Source attribution of air pollutant concentrations and trends in the southeastern aerosol research and characterization (SEARCH) network.

A new approach for determining the contributions of emission sources to trends in concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI).

Source contributions to atmospheric gases and particulate matter in the southeastern United States.

A new approach for determining the contributions of emission sources to concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI).

Spatial and temporal characterization of PM2.5 mass concentrations in California, 1980-2007.

Systematic measurement of fine particulate matter (aerodynamic diameter less than 2.5 microm [PM2.5]) mass concentrations began nationally with implementation of the Federal Reference Method (FRM) network in 1998 and 1999.

Differences between weekday and weekend air pollutant levels in Atlanta; Baltimore; Chicago; Dallas-Fort Worth; Denver; Houston; New York; Phoenix; Washington, DC; and surrounding areas.

We evaluated day-of-week differences in mean concentrations of ozone (O3) precursors (nitric oxide [NO], nitrogen oxides [NOx], carbon monoxide [CO], and volatile organic compounds [VOCs]) at monitoring sites in 23 states comprising seven geographic focus areas over the period 1998-2003. Data for VOC measurements were available for six metropolitan areas in five regions. We used Wednesdays to represent weekdays and Sundays to represent weekends; we also analyzed Saturdays.

Effects of sulfur dioxide and oxides of nitrogen emission reductions on fine particulate matter mass concentrations: regional comparisons.

Two thermodynamic equilibrium models were applied to estimate changes in mean airborne fine particle (PM2.5) mass concentrations that could result from changes in ambient concentrations of sulfate, nitric acid, or ammonia in the southeastern United States, the midwestern United States, and central California. Pronounced regional differences were found.

Weekday/Weekend differences in ambient air pollutant concentrations in atlanta and the southeastern United States.

The authors quantified changes between mean weekday and weekend ambient concentrations of ozone (O3) precursors (volatile organic compounds [VOC], carbon monoxide [CO], nitric oxide, and oxides of nitrogen [NOx]) in Atlanta and surrounding areas to observe how weekend precursor emission levels influenced ambient O3 levels. The authors analyzed CO, nitric oxide (NO), and NO, measurements from 1998 to 2002 and speciated VOC from 1996 to 2003. They observed a strong weekend effect in the Atlanta region, with median daytime (6:00 a.

Differences between weekday and weekend air pollutant levels in southern California.

Ambient air quality data were analyzed to empirically evaluate the effects of reductions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) emissions on weekday and weekend levels of ozone (O3; 1991-1998) and particulate NO3- (1980-1999) in southern California. Despite significantly lower O3 precursor levels on weekends, 20 of 28 South Coast Air Basin (SoCAB) sites (28 of all 78 southern California sites) showed statistically significant higher mean O3 levels on Sundays than on weekdays (p < 0.01); 49 of the remaining 50 sites showed no significant differences between mean weekday and Sunday peak O3 levels.

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation.

A thermodynamic equilibrium model was used to investigate the response of aerosol NO to changes in concentrations of HNO, NH, and HSO. Over a range of temperatures and relative humidities (RHs), two parameters provided sufficient information for indicating the qualitative response of aerosol NO. The first was the excess of aerosol NH plus gas-phase NH over the sum of HNO, particulate NO, and particulate SO concentrations.