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While aqueous-phase processing is known to contribute to the formation of nitrogen-containing organic compounds (NOCs), the specific pathways involved remain poorly understood. In this study, we aimed to characterize the NOCs present in both pre-fog aerosols and fog water collected at a suburban site in northern China. Fourier-transform ion cyclotron resonance mass spectrometry was utilized to analyze the molecular composition of NOCs in both negative and positive modes of electrospray ionization (ESI - and ESI +). In both pre-fog aerosols and fog water samples, NOCs constituted a significant portion, accounting for over 60 % of all assigned formulas in ESI - and more than 80 % in ESI +. By comparing the molecular composition of NOCs originating from biomass burning, coal combustion, and vehicle emissions, we identified that 72.3 % of NOCs in pre-fog aerosols were attributed to primary anthropogenic sources (pNOCs), while the remaining NOCs were categorized as secondary NOCs formed within the aerosols (saNOCs). Unique NOCs found in fog water were classified as secondary NOCs formed within the fog water (sfNOCs). Through a comprehensive "precursor–product pair" screening involving 39 reaction pathways, we observed that the nitration reaction, the amine pathway, and the intramolecular N-heterocycle pathway of NH 3 addition reactions contributed 43.6 %, 22.1 %, and 11.6 % of saNOCs, respectively. In contrast, these pathways contributed 26.8 %, 28.4 %, and 29.7 % of sfNOCs, respectively. This disparity in formation pathways is likely influenced by the diverse precursors, the aqueous acidity, and the gas-phase species partitioning. Correspondingly, saNOCs were found to contain a higher abundance of carbohydrate-like and highly oxygenated compounds with two nitrogen atoms compared to pNOCs. Conversely, sfNOCs exhibited a higher content of lipid-like compounds with fewer oxygen atoms. These results underscore the distinct secondary processes contributing to the diversity of NOCs in aerosols and fog water, which may lead to their different climate effects. [ABSTRACT FROM AUTHOR]

The formation process of in‐cloud aqueous‐phase secondary organic matter (aqSOM) and its characteristics are unclear. Herein, water‐soluble inorganic ions, oxalate, and water‐soluble organic carbon (WSOC) were determined in cloud water and aerosol (PM2.5) samples simultaneously collected at a remote mountain site in southern China during spring 2018 and winter 2020. The molecular compositions of water‐soluble organic matter (WSOM) in cloud water and aerosols were analyzed by a Fourier transform ion cyclotron resonance mass spectrometer in negative electrospray ionization (ESI‐) mode. The results showed that the mean concentration of WSOC was 6.27–8.54 mg C L−1 in cloud water and 0.60–1.37 μg C m−3 in aerosols. The strong correlation observed between WSOM and aqueous secondary matter (e.g., NO3− and oxalate), the positive matrix factorization results, and the elevated WSOM/K+ ratios observed in cloud water suggested enhanced aqSOM formation in cloud water. According to random forest analysis, the factors related to in‐cloud WSOM variation mainly included secondary ions, K+, cloud water pH, and atmospheric NOx. Additionally, 37 characteristic in‐cloud aqSOM molecules, classified as ‐Ox, ‐NOx, ‐N2Ox, and ‐N1‐2OxS, mainly consisting of dicarboxylic acids, nitrophenols, and dinitrophenols, were identified using linear discriminant analysis effect size (LefSe). The characteristic N‐ and S‐containing molecules in in‐cloud aqSOM with carbon numbers >10 had low or extremely low volatility; therefore, they might contribute to secondary organic aerosol formation after droplet evaporation. The results revealed the modifying effects of in‐cloud processes on aerosol organic composition at the molecular level and could improve our understanding of aerosol–cloud interactions. Plain Language Summary: In this study, we determined the water‐soluble ion, water‐soluble organic matter (WSOM) and organic molecular composition of cloud water and aerosol samples collected at a remote mountain site in southern China. The results indicated the formation of secondary organic matter (SOM) in cloud water, the proportion of which in total WSOM was >50%. In addition, the characteristic molecules of SOM in cloud water were identified, some of which had low or extremely low volatility and might remain in the particulate phase after droplet evaporation. This work advanced our understanding of secondary organic aerosol formation in cloud water and its implications for the climate and the environment. Key Points: The proportion of in‐cloud aqueous‐phase secondary organic matter in WSOM was >50%Some molecules, for example, diacids and dinitrophenols, were identified as characteristic molecules of in‐cloud secondary organic matterMolecules with C numbers >10 formed by in‐cloud processes had low volatility [ABSTRACT FROM AUTHOR]

