A 10‐year spatial and temporal trend of sulfate across the United States

Abstract

[1] Legislative and regulatory mandates have resulted in reduced sulfur dioxide (SO 2 ) emissions in both the eastern and western United States with anticipation that concurrent levels of ambient SO 2 , SO 4 2À, and rainwater acidity would decrease. This paper examines spatial and temporal trends in ambient SO 4 2À concentration from 1988 to 1999, SO 2 emissions from 1990 to 1999, and the relationship between these two variables. The SO 4 2À concentration data came from combining data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Clean Air Status and Trends Network (CASTNet). Over 70 sites spread across the continental United States are considered in this analysis. From a spatial perspective, the 90th percentile summer sulfate concentrations are highest along the Ohio River Valley and in central Tennessee where the emission density of SO 2 is greatest. These concentrations are a factor of 2 greater than the Northeast, northern Michigan, and coastal areas of the Southeast and about a factor of 15 greater than the central western United States. In the East, the largest SO 4 2À decreases in the 80th percentile concentrations occurred north of the Ohio River Valley, while most monitoring sites south of Kentucky and Virginia showed increasing and decreasing trends that were not statistically significant. Big Bend National Park, Texas, Cranberry, North Carolina, and Lassen Volcanic National Park, California, are the only areas that show a statistically significant increase in SO 4 2À mass concentrations. The 1990-1999 annual 80th percentile SO 4 2À time series were compared to the annual SO 2 emissions over four broad United States regions. Each region had a unique time series pattern with the SO 4 2À concentrations and SO 2 emissions closely tracking each other over the 10-year period. Both the SO 4 2À and SO 2 emissions decreased in the Northeast (28%) and the West (15%), while there was little change in the Southeast and a 15% increase over Texas, New Mexico, and Colorado.

A critical review of filter transmittance measurements for aerosol light absorption, and de novo calibration for a decade of monitoring on PTFE membranes

“…Tracking multi-year trends in regional haze aerosols is a key function of the IMPROVE program (Malm et al 2002;White et al 2005;Murphy et al 2011;Hand et al 2012aHand et al ,b, 2013Hand et al , 2014. Consistent absorption data from the HIPS measurements have not previously been available for such analysis, so we will conclude this article by examining the implications for Fabs trends of the retrospective calibration introduced here.…”

Estimating Precision Using Duplicate Measurements

“…IMPROVE is a cooperative measurement effort in the United States designed to characterize current visibility and aerosol conditions in scenic areas (primarily national parks and forests) and to identify chemical species responsible for existing manmade visibility impairment. [13][14][15] IMPROVE measures suspended particulate matter concentrations by collecting 24-hr filter samples at approximately 170 sites every 3 days.…”

Organic PM2.5: Fractionation by Polarity, FTIR Spectroscopy, and OM/OC Ratio for the Pittsburgh Aerosol

“…Organic compounds account for 10-70% of the fine particulate matter (PM 2.5 ) mass and are comprised of a myriad of individual species with vastly different chemical and thermodynamic properties (Turpin et al 2000;Malm et al 2002;USEPA 2004;Goldstein and Galbally 2007). Only about 10-20% of the organic PM 2.5 mass is typically identified at the molecular level, and the characterization of polar organic PM is particularly challenging (Saxena and Hildemann 1996;Turpin et al 2000).…”