Temperature-dependent composition of summertime PM in observations and model predictions across the Eastern U.S.

Throughout the U.S., summertime fine particulate matter (PM) exhibits a strong temperature (T) dependence.

Sustained Reductions of Bay Area CO Emissions 2018-2022.

Cities represent a significant and growing portion of global carbon dioxide (CO) emissions. Quantifying urban emissions and trends over time is needed to evaluate the efficacy of policy targeting emission reductions as well as to understand more fundamental questions about the urban biosphere. A number of approaches have been proposed to measure, report, and verify (MRV) changes in urban CO emissions.

Improved Spatial Resolution in Modeling of Nitrogen Oxide Concentrations in the Los Angeles Basin.

The extent to which emission control technologies and policies have reduced anthropogenic NO emissions from motor vehicles is large but uncertain. We evaluate a fuel-based emission inventory for southern California during the June 2021 period, coinciding with the Re-Evaluating the Chemistry of Air Pollutants in CAlifornia (RECAP-CA) field campaign. A modified version of the Fuel-based Inventory of Vehicle Emissions (FIVE) is presented, incorporating 1.

Methane Emissions from Dairy Operations in California's San Joaquin Valley Evaluated Using Airborne Flux Measurements.

State inventories indicate that dairy operations account for nearly half of California's methane budget. Recent analyses suggest, however, that these emissions may be underestimated, complicating efforts to develop emission reduction strategies. Here, we report estimates of dairy methane emissions in the southern San Joaquin Valley (SJV) of California in June 2021 using airborne flux measurements.

Space-Based Observations of Ozone Precursors within California Wildfire Plumes and the Impacts on Ozone-NO-VOC Chemistry.

The frequency of wildfires in the western United States has escalated in recent decades. Here we examine the impacts of wildfires on ground-level ozone (O) precursors and the O-NO-VOC chemistry from the source to downwind urban areas. We use satellite retrievals of nitrogen dioxide (NO) and formaldehyde (HCHO, an indicator of VOC) from the Tropospheric Monitoring Instrument (TROPOMI) to track the evolution of O precursors from wildfires over California from 2018 to 2020.

Measurements of Atmosphere-Biosphere Exchange of Oxidized Nitrogen and Implications for the Chemistry of Atmospheric NO.

ConspectusThe atmosphere-biosphere exchange of nitrogen oxides plays a key role in determining the composition of reactive nitrogen in terrestrial vegetated environments. The emission of nitric oxide (NO) from soils is an important atmospheric source of reactive nitrogen. NO is rapidly interconverted with NO, making up the chemical family NO (NO ≡ NO + NO).

Elucidating Contributions of Anthropogenic Volatile Organic Compounds and Particulate Matter to Ozone Trends over China.

In China, emissions of ozone (O)-producing pollutants have been targeted for mitigation to reduce O pollution. However, the observed O decrease is slower than/opposite to expectations affecting the health of millions of people. For a better understanding of this failure and its connection with anthropogenic emissions, we quantify the summer O trends that would have occurred had the weather stayed constant by applying a numerical tool that "de-weathers" observations across 31 urban regions (123 cities and 392 sites) over 8 years.

Two Decades of Changes in Summertime Ozone Production in California's South Coast Air Basin.

Tropospheric ozone (O) continues to be a threat to human health and agricultural productivity. While O control is challenging, tracking underlying formation mechanisms provides insights for regulatory directions. Here, we describe a comprehensive analysis of the effects of changing emissions on O formation mechanisms with observational evidence.

A multi-city urban atmospheric greenhouse gas measurement data synthesis.

Urban regions emit a large fraction of anthropogenic emissions of greenhouse gases (GHG) such as carbon dioxide (CO) and methane (CH) that contribute to modern-day climate change. As such, a growing number of urban policymakers and stakeholders are adopting emission reduction targets and implementing policies to reach those targets. Over the past two decades research teams have established urban GHG monitoring networks to determine how much, where, and why a particular city emits GHGs, and to track changes in emissions over time.

Estimate of OH trends over one decade in North American cities.

The hydroxyl radical (OH) is the most important oxidant on global and local scales in the troposphere. Urban OH controls the removal rate of primary pollutants and triggers the production of ozone. Interannual trends of OH in urban areas are not well documented or understood due to the short lifetime and high spatial heterogeneity of OH.

Observing Annual Trends in Vehicular CO Emissions.

Transportation emissions are the largest individual sector of greenhouse gas (GHG) emissions. As such, reducing transportation-related emissions is a primary element of every policy plan to reduce GHG emissions. The Berkeley Environmental Air-quality and CO Observation Network (BEACON) was designed and deployed with the goal of tracking changes in urban CO emissions with high spatial (∼1 km) and temporal (∼1 hr) resolutions while allowing the identification of trends in individual emission sectors.

Combining Machine Learning and Satellite Observations to Predict Spatial and Temporal Variation of near Surface OH in North American Cities.