While aqueous-phase processing contributes to the formation of nitrogen-containing organic compounds (NOCs), the detailed pathways are not well understood. In this study, the molecular composition of NOCs in both pre-fog aerosols and fog water collected at a suburban site in northern China was characterized using Fourier-transform ion cyclotron resonance mass spectrometry in both negative and positive modes of electrospray ionization (ESI- and ESI+). In both pre-fog aerosols and fog water, NOCs account for number fractions of more than 60 % in all assigned formulas in ESI- mode and more than 80 % in ESI+ mode. By comparing the molecular composition of biomass burning, coal combustion, and vehicle emissions, 72.3 % of NOCs in pre-fog aerosols were assigned as originating from these primary anthropogenic sources (pNOCs), while the remaining NOCs were regarded as secondary NOCs formed in aerosol (saNOCs). On the other hand, the unique NOCs in fog water were regarded as secondary NOCs formed in fog (sfNOCs). According to "precursor-product pair" screening involving 39 reaction pathways, we found that the nitration reaction, the amine pathway and the intramolecular N-heterocycle pathway of NH3 addition reactions contribute to 43.6 %, 22.1 %, and 11.6 % of saNOCs, but 26.8 %, 28.4 %, and 29.7 % of sfNOCs, respectively. Such distinct formation pathways are most likely attributed to the diverse precursors and the aqueous acidity. Correspondingly, saNOCs contain more abundant carbohydrates-like and highly oxygenated compounds with two nitrogen atoms compared to pNOCs, whereas sfNOCs contain more lipids-like with fewer oxygen atoms. The results reveal the disparity in secondary processes that contribute to the richness of NOCs in aerosols and fog water. The findings are valuable for understanding the formation and control of organic nitrogen pollution. [ABSTRACT FROM AUTHOR]

The radiative forcing of soot is dependent on the morphology, mixing state and structure. Cloud processing has been predicted to affect their mixing properties but little is known about the resulting light absorption properties. We collected ambient particles in the pre‐cloud period, the cloud residues and interstitials in the in‐cloud period at Mt. Tianjing (southern China). The morphology parameters of soot aggregates with varying mixing materials [sulfate (S) and organics (OM)] and mixing structures were investigated by a transmission electron microscope, and their absorption cross section were calculated based on discrete dipole approximation. We found that the number contribution of soot‐S decreased from 45% in the pre‐cloud period to 32% in the in‐cloud period, and that of soot‐OM increased from 44% to 60%. Moreover, the number proportion of soot‐OM with fully embedded structure increased remarkably in the in‐cloud period (29%), compared with that in the pre‐cloud period (3%). In addition, the soot‐S aggregates became denser after in‐cloud aqueous process. However, for soot‐OM aggregates, the morphology remained relatively constant. The distinctly different change of soot‐S and soot‐OM in morphology highlights the chemically resolved reconstruction of soot morphology. Theoretical calculation further shows that the changes of soot particles in the mixing state and morphological characteristics by the cloud process resulted in the light absorption enhancement increase from 1.57 to 2.01. This study highlights that the evolution of microphysical properties upon cloud processing should also be considered in climate models to more accurately evaluate the impacts of soot particles. Plain Language Summary: While soot particles are the main component of aerosols that produce positive radiative forcing in clouds, the impact of in‐cloud processes on key factors (mixing state and microphysical property) for evaluating the optical properties of soot particles is unclear. Here, we report the detailed information on several parameters required to calculate the optical properties of soot particles, throughout the cloud events. And we found that changes in the mixing state, mixing structure, and morphology of soot particles under the influence of in‐cloud processes lead to a significant light absorption enhancement. The results also highlight the role of in‐cloud aqueous formation of secondary compositions in reshaping the soot particles, which has substantial implications for the climate impact of soot particles. Given that ∼70% of the Earth's surface is covered by clouds, taking the mixing state and microphysical properties of soot particles into account in climate models may help constrain the contribution of soot particles to global radiative forcing. Key Points: Cloud processing contributes to the increase of organic coating on soot aggregates, especially for those with fully embedded structureThe sulfate coating causes more compaction of soot aggregates than the organic coating upon cloud processingChanges in the microphysical properties of soot particles driven by one cloud event increase their absorption enhancement by 1.29 times [ABSTRACT FROM AUTHOR]

