scholarly journals Measurement report: Source apportionment of carbonaceous aerosol using dual-carbon isotopes (<sup>13</sup>C and <sup>14</sup>C) and levoglucosan in three northern Chinese cities during 2018–2019

2021 ◽  
Author(s):  
Huiyizhe Zhao ◽  
Zhenchuan Niu ◽  
Weijian Zhou ◽  
Sen Wang ◽  
Xue Feng ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Fossil Fuels ◽  
Action Plan ◽  
Pollution Prevention ◽  
Latin Hypercube Sampling ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Carbonaceous Aerosols ◽  
Chinese Cities ◽  
Northern Chinese

Abstract. In this study, we investigated the characteristics of and changes in the sources of carbonaceous aerosols in northern Chinese cities after the implementation of the Action Plan for Air Pollution Prevention and Control in 2013. We collected PM2.5 samples from three representative inland cities, viz. Beijing (BJ), Xi’an (XA), and Linfen (LF) from January 2018 to April 2019. Elemental carbon (EC), organic carbon (OC), levoglucosan, stable carbon, and radiocarbon were measured in PM2.5 to quantify the sources of carbonaceous aerosol employing Latin hypercube sampling. The best estimate of source apportionment showed that the emissions from liquid fossil fuels contributed 33.6 ± 12.9 %, 26.6 ± 16.4 %, and 24.6 ± 13.4 % of the total carbon (TC) in BJ, XA, and LF, whereas coal combustion contributed 11.2 ± 9.1 %, 19.2 ± 12.3 %, and 39.2 ± 20.5 %, respectively. Non-fossil sources accounted for 55 ± 11 %, 54 ± 10 %, and 36 ± 14 % of the TC in BJ, XA, and LF, respectively. In XA, 48.34 ± 32.01 % of non-fossil sources was attributed to biomass burning. The highest contributors to OC in LF and XA were fossil sources (65.4 ± 14.9 % and 44.9 ± 9.5 %, respectively), whereas that in BJ was non-fossil sources in BJ (56.1 ± 16.7 %). The main contributors to EC were fossil sources, accounting for 92.9 ± 6.13 %, 69.9 ± 20.9 %, and 90.8 ± 9.9 % of the total EC in BJ, XA, and LF, respectively. The decline (6–17 %) in fossil source contributions in BJ and XA since the implementation of the Action Plan indicates the effectiveness of air quality management. We suggest that measures targeted to each city should be strengthened in the future.

scholarly journals Sources of non-fossil fuel emissions in carbonaceous aerosols during early winter in Chinese cities

2017 ◽  
Author(s):  
Di Liu ◽  
Jun Li ◽  
Zhineng Cheng ◽  
Guangcai Zhong ◽  
Sanyuan Zhu ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Fossil Fuel ◽  
Carbon Sources ◽  
Northern China ◽  
Pollution Source ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Carbonaceous Aerosols ◽  
Aerosol Composition ◽  
Chinese Cities

Abstract. China experiences frequent and severe haze outbreaks from the beginning of winter. Carbonaceous aerosols are regarded as an essential factor in controlling the formation and evolution of haze episodes. To elucidate the carbon sources of air pollution, source apportionment was conducted using radiocarbon (14C) and unique molecular organic tracers. Daily 24-hour PM2.5 samples were collected continuously from October 2013 to November 2013 in 10 Chinese cities. The 14C results indicated that non-fossil fuel (NF) emissions were predominant in total carbon (TC; average = 65 ± 7 %). Approximately half of the EC was derived primarily from biomass burning (BB) (average = 46 ± 11 %), while over half of the OC fraction comprised NF (average = 68 ± 7 %). On average, the largest contributor to TC was NF-derived secondary OC (SOCnf), which accounted for 46 ± 7 % of TC, followed by SOC derived from fossil fuels (FF) (SOCf; 16 ± 3 %), BB-derived primary OC (POCbb; 13 ± 5 %), POC derived from FF (POCf; 12 ± 3 %), EC derived from FF (ECf; 7 ± 2 %) and EC derived from BB (ECbb; 6 ± 2 %). The regional background carbonaceous aerosol composition was characterized by NF sources; POCs played a major role in northern China, while SOCs contributed more in other regions. However, during haze episodes, there were no dramatic changes in the carbon source or composition in the cities under study, but the contribution of POC from both FF and NF increased significantly.

