The optical properties and in-situ observational evidence for the formation of brown carbon in cloud

Abstract. Atmospheric brown carbon (BrC) makes a substantial contribution to aerosol light-absorbing and thus the global radiative forcing. Although BrC may change the lifetime of the cloud and ultimately affect precipitation, little is known regarding the optical properties and formation of BrC in the cloud. In the present study, the light-absorption properties of cloud droplet residual (cloud RES) were measured by coupled a ground-based counterflow virtual impactor (GCVI) and an Aethalometer (AE-33), in addition to the cloud interstitial (cloud INT) and ambient (cloud-free) particles by PM2.5 inlet-AE-33, at Mt. Tianjing (1690 m a.s.l.), a remote mountain site in southern China, from November to December 2020. Meanwhile, the light-absorption and fluorescence properties of water-soluble organic carbon (WSOC) in the collected cloud water and PM2.5 samples were also obtained, associated with the concentration of water-soluble ions. The mean light-absorption coefficient (Abs370) of the cloud RES, cloud INT, and cloud-free particles were 0.25 ± 0.15, 1.16 ± 1.14, and 1.47 ± 1.23 Mm−1, respectively. The Abs365 of WSOC was 0.11 ± 0.08 Mm−1 in cloud water and 0.40 ± 0.31 Mm−1 in PM2.5, and the corresponding mass absorption efficiency (MAE365) was 0.17 ± 0.07 and 0.31 ± 0.21 m2·g−1, respectively. A comparison of the light-absorption coefficient between BrC in the cloud RES/cloud INT and WSOC in cloud water/PM2.5 indicates a considerable contribution (48–75 %) of water-insoluble BrC to total BrC light-absorption. Secondary BrC estimated by minimum R squared (MRS) method dominated the total BrC in cloud RES (67–85 %), rather than in the cloud-free (11–16 %) and cloud INT (9–23 %) particles. It may indicate the formation of secondary BrC during cloud processing. Supporting evidence includes the enhanced WSOC and dominant contribution of secondary formation/biomass burning factor (> 80 %) to Abs365 in cloud water provided by Positive Matrix Factorization (PMF) analysis. In addition, we showed that the light-absorption of BrC in cloud water was closely related to humic-like substances and tyrosine/proteins-like substances (r > 0.63, p < 0.01), whereas only humic-like substances for PM2.5, as identified by excitation-emission matrix fluorescence spectroscopy.

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The Effect of Carbon Defects in the Coal–Pyrite Vacancy on the Electronic Structure and Optical Properties: A DFT + U Study

Minerals ◽

10.3390/min10090815 ◽

2020 ◽

Vol 10 (9) ◽

pp. 815

Author(s):

Wei Cheng ◽

Chen Cheng ◽

Baolin Ke

Keyword(s):

Optical Properties ◽

Electronic Structure ◽

Absorption Coefficient ◽

Light Absorption ◽

Density Functional ◽

Doping Concentration ◽

Carbon Doping ◽

Photovoltaic Materials ◽

Light Absorption Coefficient ◽

Carbon Impurities

Pyrite is a mineral often associated with coal in coal seams and is a major source of sulfur in coal. Coal–pyrite is widely distributed, easily available, low-cost, and non-toxic, and has high light absorption coefficient. So, it shows potential for various applications. In this paper, the density-functional theory (DFT + U) is used to construct coal–pyrite with carbon doped in the sulfur and iron vacancies of pyrite. The effects of different carbon defects, different carbon doping concentrations, and different doping distributions in the same concentration on the electronic structure and optical properties of coal–pyrite were studied. The results show that the absorption coefficient and reflectivity of coal–pyrite, when its carbon atom substitutes the iron and sulfur atoms in the sulfur and iron vacancies, are significantly higher than those of the perfect pyrite, indicating that coal–pyrite has potential for application in the field of photovoltaic materials. When carbon is doped in the sulfur vacancy, this impurity state reduces the width of the forbidden band; with the increase in the doping concentration, the width of the forbidden band decreases and the visible-light absorption coefficient increases. The distribution of carbon impurities impacts the band gap but has almost no effect on the light absorption coefficient, complex dielectric function, and reflectivity, indicating that the application of coal–pyrite to photovoltaic materials should mainly consider the carbon doping concentration instead of the distribution of carbon impurities. The research results provide a theoretical reference for the application of coal–pyrite in the field of photoelectric materials.