While the formation and evolution of nitrate in airborne particles are extensively investigated, little is known about the processing of nitrate in clouds. Here we present a detailed investigation on the in-cloud formation of nitrate, based on the size-resolved mixing state of nitrate in the individual cloud residual and cloud-free particles obtained by single particle mass spectrometry, and also the mass concentrations of nitrate in the cloud water and PM 2.5 at a mountain site (1690 m a.s.l. – above sea level) in southern China. The results show a significant enhancement of nitrate mass fraction and relative intensity of nitrate in the cloud water and the cloud residual particles, respectively, reflecting a critical role of in-cloud processing in the formation of nitrate. We first exclude the gas-phase scavenging of HNO 3 and the facilitated activation of nitrate-containing particles as the major contribution for the enhanced nitrate, according to the size distribution of nitrate in individual particles. Based on regression analysis and theoretical calculations, we then highlight the role of N 2 O 5 hydrolysis in the in-cloud formation of nitrate, even during the daytime, attributed to the diminished light in clouds. Nitrate is highly related (R2= ∼ 0.6) to the variations in [NO x ][O 3 ], temperature, and droplet surface area in clouds. Accounting for droplet surface area greatly enhances the predictability of the observed nitrate, compared with using [NO x ][O 3 ] and temperature. The substantial contribution of N 2 O 5 hydrolysis to nitrate in clouds with diminished light during the daytime can be reproduced by a multiphase chemical box model. Assuming a photolysis rate at 30 % of the default setting, the overall contribution of N 2 O 5 hydrolysis pathway to nitrate formation increases by ∼ 20 % in clouds. Given that N 2 O 5 hydrolysis acts as a major sink of NO x in the atmosphere, further model updates would improve our understanding about the processes contributing to nitrate production in cloud and the cycling of odd nitrogen. [ABSTRACT FROM AUTHOR]

Atmospheric brown carbon (BrC) makes a substantial contribution to aerosol light absorption and thus global radiative forcing. Although BrC may change the lifetime of the clouds and ultimately affect precipitation, little is known regarding the optical properties and formation of BrC in the clouds. 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 PM 2.5 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 PM 2.5 samples were also obtained, associated with the concentration of water-soluble ions. The mean light-absorption coefficient (Abs 370) 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 Abs 365 of WSOC was 0.11 ± 0.08 Mm -1 in cloud water and 0.40 ± 0.31 Mm -1 in PM 2.5 , and the corresponding mass absorption efficiency (MAE 365) was 0.17 ± 0.07 and 0.31 ± 0.21 m 2 g -1 , respectively. A comparison of the light-absorption coefficient between BrC in cloud RES and cloud INT particles, and WSOC in cloud water and PM 2.5 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 the secondary formation and biomass burning factor (>80 %) to Abs 365 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-like and/or protein-like substances (r>0.63 , p<0.01), whereas only humic-like substances for PM 2.5 , as identified by excitation-emission matrix fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Characterizing the molecular composition of cloud water could provide unique insights into aqueous chemistry. Field measurements were conducted at Mt. Tianjing in southern China in May, 2018. There are thousands of formulas (C5–30 H4–55 O1–15 N0–2 S0–2) identified in cloud water by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). CHON formulas (formulas containing C, H, O, and N elements; the same is true for CHO and CHOS) represent the dominant component (43.6 %–65.3 % of relative abundance), followed by CHO (13.8 %–52.1%). S-containing formulas constitute ∼ 5 %–20 % of all assigned formulas. Cloud water has a relative-abundance-weighted average O/C of 0.45–0.56, and the double bond equivalent of 5.10–5.70. Most of the formulas (>85 %) are assigned as aliphatic and olefinic species. No statistical difference in the oxidation state is observed between cloud water and interstitial PM2.5. CHON with aromatic structures are abundant in cloud water, suggesting their enhanced in-cloud formation. Other organics in cloud water are mainly from biomass burning and oxidation of biogenic volatile organic compounds. The cloud water contains more abundant CHON and CHOS at night, which are primarily contributed by -N2 O5 function and organosulfates, demonstrating the enhanced formation in dark aqueous or multi-phase reactions. While more abundant CHO is observed during the daytime, likely due to the photochemical oxidation and photolysis of N- or S-containing formulas. The results provide an improved understanding of the in-cloud aqueous-phase reactions. [ABSTRACT FROM AUTHOR]