scholarly journals Sources of non-fossil-fuel emissions in carbonaceous aerosols during early winter in Chinese cities

2017 ◽  
Vol 17 (18) ◽  
pp. 11491-11502 ◽  
Author(s):  
Di Liu ◽  
Jun Li ◽  
Zhineng Cheng ◽  
Guangcai Zhong ◽  
Sanyuan Zhu ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Fossil Fuel ◽  
Carbon Sources ◽  
Northern China ◽  
Pollution Source ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Carbonaceous Aerosols ◽  
Aerosol Composition ◽  
Chinese Cities

Abstract. China experiences frequent and severe haze outbreaks from the beginning of winter. Carbonaceous aerosols are regarded as an essential factor in controlling the formation and evolution of haze episodes. To elucidate the carbon sources of air pollution, source apportionment was conducted using radiocarbon (14C) and unique molecular organic tracers. Daily 24 h PM2. 5 samples were collected continuously from October 2013 to November 2013 in 10 Chinese cities. The 14C results indicated that non-fossil-fuel (NF) emissions were predominant in total carbon (TC; average  =  65 ± 7 %). Approximately half of the EC was derived primarily from biomass burning (BB) (average  =  46 ± 11 %), while over half of the organic carbon (OC) fraction comprised NF (average  =  68 ± 7 %). On average, the largest contributor to TC was NF-derived secondary OC (SOCnf), which accounted for 46 ± 7 % of TC, followed by SOC derived from fossil fuels (FF) (SOCf; 16 ± 3 %), BB-derived primary OC (POCbb; 13 ± 5 %), POC derived from FF (POCf; 12 ± 3 %), EC derived from FF (ECf; 7 ± 2 %) and EC derived from BB (ECbb; 6 ± 2 %). The regional background carbonaceous aerosol composition was characterized by NF sources; POCs played a major role in northern China, while SOCs contributed more in other regions. However, during haze episodes, there were no dramatic changes in the carbon source or composition in the cities under study, but the contribution of POC from both FF and NF increased significantly.

scholarly journals Source apportionment of the summer time carbonaceous aerosol at Nordic rural background sites

2011 ◽  
Vol 11 (6) ◽  
pp. 16369-16416 ◽  
Author(s):  
K. E. Yttri ◽  
D. Simpson ◽  
J. K. Nøjgaard ◽  
K. Kristensen ◽  
J. Genberg ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Fossil Fuel ◽  
Late Summer ◽  
Latin Hypercube Sampling ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Anthropogenic Sources ◽  
Minor Variation ◽  
Rural Background ◽  
Summer Time

Abstract. In the present study, natural and anthropogenic sources of particulate organic carbon (OCp) and elemental carbon (EC) have been quantified based on weekly filter samples of PM10 collected at four Nordic rural background sites (Birkenes (Norway), Hyytiälä (Finland) Vavihill (Sweden), Lille Valby (Denmark)) during late summer (5 August–2 September 2009). Levels of source specific tracers, i.e. cellulose, levoglucosan, mannitol and the 14C/12C ratio of total carbon (TC), have been used as input for source apportionment of the carbonaceous aerosol, whereas Latin Hypercube Sampling (LHS) was used to statistically treat the multitude of possible combinations resulting from this approach. The carbonaceous aerosol (here: TCp; i.e. particulate TC) was totally dominated by natural sources (69–86 %), with biogenic secondary organic aerosol (BSOA) being the single most important source (48–57 %). Interestingly, primary biological aerosol particles (PBAP) were the second most important source (20–32 %). The anthropogenic contribution was mainly attributed to fossil fuel sources (OCff and ECff (10–24 %), whereas no more than 3–7 % was explained by combustion of biomass (OCbb and ECbb in this late summer campaign i.e. emissions from residential wood burning and/or wild/agricultural fires. Fossil fuel sources totally dominated the ambient EC loading, accounting for 4–12 % of TCp, whereas <1.5 % was attributed to combustion of biomass. The carbonaceous aerosol source apportionment showed only minor variation between the four selected sites. However, Hyytiälä and Birkenes showed greater resemblance to each other, as did Lille Valby and Vavihill, the two latter being somewhat more influenced by anthropogenic sources. Ambient levels of organosulphates and nitrooxy-organosulphates in the Nordic rural background environment are reported for the first time in the present study. The most abundant organosulphate compounds were an organosulphate of isoprene and nitrooxy-organosulphates of α- and β-pinene and limonene.

