",
year = "2021",
month = jun,
day = "15",
doi = "10.1021/acs.est.0c05749",
language = "English (US)",
volume = "55",
pages = "7776--7785",
journal = "Environmental Science and Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "12",
}