Amplification of black carbon light absorption induced by atmospheric aging: temporal variation at seasonal and diel scales in urban Guangzhou

Abstract. Black carbon (BC) is an important climate forcer in the atmosphere. Amplification of light absorption can occur by coatings on BC aerosols, an effect that remains one of the major sources of uncertainties for accessing the radiative forcing of BC. In this study, the absorption enhancement factor (Eabs) was quantified by the minimum R squared (MRS) method using elemental carbon (EC) as the tracer. Two field campaigns were conducted in urban Guangzhou at the Jinan university super site during both wet season (July 31–September 10, 2017) and dry season (November 15, 2017–January 15, 2018) to explore the temporal dynamics of BC optical properties. The average concentration of EC was 1.94 ± 0.93 and 2.81 ± 2.01 μgC m−3 in the wet and dry seasons, respectively. Mass absorption efficiency at 520 nm by primary aerosols (MAEp520) determined by MRS exhibit a strong seasonality (8.6 m2g−1 in the wet season and 16.8 m2g−1 in the dry season). Eabs520 was higher in the wet season (1.51 ± 0.50) and lower in the dry season (1.29 ± 0.28). Absorption Ångström exponent (AAE470-660) in the dry season (1.46 ± 0.12) were higher than that in the wet season (1.37 ± 0.10). Collective evidence showed that the active biomass burning (BB) in dry season effectively altered optical properties of BC, leading to elevated MAE, MAEp and AAE in dry season comparing to those in wet season. Diurnal Eabs520 was positively correlated with AAE470-660 (R2 = 0.71) and negatively correlated with the AE33 aerosol loading compensation parameter (k) (R2 = 0.74) in the wet season, but these correlations were significantly weaker in the dry season, which may be related to the impact of BB. This result suggests that lensing effect was dominating the AAE diurnal variability during the wet season. The effect of secondary processing on Eabs diurnal dynamic were also investigated. The Eabs520 exhibit a clear dependency on secondary organic carbon to organic carbon ratio (SOC/OC). Eabs520 correlated well with nitrate, implying that gas-particle partitioning of semi-volatile compounds may potentially play an important role in steering the diurnal fluctuation of Eabs520. In dry season, the diurnal variability of Eabs520 was associated with photochemical aging as evidenced by the good correlation (R2 = 0.69) between oxidant concentrations (Ox=O3+NO2) and Eabs520.

Download Full-text

Amplification of black carbon light absorption induced by atmospheric aging: temporal variation at seasonal and diel scales in urban Guangzhou

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-2445-2020 ◽

2020 ◽

Vol 20 (4) ◽

pp. 2445-2470 ◽

Cited By ~ 6

Author(s):

Jia Yin Sun ◽

Cheng Wu ◽

Dui Wu ◽

Chunlei Cheng ◽

Mei Li ◽

...

Keyword(s):

Optical Properties ◽

Organic Carbon ◽

Black Carbon ◽

Light Absorption ◽

Dry Season ◽

Diurnal Fluctuation ◽

Absorption Enhancement ◽

Wet Season ◽

Diurnal Variability ◽

Atmospheric Aging

Abstract. Black carbon (BC) aerosols have been widely recognized as a vital climate forcer in the atmosphere. Amplification of light absorption can occur due to coatings on BC during atmospheric aging, an effect that remains uncertain in accessing the radiative forcing of BC. Existing studies on the absorption enhancement factor (Eabs) have poor coverage on both seasonal and diurnal scales. In this study, we applied a recently developed minimum R squared (MRS) method, which can cover both seasonal and diurnal scales, for Eabs quantification. Using field measurement data in Guangzhou, the aims of this study are to explore (1) the temporal dynamics of BC optical properties at seasonal (wet season, 31 July–10 September; dry season, 15 November 2017–15 January 2018) and diel scales (1 h time resolution) in the typical urban environment and (2) the influencing factors on Eabs temporal variability. Mass absorption efficiency at 520 nm by primary aerosols (MAEp520) determined by the MRS method exhibited a strong seasonality (8.6 m2 g−1 in the wet season and 16.8 m2 g−1 in the dry season). Eabs520 was higher in the wet season (1.51±0.50) and lower in the dry season (1.29±0.28). Absorption Ångström exponent (AAE470–660) in the dry season (1.46±0.12) was higher than that in the wet season (1.37±0.10). Collective evidence showed that the active biomass burning (BB) in the dry season effectively altered the optical properties of BC, leading to elevated MAE, MAEp and AAE in the dry season compared to those in the wet season. Diurnal Eabs520 was positively correlated with AAE470–660 (R2=0.71) and negatively correlated with the AE33 aerosol loading compensation parameter (k) (R2=0.74) in the wet season, but these correlations were significantly weaker in the dry season, which may be related to the impact of BB. This result suggests that during the wet season, the lensing effect was more likely dominating the AAE diurnal variability rather than the contribution from brown carbon (BrC). Secondary processing can affect Eabs diurnal dynamics. The Eabs520 exhibited a clear dependency on the ratio of secondary organic carbon to organic carbon (SOC∕OC), confirming the contribution of secondary organic aerosols to Eabs; Eabs520 correlated well with nitrate and showed a clear dependence on temperature. This new finding implies that gas–particle partitioning of semivolatile compounds may potentially play an important role in steering the diurnal fluctuation of Eabs520. In the dry season, the diurnal variability in Eabs520 was associated with photochemical aging as evidenced by the good correlation (R2=0.69) between oxidant concentrations (Ox=O3+NO2) and Eabs520.