scholarly journals Source apportionment of carbonaceous aerosol in southern Sweden

2011 ◽  
Vol 11 (22) ◽  
pp. 11387-11400 ◽  
Author(s):  
J. Genberg ◽  
M. Hyder ◽  
K. Stenström ◽  
R. Bergström ◽  
D. Simpson ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Fossil Fuels ◽  
Elemental Carbon ◽  
Transport Model ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Anthropogenic Sources ◽  
Biomass Combustion ◽  
Southern Sweden

Abstract. A one-year study was performed at the Vavihill background station in southern Sweden to estimate the anthropogenic contribution to the carbonaceous aerosol. Weekly samples of the particulate matter PM10 were collected on quartz filters, and the amounts of organic carbon, elemental carbon, radiocarbon (14C) and levoglucosan were measured. This approach enabled source apportionment of the total carbon in the PM10 fraction using the concentration ratios of the sources. The sources considered in this study were emissions from the combustion of fossil fuels and biomass, as well as biogenic sources. During the summer, the carbonaceous aerosol mass was dominated by compounds of biogenic origin (80%), which are associated with biogenic primary and secondary organic aerosols. During the winter months, biomass combustion (32%) and fossil fuel combustion (28%) were the main contributors to the carbonaceous aerosol. Elemental carbon concentrations in winter were about twice as large as during summer, and can be attributed to biomass combustion, probably from domestic wood burning. The contribution of fossil fuels to elemental carbon was stable throughout the year, although the fossil contribution to organic carbon increased during the winter. Thus, the organic aerosol originated mainly from natural sources during the summer and from anthropogenic sources during the winter. The result of this source apportionment was compared with results from the EMEP MSC-W chemical transport model. The model and measurements were generally consistent for total atmospheric organic carbon, however, the contribution of the sources varied substantially. E.g. the biomass burning contributions of OC were underestimated by the model by a factor of 2.2 compared to the measurements.

scholarly journals Source apportionment of carbonaceous aerosol in southern Sweden

2011 ◽  
Vol 11 (5) ◽  
pp. 13575-13616 ◽  
Author(s):  
J. Genberg ◽  
M. Hyder ◽  
K. Stenström ◽  
R. Bergström ◽  
D. Simpson ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Fossil Fuels ◽  
Elemental Carbon ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Anthropogenic Sources ◽  
Biomass Combustion ◽  
Southern Sweden ◽  
One Year

Abstract. A one-year study was performed at the Vavihill background station in southern Sweden to estimate the anthropogenic contribution to the carbonaceous aerosol. Weekly samples of the particulate matter PM10 were collected on quartz filters, and the amounts of organic carbon, elemental carbon, radiocarbon (14C) and levoglucosan were measured. This approach enabled source apportionment of the total carbon in the PM10 fraction using the concentration ratios of the sources. The sources considered in this study were emissions from the combustion of fossil fuels and biomass, as well as biogenic sources. During the summer, the carbonaceous aerosol mass was dominated by compounds of biogenic origin (82 %), which are associated with biogenic primary and secondary organic aerosols. During the winter months, biomass combustion (38 %) and fossil fuel combustion (33 %) were the main contributors to the carbonaceous aerosol. Elemental carbon concentrations in winter were about twice as large as during summer, and can be attributed to biomass combustion, probably from domestic wood burning. The contribution of fossil fuels to elemental carbon was stable throughout the year, although the fossil contribution to organic carbon increased during the winter. Thus, the organic aerosol originated mainly from natural sources during the summer and from anthropogenic sources during the winter. The result of this source apportionment was compared with results from the EMEP model. The model and measurements were generally consistent for total atmospheric organic carbon, however, the contribution of the sources varied substantially. E.g. the biomass burning contributions of OC were underestimated by the model by a factor of 8.2 compared to the measurements.