Mixing state of black carbon (BC) with secondary species has been highlighted as a major uncertainty in assessing its radiative forcing. While recent laboratory simulation has demonstrated that BC could serve as a catalyst to enhance the formation of sulfate, its role in the formation and evolution of secondary aerosols in the real atmosphere remains poorly understood. In the present study, the mixing of BC with sulfate/nitrate in the atmosphere of Guangzhou (China) was directly investigated with a single particle aerosol mass spectrometer (SPAMS). The peak area ratios of sulfate to nitrate (SNRs) for the BC‐containing particles are constantly higher than those of the BC‐free particles (defined as particles with negligible BC signals). Furthermore, the seasonal SNR peak is observed in summer and autumn, and the diurnal peak is found in the afternoon, consistent with the trends of radiation‐related parameters (i.e., solar radiation and temperature), pointing to the BC‐induced photochemical production of sulfate. Such hypothesis is further supported by the multilinear regression and random forest analysis, showing that the variation of SNRs associated with the BC‐containing particles could be well explained (R2 = ∼0.7–0.8) by the radiation‐related parameters (>30% of the variance) and the relative BC content (∼20%) in individual particles, but with limited influence of precursors (SO2/NOx: <5%). Differently, the radiation‐related factors only explain <10% of the SNR variation for the BC‐free particles. These results provide ambient observational evidence pointing to a unique role of BC on the photochemical formation and evolution of sulfate, which merits further quantitative evaluations. Plain Language Summary: Despite ubiquitous in the atmosphere, the potential role of BC black carbon (BC) in the formation and evolution of secondary aerosols in the real atmosphere remains poorly understood. Here, we have investigated the detailed mixing state of BC with sulfate/nitrate in the atmosphere of Guangzhou in real‐time by a Single Particle Aerosol Mass Spectrometer. We show that the distinct seasonal and diurnal variation of the enhanced sulfate/nitrate ratios is most likely driven by the BC catalytic photochemistry. Our results provide first ambient observational evidence, extending the laboratory results to the ambient atmosphere that BC could act as a photoactive and absorbing substrate, leading to an enrichment of sulfate, in particular, during summer and autumn. Thus, the BC emission controls may also mitigate the formation and evolution of sulfate and it is essential to include BC involved photochemistry in the models to account for the evolution and climate impact of BC accurately. Key Points: Enhanced sulfate to nitrate ratios (SNRs) are observed for the black carbon (BC)‐containing particlesThe distinct diurnal variation of the enhanced SNRs is most likely attributed to BC catalytic photochemistrySNRs in individual BC‐containing particles could be well predicted by the radiation‐related parameters and the relative BC content [ABSTRACT FROM AUTHOR]

Characterizing the molecular composition of cloud water could provide unique insight into the aqueous chemistry. Field measurement was conducted at Mt. Tianjing in southern China during May' 2018. Thousands of formulas (C5.30H4.55O1. I[SUB 5]N[SUB 0].[SUB 2]S[SUB 0].2) were identified in cloud water by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). CHON represents the dominant component (43.6-65.3% of relative abundance)' followed by CHO (13.8-52.1%). S-containing formulas constitute the remaining ~10-20%. Molecules have O/C of 0.45-0.56 and the double-bond equivalent of 5.10-5.70. More than 90% are assigned as aliphatic and olefinic species. No statistical difference of oxidation state is observed between cloud water and interstitial PM2.5. CHON with aromatic structures are abundant in cloud water' suggesting their enhanced in- cloud formation. Other organics in cloud water are mainly from biomass burning and oxidation of biogenic volatile organic compounds. The cloud water contains more abundant CHON and CHOS at night' which are mainly contributed by -N2O5 function and organosulfates' demonstrating the enhanced formation in dark aqueous or multi-phase reactions. While more abundant CHO are observed during the daytime' likely due to the photochemical oxidation and photolysis of N-/S-containing formulas. The results provide an improved understanding on the in-cloud aqueous-phase reactions. [ABSTRACT FROM AUTHOR]

