Seasonal cycles of secondary organic aerosol tracers in rural Guangzhou, Southern China: The importance of atmospheric oxidants

Yuan, Qi; Lai, Shengli; Song, Junwei; Ding, Xiang; Li, Zheng; Wang, Xinming; Yan, Zhao; Zheng, Junyu; Yue, Dingli; Zhong, Lexuan; Niu, Xiaojun; Zhang, Yingyi

doi:10.1016/j.envpol.2018.05.009

Cited by 53 publications

(35 citation statements)

References 73 publications

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“…The correlation of SOC with isoprene peaks in July ( R 2 = 0.56). The contribution of isoprene to SOC formation in this region was previously studied using the tracer‐based method (Wang et al, ; Yu et al, ; Yuan et al, ). Yuan et al () observed an isoprene derived SOC of 0.18 ± 0.22 μgC/m 3 during March 2012 to February 2013.…”

Section: Resultsmentioning

confidence: 99%

“…The contribution of isoprene to SOC formation in this region was previously studied using the tracer‐based method (Wang et al, ; Yu et al, ; Yuan et al, ). Yuan et al () observed an isoprene derived SOC of 0.18 ± 0.22 μgC/m 3 during March 2012 to February 2013. Wang et al () found that the isoprene‐derived SOC accounts for up to 11% of total SOC during 2012 summer in Guangzhou.…”

Section: Resultsmentioning

confidence: 99%

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Estimation and Uncertainty Analysis of Secondary Organic Carbon Using 1 Year of Hourly Organic and Elemental Carbon Data

Wang

2019

JGR Atmospheres

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Hourly particulate matter 2.5 organic carbon (OC) and elemental carbon (EC) ambient concentrations were measured from February 2012 to January 2013 at a suburban site in the city of Guangzhou, China. The major primary OC and EC sources at this site are vehicular exhaust and regional combustion sources. The annual average OC and EC concentrations (±1SD) were 7.30 ± 5.68 and 2.67 ± 2.28 μgC/m3, respectively. Taking advantage of this large data set of more than 7,000 measurements, we examined the diurnal variation dynamics of the primary OC‐to‐EC ratio ([OC/EC]pri), derived using the minimum R squared (MRS) method, which deploys an algorithm that calculates (OC/EC)pri by exploring the assumed independency between EC and secondary OC (SOC). The MRS‐derived hour‐by‐hour (OC/EC)pri was the lowest (1.8–2.0) for the morning hours while higher (2.4–3.0) for the afternoon and evening hours. Cumulative evidence from other pollutant measurements suggests that the increase in MRS‐derived (OC/EC)pri in the afternoon and evening was a result of SOC formation from photooxidation of precursors that covary with EC (e.g., vehicular exhaust) and thereby inflate (OC/EC)pri. We subsequently separate SOC into two categories based on their correlations with EC, that is, SOCa that covary with EC and SOCb that is unassociated with EC variations. SOCa and SOCb make comparable contributions to SOC, demonstrating that their separation is essential for a more accurate SOC estimation. Otherwise, SOCa would be mistakenly accounted as primary OC. This approach in estimating SOC may underestimate SOCa and subject to bias stemming from OC emissions from cooking and biomass burning.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Estimation and Uncertainty Analysis of Secondary Organic Carbon Using 1 Year of Hourly Organic and Elemental Carbon Data

Wang

2019

JGR Atmospheres

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“…In rural sites, the trend becomes more complicated as vegetation, as major biogenic SOA emission sources, is more active in summer time (Yuan et al, 2018;Seinfeld and Pandis, 2016). Samples influenced by burning are also estimated to have higher OM/OC in summer when samples are affected by wildfires compared to winter when samples are mostly affected by residential wood burning.…”

Section: Om/oc Ratiomentioning

confidence: 99%

Estimating mean molecular weight, carbon number, and OM/OC with mid-infrared spectroscopy in organic particulate matter samples from a monitoring network