scholarly journals Source apportionment of the summer time carbonaceous aerosol at Nordic rural background sites

2011 ◽  
Vol 11 (24) ◽  
pp. 13339-13357 ◽  
Author(s):  
K. E. Yttri ◽  
D. Simpson ◽  
J. K. Nøjgaard ◽  
K. Kristensen ◽  
J. Genberg ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Fossil Fuel ◽  
Late Summer ◽  
Latin Hypercube Sampling ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Anthropogenic Sources ◽  
Minor Variation ◽  
Rural Background ◽  
Summer Time

Abstract. In the present study, natural and anthropogenic sources of particulate organic carbon (OCp) and elemental carbon (EC) have been quantified based on weekly filter samples of PM10 (particles with aerodynamic diameter <10 μm) collected at four Nordic rural background sites [Birkenes (Norway), Hyytiälä (Finland), Vavihill (Sweden), Lille Valby, (Denmark)] during late summer (5 August–2 September 2009). Levels of source specific tracers, i.e. cellulose, levoglucosan, mannitol and the 14C/12C ratio of total carbon (TC), have been used as input for source apportionment of the carbonaceous aerosol, whereas Latin Hypercube Sampling (LHS) was used to statistically treat the multitude of possible combinations resulting from this approach. The carbonaceous aerosol (here: TCp; i.e. particulate TC) was totally dominated by natural sources (69–86%), with biogenic secondary organic aerosol (BSOA) being the single most important source (48–57%). Interestingly, primary biological aerosol particles (PBAP) were the second most important source (20–32%). The anthropogenic contribution was mainly attributed to fossil fuel sources (OCff and ECff) (10–24%), whereas no more than 3–7% was explained by combustion of biomass (OCbb and ECbb) in this late summer campaign i.e. emissions from residential wood burning and/or wild/agricultural fires. Fossil fuel sources totally dominated the ambient EC loading, which accounted for 4–12% of TCp, whereas <1.5% of EC was attributed to combustion of biomass. The carbonaceous aerosol source apportionment showed only minor variation between the four selected sites. However, Hyytiälä and Birkenes showed greater resemblance to each other, as did Lille Valby and Vavihill, the two latter being somewhat more influenced by anthropogenic sources. Ambient levels of organosulphates and nitrooxy-organosulphates in the Nordic rural background environment are reported for the first time in the present study. The most abundant organosulphate compounds were an organosulphate of isoprene and nitrooxy-organosulphates of α- and β-pinene and limonene.

scholarly journals On the isolation of OC and EC and the optimal strategy of radiocarbon-based source apportionment of carbonaceous aerosols

2012 ◽  
Vol 12 (22) ◽  
pp. 10841-10856 ◽  
Author(s):  
Y. L. Zhang ◽  
N. Perron ◽  
V. G. Ciobanu ◽  
P. Zotter ◽  
M. C. Minguillón ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Optimal Strategy ◽  
Complete Removal ◽  
Water Soluble ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Pure Oxygen ◽  
Carbonaceous Aerosols ◽  
Set Up

