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Accurate Quantification of Multifunctional C_2–3 Organosulfates in Atmospheric Aerosols Using Liquid Chromatography-Electrospray Ionization Mass Spectrometry: Overcoming Matrix Effects and Underestimation Shumin Liang, Yuchen Wang, Hanzhe Chen, Wan Chan, and Jian Zhen Yu Environmental Science & Technology, 2025, 59, 25, 12812-12821. Link>>
	RPLC Significantly Underestimates Polar C_2–3 Organosulfates, with measurement bias of 1–2 orders of magnitude observed due to strong matrix effects and poor retention in PM analysis. HILIC-ESI-MS Offers Superior Retention and Accuracy, as hydrophilic interaction chromatography overcomes matrix suppression, enabling accurate quantification of multifunctional organosulfates. Improved method reveals six previously undetected C_2–3 Organosulfates, expanding our understanding of isoprene oxidation products.

Ambient Measurements of Daytime Decay Rates of Levoglucosan, Mannosan, and Galactosan Qiongqiong Wang, Shan Wang, Hanzhe Chen, Zijing Zhang, Huan Yu, Man Nin Chan, and Jian Zhen Yu Journal of Geophysical Research - Atmosphere, 2025, 130, 8, e2024JD042423. Link>>
	Bihourly measurements of levoglucosan, mannosan, and galactosan allowed first-time calculation of their decay rates under ambient conditions The estimated daytime lifetime of levoglucosan was 13±7 hr under the varying atmospheric conditions encountered in this study The decay rates of mannosan and galactosan were 34% and 40% higher than that of levoglucosan

Nitrogen Dominates Global Atmospheric Organic Aerosol Absorption Yumin Li, Tsung-May Fu, Jian Zhen Yu, Aoxing Zhang, Xu Yu, Jianhuai Ye, Lei Zhu, Huizhong Shen, Chen Wang, Xin Yang, Shu Tao, Qi Chen, Ying Li, Lei Li, Huizheng Che, Colette L. Heald Science, 2025, 387, 6737, 989-995. Link1>> Link2>>
	BrN contributes 76% of organic aerosol (OA) light absorption over the U.S. and 61% globally, with biomass burning as the largest source. BrN's absorptive capacity decreases significantly with aging, with variability driven by seasonal and spatial factors. BrN accounts for 18% of the global absorptive direct radiative effect of carbonaceous aerosols, with a mean radiative forcing of 0.034 W/m². The study provides a nitrogen-focused approach to assessing the climate impacts of OAs, emphasizing the role of BrN's chemical evolution and its contribution to radiative absorption.

An Online Instrument for Assessing Oxidative Potential of Ambient Particulate Matter via Dithiothreitol Assay, using Particle-Into-LIquid Sampler (PILS) coupled with Improved Light Absorption Measurement Hanzhe Chen and Jian Zhen Yu Atmospheric Environment, 2025, 343, 120980. Link>>
	Developed an online system for hourly OP measurement by the acellular DTT assay. The system features a simple and cost-effective design in flow cell and light source. The detection module is tailored to attain high precision absorption measurements. Field deployment shows high detection capability of OP for PM_2.5 down to a few micrograms per cubic meter. Field test demonstrates the system's ability to capture dynamic OP variations.

New Analytical Paradigm to Determine Concentration of Brown Carbon and Its Sample-by-Sample Mass Absorption Efficiency Kezheng Liao, Yuk Ying Cheng, Sui Shing Yea, L. -W. Antony Chen, John H. Seinfeld, and Jian Zhen Yu Environmental Science & Technology, 2024, 58, 39, 17386-17395. Link>>
	The study introduces a Bayesian inference (BI) model to resolve concentrations of brown carbon (BrC), black carbon (BC), and white carbon (WtC), along with BrC's mass absorption efficiency (MAE) and absorption Ångström exponent (AAE) on a sample-by-sample basis. The BI model enables the first-time observation of diel variations in BrC's MAE, revealing darkening-bleaching transitions influenced by solar irradiance and nitrogen oxide (NO_x) concentrations. Compared to previous methods, the BI model provides more accurate BrC MAE estimates and resolves its variability with high temporal resolution, enhancing understanding of BrC's photochemical transformations. The method facilitates large-scale, high-resolution data collection for BrC, improving its representation in climate models and advancing the understanding of its radiative effects and atmospheric aging processes.