Yazdani¹,

Dillner²,

Takahama³

2020

Preprint

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Abstract. Organic matter (OM) is a major constituent of fine particulate matter which contributes significantly to degradation of visibility, radiative forcing, and causes adverse health effects. However, due to its sheer compositional complexity, OM is difficult to characterize in its entirety. Mid-infrared spectroscopy has previously proven useful in the study of OM by providing extensive information about functional group composition with high mass recovery. Herein, we introduce a new method for obtaining additional characteristics such as mean carbon number and molecular weight of these complex organic mixtures using the aliphatic C–H absorbance profile in mid-infrared spectrum. We apply this technique to spectra acquired non-destructively from Teflon filters used for fine particulate matter quantification at selected sites of Inter-agency Monitoring of PROtected Visual Environments (IMPROVE) network. Since carbon number and molecular weight are important characteristics used by recent models to describe evolution in OM composition, this technique can provide semi-quantitative, observational constraints of these variables at the scale of the network. For this task, multivariate statistical models are trained on calibration spectra prepared from atmospherically relevant laboratory standards and are applied to ambient samples. Then, the physical basis linking the absorbance profile of this relatively narrow region in the mid-infrared spectrum to the molecular structure is investigated using a classification approach. The multivariate statistical models predict mean carbon number and molecular weight that are consistent with previous values of organic-mass-to-organic-carbon (OM/OC) ratios estimated for the network using different approaches. The results are also consistent with temporal and spatial variations in these quantities associated with aging processes, and different source classes (anthropogenic, biogenic, and burning sources). For instance, the models estimate higher mean carbon number for urban samples and smaller, more fragmented molecules for samples in which substantial aging is anticipated.

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“…The molecular distributions at Mt. Tai were also found in other regions such as oceans (Fu et al, 2011;Hu et al, 2013), mountains (Hong et al, 2019;Ren et al, 2019) and continents (Yuan et al, 2018). Previous studies have suggested that both cis-pinonic acid and cis-pinic acid can be further photodegraded into MBTCA (Szmigielski et al, 2007;Ding et al, 2012).…”

Section: Monoterpene Soa Tracersmentioning

confidence: 62%

“…Tai were summarized in Table 2 during the summertime. The total concentrations of isoprene SOA tracers during daytime (71.6 ± 46.2 ng m -3 ) were higher than those during nighttime (65.4 ± 39.4 ng m -3 ), largely because the stronger solar radiation and higher temperature conditions in daytime can accelerate the emission of biogenic VOCs and the production of SOA (Yuan et al, 2018).…”

Section: Diurnal Characteristics Of Bsoa Tracersmentioning

confidence: 89%

Molecular Characteristics and Formation Mechanisms of Biogenic Secondary Organic Aerosols in the Summer Atmosphere at Mt. Tai on the North China Plain

Meng

Hou

et al. 2019

Aerosol Air Qual. Res.

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To investigate the molecular characteristics and formation mechanisms of biogenic secondary organic aerosol (BSOA), daytime and nighttime PM 2.5 samples were collected at the summit of Mt. Tai during the summer of 2016. The critical indicators of primary sources, such as elemental carbon (EC) and levoglucosan, displayed similar values during the daytime and nighttime, suggesting that changes in the boundary layer heights (BLHs) produced only inconsequential effects during the observation campaign. The molecular distributions of the BSOA were dominated by isoprene SOA tracers (68.5 ± 42.6 ng m-3), followed by monoterpene (43.5 ± 24.4 ng m-3) and β-caryophyllene (16.3 ± 8.6 ng m-3) SOA tracers. Due to the higher diurnal temperatures and solar radiation, the concentrations of all of the tracers were higher during the day than at night. The ratio of the combined cis-pinonic and cis-pinic acid to the MBTCA (P/M) was much lower than in Chinese cities and at the Tibetan background site, indicating that the monoterpene SOA was relatively aged in the mountainous atmosphere, in large part because of the stronger solar radiation at the peak of Mt. Tai. The concentrations of the BSOA products exhibited a significantly positive correlation with the level of ozone during the daytime (R 2 = 0.58-0.86) and the temperature over the whole sampling period (R 2 = 0.37-0.75), as higher temperatures can accelerate the emission of biogenic volatile organic compounds and the formation of SOA. By contrast, the BSOA tracers displayed a negative linear correlation with the relative humidity (RH) (R 2 = 0.43-0.84) and the in situ particle pH (pH is) (R 2 = 0.55-0.70) because high RH can inhibit the acid-catalyzed formation of BSOA due to the dilution of the aerosol acidity. No correlation between the BSOA tracers and anthropogenic pollutants (e.g., levoglucosan, SO 4 2-, NO 3and EC) was observed during the daytime or nighttime, suggesting that BSOA tracers in the atmosphere of Mt. Tai during summer were primarily derived from the local oxidation of BVOCs rather than long-distance-transported anthropogenic emissions from the lowlands.

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Seasonal cycles of secondary organic aerosol tracers in rural Guangzhou, Southern China: The importance of atmospheric oxidants

Cited by 53 publications

References 73 publications

Estimation and Uncertainty Analysis of Secondary Organic Carbon Using 1 Year of Hourly Organic and Elemental Carbon Data

Estimation and Uncertainty Analysis of Secondary Organic Carbon Using 1 Year of Hourly Organic and Elemental Carbon Data

Estimating mean molecular weight, carbon number, and OM/OC with mid-infrared spectroscopy in organic particulate matter samples from a monitoring network

Molecular Characteristics and Formation Mechanisms of Biogenic Secondary Organic Aerosols in the Summer Atmosphere at Mt. Tai on the North China Plain

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