Jialiang Ma

Organic peroxides are recognized as major contributors to the toxicity and adverse health effects of secondary organic aerosols (SOA). However, their molecular composition and chemical properties in SOA remain largely unexplored. Here we develop a novel analytical strategy for the molecular characterization of organic peroxides in α-pinene SOA, combining iodometry kinetic experiments with liquid chromatography–high-resolution mass spectrometry. Using non-targeted analysis, we identify over 300 organic peroxides in α-pinene SOA, showing a wide range of reactivities with iodide, spanning 4 orders of magnitude. The structures of 12 organic peroxides derived from stabilized Criegee intermediates are further proposed and discussed. Our findings present a reliable, standard-free methodology for identifying previously uncharacterized organic peroxides in SOA at the molecular level, offering new avenues for investigating formation pathways and health impacts of this large, diverse, yet rarely explored compound class. Additionally, we propose peroxide-iodide reactivity as a novel metric for future predictions of oxidative potentiala key indicator of toxicityand for elucidating the structure of individual organic peroxides in SOA.

Organosulfates are key compounds driving the anthropogenic enhancement of ambient organic aerosol, however, total organosulfate quantification remains elusive due to their molecular diversity and the scarcity of authentic standards. Here, we present a solid-phase extraction method that isolates organosulfates from ambient aerosol samples and enables their identification and quantification using mass spectrometry and a charged aerosol detector, respectively. We investigate ambient aerosol samples from urban China and rural Germany and quantify ~130 and ~65 chromatographically resolved organosulfates, respectively, contributing less than ~2% to the total organic matter. We find a significantly larger organosulfate fraction appearing as a broad peak in the chromatograms from the charged aerosol detector. Confirming its origin from chromatographically non-resolved organosulfates, an all-ion fragmentation experiment reveals specific sulfate-related ions. Integrating this peak, we find the contribution of organosulfates to organic aerosol is 12-17% and ~21% in samples from urban China and rural Germany, respectively. These findings emphasise the potential of sulfur emission reduction for mitigating both sulfate-related and organic aerosol pollution.

Organic aerosols constitute 20-90% of fine particles in the lower atmosphere. They contribute to climate cooling by reflecting sunlight and influencing cloud formation. Moreover, organic aerosols also degrade air quality and heighten health risks, leading to respiratory and cardiovascular issues. Understanding the chemical composition and atmospheric transformation of organic aerosols is crucial for identifying their sources and developing mitigation strategies. Organosulfates, a significant subclass of organic aerosols, form through various chemical pathways. However, accurately quantifying total organosulfates remains challenging due to their molecular diversity and the limited availability of authentic standards. Additionally, higher organosulfate concentrations are consistently observed through indirect methods, which involve calculating the difference between total sulfur (measured by X-ray fluorescence) and inorganic sulfate (measured by ion chromatography). This suggests that direct quantification methods, such as those based on mass spectrometry of individual organosulfate, may underestimate the total organosulfates concentration in ambient organic aerosols. Here, in this accumulative thesis, I present a collection of five papers, with two as my main projects as the lead author. These two manuscripts primarily focus on the non-target analysis of organic aerosol and the development of a novel quantitative method for organosulfate. The first paper demonstrates the potential of using non-target screening combined with hierarchical cluster analysis to better understand the molecular composition and sources of organic aerosol in urban environments. We report the seasonal variations in the molecular composition of organic aerosol based on 172 PM2.5 filter samples collected over 13 months in Beijing. By applying hierarchical cluster analysis to the extensive non-target screening dataset, we found a strong seasonal difference in the chemical composition of organic aerosol. Molecular fingerprints of the major compound clusters exhibit a unique molecular pattern in the Van Krevelen-space. The summer organic aerosol in Beijing features a higher degree of oxidation and a higher proportion of organosulfate in comparison to organic aerosol during wintertime, which exhibits a high contribution from (nitro-)aromatic compounds. Organosulfate were particularly prominent during summer haze conditions, highlighting the significant impact of anthropogenic activities on the enhancement of secondary organic aerosol in summer Beijing. Furthermore, we quantified the contribution of the four main compound clusters to total organic aerosol using surrogate standards. With this approach, we explain a small fraction (∼11−14%) of the organic aerosol monitored by the Time-of-Flight Aerosol Chemical Speciation Monitor. The organosulfate cluster contributes only ~2% of the organic aerosol—a significantly smaller fraction than in studies using the indirect approach. Therefore, in our second study, we developed a novel solid phase extraction method to isolate organosulfates from ambient samples. This method enables both the identification and quantification of organosulfates using high-resolution mass spectrometry and a charged aerosol detector, respectively. The charged aerosol detector signal, being directly proportional to the mass of non-volatile compounds, enables the universal quantification based on calibration with only a few non-volatile standards. We measured ambient samples from urban China and rural Germany and quantified ~130 and ~65 chromatographically resolved organosulfate, contributing ~1% and ~2% to total organic aerosol, respectively. A significantly larger OS signal appears as a broad peak in the charged aerosol detector. Confirming its origin from chromatographically non-resolved organosulfates, an all-ion-fragmentation experiment detected organosulfate-specific ion fragments. With this peak integrated, we find the total organosulfate contribution to total organic aerosol is 12-17% and ~21% in urban China and rural Germany samples, respectively. These findings emphasize the potential of sulfur emission reduction not only for mitigating sulfate-related air pollution but also for addressing organic aerosol pollution. The remaining three studies employed nontarget screening and advanced mass spectrometry techniques to deepen our understanding of atmospheric sulfate formation and air pollution sources in Beijing. Two of these studies investigated SO₂ uptake in droplets, revealing that mixtures of biomass burning or incense smoke extracts with sodium chloride significantly enhance sulfate production compared to sodium chloride alone, likely due to photosensitization effects. Additionally, using complementary mass spectrometry for near-molecular observations, we quantified organic aerosol sources in central Beijing and identified the primary sources of secondary organic aerosol impacting the city, extending clearly beyond local emissions.