The composition, morphology, and mixing structure of individual cloud residues (RES) and interstitial particles (INT) at a mountaintop site were investigated. Eight types of particles were identified, including sulfate-rich (S-rich), S-organic matter (OM), aged soot, aged mineral dust, aged fly ash, aged metal, refractory, and aged refractory mixture. A shift of dominant particle types from S-rich (29 %) and aged soot (27 %) in the INT to aged refractory mixture (23 %) and S-OM (22 %) in the RES is observed. In particular, particles with organic shells are enriched in the RES (27 %) relative to the INT (12 %). Our results highlight that the formation of more oxidized organic matter in the cloud contributes to the existence of organic shells after cloud processing. The fractal dimension (Df), a morphologic parameter to represent the branching degree of particles, for soot particles in the RES (1.82 ± 0.12) is lower than that in the INT (2.11 ± 0.09), which indicates that in-cloud processes may result in less compact soot. This research emphasizes the role of in-cloud processes in the chemistry and microphysical properties of individual particles. Given that organic coatings may determine the particle hygroscopicity, activation ability, and heterogeneous chemical reactivity, the increase of OM-shelled particles upon in-cloud processes should have considerable implications. [ABSTRACT FROM AUTHOR]

Heterogeneous reactions on sea spray aerosols (SSA) are the main pathway to drive the circulation of chlorine, nitrogen, and sulfur in the atmosphere. The release of Cl will significantly affect the physicochemical properties of SSA. However, the impact of organic acids and mixing state on chloride depletion of SSA is still unclear. Hence, the size and chemical composition of individual SSA particles during the East Asian summer monsoon were investigated by a single particle aerosol mass spectrometer (SPAMS). According to the chemical composition, SSA particles were classified into SSA-Aged, SSA-Bio and SSA-Ca. In comparison to the aged Na-rich SSA particles (SSA-Aged), some additional organic species related to biological origin were observed in SSA-Bio, and each of two types accounts for approximately 50 % of total SSA particles. SSA-Ca may associated with organic shell of Na-rich SSA particles, which only accounts for ~ 3 %. Strongly positive correlations between Na and organic acids (including formate, acetate, propionate, pyruvate, oxalate, malonate, succinate, and glutarate) were observed for the SSA-Aged (r² = 0.52, p < 0.01) and SSA-Bio (r² = 0.61, p < 0.01), indicating the significance of organic acids in the chloride depletion during inland transport. The contribution of these organic acids to the chloride depletion is estimated to be up to 34 %. Interestingly, the degree of chloride depletion is distinctly different between SSA-Aged and SSA-Bio. It is most probably attributed to the associated organic coating in the SSA-Bio particles, which inhibit the displacement reactions between acids and chloride. As revealed from the mixing state of SSA-Bio, Cl / Na ratio increases with increasing phosphate and organic nitrogen, which is known to originate from biological activities. This finding provides some basis for the improvement of modeling simulations in chlorine circulation and a comprehensive understanding of the effects of organics on chloride depletion of SSA particles. [ABSTRACT FROM AUTHOR]

