Two-Years PM2.5 Observations at Four Urban Sites along the Coast of Southeastern China

Abstract

PM 2.5 samples from four coastal urban sites (Fuzhou, Putian, Quanzhou, and Xiamen) in Southeastern China were collected to analyze their major chemical composition including inorganic ions, organic carbon (OC), elemental carbon (EC), and inorganic elements. Organic matter (OM = 1.6 × OC) was the largest contributor, accounting for 30.2% of PM 2.5 mass concentration, and followed by sulfate (19.8%), ammonium (10.6%), and nitrate (9.7%), with minor contribution from trace species (5.1%), crustal species (4.7%) and EC (2.9%). Sea-salt and biomass burning potassium together contributed less than 2%. At the four sites, higher PM 2.5 and its major components were observed in the northeast monsoon season while lower levels were found in the southwest monsoon season. The periodic PM 2.5 cycle was observed and influenced mainly by rain wash out. However, regular diurnal variations of PM 2.5 with high concentration during daytime were only observed in summer due to the greater production of sulfate and organic aerosols in spite of the fact that the vertical mixing coefficients were lower during nighttime. The relative contributions of secondary inorganic aerosols (sulfate, nitrate, and ammonium) to PM 2.5 increased rapidly while the contribution of OM decreased during the haze episodes. The reconstructed visibility using revised IMPROVE method correlated well with the measured values. At Xiamen and Fuzhou sites, the major contributors of light extinction coefficient were ammonium sulfate, ammonium nitrate, OM and coarse mass, and accounted for more than 80% of the light extinction coefficient on average.

Characteristics of Atmospheric PM2.5 in a Densely Populated City with Multi-Emission Sources

“…The low values of NOR and SOR for summer show that the potential for secondary formation of NO 3 -and SO 4 2-were low and mostly were sourced from local, pollution while it was high for spring, autumn and winter which shows the potential to convert SO 2 and NO x to particulate form via secondary transformation (Zhou et al, 2009;Li et al, 2016). This can also be attributed to lack of favorable conditions such as low PM 2.5 concentrations reported earlier or low abundance of nitrogen due to the loss of NH 4 NO 3 at high temperatures (Zhou et al, 2009;Wu et al, 2015).…”

Biomass burning contributions to urban PM_2.5 along the coastal lines of southeastern China

“…During the summer sampling periods, the prevailing wind direction is southeastÁsouthwest ( Supplementary Fig. 2) and the input of clean marine air masses transported over South China Sea could more readily dilute the PM 2.5 along the coastal region (Wu et al, 2015a(Wu et al, , 2015b. Moreover, fewer biomass burning activities were observed in the upwind regions of Philippines during the summer sampling periods, as seen from MODIS fire counts (Supplementary Fig.…”

“…and WSOC) and light absorption at 365 nm (Abs 365 ) Reche et al, 2012 (Zhang et al, 2008Giannoni et al, 2012;Zhu et al, 2015) and similar to those of polycyclic aromatic hydrocarbons, dicarboxylic acids and other major water soluble ions associated with particulate matter observed in this region in different years Xu et al, 2012a;Wu et al, 2014Wu et al, , 2015aWu et al, , 2015b. As discussed previously, the seasonal pattern can be partly explained by the transport of air masses from upwind sources under the influence of the East Asian monsoons.…”

“…2, there was a substantial day-to-day variation in the LG concentration at the same site in the same sampling period. Although there is some coherence between the time series of rainfall and low LG level, LG concentration didn't correlate well with rainfall, probably due to the ineffective wash-out of PM 2.5 by the light rain and/or a time lag between the reduction of PM 2.5 and the rain event (Wu et al, 2015a). In addition, occasional local biomass burning activities such as outdoor and indoor incense and joss paper burning as well as open burning of weeds, leaves and other plant materials on graveyards around the traditional Ching-Ming festival (the 4th of April in 2012 and 2013) to worship deceased ancestors might contribute to some short-lived enhancements of LG in this study Sang et al, 2011 Fig.…”

“…Furthermore, Fujian's coastal area is a perfect region to capture the signals of biomass burning from the upwind sources during the northeast monsoon and southwest monsoon periods. The seasonal patterns of PM 2.5 and its major components from the four sites at Xiamen, Quanzhou, Putian and Fuzhou cities along the coastal line coincided well with the monsoon cycles during a 2-yr monitoring period (Wu et al, 2015a). Organic matter (01.6)OC) was suggested to be the largest contributor, accounting for 30.2 % of PM 2.5 , followed by SO 4 2( (19.8 %), NH 4 ' (10.6 %) and NO 3 ( (9.7 %).…”