A5035281757- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Air Quality and Health Impacts
- Atmospheric aerosols and clouds
- Air Quality Monitoring and Forecasting
- Fire effects on ecosystems
- Mass Spectrometry Techniques and Applications
- Vehicle emissions and performance
- Spectroscopy and Laser Applications
- Advanced Chemical Sensor Technologies
- Isotope Analysis in Ecology
- Food Supply Chain Traceability
- Odor and Emission Control Technologies
- Cryospheric studies and observations
- Climate variability and models
- Water Quality Monitoring and Analysis
- Meat and Animal Product Quality
- Analytical chemistry methods development
- Ocean Acidification Effects and Responses
- Mercury impact and mitigation studies
- Fire dynamics and safety research
- Heat and Mass Transfer in Porous Media
- Industrial Gas Emission Control
- Meteorological Phenomena and Simulations
Georgia Institute of Technology
2016-2025
University of Maryland, Baltimore County
2024
NSF National Center for Atmospheric Research
1995-2003
City College of New York
2003
Massey University
2003
University of Hawaiʻi at Mānoa
1998
University of Hawaii System
1998
University of Colorado Boulder
1997-1998
Cooperative Institute for Research in Environmental Sciences
1998
Phillips Academy
1997
Simultaneous measurements of aerosol particles and their expected gas phase precursors were made at Idaho Hill, Colorado, a remote continental site. This study used apparatus techniques similar to those employed in an earlier the Mauna Loa Observatory, Hawaii [ Weber et al. , 1995]. New particle formation, identified by presence ultrafine (nominally 3 4 nm diameter), was commonly observed downslope (westerly) air correlated with high sulfuric acid (H 2 SO ) concentrations, low relative...
Measurements of gas phase sulfuric and methane sulfonic acid (MSA) have been performed using a relatively new atmospheric pressure selected ion chemical ionization mass spectrometric technique at two field sites. Both acids are photooxidation products, their concentrations seen to qualitatively follow solar flux. While typically decline in conjunction with declining radiation, they sometimes level off the mid 10 5 –10 6 molecules cm −3 range after dark, even clean air. The reason for this...
Measured production rates of tropospheric ultrafine particles (˜3nm diameter) are reported for the first time and shown to be orders magnitude greater than nucleation predicted by binary theory homogeneous sulfuric acid water. Furthermore, functional dependence observed particle formation on vapor concentrations is much weaker theory. We present arguments show that these discrepancies might due participation a species such as ammonia which could stabilize subcritical clusters, thereby...
Abstract Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured aircraft during Studies Emissions and Atmospheric Composition, Clouds Climate Coupling by Regional Surveys (SEAC 4 RS) Biomass Burning Observation Project (BBOP), both summer 2013. This study reports an extensive set emission factors (EFs) for over 80 gases 5 components submicron particulate matter (PM 1 ) these temperate wildfires. These include...
Wildfires are a substantial but poorly quantified source of tropospheric ozone (O3). Here, to investigate the highly variable O3 chemistry in wildfire plumes, we exploit situ chemical characterization western wildfires during FIREX-AQ flight campaign and show that production can be predicted as function experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, fate peroxy radicals. The exhibits rapid transition regimes. Within few daylight hours, formation...
Significance Understanding the sources of tropospheric ozone is important for effective air quality management and accurate radiative forcing attribution. Biomass burning emits large quantities precursors to lower atmosphere. This source can drive regional-scale production, but its impact on global poorly constrained. Here, we present unique in situ aircraft observations continental pollution tracers. Ozone enhancements attributable biomass equal or exceed those from urban emissions, a...
Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced species, and aerosol emissions from US wild prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments Air Quality campaign (FIREX-AQ). Here, we report atmospheric enhancement ratios (ERs) inferred emission factors (EFs) for compounds measured board NASA DC-8 research aircraft nine wildfires one fire, which encompass a range...
We have developed a thermal dissociation–chemical ionization mass spectrometry (TD‐CIMS) technique for fast measurements of series peroxyacyl nitrates and dinitrogen pentoxide. Thermally generated acylperoxy radicals react with I − to produce carboxylate ion that is unique each parent species. NO 3 resulting from the decomposition N 2 O 5 reacts form . The measurement was verified PAN PPN during an informal comparison gas chromatograph (GC) equipped electron capture detector (ECD) in...
During November and December 1995 the First Aerosol Characterization Experiment (ACE 1) was undertaken as part of International Global Atmospheric Chemistry (IGAC) Program. A key objective aircraft component this experiment included identification source regions for new particles in remote marine atmosphere. No evidence found particle production boundary layer (MBL), but extensive observations enhanced layers “new” were free troposphere (FT). These generally at altitudes that corresponded to...
Measurements show that new particles are formed by homogenous nucleation over a wide range of conditions in the remote troposphere. In our studies, large events found exclusively regions enhanced sulfuric acid vapor (H 2 SO 4g ) concentrations, with maximum concentrations never exceeding 5×10 7 molecules cm −3 . Although these data suggest H participated, comparisons between ambient to necessary for binary 4 water O) indicate mechanism may vary elevation. marine regions, at altitudes greater...