The coexistence of Pb‐Zn deposits and oil/gas reservoirs demonstrates that a close genetic connection exists between them. The spatiotemporal relationship between Pb‐Zn mineralization and hydrocarbon accumulation is the key to understanding this genetic connection. The Mayuan large‐scale Pb‐Zn metallogenic belt is composed of a number of Mississippi Valley‐type (MVT) Pb‐Zn deposits that were recently discovered on the northern margin of the Yangtze Block, China. It is hosted in the dolostone of the Sinian (Ediacaran) Dengying Formation (Z2dn). In addition to the abundant bitumen in the Mayuan Pb‐Zn metallogenic belt, the paleo‐oil reservoir and the MVT Pb‐Zn deposit overlap in space. In this study, two precise ages of 468.3 ± 3.8 Ma and 206.0 ± 6.5 Ma were obtained via the Rb‐Sr isotopic dating of galena and sphalerite from the Mayuan Pb‐Zn metallogenic belt, respectively. The early metallogenic age of 468.3 ± 3.8 Ma is similar to the previously published age of 486 ± 12 Ma. The age of 206.0 ± 6.5 Ma is consistent with the age of the metallogenic event that occurred at 200 Ma in the Upper Yangtze Pb–Zn metallogenic province of the Sichuan‐Yunnan‐Guizhou polymetallic zone, which is located on the southwest margin of the Sichuan Basin, suggesting that the metallogenic effects of this period were regional in scale in the peripheral areas of the Sichuan Basin. Previous studies have shown that two periods of hydrocarbon accumulation occurred in the oil/gas reservoir that coexists with the Pb‐Zn deposits in the study area. The Pb‐Zn mineralization at 468.3 ± 3.8 Ma occurred during the first period of hydrocarbon accumulation, while the second mineralization at 206.0 ± 6.5 Ma occurred during the transformation of the paleo‐oil reservoir to a paleogas reservoir. The spatial relationship between the paleo‐oil/‐gas reservoir and the MVT Pb‐Zn deposits and the temporal relationship between mineralization and hydrocarbon accumulation show that a close genetic relationship exists between the MVT Pb‐Zn mineralization and hydrocarbon accumulation. Analysis of metals in the source rocks forming the paleo‐oil/‐gas reservoirs show that source rocks which formed paleo‐oil/‐gas reservoirs may have provided metals for Pb‐Zn mineralization. Both the paleo‐oil/‐gas reservoirs and Pb‐Zn mineralizing fluids had the same origin. [ABSTRACT FROM AUTHOR]

Nitrogen-containing organic compounds (NOCs) substantially contribute to light-absorbing organic aerosols, although the atmospheric processes responsible for the secondary formation of these compounds are poorly understood. In this study, seasonal atmospheric processing of NOCs is investigated using single-particle mass spectrometry in urban Guangzhou from 2013 to 2014. The relative abundance of NOCs is found to be strongly enhanced when they are internally mixed with photochemically produced secondary oxidized organics (i.e., formate, acetate, pyruvate, methylglyoxal, glyoxylate, oxalate, malonate, and succinate) and ammonium (NH4+). Moreover, both the hourly detected particle number and the relative abundance of NOCs are highly correlated with those of secondary oxidized organics and NH4+. Therefore, it is hypothesized that the secondary formation of NOCs is most likely linked to oxidized organics and NH4+. Results from both multiple linear regression analysis and positive matrix factorization analysis further show that the relative abundance of NOCs could be well predicted (R2 > 0.7, p < 0.01) by oxidized organics and NH4+. Interestingly, the relative abundance of NOCs is inversely correlated with NH4+ , whereas their number fractions are positively correlated. This result suggests that although the formation of NOCs does require the involvement of NH3/NH4+ , the relative amount of NH4+ may have a negative effect. Higher humidity and NOx likely facilitates the conversion of oxidized organics to NOCs. Due to the relatively high oxidized organics and NH3/NH4+ , the relative contributions of NOCs in summer and fall were higher than those in spring and winter. To the best of our knowledge, this is the first direct field observation study reporting a close association between NOCs and both oxidized organics and NH4+. These findings have substantial implications for the role of NH4+ in the atmosphere, particularly in models that predict the evolution and deposition of NOCs. Highlights. NOCs were highly internally mixed with photochemically produced secondary oxidized organics NOCs could be well predicted by the variations of these oxidized organics and NH4+ Higher relative humidity and NOx may facilitate the conversion of these oxidized organics to NOCs [ABSTRACT FROM AUTHOR]

