Polar organic tracers in PM<sub>2.5</sub> aerosols from forests in eastern China

Abstract

Abstract. Photooxidation products of biogenic volatile organic compounds, mainly isoprene and monoterpenes, are significant sources of atmospheric particulate matter in forested regions. The objectives of this study were to examine time series and diel variations of polar organic tracers for the photooxidation of isoprene and α-pinene to investigate whether they are linked with meteorological parameters or trace gases, and to determine their carbon contributions. In addition, the biogenic secondary organic carbon contributions from isoprene were estimated. PM 2.5 (particulate matter with an aerodynamic diameter <2.5 µm) aerosol samples were collected from forests in eastern China and compared with data from forested sites in Europe and America. Aerosol sampling was conducted at four sites located along a gradient of ecological succession in four different regions, i.e. Changbai Mountain Nature Reserve (boreal-temperate), Chongming National Forest Park (temperate), Dinghu Mountain Nature Reserve (subtropical) and Jianfengling Nature Reserve in Hainan (tropical) during summer periods when the meteorological conditions are believed to be favorable for photochemical processes. Fifty PM 2.5 samples were collected; eighteen organic compounds, organic carbon (OC), elemental carbon and trace gases were measured. Results indicate that the concentration trends of the secondary organic compounds reflected those of the trace gases and meteorological parameters. Very good correlations between the sum concentrations of isoprene oxidation products and atmoCorrespondence to: W. Wang (wangwu@shu.edu.cn) spheric SO 2 , O 3 , NO 2 , NO x , as well as CO 2 , at the Changbai site were found. The secondary OC due to isoprene was relatively high in tropical Hainan (0.27 µgC/m 3 ) where isoprene-emitting broadleaf species are dominant, but was comparable in boreal Changbai (0.32 µgC/m 3 ) where coniferous species are prevalent. The contribution of malic acid, which may have both biogenic and anthropogenic sources, to the OC mass was comparable at the four sites.

Characteristics of concentrations and chemical compositions for PM&lt;sub&gt;2.5&lt;/sub&gt; in the region of Beijing, Tianjin, and Hebei, China

“…So data for PM 2.5 concentration and composition could not be systematically acquired in most parts of China by now. In China, studies for PM 2.5 have been gradually carried out since 2000, and mainly focused on the urban areas of the Pearl River Delta (Cao et al, 2004;Hagler et al, 2006;Duan et al, 2007;, the Yangtze River Delta (Ye et al, 2003;Yang et al, 2005;Wang et al, 2008;Li et al, 2011), and the BTH region.…”

Aircraft measurements of polar organic tracer compounds in tropospheric particles (PM&lt;sub&gt;10&lt;/sub&gt;) over central China

“…Further, the aerosol accumulation mode number concentrations in this region are postulated to be the highest in the world (Andreae and Rosenfeld, 2008). Up until now, several studies have been conducted in urban and forest areas from North to South China, focusing on the SOA tracers from the oxidation of BVOCs such as isoprene, monoterpenes and sesquiterpenes (Hu et al, 2008;Wang et al, 2008;Fu et al, 2010;Gao et al, 2012). During the ACE-Asia campaign, remarkably high organic carbon concentrations (mean 4 µgC m −3 up to 6.5 km altitude) in the free troposphere were obtained by aircraft measurements (Huebert et al, 2003).…”

“…Nevertheless, our results are similar to those (0-1380 ng m −3 , 250 ng m −3 ) reported in Research Triangle Park, NC, in 2006 (Offenberg et al, 2011), and also similar to those reported at the ground surface in China. For example, Wang et al (2008) investigated the summertime SOC levels from isoprene oxidation in four forests in East China; the estimated isoprene-SOC concentrations were 320 ng m −3 for Changbai Mountains, 30 ng m −3 for Chongming, 160 ng m −3 for Dinghu, and 270 ng m −3 for Hainan. Such a similarity strongly suggests the presence of a large amount of biogenic SOA not only near the ground surface but also aloft in the troposphere over central China.…”

Linking biogenic hydrocarbons to biogenic aerosol in the Borneo rainforest

“…Atmospheric oxidation of BVOCs by the hydroxyl radical, ozone and nitrate radical leads to the formation of more oxidised compounds, which can lead to the formation of secondary organic aerosol (SOA). The majority of studies of organic aerosol composition in forested regions have taken place in boreal (Kristensen and Glasius, 2011;Kallio et al, 2006) and temperate forests (Gomez-Gonzalez et al, 2012;Surratt et al, 2007;Wang et al, 2008) of the Northern Hemisphere. The tree species found in tropical rainforests are very different, being dominated by lowland evergreen broadleaf rainforest.…”