Abstract. Radiocarbon (14C) measurements of elemental carbon (EC) and organic carbon (OC) separately (as opposed to only total carbon, TC) allow an unambiguous quantification of their non-fossil and fossil sources and represent an improvement in carbonaceous aerosol source apportionment. Isolation of OC and EC for accurate 14C determination requires complete removal of interfering fractions with maximum recovery. The optimal strategy for 14C-based source apportionment of carbonaceous aerosols should follow an approach to subdivide TC into different carbonaceous aerosol fractions for individual 14C analyses, as these fractions may differ in their origins. To evaluate the extent of positive and negative artefacts during OC and EC separation, we performed sample preparation with a commercial Thermo-Optical OC/EC Analyser (TOA) by monitoring the optical properties of the sample during the thermal treatments. Extensive attention has been devoted to the set-up of TOA conditions, in particular, heating program and choice of carrier gas. Based on different types of carbonaceous aerosols samples, an optimised TOA protocol (Swiss_4S) with four steps is developed to minimise the charring of OC, the premature combustion of EC and thus artefacts of 14C-based source apportionment of EC. For the isolation of EC for 14C analysis, the water-extraction treatment on the filter prior to any thermal treatment is an essential prerequisite for subsequent radiocarbon measurements; otherwise the non-fossil contribution may be overestimated due to the positive bias from charring. The Swiss_4S protocol involves the following consecutive four steps (S1, S2, S3 and S4): (1) S1 in pure oxygen (O2) at 375 °C for separation of OC for untreated filters and water-insoluble organic carbon (WINSOC) for water-extracted filters; (2) S2 in O2 at 475 °C followed by (3) S3 in helium (He) at 650 °C, aiming at complete OC removal before EC isolation and leading to better consistency with thermal-optical protocols like EUSAAR_2, compared to pure oxygen methods; and (4) S4 in O2 at 760 °C for recovery of the remaining EC. WINSOC was found to have a significantly higher fossil contribution than the water-soluble OC (WSOC). Moreover, the experimental results demonstrate the lower refractivity of wood-burning EC compared to fossil EC and the difficulty of clearly isolating EC without premature evolution. Hence, simplified techniques of EC isolation for 14C analysis are prone to a substantial bias and generally tend towards an overestimation of fossil sources. To obtain the comprehensive picture of the sources of carbonaceous aerosols, the Swiss_4S protocol is not only implemented to measure OC and EC fractions, but also WINSOC as well as a continuum of refractory OC and non-refractory EC for 14C source apportionment. In addition, WSOC can be determined by subtraction of the water-soluble fraction of TC from untreated TC. Last, we recommend that 14C results of EC should in general be reported together with the EC recovery.

scholarly journals On the isolation of OC and EC and the optimal strategy of radiocarbon-based source apportionment of carbonaceous aerosols

2012 ◽  
Vol 12 (7) ◽  
pp. 17657-17702 ◽  
Author(s):  
Y. L. Zhang ◽  
N. Perron ◽  
V. G. Ciobanu ◽  
P. Zotter ◽  
M. C. Minguillón ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Optimal Strategy ◽  
Complete Removal ◽  
Water Soluble ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Pure Oxygen ◽  
Carbonaceous Aerosols ◽  
Set Up

Abstract. Radiocarbon (14C) measurements of elemental carbon (EC) and organic carbon (OC) separately (as opposed to only total carbon, TC) allow an unambiguous quantification of their non-fossil and fossil sources and represent an improvement in carbonaceous aerosol source apportionment. Isolation of OC and EC for accurate 14C determination requires complete removal of interfering fractions with maximum recovery. To evaluate the extent of positive and negative artefacts during OC and EC separation, we performed sample preparation with a commercial Thermo-Optical OC/EC Analyser (TOA) by monitoring the optical properties of the sample during the thermal treatments. Extensive attention has been devoted to the set-up of TOA conditions, in particular, heating program and choice of carrier gas. Based on different types of carbonaceous aerosols samples, an optimised TOA protocol (Swiss_4S) with four steps is developed to minimise the charring of OC, the premature combustion of EC and thus artefacts of 14C-based source apportionment of EC. For the isolation of EC for 14C analysis, the water-extraction treatment on the filter prior to any thermal treatment is an essential prerequisite for subsequent radiocarbon; otherwise the non-fossil contribution may be overestimated due to the positive bias from charring. The Swiss_4S protocol involves the following consecutive four steps (S1, S2, S3 and S4): (1) S1 in pure oxygen (O2) at 375 °C for separation of OC for untreated filters, and water-insoluble organic carbon (WINSOC) for water-extracted filters; (2) S2 in O2 at 475 °C, followed by (3) S3 in helium (He) at 650 °C, aiming at complete OC removal before EC isolation and leading to better consistency with thermal-optical protocols like EUSAAR_2, compared to pure oxygen methods; and (4) S4 in O2 at 760 °C for recovery of the remaining EC. WINSOC was found to have a significantly higher fossil contribution than the water-soluble OC (WSOC). Moreover, the experimental results demonstrate the lower refractivity of wood-burning EC compared to fossil EC and the difficulty of clearly isolating EC without premature evolution. Hence, simplified techniques of EC isolation for 14C analysis are prone to a substantial bias and generally tend towards an underestimation of the non-fossil sources. Consequently, the optimal strategy for 14C-based source apportionment of carbonaceous aerosols should follow an approach to subdivide TC into different carbonaceous aerosol fractions for individual 14C analyses, as these fractions differ in their origins. To obtain the comprehensive picture of the sources of carbonaceous aerosols, the Swiss_4S protocol is not only implemented to measure OC and EC fractions, but also WINSOC as well as a continuum of refractory OC and non-refractory EC for 14C source apportionment. In addition, WSOC can be determined by subtraction of the water-soluble fraction of TC from untreated TC. Last, we recommend that 14C results of EC should in general be reported together with the EC recovery.

