Long-term trends of fine particulate matter and chemical composition in the Pearl River Delta Economic Zone (PRDEZ), China

Understanding the trends in PM2.5 levels is essential for formulating clean air plans. This paper analyzes PM2.5 data from various published sources for the years 2000 to 2010 in the Pearl River Delta Economic Zone (PRDEZ). The long-term variation in PM2.5 mass concentration is analyzed. Results show that PM2.5, organic carbon (OC), elemental carbon (EC), and SO42 show a similar trend, increasing before 2005 and then decreasing slightly. The annual average PM2.5 concentration ranges from 49.1 mu g.m(-3) in 2000 to 64.3 mu g.m(-3) in 2010, with a peak of 84.1 mu g.m(-3) in 2004. None of these 11 years meets the new National Ambient Air Quality standard (NAAQS) for PM2.5 (35 mu g.m(-3)). Overall average concentrations of OC, EC, and SO42- are 13.0, 6.5, and 11.8 mu g.m(-3), respectively. NO3- and NHA(4)(+) respectively have concentrations of 1.5 mu g.m(-3) and 2.9 mu g.m(-3) in 2000 and 6.4 mu g.m(-3) and 5.3 mu g.m(-3) in 2010, with a statistically significant average annual trend of + 0.2 mu g.m(-3).yr(-1) and + 0.1 mu g.m(-3).yr(-1). In certain geographic regions, OC and EC contribute most of the PM2.5, while in other regions secondary water-soluble ions are more important. In general, OC and SO42- are the dominant components of PM2.5, contributing 20.6% and 18.6%, respectively. These results provide, for the first time, a better understanding of the long-term PM2.5 characteristics and trends, on a species-by-species basis, in the PRDEZ. The results indicate that PM2.5 abatement needs to prioritize secondary species.