scholarly journals The effects of isoprene and NO<sub><i>x</i></sub> on secondary organic aerosols formed through reversible and irreversible uptake to aerosol water

2017 ◽  
Author(s):  
Marwa M. H. El-Sayed ◽  
Diana L. Ortiz-Montalvo ◽  
Christopher J. Hennigan
Keyword(s):  
Secondary Organic Aerosols ◽  
Time Lag ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Oxidation Products ◽  
Eastern United States ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Isoprene Oxidation ◽  
Organic Gases

Abstract. Isoprene oxidation produces water-soluble organic gases capable of partitioning to aerosol liquid water. The formation of secondary organic aerosols through such aqueous pathways (aqSOA) can take place either reversibly or irreversibly; however, the split between these fractions in the atmosphere is highly uncertain. The aim of this study was to characterize the reversibility of aqSOA formed from isoprene at a location in the eastern United States under substantial influence from both anthropogenic and biogenic emissions. The reversible and irreversible uptake of water-soluble organic gases to aerosol water was characterized in Baltimore, MD using measurements of particulate water-soluble organic carbon (WSOCp) in alternating dry and ambient configurations. WSOCp evaporation with drying was observed systematically throughout the late spring and summer, indicating reversible aqSOA formation during these times. We show through time lag analyses that WSOCp concentrations, including the WSOCp that evaporates with drying, peak ~ 6–11 h after isoprene concentrations, with maxima at a time lag of 9 h. The absolute reversible aqSOA concentrations, as well as the relative amount of reversible aqSOA, increased with decreasing NOx/isoprene ratios, suggesting that isoprene epoxydiol (IEPOX) or other low-NOx oxidation products were responsible for these effects. The observed relationships with NOx and isoprene suggest that this process occurs widely in the atmosphere, and is likely more important in other locations characterized by higher isoprene and/or lower NOx levels. It is also likely that this phenomenon will increase in importance in the future, given predictions of biogenic and anthropogenic emissions under future regulatory and climate scenarios.

scholarly journals The effects of isoprene and NO<sub><i>x</i></sub> on secondary organic aerosols formed through reversible and irreversible uptake to aerosol water

2018 ◽  
Vol 18 (2) ◽  
pp. 1171-1184 ◽  
Author(s):  
Marwa M. H. El-Sayed ◽  
Diana L. Ortiz-Montalvo ◽  
Christopher J. Hennigan
Keyword(s):  
Secondary Organic Aerosols ◽  
Time Lag ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Oxidation Products ◽  
Eastern United States ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Isoprene Oxidation ◽  
Organic Gases

Abstract. Isoprene oxidation produces water-soluble organic gases capable of partitioning to aerosol liquid water. The formation of secondary organic aerosols through such aqueous pathways (aqSOA) can take place either reversibly or irreversibly; however, the split between these fractions in the atmosphere is highly uncertain. The aim of this study was to characterize the reversibility of aqSOA formed from isoprene at a location in the eastern United States under substantial influence from both anthropogenic and biogenic emissions. The reversible and irreversible uptake of water-soluble organic gases to aerosol water was characterized in Baltimore, Maryland, USA, using measurements of particulate water-soluble organic carbon (WSOCp) in alternating dry and ambient configurations. WSOCp evaporation with drying was observed systematically throughout the late spring and summer, indicating reversible aqSOA formation during these times. We show through time lag analyses that WSOCp concentrations, including the WSOCp that evaporates with drying, peak 6 to 11 h after isoprene concentrations, with maxima at a time lag of 9 h. The absolute reversible aqSOA concentrations, as well as the relative amount of reversible aqSOA, increased with decreasing NOx ∕ isoprene ratios, suggesting that isoprene epoxydiol (IEPOX) or other low-NOx oxidation products may be responsible for these effects. The observed relationships with NOx and isoprene suggest that this process occurs widely in the atmosphere, and is likely more important in other locations characterized by higher isoprene and/or lower NOx levels. This work underscores the importance of accounting for both reversible and irreversible uptake of isoprene oxidation products to aqueous particles.

scholarly journals Organic Molecular Tracers in PM2.5 at Urban Sites during Spring and Summer in Japan: Impact of Secondary Organic Aerosols on Water-Soluble Organic Carbon

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 579
Author(s):  
Fumikazu Ikemori ◽  
Rie Nishimura ◽  
Shinji Saito ◽  
Masayuki Akiyama ◽  
Shigekazu Yamamoto ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Urban Areas ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Gas Chromatography Mass Spectrometry ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Molecular Tracers ◽  
Urban Sites

