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Anthropogenic emissions alter biogenic secondary organic aerosol (SOA) formation from naturally emitted volatile organic compounds (BVOCs). We review the major laboratory and field findings with regard to effects of anthropogenic pollutants (NO x , anthropogenic aerosols, SO 2 , NH 3 ) on biogenic SOA formation. NO x participate in BVOC oxidation through changing the radical chemistry and oxidation capacity, leading to a complex SOA composition and yield sensitivity towards NO x level for different or even specific hydrocarbon precursors. Anthropogenic aerosols act as an important intermedium for gas—particle partitioning and particle-phase reactions, processes of which are influenced by the particle phase state, acidity, water content and thus associated with biogenic SOA mass accumulation. SO 2 modifies biogenic SOA formation mainly through sulfuric acid formation and accompanies new particle formation and acid-catalyzed heterogeneous reactions. Some new SO 2 -involved mechanisms for organosulfate formation have also been proposed. NH 3 /amines, as the most prevalent base species in the atmosphere, influence biogenic SOA composition and modify the optical properties of SOA. The response of SOA formation behavior to these anthropogenic pollutants varies among different BVOCs precursors. Investigations on anthropogenic—biogenic interactions in some areas of China that are simultaneously influenced by anthropogenic and biogenic emissions are summarized. Based on this review, some recommendations are made for a more accurate assessment of controllable biogenic SOA formation and its contribution to the total SOA budget. This study also highlights the importance of controlling anthropogenic pollutant emissions with effective pollutant mitigation policies to reduce regional and global biogenic SOA formation.

Quantifying differences in secondary organic aerosols (SOAs) between the preindustrial period and the present day is crucial to assess climate forcing and environmental effects resulting from anthropogenic activities. The lack of vegetation information for the preindustrial period and the uncertainties in describing SOA formation are two leading factors preventing simulation of SOA. This study calculated the online emissions of biogenic volatile organic compounds (VOCs) in the Aerosol and Atmospheric Chemistry Model of the Institute of Atmospheric Physics (IAP-AACM) by coupling the Model of Emissions of Gases and Aerosols from Nature (MEGAN), where the input vegetation parameters were simulated by the IAP Dynamic Global Vegetation Model (IAP-DGVM). The volatility basis set (VBS) approach was adopted to simulate SOA formation from the nontraditional pathways, i.e., the oxidation of intermediate VOCs and aging of primary organic aerosol. Although biogenic SOAs (BSOAs) were dominant in SOAs globally in the preindustrial period, the contribution of nontraditional anthropogenic SOAs (ASOAs) to the total SOAs was up to 35.7%. In the present day, the contribution of ASOAs was 2.8 times larger than that in the preindustrial period. The contribution of nontraditional sources of SOAs to SOA was as high as 53.1%. The influence of increased anthropogenic emissions in the present day on BSOA concentrations was greater than that of increased biogenic emission changes. The response of BSOA concentrations to anthropogenic emission changes in the present day was more sensitive than that in the preindustrial period. The nontraditional sources and the atmospheric oxidation capability greatly affect the global SOA change.

The North China Plain (NCP) is a region that experiences serious aerosol pollution. A number of studies have focused on aerosol pollution in urban areas in the NCP region; however, research on characterizing aerosols in rural NCP areas is comparatively limited. In this study, we deployed a TD-HR-AMS (thermodenuder high-resolution aerosol mass spectrometer) system at a rural site in the NCP region in summer 2013 to characterize the chemical compositions and volatility of submicron aerosols (PM 1 ). The average PM 1 mass concentration was 51.2 ± 48.0 µg m −3 and organic aerosol (OA) contributed most (35.4%) to PM 1 . Positive matrix factorization (PMF) analysis of OA measurements identified four OA factors, including hydrocarbon-like OA (HOA, accounting for 18.4%), biomass burning OA (BBOA, 29.4%), less-oxidized oxygenated OA (LO-OOA, 30.8%) and more-oxidized oxygenated OA (MO-OOA, 21.4%). The volatility sequence of the OA factors was HOA > BBOA > LO-OOA > MO-OOA, consistent with their oxygen-to-carbon (O:C) ratios. Additionally, the mean concentration of organonitrates (ON) was 1.48–3.39 µg m −3 , contributing 8.1%–19% of OA based on cross validation of two estimation methods with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement. Correlation analysis shows that ON were more correlated with BBOA and black carbon emitted from biomass burning but poorly correlated with LO-OOA. Also, volatility analysis for ON further confirmed that particulate ON formation might be closely associated with primary emissions in rural NCP areas.