scholarly journals Source apportionment of carbonaceous aerosols in Beijing with radiocarbon and organic tracers: insight into the differences between urban and rural sites

2021 ◽  
Vol 21 (10) ◽  
pp. 8273-8292
Author(s):  
Siqi Hou ◽  
Di Liu ◽  
Jingsha Xu ◽  
Tuan V. Vu ◽  
Xuefang Wu ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Biomass Burning ◽  
Fine Particles ◽  
Water Soluble ◽  
Carbonaceous Aerosol ◽  
Balance Model ◽  
Gas Chromatography Mass Spectrometry ◽  
Urban Site ◽  
Carbonaceous Aerosols ◽  
Carbonaceous Particles

Abstract. Carbonaceous aerosol is a dominant component of fine particles in Beijing. However, it is challenging to apportion its sources. Here, we applied a newly developed method which combined radiocarbon (14C) with organic tracers to apportion the sources of fine carbonaceous particles at an urban (IAP) and a rural (PG) site of Beijing. PM2.5 filter samples (24 h) were collected at both sites from 10 November to 11 December 2016 and from 22 May to 24 June 2017. 14C was determined in 25 aerosol samples (13 at IAP and 12 at PG) representing low pollution to haze conditions. Biomass burning tracers (levoglucosan, mannosan, and galactosan) in the samples were also determined using gas chromatography–mass spectrometry (GC-MS). Higher contributions of fossil-derived OC (OCf) were found at the urban site. The OCf / OC ratio decreased in the summer samples (IAP: 67.8 ± 4.0 % in winter and 54.2 ± 11.7 % in summer; PG: 59.3 ± 5.7 % in winter and 50.0 ± 9.0 % in summer) due to less consumption of coal in the warm season. A novel extended Gelencsér (EG) method incorporating the 14C and organic tracer data was developed to estimate the fossil and non-fossil sources of primary and secondary OC (POC and SOC). It showed that fossil-derived POC was the largest contributor to OC (35.8 ± 10.5 % and 34.1 ± 8.7 % in wintertime for IAP and PG, 28.9 ± 7.4 % and 29.1 ± 9.4 % in summer), regardless of season. SOC contributed 50.0 ± 12.3 % and 47.2 ± 15.5 % at IAP and 42.0 ± 11.7 % and 43.0 ± 13.4 % at PG in the winter and summer sampling periods, respectively, within which the fossil-derived SOC was predominant and contributed more in winter. The non-fossil fractions of SOC increased in summer due to a larger biogenic component. Concentrations of biomass burning OC (OCbb) are resolved by the extended Gelencsér method, with average contributions (to total OC) of 10.6 ± 1.7 % and 10.4 ± 1.5 % in winter at IAP and PG and 6.5 ± 5.2 % and 17.9 ± 3.5 % in summer, respectively. Correlations of water-insoluble OC (WINSOC) and water-soluble OC (WSOC) with POC and SOC showed that although WINSOC was the major contributor to POC, a non-negligible fraction of WINSOC was found in SOC for both fossil and non-fossil sources, especially during winter. In summer, a greater proportion of WSOC from non-fossil sources was found in SOC. Comparisons of the source apportionment results with those obtained from a chemical mass balance model were generally good, except for the cooking aerosol.

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