Download Full-text

Aerosol characterisation including oxidative potential as a proxy of health impact

Clean Air Journal ◽

10.17159/caj/2019/29/2.7517 ◽

2019 ◽

Vol 29 (2) ◽

Author(s):

Miroslav Josipovic ◽

Catherine Leal-Liousse ◽

Belinda Crobeddu ◽

Armelle Baeza-Squiban ◽

C. Keitumetse Segakweng ◽

...

Keyword(s):

Organic Carbon ◽

Black Carbon ◽

Fine Fraction ◽

Health Impact ◽

Coarse Fraction ◽

Dry Season ◽

Wet Season ◽

Oxidative Potential ◽

Ionic Content ◽

Vaal Triangle

This study aimed to characterise aerosols sampled in the vicinity of a major industrialised area, i.e. the Vaal Triangle. It included thedetermination of oxidative potential as a predictive indicator of particle toxicity. Aerosol samples were collated through the cascadefiltering during an eight-month period (12 h over three days in one week). Three size fractions were analysed for organic carbon(OC), black carbon (BC) and oxidative potential (OP), while ionic content was presented as monthly and seasonal concentrations. Thecontinuous measurement of black carbon by an optical attenuation instrument was collated concurrently with cascade filtering. Thecarbonaceous content was low compared to the ionic one. Within the carbonaceous concentrations, the organic carbon was higherthan concentrations of black carbon in both seasons in the ultra-fine fraction; the opposite was the case for the fine fraction, whilethe coarse fraction concentrations of organic carbon in the dry season had higher concentrations than black carbon in the wet seasonand organic carbon in the wet season. The OP tended to increase as the size was decreasing for wet season aerosols, whereas, forthe dry season, the highest OP was exerted by the fine fraction. The ultrafine fraction was the one showing the most contrasting OPbetween the two seasons. Continuous monitoring indicated that the higher BC concentrations were recorded in the dry/winter partof the year, with the daily pattern of concentrations being typically bimodal, having both the morning and evening peaks in bothseasons. Within the ionic content, the dominance of sulphate, nitrate and ammonium was evident. Multiple linear correlations wereperformed between all determined compounds. Strong correlations of carboxylic acids with other organic compounds were revealed.These acids point to emissions of VOC, both anthropogenic and biogenic. Since they were equally present in both seasons, a mixtureof sources was responsible, both present in the wider area and throughout the year.

Download Full-text

Biomass burning and urban emission impacts in the Andes Cordillera region based on in situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.)

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-14805-2019 ◽

2019 ◽

Vol 19 (23) ◽

pp. 14805-14824

Author(s):

Aurélien Chauvigné ◽

Diego Aliaga ◽

Karine Sellegri ◽

Nadège Montoux ◽

Radovan Krejci ◽

...