Organic peroxides are health-relevant organic components in secondary organic aerosols (SOA), which is also a major compound class substantially contributing to SOA mass. However, their molecular identification in SOA is highly challenging and uncertain. Iodide is known to selectively react with peroxides, and their kinetics are fundamentally determined by the structures of individual peroxides. Here we extrapolate this knowledge and develop a novel analytical strategy for molecular characterization of organic peroxides in α-pinene SOA via iodometry kinetic experiments, using liquid chromatography–high resolution mass spectrometry. Through non-targeted analysis, more than 300 organic peroxides are identified in α-pinene SOA with unprecedented accuracy of their chemical formula. Their reactivity with iodide is highly compound-dependent and can vary four orders of magnitude, within the range observed for some commercial organic peroxides with known structures. In particular, more than 65% of organic peroxides in α-pinene SOA exhibit a slow reactivity with iodide, with an e-folding lifetime exceeding one day. The structures of 12 organic peroxides derived from stabilized Criegee intermediates are further proposed and discussed based on different experimental evidences. Our study improves the molecular-level identification and understanding of organic peroxides in SOA, offering numerous opportunities for further investigation into their formation chemistry, atmospheric transformation, and health impact. Additionally, the peroxide-iodide reactivity is proposed as a new metric that can provide both information on the oxidizing capability and structure of individual organic peroxide in SOA.

The study on the Zhangjialiang No. 2 coal of Middle Jurassic Yan'an Formation in the northeastern Ordos Basin has been analyzed by gas chromatography-mass spectrometry (GC-MS) to determine geochemical characteristics and reconstruct palaeovegetation and palaeoclimate changes. The distribution of n-alkanes is mainly unimodal, with a medium and high molecular weight. Pr/Ph ratio (2.03–10.6) is high in most samples. The values of Tm/Ts ratio are between 1.42 and 4.92, and a predominance of C₂₉ over C₂₇ steranes has been found for the analyzed samples. These parameters indicate that all samples were deposited in an oxidizing freshwater environment, and the organic matter was mainly derived from terrestrial higher plants, with a small amount of aquatic organisms. Thermal maturity parameters such as C₃₁22S/(22S + 22R) homohopane, C₃₀αβ/(αβ + βα) hopane, together with the total organic carbon (TOC) contents (43.1% - 58.6% (except floor 2-13)) and the detected of C₂₇17β(H)-22, 29, 30-trisnorhopane (βTm), suggest that most of samples have a relatively low maturity in the early stage. Besides, gymnosperm-derived biomarkers, including labdane, norpimarane, isopimarane, phyllocladane, abietane, rimuane, ent-beyerane, ent-kaurane, suggest that the vegetation during the Middle Jurassic Yan’an Formation was characterized by conifers.