Tracking Source Variations of Inhalation Cancer Risks in Hong Kong, China over Two Decades (2000–2020) Using Toxic Air Pollutant Monitoring Data Yee Ka Wong, Wai Wai Chan, Dasa Gu, Jian Zhen Yu, and Alexis K. H. Lau Environment & Health, 2024, 2, 6, 411-421. Link>>
	Between 2000 and 2020, ICRs in Hong Kong decreased by 73%, primarily due to reductions in diesel particulate matter (DPM), VOCs from solvent/gasoline sources, and coal/biomass combustion-related pollutants, highlighting the effectiveness of air pollution control measures. While DPM risks declined, VOCs from industry and halogenated solvents became the largest non-DPM ICR contributors by 2016–2020, emphasizing the need for targeted control of industrial emissions. OFP contributions shifted from solvent/gasoline dominance in 2000 to a more even distribution among multiple VOC and carbonyl sources by 2020, complicating prioritization for ozone mitigation strategies. A pan-Greater Bay Area TAP monitoring network is proposed to better track toxic air pollutants, assess regional health risks, and guide effective air quality management strategies for Hong Kong and neighboring regions.

New Measurements Reveal a Large Contribution of Nitrogenous Molecules to Ambient Organic Aerosol Xu Yu, Qianfeng Li, Kezheng Liao, Yumin Li, Xinming Wang, Yang Zhou, Yongmei Liang, and Jian Zhen Yu npj Climate and Atmospheric Science, 2024, 7, 72. Link1>> Link 2>>
	Nitrogen-containing organic molecules are estimated to contribute 37–50% of total organic aerosols (OA), with a 95% confidence interval of [12%, 94%], revealing their substantial presence in atmospheric particles. Biomass burning (21–24%) and secondary formation (~30%) are the dominant sources of ON, with primary biological aerosols contributing significantly in non-urban areas (7–18%). Higher ON levels were observed in northern China compared to southern China, while urban environments showed slightly elevated ON concentrations compared to suburban/rural areas. Biomass burning dominated during winter, while secondary processes were prominent year-round. The study highlights the underappreciated role of nitrogen in OA chemistry and emphasizes the need to integrate ON measurements with molecular speciation to improve modeling of nitrogen cycles and environmental impacts.

Unambiguous Analysis and Systematic Mapping of Oxygenated Aromatic Compounds in Atmospheric Aerosols Using Ultrahigh-Resolution Mass Spectrometry Xiao He, X. H. Hilda Huang, Yingge Ma, Cheng Huang, and Jian Zhen Yu Analytical Chemistry, 2024, 96, 5, 1880-1889. Link>>
	A novel multidimensional Kendrick mass defect (KMD) framework was developed for systematically mapping mono- and dioxygenated aromatic compounds (CHO1 and CHO2) in atmospheric organic aerosols (OAs), enhancing the understanding of their molecular structures and functional groups. Ultrahigh-resolution mass spectrometry (UHRMS) detected over 150 unique CHO1 and CHO2 formulas in ambient and biomass burning (BB) aerosols, revealing significant chemical transformations and secondary formation in ambient samples compared to BB sources. The study revealed a higher abundance of oxidized oxygen- and nitrogen-containing species in ambient aerosols, with BB contributing nitrogen-rich compounds and condensed aromatic structures linked to light absorption. The framework enables detailed analysis of toxic oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs), providing critical insights into their environmental behavior, health risks, and potential control strategies for air quality management.

Concurrent Measurements of Nitrate at Urban and Suburban Sites Identify Local Nitrate Formation as a Driver for Urban Episodic PM_2.5 Pollution Jinjian Li, Simon C.H. Ho, Stephen M. Griffith, Yeqi Huang, Rico K.Y. Cheung, Mattias Hallquist, Åsa M. Hallquist, Peter K.K. Louie, Jimmy C.H. Fung, Alexis K.H. Lau, and Jian Zhen Yu Science of the Total Environment, 2023, 897, 165351. Link>>
	PM_2.5 NO₃⁻ formation concurrently probed at urban and suburban sites in Hong Kong. 91% (urban) and 76% (suburban) of the measurement periods were ammonium-rich. Consistently higher NO₃⁻ at the urban site was attributed to local NO_x oxidation. Local NO₃⁻ formation contributed significantly to elevated PM_2.5 at the urban site.