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Measurement Report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China: insights from organic molecular compositions

10.5194/acp-2021-1045 ◽

2022 ◽

Author(s):

Junjun Deng ◽

Hao Ma ◽

Xinfeng Wang ◽

Shujun Zhong ◽

Zhimin Zhang ◽

...

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

North China ◽

Water Soluble ◽

Formation Mechanisms ◽

Chemical Compositions ◽

Brown Carbon ◽

Near Ultraviolet

Abstract. Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) to visible light. However, the optical properties and formation mechanisms of ambient BrC remain poorly understood, limiting the estimation of their radiative forcing. In the present study, fine aerosols (PM2.5) were collected during 2016–2017 on a day/night basis over urban Tianjin, a megacity in North China, to obtain seasonal and diurnal patterns of atmospheric water-soluble BrC. There were obvious seasonal but no evident diurnal variations in light absorption properties of BrC. In winter, BrC showed much stronger light absorbing ability since mass absorption efficiency at 365 nm (MAE365) (1.54 ± 0.33 m2 g−1), which was 1.8 times larger than that (0.84 ± 0.22 m2 g−1) in summer. Direct radiative effects by BrC absorption relative to black carbon in the UV range were 54.3 ± 16.9 % and 44.6 ± 13.9 %, respectively. In addition, five fluorescent components in BrC, including three humic-like fluorophores and two protein-like fluorophores were identified with excitation-emission matrix fluorescence spectrometry and parallel factor (PARAFAC) analysis. The lowly-oxygenated components contributed more to winter and nighttime samples, while more-oxygenated components increased in summer and daytime samples. The higher humification index (HIX) together with lower biological index (BIX) and fluorescence index (FI) suggest that the chemical compositions of BrC were associated with a high aromaticity degree in summer and daytime due to photobleaching. Fluorescent properties indicate that wintertime BrC were predominantly affected by primary emissions and fresh secondary organic aerosol (SOA), while summer ones were more influenced by aging processes. Results of source apportionments using organic molecular compositions of the same set of aerosols reveal that fossil fuel combustion and aging processes, primary bioaerosol emission, biomass burning, and biogenic and anthropogenic SOA formation were the main sources of BrC. Biomass burning contributed much larger to BrC in winter and at nighttime, while biogenic SOA contributed more in summer and at daytime. Especially, our study highlights that primary bioaerosol emission is an important source of BrC in urban Tianjin in summer.

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Contributions of nitrated aromatic compounds to the light absorption of water-soluble and particulate brown carbon in different atmospheric environments in Germany and China

10.5194/acp-2016-647 ◽

2016 ◽

Cited By ~ 2

Author(s):

Monique Teich ◽

Dominik van Pinxteren ◽

Michael Wang ◽

Simonas Kecorius ◽

Zhibin Wang ◽

...

Keyword(s):