As the key precursors of O 3 , anthropogenic non-methane volatile organic compounds (NMVOCs) have been studied intensively. This paper performed a meta-analysis on the spatial and temporal variations of NMVOCs, their roles in photochemical reactions, and their sources in China, based on published research. The results showed that both non-methane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs) in China have higher mixing ratios in the eastern developed cities compared to those in the central and western areas. Alkanes are the most abundant NMHCs species in all reported sites while formaldehyde is the most abundant among the OVOCs. OVOCs have the highest mixing ratios in summer and the lowest in winter, which is opposite to NMHCs. Among all NMVOCs, the top eight species account for 50%–70% of the total ozone formation potential (OFP) with different compositions and contributions in different areas. In devolved regions, OFP-NMHCs are the highest in winter while OFP-OVOCs are the highest in summer. Based on positive matrix factorization (PMF) analysis, vehicle exhaust, industrial emissions, and solvent usage in China are the main sources for NMHCs. However, the emission trend analysis showed that solvent usage and industrial emissions will exceed vehicle exhaust and become the two major sources of NMVOCs in near future. Based on the meta-analysis conducted in this work, we believe that the spatio-temporal variations and oxidation mechanisms of atmospheric OVOCs, as well as generating a higher spatial resolution of emission inventories of NMVOCs represent an area for future studies on NMVOCs in China.

Multiaxis differential absorption spectroscopy (MAX-DOAS) is a newly developed advanced vertical profile detection method, but the vertical nitrogen dioxide (NO 2 ) profiles measured by MAX-DOAS have not yet been fully verified. In this study, we perform MAX-DOAS and tower gradient observations to simultaneously acquire tropospheric NO 2 observations in the Beijing urban area from 1 April to 31 May 2019. The average values of the tropospheric NO 2 vertical column densities measured by MAX-DOAS and the tropospheric monitoring instrument are 15.8 × 10 15 and 12.4 × 10 15 molecules cm −2 , respectively, and the correlation coefficient R reaches 0.87. The MAX-DOAS measurements are highly consistent with the tower-based in situ measurements, and the correlation coefficients R from the ground to the upper air are 0.89 (60 m), 0.87 (160 m), and 0.76 (280 m). MAX-DOAS accurately measures the trend of NO 2 vertical profile changes, although a large underestimation occurs by a factor of two. By analyzing the NO 2 vertical profile, the NO 2 concentration reveals an exponential decrease with height. The NO 2 vertical profile also coincides with the evolution of the boundary layer height. The study shows that the NO 2 over Beijing mainly originates from local sources and occurs in the boundary layer, and its vertical evolution pattern has an important guiding significance to better understand nitrate production and ozone pollution.

Iron and oxalic acids are widely distributed in the atmosphere and easily form ferric oxalate complex (Fe(III)-Ox). The tropospheric aqueous-phase could provide a medium to enable the photo-Fenton reaction with Fe(III)-Ox under solar irradiation. Although the photolysis mechanisms of Fe(III)-Ox have been investigated extensively, information about the oxidation of volatile organic compounds (VOC), specifically the potential for Secondary Organic Aerosol (SOA) formation in the Fe(III)-Ox system, is lacking. In this study, a ubiquitous VOC methacrolein (MACR) is chosen as a model VOC, and the oxidation of MACR with Fe(III)-Ox is investigated under typical atmospheric water conditions. The effects of oxalate concentration, Fe(III) concentration, MACR concentration, and pH on the oxidation of MACR are studied in detail. Results show that the oxidation rate of MACR greatly accelerates in the presence of oxalate when compared with only Fe(III). The oxidation rate of MACR also accelerates with increasing concentration of oxalate. The effect of Fe(III) is found to be more complicated. The oxidation rate of MACR first increases and then decreases with increasing Fe(III) concentration. The oxidation rate of MACR increases monotonically with decreasing pH in the common atmospheric water pH range or with decreasing MACR concentration. The production of ferrous and hydrogen peroxide, pH, and aqueous absorbance are monitored throughout the reaction process. The quenching experiments verify that · OH and O 2 . ¯ are both responsible for the oxidation of MACR. MACR is found to rapidly oxidize into small organic acids with higher boiling points and oligomers with higher molecular weight, which contributes to the yield of SOA. These results suggest that Fe(III)-Ox plays an important role in atmospheric oxidation.

