Jeffrey Geddes

• PhD Chemistry
• Assistant Professor at Boston University

We use a multi‐year record of Pandora‐derived NO2 total column abundance in Boston to examine the influence of atmospheric transport on column NO2 and its surface concentrations during the warm season in a coastal urban environment. We derive tropospheric NO2 estimates from the total column with a measurement‐model fusion approach using near‐real‐t...

Coastal urban environments face unique challenges associated with air quality‐meteorology interactions. In this study, high resolution chemical transport modeling over the Greater Boston area was performed to improve our understanding of sea breezes impacts on the spatiotemporal variability of primary and secondary pollutants. We perform WRF‐Chem s...

Satellite retrievals of tropospheric-column formaldehyde (HCHO) and nitrogen dioxide (NO2) are frequently used to investigate the sensitivity of ozone (O3) production to emissions of nitrogen oxides and volatile organic carbon compounds. This study inter-compared the systematic biases and uncertainties in retrievals of NO2 and HCHO, as well as resu...

Satellite retrievals of tropospheric column formaldehyde (HCHO) and nitrogen dioxide (NO2) are frequently used to investigate the sensitivity of ozone (O3) production to concentrations and emissions of nitrogen oxides (NOx) and volatile organic carbon compounds (VOCs). Space-based remote-sensing information of chemical proxies for NOx (i.e., NO2) a...

Reductions in anthropogenic emissions have drawn increasing attention to the role of the biosphere in O3 production chemistry in U.S. cities. We report the results of chemical transport model sensitivity simulations exploring the relative impacts of biogenic isoprene and soil nitrogen oxides (NOx) emissions on O3 and its temporal variability. We co...

Dry deposition could partially explain the observed response in ambient ozone to extreme hot and dry episodes. We examine the response of ozone deposition to heat and dry anomalies using three long‐term co‐located ecosystem‐scale carbon dioxide, water vapor and ozone flux measurement records. We find that, as expected, canopy stomatal conductance g...

Earth system and environmental impact studies need high quality and up-to-date estimates of atmospheric deposition. This study demonstrates the methodological benefits of multimodel ensemble and measurement-model fusion mapping approaches for atmospheric deposition focusing on 2010, a year for which several studies were conducted. Global model-only...

Our work explores the impact of two important dimensions of land system changes, land use and land cover change (LULCC) as well as direct agricultural reactive nitrogen (Nr) emissions from soils, on ozone (O3) and fine particulate matter (PM2.5) in terms of air quality over contemporary (1992 to 2014) timescales. We account for LULCC and agricultur...

Environmental impact assessments (EIAs) effectiveness and accessibility by the public is determined by local environmental enforcement and regulation. Massive energy infrastructure projects like China's Belt and Road initiative (BRI) could accentuate social and economic costs, as regulation is deferred to host countries with varying levels of domes...

We present an analysis of sea breeze conditions for the Boston region and examine their impact on the concentration of local air pollutants over the past decade. Sea breezes occur about one‐third of the days during the summer and play an important role in the spatial distribution and temporal evolution of NO2 and O3 across the urban area. Mornings...

Our work explores the impact of two important dimensions of land system changes, land use and land cover change (LULCC) and direct agricultural reactive nitrogen (Nr) emissions from soils, on ozone (O3) and fine particulate matter (PM2.5) air quality over contemporary (1992 to 2014) time scales. We account for LULCC and agricultural Nr emissions ch...

Houston, Texas is a major U.S. urban and industrial area where poor air quality is unevenly distributed and a disproportionate share is located in low-income, non-white, and Hispanic neighborhoods. We have traditionally lacked city-wide observations to fully describe these spatial heterogeneities in Houston and in cities globally, especially for re...

Lightning is a large and variable source of nitrogen oxides (NOx ≡ NO + NO2) to the upper troposphere. Precise estimates of lightning NOx (LNOx) production rates are needed to constrain tropospheric oxidation chemistry; however, controls over LNOx variability are poorly understood. Here, we describe an observational analysis of variability in LNO2...

Dry deposition is a major sink of tropospheric ozone. Increasing evidence has shown that ozone dry deposition actively links meteorology and hydrology with ozone air quality. However, there is little systematic investigation on the performance of different ozone dry deposition parameterizations at the global scale and how parameterization choice ca...