To understand the characteristics of secondary organic aerosols (SOAs) and estimate their impact on water-soluble organic carbon (WSOC) in urban areas in Japan, we measured 17 organic tracers using gas chromatography–mass spectrometry from particulate matter with an aerodynamic diameter smaller than 2.5 μm collected at five urban sites in Japan during spring and summer. Most anthropogenic, monoterpene-derived, and isoprene-derived SOA tracers showed meaningful correlations with potential ozone in both these seasons. These results indicate that oxidants play an important role in SOAs produced during both seasons in urban cities in Japan. WSOC was significantly affected by anthropogenic and monoterpene-derived SOAs during spring and three SOA groups during summer at most of the sites sampled. The total estimated secondary organic carbons (SOCs), including mono-aromatic, di-aromatic, monoterpene-derived, and isoprene-derived SOCs, could explain the WSOC fractions of 39–63% in spring and 46–54% in summer at each site. Notably, monoterpene-derived and mono-aromatic SOCs accounted for most of the total estimated SOCs in both spring (85–93%) and summer (75–82%) at each site. These results indicate that SOAs significantly impact WSOC concentrations during both these seasons at urban sites in Japan.

scholarly journals Significant Seasonal Change in Optical Properties by atmospheric humic-like substances (HULIS) in Water-Soluble Organic Carbon Aerosols

2017 ◽  
Author(s):  
Heejun Han ◽  
Guebuem Kim
Keyword(s):  
Optical Properties ◽  
Organic Carbon ◽  
Uv Radiation ◽  
Dominant Role ◽  
Critical Role ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Photochemical Degradation ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon

Abstract. Atmospheric humic-like substance (HULIS) is an important fraction of water-soluble organic carbon (WSOC) accounting for the light-absorbing properties of organic aerosols. HULIS is responsible for light-absorbing properties of organic aerosols in the atmosphere. Although various sources of HULIS have been studied extensively, its sinks are poorly constrained. In this study, we found seasonal changes in the optical and chemical characteristics of HULIS and WSOC, which are decreased by approximately 80 % and 30 %, respectively, from the cold season (Oct–Jan) to the warm season (Jun–Sep) due to enhanced solar ultraviolet (UV) radiation. The dominant role of photochemical degradation on light-absorbing organic aerosols, as a sink of HULIS, was further confirmed based on a laboratory experiment by evaluating impact of UV radiation on the optical properties of HULIS and WSOC contents. Our results suggest that seasonal variation of HULIS in WSOC is resulted mainly by photo-induced degradation in the atmosphere. Thus, photochemical degradation of HULIS seems to play a critical role on seasonal variations in the light-absorbing properties of organic aerosols as well as the biogeochemical impact of WSOC on Earth’s surface.

scholarly journals Gas-particle partitioning of polyol tracers in the western Yangtze River Delta, China: Absorptive or Henry's law partitioning?

2021 ◽  
Author(s):  
Chao Qin ◽  
Yafeng Gou ◽  
Yuhang Wang ◽  
Yuhao Mao ◽  
Hong Liao ◽  
...  
Keyword(s):  
Yangtze River ◽  
Organic Aerosols ◽  
Yangtze River Delta ◽  
Water Soluble ◽  
Oxidation Products ◽  
Particle Phase ◽  
Henry's Law ◽  
Henry’S Law ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. Gas-particle partitioning of water-soluble organic compounds plays a significant role in the formation and source apportionment of organic aerosols, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9–99.8 %), and their average particle-phase fractions were not strictly dependent on vapor pressures. Moreover, the measurement-based partitioning coefficients (Kp,OM) of isoprene oxidation products and levoglucosan were 102 to 104 times larger than their predicted Kp,OM based on the equilibrium absorptive partitioning model. These are likely attributed to the hygroscopic properties of polyol tracers and high aerosol liquid water (ALW) concentrations (~20 µg m−3) of the study location. Due to the large gaps (up to 107) between measurement-based effective Henry's law coefficients (KH,e) and predicted values in pure water (KH,w), the gas-particle partitioning of polyol tracers could not be depicted using Henry's law alone either. The regressions of log (KH,w/KH,e) versus molality of major water-soluble components in ALW indicated that sulfate ions (salting-in effect) and water-soluble organic carbon can promote the partitioning of polyol tracers into the aqueous phase. These results suggest a partitioning mechanism of enhanced aqueous-phase uptake for polyol tracers, which partly reveals the discrepancy between observation and modeling of secondary organic aerosols.