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Light Absorption ◽

Amazon Basin ◽

Dry Season ◽

La Paz ◽

Extinction Coefficients ◽

Aerosol Emission ◽

El Alto ◽

The Impact

Abstract. This study documents and analyses a 4-year continuous record of aerosol optical properties measured at the Global Atmosphere Watch (GAW) station of Chacaltaya (CHC; 5240 m a.s.l.), in Bolivia. Records of particle light scattering and particle light absorption coefficients are used to investigate how the high Andean Cordillera is affected by both long-range transport and by the fast-growing agglomeration of La Paz–El Alto, located approximately 20 km away and 1.5 km below the sampling site. The extended multi-year record allows us to study the properties of aerosol particles for different air mass types, during wet and dry seasons, also covering periods when the site was affected by biomass burning in the Bolivian lowlands and the Amazon Basin. The absorption, scattering, and extinction coefficients (median annual values of 0.74, 12.14, and 12.96 Mm−1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94, and 8.68 Mm−1 respectively) and higher values during the dry season (0.80, 11.23, and 14.51 Mm−1 respectively). The record is driven by variability at both seasonal and diurnal scales. At a diurnal scale, all records of intensive and extensive aerosol properties show a pronounced variation (daytime maximum, night-time minimum), as a result of the dynamic and convective effects. The particle light absorption, scattering, and extinction coefficients are on average 1.94, 1.49, and 1.55 times higher respectively in the turbulent thermally driven conditions than the more stable conditions, due to more efficient transport from the boundary layer. Retrieved intensive optical properties are significantly different from one season to the other, reflecting the changing aerosol emission sources of aerosol at a larger scale. Using the wavelength dependence of aerosol particle optical properties, we discriminated between contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass burning and urban transport or industries) emissions according to seasons and local circulation. The main sources influencing measurements at CHC are from the urban area of La Paz–El Alto in the Altiplano and from regional biomass burning in the Amazon Basin. Results show a 28 % to 80 % increase in the extinction coefficients during the biomass burning season with respect to the dry season, which is observed in both tropospheric dynamic conditions. From this analysis, long-term observations at CHC provide the first direct evidence of the impact of biomass burning emissions of the Amazon Basin and urban emissions from the La Paz area on atmospheric optical properties at a remote site all the way to the free troposphere.

Download Full-text

Seasonal dynamics of atmospheric and river inputs of black carbon, and impacts on biogeochemical cycles in Halong Bay, Vietnam

Elem Sci Anth ◽

10.1525/elementa.255 ◽

2017 ◽

Vol 5 ◽

Cited By ~ 4

Author(s):

Xavier Mari ◽

Thuoc Chu Van ◽

Benjamin Guinot ◽

Justine Brune ◽

Jean-Pierre Lefebvre ◽

...

Keyword(s):

Organic Carbon ◽

Black Carbon ◽

River Runoff ◽

Marine Ecosystem ◽

Dry Season ◽

Asia Pacific ◽

Surface Microlayer ◽

Wet Season ◽

Sea Surface Microlayer ◽

Halong Bay

Emissions of black carbon (BC), a product of incomplete combustion of fossil fuels, biofuels and biomass, are high in the Asia-Pacific region, yet input pathways and rates to the ocean are not well constrained. Atmospheric and riverine inputs of BC in Halong Bay (Vietnam), a hotspot of atmospheric BC, were studied at monthly intervals during one year. Climate in Halong Bay is governed by the monsoon regime, characterized by a northeast winter monsoon (dry season) and southeast summer monsoon (wet season). During the dry season, atmospheric BC concentrations averaged twice those observed during the wet season. In the sea surface microlayer (SML) and underlying water (ULW), concentrations of particulate BC (PBC) averaged 539 and 11 µmol C L–1, respectively. Dissolved BC (DBC) concentrations averaged 2.6 µmol C L–1 in both the SML and ULW. Seasonal variations indicated that PBC concentration in the SML was controlled by atmospheric deposition during the dry season, while riverine inputs controlled both PBC and DBC concentrations in ULW during the wet season. Spatiotemporal variations of PBC and DBC during the wet season suggest that river runoff was efficient in transporting PBC that had accumulated on land during the dry season, and in mobilizing and transporting DBC to the ocean. The annual river flux of PBC was about 3.8 times higher than that of DBC. The monsoon regime controls BC input to Halong Bay by favoring dry deposition of BC originating from the north during the dry season, and wet deposition and river runoff during the wet season. High PBC concentrations seem to enhance the transfer of organic carbon from dissolved to particulate phase by adsorbing dissolved organic carbon and stimulating aggregation. Such processes may impact the availability and biogeochemical cycling of other dissolved substances, including nutrients, for the coastal marine ecosystem.

Download Full-text

Influence of photochemical aging on light absorption of atmospheric black carbon and aerosol single scattering albedo

10.5194/acp-2018-59 ◽

2018 ◽

Cited By ~ 1

Author(s):

Xuezhe Xu ◽

Weixiong Zhao ◽

Xiaodong Qian ◽

Shuo Wang ◽

Bo Fang ◽

...

Keyword(s):