Atmospheric measurements of expected homogeneous nucleation precursors and aerosols were made at the Mauna Loa Observatory, Hawaii, from 28 June to 27 July 1992. Large molecular clusters gas phase species including sulfuric acid (H2SO4), methane sulfonic (MSA), OH measured with a mass spectrometer. Aerosol consisted ultrafine particle concentrations (∼3–4 nm diameter) fine size distributions (15–500 diameter). The altitude observatory (average pressure 680 mb) presence mountain–valley winds...
A simple dimensionless parameter, L , is shown to determine whether or not new particle formation can occur in the atmosphere on a given day. The criterion accounts for probability that clusters, formed by nucleation, will coagulate with preexisting particles before they grow detectable size. Data acquired an intensive atmospheric measurement campaign Atlanta, Georgia, during August 2002 (ANARChE) were used test validity of this criterion. Measurements included aerosol size distributions...
Measurements are presented of ambient nanoparticle distributions (2.7 to 10 nm diameter) in regions high biogenic emissions encountered during the First Aerosol Characterization Experiment (ACE 1), November 15 December 14, 1995. Large numbers newly formed nanoparticles were observed directly downwind penguin colonies on Macquarie Island (54.5°S, 159.0°W). In these regions, concentrations also correlated with sulfuric acid (H 2 SO 4(g) ) gas concentrations. The measurements show that species,...
Reported here are the first Austral summer measurements of NO at South Pole (SP). They unique in that levels one to two orders magnitude higher (i.e., median, 225 pptv) than measured other polar sites. The available evidence suggests these elevated result photodenitrification snowpack, conjunction with a very thin atmospheric mixing depth. Important chemical consequences included finding oxidizing power SP be an order expected.
A highly sensitive real‐time ion‐assisted OH measurement technique has recently been developed and tested. It offers an detection sensitivity of about 1×10 5 molecules/cm 3 with a 300‐s integration time provides useful concentration measurements on 10‐s scale. Measurements are seen to track solar flux during both short long periods cloudiness. Good temporal correspondence between changes in O as differing air masses pass the site also observed discussed. The present new opportunity for fast...
New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked natural sulfur cycle. This conclusion based on real-time observations dimethylsulfide, dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, size number distribution, total surface area. Classic binary theory predicts no under...
The mobility of electrons on the surface liquid $^{4}\mathrm{He}$ has been measured from 0.9 to 3.2\ifmmode^\circ\else\textdegree\fi{}K. Although scattering atoms in vapor appears be dominant mechanism, is significantly lower than that free vapor. No evidence for surface-wave discernible.
Abstract Emissions from 15 agricultural fires in the southeastern U.S. were measured NASA DC‐8 research aircraft during summer 2013 Studies of and Atmospheric Composition, Clouds Climate Coupling by Regional Surveys (SEAC 4 RS) campaign. This study reports a detailed set emission factors (EFs) for 25 trace gases 6 fine particle species. The chemical evolution primary emissions seven plumes was examined detail ~1.2 h. A Lagrangian plume cross‐section model used to simulate ozone (O 3 ),...
Emission of bromine from sea‐salt aerosol, frost flowers, ice leads, and snow results in the nearly complete removal surface ozone during Arctic spring. Regions enhanced total column BrO observed by satellites have traditionally been associated with these emissions. However, airborne measurements O 3 within convective boundary layer (CBL) ARCTAS ARCPAC field campaigns at times bear little relation to BrO. We show that locations numerous satellite “hotspots” spring are consistent observations...
[1] A measurement intensive was carried out in Barrow, Alaska, spring 2009 as part of the Ocean-Atmosphere-Sea-Ice–Snowpack (OASIS) program. The central focus this campaign role halogen chemistry Arctic. chemical ionization mass spectrometer (CIMS) performed situ bromine oxide (BrO) measurements. In addition, a long path-differential optical absorption (LP-DOAS) measured average concentration BrO along light paths either 7.2 or 2.1 km. comparison 1 min observations from both instruments is...
Abstract. Volatile organic compounds (VOCs) and carbonaceous aerosol were measured at a sub-urban site near Mexico City in March of 2006 during the MILAGRO study (Megacity Initiative: Local Global Research Objectives). Diurnal variations hydrocarbons, elemental carbon (EC) hydrocarbon-like (HOA) dominated by high peak early morning when local emissions accumulated shallow boundary layer, minimum afternoon diluted significantly expanded layer and, case reactive gases, removed OH. In...
Abstract. The implementation of stringent emission regulations has resulted in the decline anthropogenic pollutants including sulfur dioxide (SO2), nitrogen oxides (NOx), and carbon monoxide (CO). In contrast, ammonia (NH3) emissions are largely unregulated, with projected to increase future. We present real-time aerosol gas measurements from a field study conducted an agriculturally intensive region southeastern US during fall 2016 investigate how NH3 affects particle acidity secondary...