Bayesian Inference Approach to Quantify Primary and Secondary Organic Carbon in Fine Particulate Matter Using Major Species Measurements Kezheng Liao, Qiongqiong Wang, Shan Wang, and Jian Zhen Yu Environmental Science & Technology, 2023, 57, 13, 5169-5179. Link>>
	A novel Bayesian Inference (BI) approach was developed to accurately quantify primary organic carbon (POC) and secondary organic carbon (SOC) in fine particulate matter (PM_2.5) using only major species data (e.g., OC, EC, sulfate), outperforming traditional methods such as EC-tracer and multiple linear regression (MLR). The BI model demonstrated superior accuracy in estimating POC and SOC levels, with the BI-SO4 model (using sulfate as a SOC tracer) yielding the best results in two case studies: the Pearl River Delta (2012) and Dianshan Lake (2019). The BI method relies on commonly available measurements, making it a valuable tool for assessing PM_2.5 sources, evaluating atmospheric aging processes, and improving regional emission inventories. By providing more reliable estimates of POC and SOC, the BI approach facilitates better evaluation of PM-related environmental impacts, aiding climate and air quality research and policy development.

Large Presence of Bromine and Toxic Metals in Ambient Fine Particles from Urban Fires Tao Li, Hanzhe Chen, Jimmy C. H. Fung, Damgy H. L. Chan, Alfred L. C. Yu, Kenneth K. M. Leung, and Jian Zhen Yu Atmospheric Environment, 2023, 295, 119554. Link>>
	Hourly element data in PM_2.5 at five sites in Hong Kong revealed impacts of urban fires. Large co-emissions of Br, Pb, and other toxic metals from urban fires were observed. Urban fire-impacted PM_2.5 had much higher enrichment of Pb–Zn–Cu–Br–Cl than hill fires. Brominated synthetic chemicals likely facilitated mobilization of toxic metals during fires.

Measurement Report: Ten-year Trend of PM_2.5 Major Components and Source Tracers from 2008 to 2017 in an Urban Site of Hong Kong, China Wing Sze Chow, Kezheng Liao, X. H. Hilda Huang, Ka Fung Leung, Alexis K. H. Lau, and Jian Zhen Yu Atmospheric Chemistry & Physics, 2022, 22, 11557-11577. Link>>
	This research provides a comprehensive 10-year analysis (2008–2017) of PM_2.5 chemical composition and source tracers in Hong Kong, offering critical insights into the effectiveness of air quality control measures. It highlights the significant reductions in PM_2.5 components due to targeted policies, such as vehicular emission controls (hopanes: −75%, EC: −60%) and shipping regulations (~35% reduction in vanadium and nickel). The study underscores the need to address persistent sources like biomass burning and regional industrial emissions, which showed slower progress after 2015. Additionally, it emphasizes the role of meteorology (e.g., La Niña events) in influencing pollutant levels, guiding future policy and research.

Hourly Organic Tracers-based Source Apportionment of PM_2.5 before and during the Covid-19 Lockdown in Suburban Shanghai, China: Insights into Regional Transport Influences and Response to Urban Emission Reductions Shan Wang, Qiongqiong Wang, Shuhui Zhu, Min Zhou, Liping Qiao, Dandan Huang, Yingge Ma, Yiqun Lu, Cheng Huang, Qingyan Fu, Yusen Duan, and Jian Zhen Yu Atmospheric Environment, 2022, 289, 119308. Link>>
	Covid lockdown lowered PM_2.5 and NOx while increased O₃ levels in suburban Shanghai. Nitrate was the most prominent contributor to PM_2.5 reduction during lockdown. Lockdown led to reduced PM_2.5 contributions by eight primary and five secondary sources. Contribution percent drop from industrial and vehicular sources were as high as 87%. Lockdown effects on SOA formation likely differ in suburban and urban environments.

Online Measurement of Aerosol Inorganic and Organic Nitrogen based on Thermal Evolution and Chemiluminescent Detection Jinjian Li, Xu Yu, Qianfeng Li, Shan Wang, Yuk Ying Cheng, and Jian Zhen Yu Atmospheric Environment, 2022, 271, 118905. Link>>
	The first online instrument for quantification of aerosol inorganic nitrogen (IN) and organic nitrogen (ON) was developed. Bulk aerosol ON accounted for 13.0% of TN at a suburban site in Hong Kong. Biomass burning and secondary formation processes could be important ON sources.