Light Absorption ◽

Strong Influence ◽

Water Soluble ◽

Absorption Properties ◽

Brown Carbon ◽

Light Absorption Coefficient ◽

Alkaline Conditions ◽

Acidic Conditions ◽

The Mean ◽

Biogenic Aerosols

Abstract. The relative contribution of eight nitrated aromatic compounds (NACs, nitrophenols + nitrated salicylic acids) to the light absorption of aqueous particle extracts and particulate brown carbon were determined from aerosol particle samples collected in Germany and China. High-volume filter samples were collected during six campaigns, performed at five locations in two seasons: (I) two campaigns with strong influence of biomass burning (BB) aerosol – at the TROPOS institute (winter, 2014, urban background, Leipzig, Germany) and the Melpitz research site (winter, 2014, rural background); (II) two campaigns with strong influence from biogenic emissions – at Melpitz (summer, 2014) and the forest site Waldstein (summer, 2014, Fichtelgebirge, Germany), and (III) two CAREBeijing-NCP campaigns – at Xianghe (summer, 2013, anthropogenic polluted background) and Wangdu (summer, 2014, anthropogenic polluted background with a distinct BB-episode), both in the North China Plain. The filter samples were analyzed for NAC concentrations and the light absorption of aqueous filter extracts was determined. Light absorption properties of particulate brown carbon were derived from a seven-wavelength Aethalometer during the campaigns at TROPOS (winter) and Waldstein (summer). The light absorption of the aqueous filter extracts was found to be pH dependent: at pH 10, the aqueous light absorption coefficient Abs370 and the mass absorption efficiency (MAE370) at 370 nm were a factor of 1.6 and 1.4 larger than at pH 2, respectively. In general, Abs370 ranged from 0.21–21.8 Mm−1 under acidic conditions and 0.63–27.2 Mm−1 under alkaline conditions, over all campaigns. The observed MAE370 was in a range of 0.10–1.79 m2 g−1 and 0.24–2.57 m2 g−1 for acidic and alkaline conditions, respectively. For MAE370 and Abs370, the observed values were higher in winter than in summer, in agreement with other studies. Furthermore, it was found that the MAE370 values in winter in Germany exceeded those of the Chinese summer background stations (average of 0.85±0.24 m2 g−1 compared to 0.47±0.15 m2 g−1). The lowest MAE was observed for the Waldstein (summer) campaign (average of 0.17±0.03 m2 g−1), indicating that freshly emitted biogenic aerosols are only weakly absorbing. In contrast, a strong relationship was found between the light absorption properties and the concentrations of levoglucosan, corroborating findings from other studies. Regarding the particulate light absorption at 370 nm, a mean particulate light absorption coefficient babs,370 of 54 Mm−1 and 6.0 Mm−1 was determined for the TROPOS (winter) and Waldstein (summer) campaigns, respectively, with average contributions of particulate brown carbon to babs,370 of 46 % at TROPOS (winter) and 15 % at Waldstein (summer). The absorption Ångström exponent of the ambient aerosol during the campaigns at TROPOS (winter) and Waldstein (summer) was found to be 1.5±0.1 and 1.2±0.3, respectively. Thus, the Aethalometer measurements support the findings from aqueous filter extracts of only weakly absorbing biogenic aerosols in comparison to the more polluted and BB influenced aerosol at TROPOS (winter). The mean contribution of NACs to the aqueous extract light absorption over all campaigns ranged from 0.10 %–1.25 % under acidic conditions and 0.13 %–3.71 % under alkaline conditions. The high variability among the measurement sites showed that the emission strengths of light absorbing compounds and the composition of brown carbon were very different for each site. The mean contribution of NACs to the particulate brown carbon light absorption was 0.10±0.06 % (acidic conditions) and 0.13±0.09 % (alkaline conditions) during the Waldstein (summer) campaign and 0.25±0.21 % (acidic conditions) and 1.13±1.03 % (alkaline conditions) during the TROPOS (winter) campaign. A correlation of NAC concentrations with Abs370 was observed for the BB-influenced campaigns at TROPOS (winter) and Melpitz (winter). The average contribution of NACs to the aqueous extract light absorption over all campaigns was found to be 5 times higher than their mass contribution to water-soluble organic carbon indicating that even small amounts of light-absorbing compounds can have a disproportionately high impact on the light absorption properties of particles.

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Spectral bio-optical properties of water of Atlantic sector of Antarctic

Marine Biological Journal ◽

10.21072/mbj.2020.05.4.06 ◽

2020 ◽

Vol 5 (4) ◽

pp. 69-78

Author(s):

N. A. Moiseeva ◽

T. Ya. Churilova ◽

T. V. Efimova ◽

V. A. Artemiev ◽

E. Yu. Skorokhod

Keyword(s):

Organic Matter ◽

Optical Properties ◽

Dissolved Organic Matter ◽

Absorption Coefficient ◽

Chlorophyll A ◽

Light Absorption ◽

Colored Dissolved Organic Matter ◽

Atlantic Sector ◽

Light Absorption Coefficient ◽

The Relationship

Studies of variability of spectral bio-optical properties of water of Atlantic sector of Antarctic were carried out during the 79th cruise of the RV “Akademik Mstislav Keldysh” (11.01.2020–04.02.2020). Chlorophyll a and phaeopigment concentration varied in the layer studied from 0.1 to 1.8 mg·m−3, except for two stations with content reaching 2.2 and 4.4 mg·m−3. The relationship was revealed between light absorption coefficient by phytoplankton and chlorophyll a concentration at a wavelength, corresponding to spectrum maxima: aph(438) = 0.044 × Ca1.2, r2 = 0.84 (n = 117); aph(678) = 0.021 × Ca1.1, r2 = 0.89 (n = 117). Spectral distribution of light absorption coefficient by non-algal particles and colored dissolved organic matter was described by exponential function. Absorption parameterization coefficients were retrieved: (1) light absorption coefficient by non-algal particles (0.001–0.027 m−1) and by colored dissolved organic matter (0.016–0.19 m−1) at a wavelength of 438 nm; (2) spectral slope coefficients of these components (0.005–0.016 and 0.009–0.022 nm−1, respectively).