“High-aluminous coal” is an important coal kind and widely distributed in North China in age of Permo-Carboniferous period. To explore their occurrence state, a total of 15 harmful elements (Li, Ga, In, Cd, Cr, Pb, Be, Mn, Zn, Ag, Co, Ni, Cu, Ba and U) in the No.9 coal and No.11 coal collected from Pingshuo mining district were determined by inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscope with energy spectrum (SEM-EDX). The results showed that the content of Li, Ga, In, Pb, Ag and U were all exceed the world hard coal. In view of the result of clustering analysis within trace elements, it was found that Co, Ni, Zn, Cu, Ag and Cr were mainly associated with sulfide minerals due to their common sulfophilic property. Manganese was mainly occurred in carbonate minerals, while Ba, Cd and U were mainly associated with total minerals. In addition, Pb was related to sulfides and Be is mainly distributed in clay minerals. The enrichment of such harmful elements in Pingshuo coal was caused by the combined effect of transgression and input of terrestrial materials in the peat accumulation stage. Li, Ga, In and Ag have reached the harmful grade.

The molecular composition of atmospheric particulate matter (PM) in the urban environment is complex, and it remains a challenge to identify its sources and formation pathways. Here, we report the seasonal variation of the molecular composition of organic aerosols (OA), based on 172 PM_2.5 filter samples collected in Beijing, China, from February 2018 to March 2019. We applied a hierarchical cluster analysis (HCA) on a large nontarget-screening data set and found a strong seasonal difference in the OA chemical composition. Molecular fingerprints of the major compound clusters exhibit a unique molecular pattern in the Van Krevelen-space. We found that summer OA in Beijing features a higher degree of oxidation and a higher proportion of organosulfates (OSs) in comparison to OA during wintertime, which exhibits a high contribution from (nitro-)aromatic compounds. OSs appeared with a high intensity in summer-haze conditions, indicating the importance of anthropogenic enhancement of secondary OA in summer Beijing. Furthermore, we quantified the contribution of the four main compound clusters to total OA using surrogate standards. With this approach, we are able to explain a small fraction of the OA (∼11–14%) monitored by the Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM). However, we observe a strong correlation between the sum of the quantified clusters and OA measured by the ToF-ACSM, indicating that the identified clusters represent the major variability of OA seasonal cycles. This study highlights the potential of using nontarget screening in combination with HCA for gaining a better understanding of the molecular composition and the origin of OA in the urban environment.

This paper provides new geochemical data focusing on valuable elements in the coal, parting, and floor samples in the No. 5 coal seam of the Taiyuan Formation from the Wujiawan mine, Datong coalfield, northern China. The minerals mainly consist of kaolinite, calcite, and pyrite, as well as trace amounts of quartz and illite. The No. 5 coal is enriched in Li, Ga, high field strength elements (HFSEs), and rare earth elements and yttrium (REY) when compared with world hard coals. Of particular interest is the high average concentration of Li (67.66 μg/g), which is around seven times higher than the value for world hard coals. Lithium, Ga, and HFSEs have strong inorganic affinities, whereas REY have organic affinities. The main carrier of Li, Ga, and HFSEs is aluminosilicate minerals, while REY appear to occur with organophosphorus. These HFSEs are enriched, both in the parting and in the adjacent coal samples. This suggests that these elements are likely to leach out during the diagenetic process. The distribution patterns of REY, along with the ratio of Al₂O₃/TiO₂ and the figure of Zr/TiO₂ vs. Nb/Y are suggestive of their derivation from felsic parent material. In the northern and eastern part of the Datong coalfield, there are several regions where the Li content is higher than the mineable grade, in particular in the northern Datong coalfield where there is a mine with an Li content of 294.6 μg/g. This is significantly higher than the mineable grade. Therefore, there is a potential for financially viable recovery of Li in these coals of the Datong coalfield.

The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal is a low ash and highly volatile A bituminous coal. Minerals in the No. 3 coal mainly comprise of kaolinite, ankerite, illite, calcite, siderite, and quartz, with varying compositions of trace amounts of pyrite, jarosite, bassanite, anatase, and rutile. According to mineral assemblage in the coal plies, three Types (A to C) can be identified in the No. 3 coal. The dominant minerals in Type A are poorly-ordered kaolinite, illite, quartz, pyrite, and jarosite. Type B is mainly composed of well-ordered kaolinite, illite, siderite, ankerite, and calcite. Type C, with just one sample (JY-3-7c), which contains high proportions of calcite (54%) and ankerite (34%). Terrigenous minerals are elevated in coal plies that typically have relatively high contents of ash yield. The formation of syngenetic pyrite was generally due to seawater, while the sulphate minerals (jarosite and coquimbite) were derived from the oxidation of pyrite. Epigenetic vein-like or fracture-fillings carbonate minerals (ankerite, calcite, and siderite), kaolinite, and pyrite, as well as authigenic quartz were derived from the influx of hydrothermal fluids during different periods, from the authigenic to epigenetic. The paragonite in the coal may have been formed by the precipitated from Na-rich hydrothermal fluids. No effects of magmatic intrusion on mineralogy were investigated in this research.