Ambient Measurements of Heterogeneous Ozone Oxidation Rates of Oleic, Elaidic, and Linoleic Acid Using a Relative Rate Constant Approach in an Urban Environment Qiongqiong Wang and Jian Zhen Yu Geophysical Research Letters, 2021, 48, e2021GL095130. Link>>
	Bihourly measured oleic, elaidic, and linoleic acid allow first-time determination of their decay rates under real-world conditions The relative decay rates of elaidic and linoleic acid versus oleic acid from the ambient data are consistent with their intrinsic reactivity Comparison of oleic acid lifetime with previous studies suggests laboratory systems are inadequate in simulating real-world conditions

Simultaneous Determination of Aerosol Inorganic and Organic Nitrogen by Thermal Evolution and Chemiluminescence Detection Xu Yu, Qianfeng Li, Yao Ge, Yumin Li, Kezheng Liao, X. H. Hilda Huang, Jinjian Li, and Jian Zhen Yu Environmental Science & Technology, 2021, 55, 11579-11589. Link>>
	Inorganic nitrogen (IN) and organic nitrogen (ON) molecules constitute a significant part of atmospheric aerosol. Unlike IN, the total ON quantity remains largely unquantified due to a lack of simple and direct measurement method. We developed an analyzer system that utilizes programmed thermo-evolution of carbonaceous and nitrogenous aerosols and chemiluminescent detection coupled with multivariate curve resolution data treatment to achieve simultaneous quantification of IN and ON. This method breakthrough opens the door to quantifying an important pool of aerosol N that was analytically inaccessible in the past.

Chemical Synthesis of Muultifunctional Air Pollutants: Terpene-Derived Nitrooxy Organosulfates Yuchen Wang, Rongbiao Tong, and Jian Zhen Yu Environmental Science & Technology, 2021, 55, 8573-8582. Link>>
	We succeed in first synthesis of terpene-derived nitrooxy organosulfates, providing indispensable standards to study multifunctional air pollutants formed between anthropogenic pollution and natural emissions. The availability of the authentic standards allows us to clarify previous misidentification and reveals the compound-specific propensity of carbon skeleton rearrangements for terpene-derived nitrooxy organosulfates during atmospheric oxidation. Environmental Advances online platform: https://mp.weixin.qq.com/s/tL3DsDM_cnKDyKS7rXKEfg

Tracer-based Chracterization of Source Variations of PM_2.5 and Organic Carbon in Shanghai Influenced by the COVID-19 Lockdown Shuhui Zhu, Qiongqiong Wang, Liping Qiao, Min Zhou, Shan Wang, Shengrong Lou, Dandan Huang, Qian Wang, Shengao Jing, Hongli Wang, Changhong Chen, Cheng Huang, and Jian Zhen Yu Faraday Discussions, 2021, 226, 112-137. Link>>
	The lockdown in the middle of COVID-19 outbreak brought about steep reductions in pollution activities. We seized this unique opportunity to study air pollution chemistry. Our comprehensive measurements of PM_2.5 chemical composition has revealed the nonlinear response of secondary pollutants to reductions in broad primary precursor pollutants. This work provides quantitative data and insights for future development of control strategies in megacities.)

Hourly Measurements of Organic Molecular Markers in Urban Shanghai, China: Primary Organic Aerosol Source Identification and Observation of Cooking Aerosol Aging Qiongqiong Wang, Xiao He, Min Zhou, Dan Dan Huang, Liping Qiao, Shuhui Zhu, Ying-ge Ma, Hong-li Wang, Li Li, Cheng Huang, X. H. Hilda Huang, Wen Xu, Douglas Worsnop, Allen H. Goldstein, Hai Guo, and Jian Zhen Yu ACS Earth & Space Chemistry, 2020, 4, 1670-1685. Link>>
	We deployed a thermal desorption aerosol gas chromatography-mass spectrometry (TAG) system at an urban location in Shanghai for three weeks in Nov 2018. We have the utility of high time-resolution organic markers in capturing the dynamic change of source emissions and atmospheric aging, providing observational evidence to support their use in source apportionment.

Hourly Measurements of Organic Molecular Markers in Urban Shanghai, China: Observation of Enhanced Formation of Secondary Organic Aerosol during Particulate Matter Episodic Periods Xiao He, Qiongqiong Wang, X. H. Hilda Huang, Dan Dan Huang, Min Zhou, Liping Qiao, Shuhui Zhu, Ying-ge Ma, Hong-li Wang, Li Li, Cheng Huang, Wen Xu, Douglas R. Worsnop, Allen H. Goldstein, and Jian Zhen Yu Atmospheric Environment, 2020, 240, 117807. Link>>
	Online measurement of individual aerosol organics was made for the first time in urban Shanghai. Significant mass enhancement of SOA tracers and nitrate was observed during five PM_2.5 episodes. Toluene SOA tracer had a mass increment of 5.6 during episodes vs. <2 for primary pollutants. The diagnostic ratio of two α-pinene SOA tracers suggested fresh SOA in urban Shanghai.

