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

Understanding the trends in PM_2.5 levels is essential for formulating clean air plans. This paper analyzes PM_2.5 data from various published sources for the years 2000 to 2010 in the Pearl River Delta Economic Zone (PRDEZ). The long-term variation in PM_2.5 mass concentration is analyzed. Results show that PM_2.5, organic carbon (OC), elemental carbon (EC), and SO42? show a similar trend, increasing before 2005 and then decreasing slightly. The annual average PM_2.5 concentration ranges from 49.1 μg·m^?3 in 2000 to 64.3 μg·m^?3 in 2010, with a peak of 84.1 μg·m^?3 in 2004. None of these 11 years meets the new National Ambient Air Quality standard (NAAQS) for PM_2.5 (35 μg·m^?3). Overall average concentrations of OC, EC, and SO42? are 13.0, 6.5, and 11.8 μg·m^?3, respectively. NO3? and NH4+ respectively have concentrations of 1.5 μg·m^?3 and 2.9 μg·m^?3 in 2000 and 6.4 μg·m^?3 and 5.3 μg·m^?3 in 2010, with a statistically significant average annual trend of+ 0.2 μg·m^?3·yr^?1 and+ 0.1 μg·m^?3·yr^?1. In certain geographic regions, OC and EC contribute most of the PM_2.5, while in other regions secondary water-soluble ions are more important. In general, OC and SO42? are the dominant components of PM_2.5, contributing 20.6% and 18.6%, respectively. These results provide, for the first time, a better understanding of the long-term PM_2.5 characteristics and trends, on a species-by-species basis, in the PRDEZ. The results indicate that PM_2.5 abatement needs to prioritize secondary species.