10-year spatial and temporal trends of PM2.5 concentrations in the southeastern US estimated using high-resolution satellite data.

X Hu,Y Liu,L A Waller,A Lyapustin,Y Wang

doi:10.5194/acp-14-6301-2014

Abstract

Long-term PM2.5 exposure has been associated with various adverse health outcomes. However, most ground monitors are located in urban areas, leading to a potentially biased representation of true regional PM2.5 levels. To facilitate epidemiological studies, accurate estimates of the spatiotemporally continuous distribution of PM2.5 concentrations are important. Satellite-retrieved aerosol optical depth (AOD) has been increasingly used for PM2.5 concentration estimation due to its comprehensive spatial coverage. Nevertheless, previous studies indicated that an inherent disadvantage of many AOD products is their coarse spatial resolution. For instance, the available spatial resolutions of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging SpectroRadiometer (MISR) AOD products are 10 and 17.6 km, respectively. In this paper, a new AOD product with 1 km spatial resolution retrieved by the multi-angle implementation of atmospheric correction (MAIAC) algorithm based on MODIS measurements was used. A two-stage model was developed to account for both spatial and temporal variability in the PM2.5–AOD relationship by incorporating the MAIAC AOD, meteorological fields, and land use variables as predictors. Our study area is in the southeastern US centered at the Atlanta metro area, and data from 2001 to 2010 were collected from various sources. The model was fitted annually, and we obtained model fitting R2 ranging from 0.71 to 0.85, mean prediction error (MPE) from 1.73 to 2.50 μg m−3, and root mean squared prediction error (RMSPE) from 2.75 to 4.10 μg m−3. In addition, we found cross-validation R2 ranging from 0.62 to 0.78, MPE from 2.00 to 3.01 μgm−3, and RMSPE from 3.12 to 5.00 μgm−3, indicating a good agreement between the estimated and observed values. Spatial trends showed that high PM2.5 levels occurred in urban areas and along major highways, while low concentrations appeared in rural or mountainous areas. Our time-series analysis showed that, for the 10-year study period, the PM2.5 levels in the southeastern US have decreased by ∼20 %. The annual decrease has been relatively steady from 2001 to 2007 and from 2008 to 2010 while a significant drop occurred between 2007 and 2008. An observed increase in PM2.5 levels in year 2005 is attributed to elevated sulfate concentrations in the study area in warm months of 2005.

Highlights

Long-term exposure to PM2.5 is associated with various adverse health outcomes including respiratory and cardiovascular diseases (Crouse et al, 2012; Peng et al, 2009)
The results show that R2 ranges from 0.71 to 0.85, mean prediction error (MPE) is from 1.73 to 2.50 μg m−3, root mean squared prediction error (RMSPE) ranges from 2.75 to 4.10 μg m−3, and relative accuracy www.atmos-chem-phys.net/14/6301/2014/
Many areas in the western part of the domain had < 5 % decreases with decreases in some parts of the mountainous region exceeding 15 %, In the Atlanta metro area, our results show decreases (< 10 %) in urban built-up areas and along major highways with some residential and suburban areas showing < 5 % increases

Summary

Introduction

Long-term exposure to PM2.5 (particle size less than 2.5 μm in the aerodynamic diameter) is associated with various adverse health outcomes including respiratory and cardiovascular diseases (Crouse et al, 2012; Peng et al, 2009). Due to the spatiotemporally continuous nature of the distribution of fine particles, obtaining long-term and spatially resolved distribution of PM2.5 concentrations is important to reduce exposure misclassification and facilitate epidemiological studies in the region. Previous research examined temporal trends in PM2.5 levels. X. Hu et al.: 10-year spatial and temporal trends of PM2.5 variations in PM2.5 concentrations at the US Environmental Protection Agency (EPA) Atlanta Supersite Experiment in August, 1999. So et al (2007) examined long-term variation in PM2.5 levels during two 12-month periods in Hong Kong. The EPA (2011) evaluated temporal trends of annual and 24 h mean PM2.5 concentrations at the national level from 2001 to 2010 and reported that annual and 24 h mean PM2.5 concentrations dropped 24 and 28 %, respectively, during these 10 years

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