The hydroxyl radical (OH) is the primary cleansing agent in the atmosphere. The abundance of OH in cities initiates the removal of local pollutants; therefore, it serves as the key species describing the urban chemical environment. We propose a machine learning (ML) approach as an efficient alternative to OH simulation using a computationally expensive chemical transport model.

Contribution of Organic Nitrates to Organic Aerosol over South Korea during KORUS-AQ.

The role of anthropogenic NO emissions in secondary organic aerosol (SOA) production is not fully understood but is important for understanding the contribution of emissions to air quality. Here, we examine the role of organic nitrates (RONO) in SOA formation over the Korean Peninsula during the Korea-United States Air Quality field study in Spring 2016 as a model for RONO aerosol in cities worldwide. We use aircraft-based measurements of the particle phase and total (gas + particle) RONO to explore RONO phase partitioning.

Accelerated reduction of air pollutants in China, 2017-2020.

Emission regulations of the power and industry sectors have been identified as the major driver of PM mitigation over China during 2013-2017. In this study, we use ground-based observations of four air pollutants (CO, NO, SO, and PM) to show that additional stringent emission policies on the industrial, transportation, and residential sectors during the new 3-year protection plan (2018-2020) have accelerated the improvement of China's air quality. Based on regional (North and South China) trends of annual mean measurements, significant reductions are observed for all four pollutants during 2017-2020.

Brain gamma-aminobutyric acid, but not glutamine and glutamate levels are lower in older adults with chronic musculoskeletal pain: considerations by sex and brain location.

Introduction And Objectives: GABAergic and glutamatergic neurotransmitter systems are central to the pathophysiology of chronic pain and are equally affected by aging processes. We measured levels of frontal gamma-aminobutyric acid (GABA) and the combined resonance of glutamate and glutamine (Glx) in vivo using proton magnetic resonance spectroscopy (H-MRS) to elucidate age-specific and pain-specific associations with clinical and experimental pain in older adults.

Methods: Younger (18-24, n = 24) and older (60-94, n = 41) individuals part of a larger study (Neuromodulatory Examination of Pain and Mobility Across the Lifespan [NEPAL]) underwent questionnaires, quantitative sensory testing, and H-MRS Mescher-Garwood point-resolved spectroscopy to measure GABA and Glx levels in prefrontal and sensorimotor brain regions.

Impact of OA on the Temperature Dependence of PM 2.5 in the Los Angeles Basin.

Air quality policy in the Los Angeles megacity is a guidepost for other megacities. Over the last 2 decades, the policy has substantially reduced aerosol (OA) concentrations and the frequency of high aerosol events in the region. During this time, the emissions contributing to, and the temperature associated with, high aerosol events have changed.

The Role of Temperature and NO in Ozone Trends in the Los Angeles Basin.

Ozone, a major contributor to poor air quality, has an array of adverse effects on human, animal, and plant health. In the Los Angeles basin, a megacity that has pursued cleaner air for decades, unhealthy levels of ozone have decreased but remain stubbornly frequent even as the ozone precursors NO (nitrogen oxides ≡ NO + NO) and VOC (volatile organic compounds) have decreased. We describe a combined analysis of decadal trends in these precursors, differences in emissions with day-of-week, and of the impact of temperature to assess the role of VOC and NO and the likely effects of additional emission reductions on the occurrence of high ozone in the region.

Assessment of NO observations during DISCOVER-AQ and KORUS-AQ field campaigns.

NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011-2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea-United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated datasets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO measurements were made, including in situ concentrations and column amounts of NO using ground- and aircraft-based instruments, while NO column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models.

Direct observation of changing NO lifetime in North American cities.

NO lifetime relates nonlinearly to its own concentration; therefore, by observing how NO lifetime changes with changes in its concentration, inferences can be made about the dominant chemistry occurring in an urban plume. We used satellite observations of NO from a new high-resolution product to show that NO lifetime in approximately 30 North American cities has changed between 2005 and 2014 in a manner consistent with our understanding of NO chemistry.

Vapor-pressure pathways initiate but hydrolysis products dominate the aerosol estimated from organic nitrates.

Organic nitrates contribute significantly to the total organic aerosol burden. However, the formation and loss mechanisms of particulate organic nitrates (PONs) remain poorly understood. In this study, with the CMAQ modeling system, we implement a detailed biogenic volatile organic carbon gas phase oxidation mechanism and an explicit representation of multiphase organic nitrate formation and loss, including both aqueous-phase uptake and vapor-pressure driven partitioning into organic aerosol as well as condensed-phase reactions.

Concentrations and Adsorption Isotherms for Amphiphilic Surfactants in PM Aerosols from Different Regions of Europe.

Predicting the activation of submicrometer particles into cloud droplets in the atmosphere remains a challenge. The importance of surface tension, σ (mN m), in these processes has been evidenced by several works, but information on the "surfactants" lowering σ in actual atmospheric particles remains scarce. In this work, PM aerosols from urban, coastal, and remote regions of Europe (Lyon, France, Rogoznica, Croatia, and Pallas, Finland, respectively) were investigated and found to contain amphiphilic surfactants in concentrations up to 2.