Amines are important for new particle formation and subsequent growth in the atmosphere. Consequently, the processes involved are receiving more attention in recent years. Here, we conduct a field observation in order to investigate the atmospheric particulate amines at a background site in the Yangtze River Delta (YRD) during the summer of 2018. Four amines in PM 2.5 , i.e., methylamine (MA), dimethylamine (DMA), diethylamine (DEA), and trimethylamine (TMA), were collected, twice daily and analyzed. During the campaign, our measurements found the concentrations of MA, DMA, DEA, and TMA of 15.0 ± 15.0, 6.3 ± 6.9, 20.4 ± 30.1, and 4.0 ± 5.9 ng m −3 , respectively, and the four amines correlated well with each other. The concentration of amines appear to be independent of whether they were collected during the day or night. Both MA and DMA exhibited a bimodal size distribution that had peaks at 0.67 and 1.1 µm, suggesting amines preferably distribute on submicron particles. Boundary layer height (BLH), relative humidity, and pH of aerosols were found have a negative relationship with amines, while aerosol liquid water content (ALWC) was found to have a positive relationship with amines. The PMF (positive matrix factorization) source apportionment results showed that the main source of amines in Chongming Island was of anthropogenic origin such as industrial and biomass emission, followed by marine sources including sea salt and marine biogenic sources. Given that the YRD region is still suffering from complex atmospheric pollution and that the knowledge on aerosol amines is still limited, more field studies are in urgent need for a better understanding of the pollution characteristics of amines.

Fine particulate matter (PM 2.5 ) and ozone (O 3 ) double high pollution (DHP) events have occurred frequently over China in recent years, but their causes are not completely clear. In this study, the spatiotemporal distribution of DHP events in China during 2013–20 is analyzed. The synoptic types affecting DHP events are identified with the Lamb–Jenkinson circulation classification method. The meteorological and chemical causes of DHP events controlled by the main synoptic types are further investigated. Results show that DHP events (1655 in total for China during 2013–20) mainly occur over the North China Plain, Yangtze River Delta, Pearl River Delta, Sichuan Basin, and Central China. The occurrence frequency increases by 5.1% during 2013–15, and then decreases by 56.1% during 2015–20. The main circulation types of DHP events are “cyclone” and “anticyclone”, accounting for over 40% of all DHP events over five main polluted regions in China, followed by southerly or easterly flat airflow types, like “southeast”, “southwest”, and “east”. Compared with non-DHP events, DHP events are characterized by static or weak wind, high temperature (20.9°C versus 23.1°C) and low humidity (70.0% versus 64.9%). The diurnal cycles of meteorological conditions cause PM 2.5 (0300–1200 LST, Local Standard Time= UTC+ 8 hours) and O 3 (1500–2100 LST) to exceed the national standards at different periods of the DHP day. Three pollutant conversion indices further indicate the rapid secondary conversions during DHP events, and thus the concentrations of NO 2 , SO 2 and volatile organic compounds decrease by 13.1%, 4.7% and 4.4%, respectively. The results of this study can be informative for future decisions on the management of DHP events.

China experienced worsening ground-level ozone (O 3 ) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature ( T 2 ), solar radiation (SW), and wind speed (WS), were classified into two aspects, (1) Photochemical Reaction Condition (PRC = T 2 × SW) and (2) Physical Dispersion Capacity (PDC = WS). In this way, a Meteorology Synthetic Index (MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O 3 pollution. The positive linear relationship between the 90th percentile of MDA8 (maximum daily 8-h average) O 3 concentration and MSI determined that the contribution of meteorological changes to ground-level O −3 varied on a latitudinal gradient, decreasing from ∼40% in southern China to 10%–20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O 3 pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O 3 variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies.

As Volatile Organic Compounds (VOCs) are one of the precursors of ozone, their distribution and variable concentrations are highly related to local ozone pollution control. In this study, we obtained vertical profiles of VOCs in Shanghai’s Jinshan district on 8 September and 9 September in 2016 to investigate their distribution and impact on local atmospheric oxidation in the near surface layer. Vertical samples were collected from heights between 50 m and 400 m by summa canisters using an unmanned aerial vehicle (UAV). Concentrations of VOCs (VOCs refers to the 52 species measured in this study) varied minimally below 200 m, and decreased by 21.2% from 100 m to 400 m. The concentrations of VOCs above 200 m decreased significantly in comparison to those below 200 m. The proportions of alkanes and aromatics increased from 55.2% and 30.5% to 57.3% and 33.0%, respectively. Additionally, the proportion of alkenes decreased from 13.2% to 8.4%. Toluene and m/p -xylene were the key species in the formation of SOA and ozone. Principal component analysis (PCA) revealed that the VOCs measured in this study mainly originated from industrial emissions.