scholarly journals Gas–particle partitioning of polyol tracers at a suburban site in Nanjing, east China: increased partitioning to the particle phase

2021 ◽  
Vol 21 (15) ◽  
pp. 12141-12153
Author(s):  
Chao Qin ◽  
Yafeng Gou ◽  
Yuhang Wang ◽  
Yuhao Mao ◽  
Hong Liao ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Oxidation Products ◽  
East China ◽  
Particle Phase ◽  
Isoprene Oxidation ◽  
Predicted Values ◽  
Suburban Site ◽  
Isoprene Oxidation Products

Abstract. Gas–particle partitioning of water-soluble organic compounds plays a significant role in influencing the formation, transport, and lifetime of organic aerosols in the atmosphere, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9 %–99.8 %). Given the uncertainties in measurements and vapor pressure predictions, a dependence of particle-phase fractions on vapor pressures cannot be determined. To explore the impact of aerosol liquid water on gas–particle partitioning of polyol tracers, three partitioning schemes (Cases 1–3) were proposed based on equilibriums of gas vs. organic and aqueous phases in aerosols. If particulate organic matter (OM) is presumed as the only absorbing phase (Case 1), the measurement-based absorptive partitioning coefficients (Kp,OMm) of isoprene oxidation products and levoglucosan were more than 10 times greater than predicted values (Kp,OMt). The agreement between Kp,OMm and Kp,OMt was substantially improved when solubility in a separate aqueous phase was included, whenever water-soluble and water-insoluble OM partitioned into separate (Case 2) or single (Case 3) liquid phases, suggesting that the partitioning of polyol tracers into the aqueous phase in aerosols should not be ignored. The measurement-based effective Henry's law coefficients (KH,em) of polyol tracers were orders of magnitude higher than their predicted values in pure water (KH,wt). Due to the moderate correlations between log⁡(KH,em/KH,wt) and molality of sulfate ions, the gap between KH,em and KH,wt of polyol tracers could not be fully parameterized by the equation defining “salting-in” effects and might be ascribed to mechanisms of reactive uptake, aqueous phase reaction, “like-dissolves-like” principle, etc. These study results also partly reveal the discrepancy between observation and modeling of organic aerosols.

scholarly journals Desiccation time and rainfall control gaseous carbon fluxes in an intermittent stream

2021 ◽  
Author(s):  
Maria Isabel Arce ◽  
Mia M. Bengtsson ◽  
Daniel von Schiller ◽  
Dominik Zak ◽  
Jana Täumer ◽  
...  
Keyword(s):  
Water Soluble ◽  
Intermittent Flow ◽  
Dry Period ◽  
Intermittent Stream ◽  
Aerobic Activity ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Microbial C ◽  
Global Biogeochemical Cycles ◽  
The Impact

AbstractDroughts are recognized to impact global biogeochemical cycles. However, the implication of desiccation on in-stream carbon (C) cycling is not well understood yet. We subjected sediments from a lowland, organic rich intermittent stream to experimental desiccation over a 9-week-period to investigate temporal changes in microbial functional traits in relation to their redox requirements, carbon dioxide (CO2) and methane (CH4) fluxes and water-soluble organic carbon (WSOC). Concurrently, the implications of rewetting by simulated short rainfalls (4 and 21 mm) on gaseous C fluxes were tested. Early desiccation triggered dynamic fluxes of CO2 and CH4 with peak values of 383 and 30 mg C m−2 h−1 (mean ± SD), respectively, likely in response to enhanced aerobic mineralization and accelerated evasion. At longer desiccation, CH4 dropped abruptly, likely because of reduced abundance of anaerobic microbial traits. The CO2 fluxes ceased later, suggesting aerobic activity was constrained only by extended desiccation over time. We found that rainfall boosted fluxes of CO2, which were modulated by rainfall size and the preceding desiccation time. Desiccation also reduced the amount of WSOC and the proportion of labile compounds leaching from sediment. It remains questionable to which extent changes of the sediment C pool are influenced by respiration processes, microbial C uptake and cell lysis due to drying-rewetting cycles. We highlight that the severity of the dry period, which is controlled by its duration and the presence of precipitation events, needs detailed consideration to estimate the impact of intermittent flow on global riverine C fluxes.

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