Source Apportionment of PM_2.5 in Shanghai based on Hourly Organic Molecular Markers and other Source Tracers Rui Li, Qiongqiong Wang, Xiao He, Shuhui Zhu, Kun Zhang, Yusen Duan, Qingyan Fu, Liping Qiao, Yangjun Wang, Li Huang, Li Li, and Jian Zhen Yu Atmospheric Chemistry & Physics, 2020, 20, 12047-12061. Link>>
	A source apportionment study was carried out through utilizing hourly measured PM_2.5 and its chemical components, including organic molecular markers. The PMF receptor modeling has resolved 11 source factors, among which 3 organics-dominated factors, namely an SOA factor, biomass burning, and cooking factor, were resolved from other sources due to the availability of the organic marker data.

Tracking Separate Contributions of Diesel and Gasoline Vehicles to Roadside PM_2.5 through Online Monitoring of Volatile Organic Compounds and PM_2.5 Organic and Elemental Carbon: a 6-year Study in Hong Kong Yee Ka Wong, X. H. Hilda Huang, Peter K. K. Louie, Alfred L. C. Yu, Damgy H. L. Chan, and Jian Zhen Yu Atmospheric Chemistry & Physics, 2020, 20, 9871-9882. Link>>
	Knowledge of the relative contribution of gasoline versus diesel powered vehicles to fine particulate matter is highly policy relevant and yet there lacks an effective observation-based method to determine this quantity, especially for its robust tracking over a period of years. In this work, we present an approach to track separate contributions by gasoline and diesel vehicles through positive matrix factorization analysis of online monitoring data (VOCs, OC and EC) measurable by relatively inexpensive analytical instruments.

Abundance and Sources of Benzo[a]pyrene and other PAHs in Ambient Air in Hong Kong: A Review of 20-year Measurements (1997-2016) Kezheng Liao and Jian Zhan Yu Chemosphere, 2020, 259, 127518. Link>>
	Benzo[a]pyrene decreased at the rate of 0.013 ng/m³/year during 1998-2016. Other 5-6 ring PAHs show similar declining trends. Major sources of PAHs are biomass burning, coal combustion and vehicular exhaust. Reductions in emission amounts of these sources have led to the declines in PAH levels.

Assessment of Interactions between Transition Metals and Atmospheric Organics: Ascorbic Acid Depletion and Hydroxyl Radical Formation in Organic-Metal Mixtures Manfei Lin and Jian Zhen Yu Environmental Science & Technology, 2020, 54, 1431-1442. Link>>
	Transition metals and certain atmospheric organics are recognized to be redox active and responsible for inducing ROS in human cells. We report here the mixture effects of metals and organics on the measured OP in the presence of ascorbic acid (AA). This work reveals that carboxylic acids enhanced the OP_AA and OP_•OH by Cu²⁺ (or Fe²⁺) while imidazoles suppressed them. While ambient HULIS showed negligible impacts, two biomass burning source HULIS samples from rice straw and sugarcane leaf burning displayed unambiguous suppression or enhancement effect on OP_AA and OP_•OH by Cu²⁺ (or Fe²⁺). The effect was metal-specific and source HULIS-specific.

Efficient Control of Atmospheric Sulfate Production based on Three Formation Regimes Jian Xue, Xin Yu, Zibing Yuan, Stephen M. Griffith, Alexis K. H. Lau, John H. Seinfeld, and Jian Zhen Yu Nature Geoscience, 2019, 12, 977-982. Link>>
	While the reactant-product link between sulfur dioxide and airborne sulfate formation is common knowledge, the complex oxidants and mechanisms that enable this transformation are not. This work describes the conceptual framework to delineate the relationship between sulfate and one set of its controllable precursors, nitrogen oxides (NO_x), laying the groundwork for formulating more effective measures of reducing sulfate.

