W.-N. Chen

High wintertime particulate matter pollution over an offshore island (Kinmen) off southeastern China: An overview

Both the Yangtze River Delta (YRD) and the Pearl River Delta (PRD), the two most rapidly developing areas in eastern China, have suffered from serious air pollution, and thus, numerous investigations were devoted to studying these problems. Other areas in eastern China have received less attention despite similar rapid development in ntheir industries and economy. In this study, we analyzed air‐quality data from Kinmen Island (24°27′26′′N, 118°19′36′′E) located off Fujian Province and between the two above‐mentioned deltas. Our results clearly show that the study area is experiencing serious air quality deterioration. Particularly, high levels of suspended particulate matter (PM) were observed during winter, when the northeasterly monsoon prevails. For example, concentrations of wintertime PM10 (particles ≤ 10 mm in diameter) frequently exceeded 100 mg/m3 in the last three years. In addition to the air‐quality data analysis, aerosol samples were collected between 22 November 2007 and 6 March 2008 and subjected to chemical analyses of various species. Our findings show that the three principal PM components include organic, mineral, and sulfate species with moderate to minor fractions of nitrate, sea salt, elemental carbon, and trace metal oxides. The high PM levels observed over the island may be partly attributed to the transport from a mixed‐type industrial area located ∼40 km northeast of Kinmen. Our study could partially fill the air quality data gap between the YRD and PRD regions, and highlight the alarming fact that air pollution has gradually expanded along eastern China’s coastal zone.

Total scatter-to-backscatter ratio of aerosol derived from aerosol size distribution measurement

Based on in-situ aerosol size-distribution measurements and Mie scattering theory, total scattering coefficients and backscattering coefficients were calculated to derived wavelength dependent lidar ratio S for 355 nm and 532 nm. Effective radius and C/F ratio of aerosol are also calculated to study the relationships between lidar ratio and particle size dependences. The results show backscatter-related scattering properties are more sensitive to coarse mode particle than total scattering. The mean values of lidar ratio for 355 nm and 532 nm are 31.9 ± 6.2 sr and 40.5 ± 6.1 sr respectively, and S355 and S532 are linear correlated for S355 < 50 sr. S355 is highly correlated with effective radius of aerosol, and S532 is highly correlated with volume C/F ratio.

Seasonality of the mass concentration and chemical composition of aerosols around an urbanized basin in East Asia

This study investigated seasonal variations in the mass concentration and chemical composition of ambient aerosols observed at three stations (coastal, mountainous and downtown sites) in northern Taiwan from March 2009 to February 2012. The results show that the major aerosol components include ammonium, sulfate, nitrate, sea salt, dust, organic carbon (OC) and elemental carbon (EC), whereas the mass fraction of each species depends on the sampling location and season. A significant correlation (ru2009=u20090.7 – 0.8) was observed in aerosol concentrations measured at the respective stations, indicating that aerosol concentrations were dominated by regional scale factors. Ammonium, sulfate and nitrate consistently reached respective peak values in the spring in conjunction with dust particle levels. This shows that the transport of dust and particulate air pollutants from the Asian continent has affected the atmospheric environment in this area. Distinct seasonality was observed for sea salt and secondary organic carbon (SOC): sea salt levels peaked in the autumn, whereas SOC levels peaked in the summer, implying that their sources were regulated by independent seasonal factors. Correlation between sea salt concentration and surface wind speed was derived from coastal measurements and showed a high value for the wind speed sensitivity parameter of around 0.37 for our location. In addition, it was revealed that the SOC concentration in aerosols was positively correlated with oxidant photolysis index (Ox*UVB), suggesting that the SOC seasonality was dominated by hydroxyl radical production.

Applying hourly measurements of meteorological data and aerosol soluble ions in Taipei Basin, Taiwan

This study applies observational data composed of hourly weather and aerosol to discuss the aerosol characteristics within different weather systems. Based on cluster analysis, spring weather in Taipei Basin 2004 was characterised as five weather systems: humid/low south wind speed, dry cold/high east wind speed, humid cold/east wind, dry cold/northeaster, and northwestern convection wind. Under the humid/low south wind speed and northwestern convection wind systems, there are predominant influences of local vehicle/motor pollutant emissions and secondary pollution on the air quality. Asian dust storms were usually occurred under the weather of dry cold/high east wind speed. The regional air quality is more acceptable during the period of prevalent humid cold/east wind and dry cold/northeaster.