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Contributions of nitrated aromatic compounds to the light absorption of water-soluble and particulate brown carbon in different atmospheric environments in Germany and China

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-1653-2017 ◽

2017 ◽

Vol 17 (3) ◽

pp. 1653-1672 ◽

Cited By ~ 58

Author(s):

Monique Teich ◽

Dominik van Pinxteren ◽

Michael Wang ◽

Simonas Kecorius ◽

Zhibin Wang ◽

...

Keyword(s):

Light Absorption ◽

Strong Influence ◽

Water Soluble ◽

Absorption Properties ◽

Brown Carbon ◽

Light Absorption Coefficient ◽

Alkaline Conditions ◽

Acidic Conditions ◽

The Mean ◽

Biogenic Aerosols

Abstract. The relative contributions of eight nitrated aromatic compounds (NACs: nitrophenols and nitrated salicylic acids) to the light absorption of aqueous particle extracts and particulate brown carbon were determined from aerosol particle samples collected in Germany and China.High-volume filter samples were collected during six campaigns, performed at five locations in two seasons: (I) two campaigns with strong influence of biomass-burning (BB) aerosol at the TROPOS institute (winter, 2014, urban background, Leipzig, Germany) and the Melpitz research site (winter, 2014, rural background); (II) two campaigns with strong influence from biogenic emissions at Melpitz (summer, 2014) and the forest site Waldstein (summer, 2014, Fichtelgebirge, Germany); and (III) two CAREBeijing-NCP campaigns at Xianghe (summer, 2013, anthropogenic polluted background) and Wangdu (summer, 2014, anthropogenic polluted background with a distinct BB episode), both in the North China Plain. The filter samples were analyzed for NAC concentrations and the light absorption of aqueous filter extracts was determined. Light absorption properties of particulate brown carbon were derived from a seven-wavelength aethalometer during the campaigns at TROPOS (winter) and Waldstein (summer). The light absorption of the aqueous filter extracts was found to be pH dependent, with larger values at higher pH. In general, the aqueous light absorption coefficient (Abs370) ranged from 0.21 to 21.8 Mm−1 under acidic conditions and 0.63 to 27.2 Mm−1 under alkaline conditions, over all campaigns. The observed mass absorption efficiency (MAE370) was in a range of 0.10–1.79 m2 g−1 and 0.24–2.57 m2 g−1 for acidic and alkaline conditions, respectively. For MAE370 and Abs370, the observed values were higher in winter than in summer, in agreement with other studies. The lowest MAE was observed for the Waldstein (summer) campaign (average of 0.17 ± 0.03 m2 g−1), indicating that freshly emitted biogenic aerosols are only weakly absorbing. In contrast, a strong relationship was found between the light absorption properties and the concentrations of levoglucosan, corroborating findings from other studies. Regarding the particulate light absorption at 370 nm, a mean particulate light absorption coefficient babs, 370 of 54 Mm−1 and 6.0 Mm−1 was determined for the TROPOS (winter) and Waldstein (summer) campaigns, respectively, with average contributions of particulate brown carbon to babs, 370 of 46 % at TROPOS (winter) and 15 % at Waldstein (summer). Thus, the aethalometer measurements support the findings from aqueous filter extracts of only weakly absorbing biogenic aerosols in comparison to the more polluted and BB influenced aerosol at TROPOS (winter). The mean contribution of NACs to the aqueous extract light absorption over all campaigns ranged from 0.10 to 1.25 % under acidic conditions and 0.13 to 3.71 % under alkaline conditions. The high variability among the measurement sites showed that the emission strengths of light-absorbing compounds and the composition of brown carbon were very different for each site. The mean contribution of NACs to the particulate brown carbon light absorption was 0.10 ± 0.06 % (acidic conditions) and 0.13 ± 0.09 % (alkaline conditions) during the Waldstein (summer) campaign and 0.25 ± 0.21 % (acidic conditions) and 1.13 ± 1.03 % (alkaline conditions) during the TROPOS (winter) campaign. The average contribution of NACs to the aqueous extract light absorption over all campaigns was found to be 5 times higher than their mass contribution to water-soluble organic carbon indicating that even small amounts of light-absorbing compounds can have a disproportionately high impact on the light absorption properties of particles.

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Optical properties of elemental carbon and water-soluble organic carbon in Beijing, China

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-6221-2011 ◽

2011 ◽

Vol 11 (2) ◽

pp. 6221-6258

Author(s):

Y. Cheng ◽

K.-B. He ◽

M. Zheng ◽

F.-K. Duan ◽

Y.-L. Ma ◽

...