Dry deposition is the second largest sink of tropospheric ozone. Increasing evidence has shown that ozone dry deposition actively links meteorology and hydrology with ozone air quality. However, there is little systematic investigation on the performance of different ozone dry deposition parameterizations at the global scale, and how parameterizati...

Drought conditions affect ozone air quality, potentially altering multiple terms in the O 3 mass balance equation. Here, we present a multiyear observational analysis using data collected before, during, and after the record-breaking California drought (2011-2015) at the O 3 -polluted locations of Fresno and Bakersfield near the Sierra Nevada footh...

Separating the stratospheric and tropospheric contributions in satellite retrievals of atmospheric NO2 column abundance is a crucial step in the interpretation and application of the satellite observations. A variety of stratosphere–troposphere separation algorithms have been developed for sun-synchronous instruments in low Earth orbit (LEO) that b...

Tropospheric ozone is an air pollutant that substantially harms vegetation and is also strongly dependent on various vegetation-mediated processes. The interdependence between ozone and vegetation may constitute feedback mechanisms that can alter ozone concentration itself but have not been considered in most studies to date. In this study we exami...

Aerosol fluxes were measured by eddy-correlation for 8 weeks of the summer and fall of 2011 above a temperate broadleaf forest in central Ontario, Canada. These size-resolved measurements apply to particles with optical diameters between 50 and 500 nm and are the first ones reported above a temperate deciduous forest. The particle spectrometer was...

Separating the stratospheric and tropospheric contributions in satellite retrievals of atmospheric NO2 column abundance is a crucial step in the interpretation and application of the satellite observations. A variety of stratosphere-troposphere separation algorithms have been developed for sun-synchronous instruments in low Earth orbit (LEO) that b...

Tropospheric ozone is a significant air pollutant with substantial harm on vegetation, but is also strongly dependent on various vegetation-mediated processes. The interdependence between ozone and vegetation may constitute feedback mechanisms that can alter ozone concentration itself but have not been considered in most studies to date. In this st...

Reactive nitrogen oxides (NOy) are a major constituent of the nitrogen deposited from the atmosphere, but observational constraints on their deposition are limited by poor or nonexistent measurement coverage in many parts of the world. Here we apply NO2 observations from multiple satellite instruments (GOME, SCIAMACHY, and GOME-2) to constrain the...

Nitrogen dioxide is a common air pollutant with growing evidence of health impacts independent of other common pollutants such as ozone and particulate matter. However, the global distribution of NO2 exposure and associated impacts on global health is still largely uncertain. To advance global exposure estimates we created a global nitrogen dioxide...

Obtaining the maximum carboxylation rate ( ) has been tedious and time consuming on the field. An algorithm of inverting using the sunlit leaf photosynthesis rate was developed and validated at six Canadian flux sites. The sunlit leaf photosynthesis rate was calculated from the sunlit gross primary productivity (GPPsun) obtained through rectangular...

Reactive nitrogen oxides (NOy) are a major constituent of the nitrogen deposited from the atmosphere, but observational constraints on their deposition are limited by poor or nonexistent measurement coverage in many parts of the world. Here we apply NO2 observations from multiple satellite instruments (GOME, SCIAMACHY, and GOME-2) to constrain the...

Anthropogenic land use change (LUC) since preindustrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation....

Anthropogenic land use change (LUC) since pre-industrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation....

Over recent decades oil palm plantations have rapidly expanded across Southeast Asia (SEA). According to the United Nations, oil palm production in SEA increased by a factor of 3 from 1995 to 2010. We investigate the impacts of current (2010) and near-term future (2020) projected oil palm expansion in SEA on surface–atmosphere exchange and the resu...

Characteristics of urban areas, such as density and compactness, are associated with local air pollution concentrations. The potential for altering air pollution through changing urban characteristics, however, is less certain, especially for expanding cities within the developing world. We examined changes in urban characteristics from 2000 to 201...

Over recent decades oil palm plantations have rapidly expanded across Southeast Asia (SEA). According to the United Nations, oil palm production in SEA increased by a factor of 3 from 1995 to 2010. We investigate the impacts of current (2010) and future (2020) oil palm expansion in SEA on surface-atmosphere exchange and the resulting air quality in...

Land use and land cover changes impact climate and air quality by altering the exchange of trace gases between the Earth's surface and atmosphere. Large-scale tree mortality that is projected to occur across the United States as a result of insect and disease may therefore have unexplored consequences for tropospheric chemistry. We develop a land u...