Growth Rate ◽

Black Carbon ◽

Light Absorption ◽

Radiative Forcing ◽

Single Scattering ◽

Single Scattering Albedo ◽

Rural Site ◽

Absorption Enhancement ◽

Diurnal Variability ◽

Photochemical Aging

Abstract. Coating enhancement of black carbon (BC) light absorption (Eabs) is a large uncertainty in modelling direct radiative forcing (DRF) by BC. Reported Eabs values after atmospheric aging vary widely and the mechanisms responsible for enhancing BC absorption remain elusive. Here, we report on the direct field measurement of size-resolved mixing state, Eabs and aerosol single scattering albedo (SSA) at λ = 532 nm at a rural site in East China from June to July 2016. Strong diurnal variability of Eabs, SSA, and Ox (Ox = NO2 + O3, a proxy for atmospheric photochemical aging) was observed. A three-stage absorption enhancement process for collapsed semispherical to fully compact spherical morphology BC with photochemical aging was suggested. For Ox below 35 ppbv, Eabs increased slowly with Ox mixing ratio and ranged from 2.0 to 2.2 (with a growth rate of ~ 0.03 ppbv−1). Eabs was stable (Eabs = 2.26 ± 0.06) between 35 to 50 ppbv Ox. Thirdly, for Ox levels above 50 ppbv, Eabs grew rapidly from 2.3 to 2.8 (at a growth rate of ~ 0.18 ppbv−1). A method that combined Eabs and SSA was developed to retrieve the fraction contribution of BC absorption (fBC), lensing driven enhancement (fLens), as well as the fractional contribution of coating absorption (fraction absorption contribution (fShell), the coated shell diameter (DShell) and the imaginary part of the complex refractive index (CRI) of the shell (kShell)). Parameterization of Eabs and SSA captures much of the influence of BC coating and the particle absorption, and provides a plausible new method to better constrain the contribution of BC to the DRF. In our measurements at this site, the absorption amplification depended mainly on the coating thickness and the absorption of coating materials. The lensing driven enhancement was reduced by light absorption of the shell. Our observations highlight the crucial role of photochemical processes in modifying the absorption of BC-containing particles. One implication of these findings is that the contribution of light-absorbing organic compounds (Brown carbon, BrC) at longer aging time should be included in climate models.

Download Full-text

Bias in quantification of light absorption enhancement of black carbon aerosol coated with low-volatility brown carbon

Aerosol Science and Technology ◽

10.1080/02786826.2021.1873909 ◽

2021 ◽

pp. 1-18

Author(s):

Nishit Shetty ◽

Payton Beeler ◽

Theodore Paik ◽

Fred J. Brechtel ◽

Rajan K. Chakrabarty

Keyword(s):

Black Carbon ◽

Light Absorption ◽

Absorption Enhancement ◽

Brown Carbon ◽

Black Carbon Aerosol

Download Full-text

Study of Temporal Variations of Equivalent Black Carbon in a Coastal City in Northwest Spain Using an Atmospheric Aerosol Data Management Software

Applied Sciences ◽

10.3390/app11020516 ◽

2021 ◽

Vol 11 (2) ◽

pp. 516

Author(s):

María Piñeiro-Iglesias ◽

Javier Andrade-Garda ◽

Sonia Suárez-Garaboa ◽

Soledad Muniategui-Lorenzo ◽

Purificación López-Mahía ◽

...

Keyword(s):

Data Management ◽

Black Carbon ◽

Light Absorption ◽

Atmospheric Aerosol ◽

Urban Areas ◽

Radiative Properties ◽

Anthropogenic Sources ◽

Biomass Combustion ◽

Management Support ◽

Diurnal Variability

Light-absorbing carbonaceous aerosols (including black carbon (BC)) pose serious health issues and play significant roles in atmospheric radiative properties. Two-year measurements (2015–2016) of aerosol light absorption, combined with measurements of sub-micrometric particles, were continuously conducted in A Coruña (northwest (NW) Spain) to determine their light absorption properties: absorption coefficients (σabs) and the absorption Ångström exponent (AAE). The mean and standard deviation of equivalent black carbon (eBC) during the period of study were 0.85 ± 0.83 µg m−3, which are lower than other values measured in urban areas of Spain and Europe. High eBC concentrations found in winter are associated with an increase in emissions from anthropogenic sources in combination with lower mixing layer heights and frequent stagnant conditions. The pronounced diurnal variability suggests a strong influence from local sources. AAE had an average value of 1.26 ± 0.22 which implies that both fossil fuel combustion and biomass burning influenced optical aerosol properties. This also highlights biomass combustion in suburban areas, where the use of wood for domestic heating is encouraged, as an important source of eBC. All data treatment was gathered using SCALA© as atmospheric aerosol data management support software program.

Download Full-text

Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

Marine and Freshwater Research ◽

10.1071/mf12114 ◽

2012 ◽

Vol 63 (9) ◽

pp. 788 ◽

Cited By ~ 17

Author(s):

N. E. Pettit ◽

T. D. Jardine ◽

S. K. Hamilton ◽

V. Sinnamon ◽

D. Valdez ◽

...

Keyword(s):

Water Quality ◽

Seasonal Changes ◽

Aquatic Macrophyte ◽

Plant Cover ◽

Critical Role ◽

Dry Season ◽

Nutrient Concentrations ◽

Wet Season ◽

Dry Tropics ◽

The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

Download Full-text