A5055361102- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Air Quality Monitoring and Forecasting
- Atmospheric and Environmental Gas Dynamics
- Air Quality and Health Impacts
- Vehicle emissions and performance
- Maritime Transport Emissions and Efficiency
- Atmospheric aerosols and clouds
- Marine and coastal ecosystems
- Odor and Emission Control Technologies
- Water Quality Monitoring and Analysis
- Soil and Water Nutrient Dynamics
- Advanced Chemical Sensor Technologies
- Groundwater and Isotope Geochemistry
- Soil Carbon and Nitrogen Dynamics
- Toxic Organic Pollutants Impact
- Mercury impact and mitigation studies
- Isotope Analysis in Ecology
- Plant responses to elevated CO2
- Mass Spectrometry Techniques and Applications
- Meteorological Phenomena and Simulations
- Ocean Acidification Effects and Responses
- Analytical Chemistry and Chromatography
- Spectroscopy and Laser Applications
- Plant Water Relations and Carbon Dynamics
NOAA Earth System Research Laboratory
2008-2018
National Oceanic and Atmospheric Administration
2004-2016
University of Colorado Boulder
2006-2015
Cooperative Institute for Research in Environmental Sciences
2006-2015
Laboratory for Atmospheric and Space Physics
2015
Environment and Climate Change Canada
2012
Sonoma State University
2011
Colgate University
2011
Montana State University
2007
Environmental Protection Agency
2006
The relationship between O 3 and NO x (NO + 2 ) which was measured during summer winter periods at Niwot Ridge, Colorado, has been analyzed compared to model calculations. Both calculations observations show that the daily production per unit of is greater for lower . Model without nonmethane hydrocarbons (NMHC) tend underestimate rate higher than 1.5 parts billion by volume opposite dependence on with NMHC are consistent observed data in this regime demonstrate importance chemistry...
Atmospheric black carbon (BC) warms Earth's climate, and its reduction has been targeted for near-term climate change mitigation. Models that include forcing by BC assume internal mixing with non-BC aerosol components enhance absorption, often a factor of ~2; such model estimates have yet to be clearly validated through atmospheric observations. Here, direct in situ measurements absorption enhancements (E(abs)) state are reported two California regions. The observed E(abs) is small-6% on...
Emission Of NO x (principally NO) and N 2 O from soils is reviewed with particular emphasis placed on the atmospheric ecological implications of this source. The photochemistry these species in atmosphere summarized as well methods available for determination fluxes. Processes which produce consume both are principally microbiological nature linked directly indirectly chemical physical factors that control gaseous transport through soil medium. Linkages among processes occur over many...
During the NEAQS‐ITCT2k4 campaign in New England, anthropogenic VOCs and CO were measured downwind from York City Boston. The emission ratios of relative to acetylene calculated using a method which ratio VOC with is plotted versus photochemical age. intercept at age zero gives ratio. so determined compared other measurement sets, including data same location 2002, canister samples collected inside Boston, aircraft measurements Los Angeles average urban composition 39 U.S. cities. All...
Abstract The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout in May, June, July 2010. organized to address issues simultaneously relevant atmospheric pollution climate change, including (1) emission inventory assessment, (2) transport dispersion, (3) chemical processing, (4) cloud‐aerosol interactions aerosol radiative effects. Measurements from networks ground sites, a research ship, tall towers, balloon‐borne ozonesondes,...
The magnitude and sources of chlorine atoms in marine air remain highly uncertain but have potentially important consequences for quality polluted coastal regions. We made continuous measurements ambient ClNO(2) Cl(2) concentrations from May 15 to June 8 aboard the Research Vessel Atlantis during CalNex 2010 field study. In Los Angeles region, was more ubiquitous than most nights study period. ranged detection limits at midday campaign maximum values night reaching 2100 200 pptv,...
A new photolytic converter for NO 2 measurement is described and its performance assessed using laboratory, ground‐, aircraft‐based field data. Focusing the output of a 200‐W short‐arc Hg lamp into cell attains conversion fractions to greater than 0.70 in residence times less second. Limiting wavelengths 350 nm by means optical filters increases specificity , affording peroxyacetyl nitrate fraction 0.006 negligible HNO 3 . Unwanted (artifact) signal clean synthetic air also greatly minimized...
Measurements of NO, NO 2 , HNO 3 particulate nitrate, peroxyacetyl nitrate (PAN), O and total reactive odd nitrogen (NO y ) were made in the nonurban troposphere during summer fall 1984. The field site was located near Niwot Ridge, Colorado, at an elevation km. measured by catalytic reduction to followed detection with a chemiluminescence instrument. other species conventional techniques. data interpretation presented focus primarily on relationships between measurement concurrent...
Tropospheric O 3 concentrations are functions of the chain lengths NO x (NO ≡ + 2 ) and HO (HO OH RO radical catalytic cycles. For a fixed source at low concentrations, kinetic models indicate rate production increases linearly with in limited). At higher predict ozone rates decrease increasing saturated). We present observations NO, , OH, H CO, actinic flux, temperature obtained during 1999 Southern Oxidant Study from June 15 to July 15, 1999, Cornelia Fort Airpark, Nashville, Tennessee....
We characterize particulate emissions on the basis of chemical, physical, and optical properties from commercial vessels. Observations during Texas Air Quality Study/Gulf Mexico Atmospheric Composition Climate Study 2006 field campaign provide chemical physical characteristics including sulfate (SO 4 2− ) mass, organic matter (OM) black carbon (BC) (PM) number concentrations (condensation nuclei (CN) > 5 nm), cloud condensation (CCN). Optical characterization included multiple wavelength...