Source Apportionment of PM_2.5 Using Hourly Measurements of Elemental Tracers and Major Constituents in an Urban Environment: Investigation of Time-Resolution Influence Qiongqiong Wang, Liping Qiao, Min Zhou, Shuhui Zhou, Stephen Griffith, Li Li, and Jian Zhen Yu Journal of Geophysical Research: Atmospheres, 2018, 123, 5284-5300. Link>>
	Using actual field data, we unequivocally demonstrated the benefits of high-time resolution chemical composition data in tracking PM_2.5 pollution. The improved robustness is achieved through better capturing of diurnal scale dynamics in source activities. Findings from this study provide implementable guidance for effective monitoring strategies

Abundance and Sources of Phthalic Acids, Benzene-Tricarboxylic Acids, and Phenolic Acids in PM_2.5 at Urban and Suburban Sites in Southern China Xiao He, X. H. Hilda Huang, Ka Shing Chow, Qiongqiong Wang, Ting Zhang, Dui Wu, and Jian Zhen Yu ACS Earth & Space Chemistry, 2018, 2, 147-158. Link>>
	The four phenolic acids, all possessing partial lignin structures, are associated with biomass burning emissions. They serve as precursors leading to significant constituents of brown carbon. The three BTCAs have a strong association with secondary formation origins. Structurally, the three BTCAs are among the logical oxidation products of PAHs and/or elemental carbon. The three phthalic acids are moderately correlated with sulfate, levoglucosan, and a number of PAHs, indicating multiple significant sources.

Impact of Secondary Organic Aerosol Tracers on Tracer-Based Source Apportionment of Organic Carbon and PM_2.5: A Case Study in the Pearl River Delta, China Qiongqiong Wang, Xiao He, X. H. Hilda Huang, Stephen M. Griffith, Yongming Feng, Ting Zhang, Qingyan Zhang, Dui Wu, and Jian Zhen Yu ACS Earth & Space Chemistry, 2017, 1, 562-571. Link>>
	SOC from specific precursors may have different formation pathways than secondary sulfate and nitrate formation processes, and their source contributions could not be properly resolved without the indicative tracers included in PMF. This study demonstrates the utility of biogenic SOA tracers in resolving isoprene-derived SOA and highlights the need for more SOAtracers, especially those specific to anthropogenic precursors, in improving the source apportionment for those broad OA sources such as industrial emissions.

Synthesis of Four Monoterpene-Derived Organosulfates and Their Quantification in Atmospheric Aerosol Samples Yuchen Wang, Jingyun Ren, X. H. Hilda Huang, Rongbiao Tong, and Jian Zhen Yu Environmental Science & Technology, 2017, 51, 6791-6801. Link>>
	We report a unified synthesis strategy starting from the respective monoterpene through Upjohn dihydroxylationor Sharpless asymmetric dihydroxylation followed bymonosulfation with the sulfur trioxide-pyridine complex. The in-house availability of the authentic standards enables us to discover that β-pinene OS, due to the sulfate group at the primary carbon, partially degrades to a dehydrogenated OS compound during LC/MS analysis and a hydroperoxy OS over a prolonged storage period (> 5 months) and forms a regioisomer through intermolecular isomerization.

Sulfate Formation Enhanced by a Cocktail of High NO_x, SO₂, Particulate Matter, and Droplet pH during Haze-Fog Events in Megacities in China: An Observation-Based Modeling Investigation Jian Xue, Zibing Yuan, Stephen M. Griffith, Xin Yu, Alexis K. H. Lau, and Jian Zhen Yu Environmental Science & Technology, 2016, 50, 7325-7334. Link>>
	At a typical haze-fogwater pH of 5.6, the most important pathway to be oxidation of S(IV) by dissolved NO₂. The unique cocktail of high fogwater pH, high concentrations of NO₂, SO₂, and PM, and small fog droplets are capable of greatly enhancing sulfate formation. Insights gained on major contributing factors imply that reduction of road dust and NO_x emissions could lessen PM_2.5 loadings in Chinese megacities during fog events.

Organosulfates in Humic-like Substance Fraction Isolated from Aerosols at Seven Locations in East Asia: A Study by Ultra-High-Resolution Mass Spectrometry Peng Lin, Jian Zhen Yu, Guenter Engling, and Markus Kalberer Environmental Science & Technology, 2012, 46, 13118-13127. Link>>
	In HULIS fraction, OS containing 10 carbon atoms were the most abundant, indicating monoterpenes as important precursors of OS. The double bond equivalent (DBE) values indicate the majority of OS (>90%) in the HULIS fraction are aliphatic. The −ONO2 group is the more readily hydrolyzed than the −OSO3 group. There is a lack of evidence for the epoxide pathway to account for the formation of OS in the CHONS subgroup.