Land use and land cover changes impact climate and air quality by altering the exchange of trace gases between the Earth's surface and atmosphere. Large-scale tree mortality that is projected to occur across the United States as a result of insect and disease may therefore have unexplored consequences for tropospheric chemistry. We develop a land u...

Air pollution is associated with morbidity and premature mortality. Satellite remote sensing provides globally consistent decadal-scale observations of ambient NO2 pollution. We determined global population-weighted annual mean NO2 concentrations from 1996 through 2012. We used observations of NO2 tropospheric column densities from three satellite...

Tropospheric ozone (O3) is a major component of photochemical smog and is a known human health hazard, as well as a damaging factor for vegetation. Its precursor compounds, nitrogen oxides (NOx) and volatile organic compounds (VOCs), have a variety of anthropogenic and biogenic sources and exhibit non-linear effects on ozone production. As an updat...

Tropospheric ozone (O3) is a major component of photochemical smog and is a known human health hazard as well as a damaging factor for vegetation. Its precursor compounds, nitrogen oxides (NOx) and volatile organic compounds (VOCs), have a variety of anthropogenic and biogenic sources and exhibit non-linear effects on ozone production. As an update...

Significant knowledge gaps persist in the understanding of forest-atmosphere exchange of reactive nitrogen oxides, partly due to a lack of direct observations. Chemical transport models require representations of dry deposition over a variety of land surface types, and the role of canopy exchange of NOx (= NO + NO2) is highly uncertain. Biosphere-a...

Significant knowledge gaps persist in the understanding of forest–atmosphere exchange of reactive nitrogen oxides, partly due to a lack of direct observations. Chemical transport models require representations of dry deposition over a variety of land surface types, and the role of canopy exchange of NOx (= NO + NO2) is highly uncertain. Biosphere–a...

Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45 degrees 17'11 '' N, 78 degrees 32'19 '' W) from June to October 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer that measures methane (CH4) at 10 Hz sampling rates. Fluxes were...

Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45°17´11´´ N, 78°32´19´´ W) from June-October, 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) from Los Gatos Research Inc. that measures metha...

Retrievals of atmospheric trace gas column densities from space are compromised by the presence of clouds, requiring most studies to exclude observations with significant cloud fractions in the instrument's field of view. Using NO2 observations at three ground stations representing urban, suburban, and rural environments, and tropospheric vertical...

This chapter discusses the formation and fate of the chemical constituents in urban smog, whose effects on human health and the environment continue to be a problem in large cities around the world. Because smog production is mainly the result of chemical reactions in the atmosphere, controlling direct emissions of primary pollutants is only part o...

Ground level ozone represents a significant air quality concern in Toronto, Canada, where the national 65 ppb 8-h standard is repeatedly exceeded during the summer. Here we present an analysis of nitrogen dioxide (NO2), ozone (O3), and volatile organic compound (VOC) data from federal and provincial governmental monitoring sites from 2000 to 2007....

The Ozone Monitoring Instrument aboard the NASA EOS-Aura satellite has been making daily global measurements of a wide range of trace atmospheric chemical species since November 2004. As an important component of anthropogenic air pollution, nitrogen dioxide (NO2) is among the more significant trace gases retrieved from OMI. Its principal sources a...

While the province of Ontario has taken several steps that have successfully reduced precursor emissions, the overall influence on ground-level ozone levels throughout the last decade has so far been unclear. Here we present an analysis of 8 years of data provided by government agency monitoring stations to assess the progress in Toronto, Canada's...

Measured ammonia concentration time series are compared between two different techniques (CIMS and QCL) over a 10 day period. The field site was situated in Edinburgh, Scotland. Conditions ranged from rainy and cold (~9°C) to warm and dry (~22°C). During the warmer period, urea was spread on the field site --- urea hydrolyzes to produce artificiall...

Satellite monitoring of nitrogen oxides (NOx) has the potential to assist in the detection and quantitative characterizations of poor air quality incidents, and the determination of the status of possible violations of air quality regulations. Two principal advantages of satellite monitoring are: (1) averaging over ~400 km2 regions, which is compar...

The Cosmonaut Sea off the coast of Antarctica is characterized by highly variable sea ice conditions. As the sea ice expands during the austral fall and winter, embayments, open bodies of water surrounded on three sides by sea ice, as well as polynyas often form. Using sea ice concentration data provided by satellite-based passive microwave instrum...