Measurements of light hydrocarbons, ozone, peroxyacetyl nitrate (PAN), HNO 3 , NO − x y and meteorological parameters were made during a 10‐day period in April May 1985 at Point Arena, coastal inflow site on the Pacific Ocean northern California. The measurements indicate that this study sampled air was usually from marine boundary layer with little land influence parameters. In mixing ratios alkanes, PAN, showed strong correlations coincident variations origins calculated parcel...
A case study from the Texas Air Quality Study 2000 field campaign illustrates complex interaction of meteorological and chemical processes that produced a high-pollution event in Houston area on 30 August 2000. High 1-h ozone concentrations nearly 200 ppb were measured near surface, vertical profile data an airborne differential-absorption lidar (DIAL) system showed these high-ozone penetrated to heights approaching 2 km into atmospheric boundary layer. This deep layer pollution was...
A national inventory of soil nitric oxide (NO) emissions with county spatial resolution and monthly time has been developed from empirical relationships that were derived NO data. The used to develop the relate emission temperature a factor which is representative an ecosystem or type land use. Most ecosystem/land use factors analyses data seven different sites in United States are three ecosystems two agricultural types. Other (crop) estimated calculated based on differences fertilization...
OH and HO 2 mixing ratios total reactivity were measured together with photolysis frequencies, NO x , O 3 many VOCs, other trace gases during the midsummer 1999 SOS campaign in Nashville, Tennessee. These measurements provided an excellent opportunity to study (collectively called ), their sources sinks a polluted metropolitan environment. generally showed expected diurnal evolution, maxima around noon of up about 0.8 pptv 80 sunny days. Overall, daytime observed factor 1.33 1.56 times...
Ship and aircraft measurements of aerosol organic matter (OM) water‐soluble carbon (WSOC) were made in fresh aged pollution plumes from major urban areas the northeastern United States framework 2004 International Consortium for Atmospheric Research on Transport Transformation (ICARTT) study. A large part variability data was quantitatively described by a simple parameterization previous study that uses measured mixing ratios CO either transport age or photochemical sampled air masses. The...
The role of nitrous acid, HONO, as a precursor for hydroxyl radicals in polluted urban air has been recognized many years. chemical processes leading to the formation HONO are, however, still not well understood. Laboratory studies show that occurs primarily on surfaces and is first order NO 2 . Water also plays an important conversion process. While latter shown laboratory, little information available regarding influence water chemistry real atmosphere. Here we present nocturnal DOAS...
At a site near Boulder, Colorado, simultaneous atmospheric measurements were made of NO, NO x , and y in field intercomparison instruments involving two currently employed techniques measurement. Both depended upon the reduction species to with detection by chemiluminescence, but different catalysts for reduction: (1) gold catalyst (with addition 0.3% CO) at 300°C, or (2) molybdenum 400°C. The systems involved photolysis 2 solid ferrous sulfate. Several times during response calibrated...
The Second Texas Air Quality Study (TexAQS II) was conducted in eastern during 2005 and 2006. This 2‐year study included an intensive field campaign, TexAQS 2006/Gulf of Mexico Atmospheric Composition Climate (GoMACCS), August–October results reported this special journal section are based on observations collected four aircraft, one research vessel, networks ground‐based air quality meteorological (surface radar wind profiler) sites Texas, a balloon‐borne ozonesonde‐radiosonde network (part...
Volatile organic compounds (VOCs) and some of their oxidants (O 3 , NO ) were measured on board the National Oceanic Atmospheric Administration research ship R/V Ronald H. Brown along coast New England, downwind York, Boston, Portsmouth large forested areas in Hampshire, Maine, Massachusetts July August 2002. The diurnal variations isoprene, monoterpenes, aromatics mainly dependent emissions abundance OH . Elevated mixing ratios short‐lived VOCs only encountered at ship, which was about 1–6...
Nocturnal chemistry in urban areas can considerably influence the composition of boundary layer by removing nitrogen oxides and hydrocarbons, as well changing size aerosol particles. Although these processes have a severe impact on pollution levels at night during following day, little quantitative information is available. In particular, vertical variation trace gas concentrations has received attention thus poorly understood. Here we present differential optical absorption spectroscopy...
The nitrate radical, NO 3 , and dinitrogen pentoxide, N 2 O 5 are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction reacts to form during course night, their fate is an determining factor overall x (=NO ). As comprehensive test nocturnal oxide chemistry, concentrations NO, HNO host other relevant compounds, aerosol abundance composition, meteorological conditions were measured marine boundary layer from NOAA...
Observations of C 1 ‐C 10 hydrocarbon mixing ratios measured by in situ instrumentation at the La Porte super site during TexAQS 2000 field experiment are reported. The data were compared to a roadway vehicle exhaust signature obtained from canister samples collected Houston Washburn tunnel same summer better understand impact petrochemical emissions hydrocarbons site. It is shown that abundance ethene, propene, 1‐butene, 2 4 alkanes, hexane, cyclohexane, methylcyclohexane, isopropylbenzene,...
Abstract. Many recent models underpredict secondary organic aerosol (SOA) particulate matter (PM) concentrations in polluted regions, indicating serious deficiencies the models' chemical mechanisms and/or missing SOA precursors. Since tropospheric photochemical ozone production is much better understood, we investigate correlation of odd-oxygen ([Ox]≡[O3]+[NO2]) and oxygenated component (OOA), which interpreted as a surrogate for SOA. OOA Ox measured Mexico City 2006 Houston 2000 were well...