Using High Time Resolution Aerosol and Number Size Distribution Measurements to Estimate Atmospheric Extinction

Abstract

Rocky Mountain National Park is experiencing reduced visibility and changes in ecosystem function due to increasing levels of oxidized and reduced nitrogen. The Rocky Mountain Atmospheric Nitrogen and Sulfur (Ro-MANS) study was initiated to better understand the origins of sulfur and nitrogen species as well as the complex chemistry occurring during transport from source to receptor. As part of the study, a monitoring program was initiated for two 1-month time periods-one during the spring and the other during late summer/fall. The monitoring program included intensive high time resolution concentration measurements of aerosol number size distribution, inorganic anions, and cations, and 24-hr time resolution of PM 2.5 and PM 10 mass, sulfate, nitrate, carbon, and soil-related elements concentrations. These data are combined to estimate high time resolution concentrations of PM 2.5 and PM 10 aerosol mass and fine mass species estimates of ammoniated sulfate, nitrate, and organic and elemental carbon. Hour-by-hour extinction budgets are calculated by using these species concentration estimates and measurements of size distribution and assuming internal and external particle mixtures. Summer extinction was on average about 3 times higher than spring extinction. During spring months, sulfates, nitrates, carbon mass, and PM 10 Ϫ PM 2.5 mass contributed approximately equal amounts of extinction, whereas during the summer months, carbonaceous material extinction was 2-3 times higher than other species. INTRODUCTIONAtmospheric nitrogen and sulfur species can cause several deleterious effects, including visibility impairment and changes in ecosystem function and surface water chemistry from atmospheric deposition. In Rocky Mountain National Park (RMNP), the most recent 12-yr-average winter fractional contributions of nitrates and sulfates to visibility impairment are 18 and 36%, respectively. However, during some days, nitrates can contribute over 50%, whereas on other days sulfates contribute over 60% to particle light extinction. Although atmospheric concentrations of sulfur species have decreased in recent years, nitrogen concentrations have not. In fact, ambient nitrate concentrations have increased by approximately 10 -20% over the past 10 yr. Nitrate wet deposition has increased by approximately the same amount, and ammonium wet deposition has increased by approximately 50%.The Rocky Mountain Atmospheric Nitrogen and Sulfur study (RoMANS) was initiated to better understand the origins and physical, chemical, and optical characteristics of sulfur and nitrogen species, as well as the complex chemistry occurring during transport from source to receptor.As part of the study, a monitoring program was conducted over two time periods-one in the spring and the other during late summer/fall-that were approximately 1

Differentiating the Contributions of Particle Concentration, Humidity, and Hygroscopicity to Aerosol Light Scattering at Three Sites in China

“…Previous studies based on field measurements and laboratory experiments have shown that the composition of submicron particles is dominated by Org, followed by NO 3 − , NH 4 + , and SO 4 2− . The contributions of Cl − and dust are negligible (Levin et al., 2014; Malm et al., 2009; Whitby, 1978; F. Zhang et al., 2014). Therefore, only Org, ammonium nitrate (NH 4 NO 3 ), sulfuric acid (H 2 SO 4 ), ammonium sulfate [(NH 4 ) 2 SO 4 ], ammonium hydrogen sulfate (NH 4 HSO 4 ), and BC were considered in this study.…”

Investigating types and sources of organic aerosol in Rocky Mountain National Park using aerosol mass spectrometry

“…From alpine meadows to stark peaks, Rocky Mountain National Park (RMNP) hosts abundant wildlife, an important water catchment, and roughly 3 million visitors per year (Annual Park Visitation Report, NPS Public Use Statistics Office). Recent studies chronicle visibility reduction in RMNP, a Clean Air Act Class I protected environment, due to fine particles, especially in the summer when concentrations are higher (Levin et al, 2009;Malm et al, 2009b). Environmental impacts from increased nutrient -and particularly nitrogen -deposition are also documented in the Colorado Rocky Mountains (Baron et al, 2000), where mountainvalley circulations periodically transport ammonium, nitrate, and other particulate species from agricultural and urban sources to the east (Benedict et al, 2013a, b).…”

High-Resolution Electrospray Ionization Mass Spectrometry Analysis of Water-Soluble Organic Aerosols Collected with a Particle into Liquid Sampler

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