Keyword(s):

Optical Properties ◽

Organic Carbon ◽

Biomass Burning ◽

Light Absorption ◽

Elemental Carbon ◽

Water Soluble ◽

Brown Carbon ◽

Sulphate Concentration ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

Abstract. The mass absorption cross-section (MAC) of elemental carbon (EC) in Beijing was quantified using a thermal-optical carbon analyzer and the influences of mixing state and sources of carbonaceous aerosol were investigated. The MAC measured at 632 nm was 29.0 and 32.0 m2 g−1 during winter and summer respectively. MAC correlated well with the organic carbon (OC) to EC ratio (R2 = 0.91) which includes important information about the extent of secondary organic aerosol (SOA) production, indicating the enhancement of MAC by coating with SOA. The extrapolated MAC value was 10.5 m2 g−1 when the OC to EC ratio is zero, which was 5.6 m2 g−1 after correction by the enhancement factor (1.87) caused by the artifacts associated with the "filter-based" methods. The MAC also increased with sulphate (R2 = 0.84) when the sulphate concentration was below 10 μg m−3, whereas MAC and sulphate were only weekly related when the sulphate concentration was above 10 μg m−3, indicating the MAC of EC was also enhanced by coating with sulphate. Based on a converting approach that accounts for the discrepancy caused by measurements methods of both light absorption and EC concentration, previously published MAC values were converted to the "equivalent MAC", which is the estimated value if using the same measurement methods as used in this study. The "equivalent MAC" was found to be much lower in the regions heavily impacted by biomass burning (e.g., India), probably due to the influence of brown carbon. Optical properties of water-soluble organic carbon (WSOC) in Beijing were also presented. Light absorption by WSOC exhibited strong wavelength (λ) dependence such that absorption varied approximately as λ−7, which was characteristic of the brown carbon spectra. The mass absorption efficiency (σabs) of WSOC (measured at 365 nm) was 1.83 and 0.70 m2 g−1 during winter and summer respectively. The seasonal pattern of σabs was attributed to the difference in the precursors of SOA, because WSOC in Beijing has been demonstrated to be strongly linked to SOA. Moreover, the σabs of WSOC in Beijing was much higher than results from the southeastern United States which were obtained using the same method as used in this study, perhaps due to the influence of biomass burning.

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Reciprocating internal combustion compression-ignition engines. Apparatus for measurement of the opacity and for determination of the light absorption coefficient of exhaust gas

10.3403/01927221u ◽

2015 ◽

Keyword(s):

Absorption Coefficient ◽

Light Absorption ◽

Internal Combustion ◽

Exhaust Gas ◽

Compression Ignition ◽

Compression Ignition Engines ◽

Light Absorption Coefficient

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Particulate light absorption and the prediction of phytoplankton biomass and planktonic metabolism in northeastern Spanish aquatic ecosystems

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f99-184 ◽

2000 ◽

Vol 57 (1) ◽

pp. 25-33 ◽

Cited By ~ 2

Author(s):

C M Duarte ◽

S Agustí ◽

J Kalff

Keyword(s):

Absorption Coefficient ◽

Light Absorption ◽

Aquatic Ecosystems ◽

Coastal Lagoons ◽

Strong Relationship ◽

Community Respiration ◽

Chl A ◽

Light Absorption Coefficient ◽

Alpine Rivers ◽

Detrital Particles

Examination of particulate light absorption and microplankton metabolism in 36 northeastern Spanish aquatic ecosystems, ranging from alpine rivers to inland saline lakes and the open Mediterranean Sea, revealed the existence of general relationships between particulate light absorption and the biomass of phytoplankton and microplankton metabolism. The particulate absorption spectra reflected a dominance of nonphotosynthetic, likely detrital, particles in rivers and a dominance of phytoplankton in coastal lagoons. There was a strong relationship between the light absorbed by phytoplankton and the chlorophyll a (Chl a) concentration of the systems, which indicated an average (±SE) Chl a specific absorption coefficient of 0.0233 ± 0.0020 m2·mg Chl a-1 for these widely diverse systems. Chl a concentration was a weaker predictor of the total particulate light absorption coefficient, pointing to an important role of nonphytoplanktonic particles in light absorption. Gross production was very closely related to the light absorption coefficient of phytoplankton, whereas community respiration was strongly correlated with the total particulate light absorption coefficient, indicating the optical signatures of sestonic particles to be reliable predictors of planktonic biomass and metabolism in aquatic ecosystems.

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