The effects of the chemical composition and size of sea-salt-containing particles on their cloud condensation nuclei (CCN) activity are incompletely understood. We used a ground-based counterflow virtual impactor (GCVI) coupled with a single-particle aerosol mass spectrometer (SPAMS) to characterize chemical composition of submicron (dry diameter of 0.2–1.0 µm) and supermicron (1.0–2.0 µm) sea-salt-containing cloud residues (dried cloud droplets) at Mount Nanling, southern China. Seven cut sizes (7.5–14 µm) of cloud droplets were set in the GCVI system. The highest number fraction of sea-salt-containing particles was observed at the cut size of 7.5 µm (26 %, by number), followed by 14 µm (17 %) and the other cut sizes (3 %–5 %). The submicron sea-salt-containing cloud residues contributed approximately 20 % (by number) at the cut size of 7.5 µm , which was significantly higher than the percentages at the cut sizes of 8–14 µm (below 2 %). This difference was likely involved in the change in the chemical composition. At the cut size of 7.5 µm , nitrate was internally mixed with over 90 % of the submicron sea-salt-containing cloud residues, which was higher than sulfate (20 %), ammonium (below 1 %), amines (6 %), hydrocarbon organic species (2 %), and organic acids (4 %). However, at the cut sizes of 8–14 µm , nitrate, sulfate, ammonium, amines, hydrocarbon organic species, and organic acids were internally mixed with > 90 %, > 80 %, 39 %–84 %, 71 %–86 %, 52 %–90 %, and 32 %–77 % of the submicron sea-salt-containing cloud residues. The proportion of sea-salt-containing particles in the supermicron cloud residues generally increased as a function of cut size, and their CCN activity was less influenced by chemical composition. This study provided a significant contribution towards a comprehensive understanding of sea-salt CCN activity. [ABSTRACT FROM AUTHOR]

The Baguamiao gold deposit in Fengxian County of Shaanxi Province is located in Fengtai polymetallic ore concentration area in the orogenic belt of West Qinling Mountain. It is a typical gold deposit under the control of brittle-ductile shear zone. The progressive deformation of brittle-ductile shear zone has been found to be closely associated with gold enrichment: the gold-bearing sulphides pyrrhotite and pyrite are distributed along blastobedding S0 in the undeformed area, they are developed along phyllitic foliation S1 (//S0) in the slightly deformed area, along mylonitic foliation (S2#S0), or S-C foliation in the highly deformed area, and they are enriched along rheological quartz vein (S2-L) and joint quartz vein (S3) in the highly deformed and the tectonic fluid area. Researches based on electron microprobe analysis and mineral-structure-geochemistry indicate that the characteristic metamorphic mineral assemblage of the brittle-ductile shear zone is albite-biotite-sericite-chlorite-quartz-ankerite, with diagenetic and metallogenic temperatures and pressures spanning from 350 to 450 °C and from 0.12 to 0.31 GPa, respectively. In addition, greenschist facies in intermediate temperature and intermediate and low-pressure environment is the metamorphic facies of shear zone in main period. A reconstruction of the palaeotemperature history, based on the biotite and chlorite compositional geothermometer, revealed an intermediate-temperature phase, a high-temperature phase, and a high-temperature critical phase. Biotitization tends to develop towards an oxidation phase, while chloritization is characterized by development towards a reduction phase, indicating large-scale gold enrichment and mineralization were accompanied by strong redox reactions in the ore-forming fluid. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosol is of great importance not only for its strong potential in heating air and impacts on cloud, but also because of its hazards to human health. Wet deposition is regarded as the main sink of BC, constraining its lifetime and thus its impact on the environment and climate. However, substantial controversial and ambiguous issues in the wet scavenging processes of BC are apparent in current studies. Despite of its significance, there are only a small number of field studies that have investigated the incorporation of BC-containing particles into cloud droplets and influencing factors, in particular, the in-cloud scavenging, because it was simplicitly considered in many studies (as part of total wet scavenging). The mass scavenging efficiencies (MSEs) of BC were observed to be varied over the world, and the influencing factors were attributed to physical and chemical properties (e.g., size and chemical compositions) and meteorological conditions (cloud water content, temperature, etc.). In this review, we summarized the MSEs and potential factors that influence the in-cloud and below-cloud scavenging of BC. In general, MSEs of BC are lower at low-altitude regions (urban, suburban, and rural sites) and increase with the rising altitude, which serves as additional evidence that atmospheric aging plays an important role in the chemical modification of BC. Herein, higher altitude sites are more representative of free-tropospheric conditions, where BC is usually more aged. Despite of increasing knowledge of BC–cloud interaction, there are still challenges that need to be addressed to gain a better understanding of the wet scavenging of BC. We recommend that more comprehensive methods should be further estimated to obtain high time-resolved scavenging efficiency (SE) of BC, and to distinguish the impact of in-cloud and below-cloud scavenging on BC mass concentration, which is expected to be useful for constraining the gap between field observation and modeling simulation results. [ABSTRACT FROM AUTHOR]