Assessment of biomass burning impact on the regional air quality of Yangtze River Delta, China

Yangtze River Delta (YRD) region experiences severe haze pollution as a result of rapid economy growth and urbanization during recent decades. Its annual average PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5μm) concentration often exceeded the National Ambient Air Quality Standards of China–Grade II (35 µg m-3) and this occurs not only in urban areas but also in suburban and rural areas as well. One of the major contributors to the decreasing air quality in this region is biomass burning. Hence, this research aims to study biomass burning impact on the air quality in YRD through the investigation of atmospheric fine aerosols. An intensive field sampling campaign was conducted at four representative sampling sites in urban, suburban and rural areas of this region from December 2014 to November 2015. The characteristics of PM2.5 samples that collected in this region were investigated through a comprehensive analysis of major components of aerosol samples, including major water soluble inorganic ions (WSII), trace metals, organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), biomass burning tracers and fungal spore tracers. The investigation of above mentioned components can provide a very comprehensive profile of PM2.5-related pollutants in YRD. In addition, air mass backward trajectory analysis and fire-spots analysis were also carried out in this study to identify air mass origins, pathways and fire events in this region. Positive matrix factorization (PMF) was also applied to estimate the contribution from biomass burning to fine aerosols in YRD. Both temporal and spatial trends of above pollutants were studied accordingly to set up seasonal and geographical profiles. In total, more than 240 PM2.5 samples were being analysed in this study. The annual average PM2.5 concentration in this region was 66.2 ± 37.7 µg m-3, and urban sites were observed with higher PM2.5 concentrations than the other two suburban and rural sites. The annual average concentration of total 12 WSII in YRD was 29.1 ± 19.9 µg m-3, dominated by SO42-, NO3-, NH4+, Cl-, and K+. The annual averaged concentration of total 20 metals in YRD was 2.8 ± 0.4 μg m-3, dominated by K, Al, Fe, Mg, Zn and V (> 100 ng m-3). The carcinogenic risk of Cr and As via ingestion is higher than the acceptable level for all residences in YRD. The annual average level of PM2.5-associated total carbon (TC) at YRD region was 14.3 ± 4.1 μg m-3, accounted for 26.2 (± 6.5) % of annual mean PM2.5 concentration. The annual averaged concentration of total 17 PAHs in YRD was 35.5 ± 12.3 ng m-3, dominated by retene, BkF, BbF, Ind, Bpe, Flt and Chr (> 2 ng m-3). The annual lifetime cancer risk of PAHs through inhalation exposure in YRD was 3.57 × 10-4. The annual average concentrations of levoglucosan and arabitol were 81.3 ± 18.2 ng m-3 and 5.6 ± 0.7 ng m-3 respectively. These compounds above exhibited similar seasonal patterns as PM2.5 with elevated level in winter and lower level in summer, except fungal spore tracers which showed the highest concentration in summer. In total, WSII, trace metals, TC, PAHs and organic tracers explained more than 69.8 % of total PM2.5 in YRD. The contribution from biomass burning to fine aerosols in YRD was 18.2%-37.4%. The concentration of biomass burning emitted PM2.5 ranged from 10.07 μg m-3 in spring to 27.60 μg m-3 in winter. Fine aerosols in southern YRD were contributed remarkably by fuel combustion such as coal and biomass burning, with less contributions from traffic emissions and soil origins, minor from sea salts. The contribution from coal combustion and biomass burning was more significant in winter and autumn than in spring and summer. The contribution from biomass burning decreased within the provincial capital municipality and the influence from biomass burning was more significant in rural area during autumn. In addition, the air mass backward trajectory analysis also showed that the contribution from transboundary transport of aerosols from highly polluted north China cannot be neglected

Comparison of physical and chemical properties of ambient aerosols during the 2009 haze and non-haze periods in Southeast Asia

Recurrent smoke-haze episodes that occur in Southeast Asia (SEA) are of much concern because of their environmental and health impacts. These haze episodes are mainly caused by uncontrolled biomass and peat burning in Indonesia. Airborne particulate matter (PM) samples were collected in the southwest coast of Singapore from 16 August to 9 November in 2009 to assess the impact of smoke-haze episodes on the air quality due to the long-range transport of biomass and peat burning emissions. The physical and chemical characteristics of PM were investigated during pre-haze, smoke-haze, and post-haze periods. Days with PM2.5 mass concentrations of ≥35 μg m−3 were considered as smoke-haze events. Using this criterion, out of the total 82 sampling days, nine smoke-haze events were identified. The origin of air masses during smoke-haze episodes was studied on the basis of HYSPLIT backward air trajectory analysis for 4 days. In terms of the physical properties of PM, higher particle surface area concentrations and particle gravimetric mass concentrations were observed during the smoke-haze period, but there was no consistent pattern for particle number concentrations during the haze period as compared to the non-haze period except that there was a significant increase at about 08:00, which could be attributed to the entrainment of PM from aloft after the breakdown of the nocturnal inversion layer. As for the chemical characteristics of PM, among the six key inorganic water-soluble ions (Cl−, NO3 −, nss-SO4 2−, Na+, NH4 +, and nss-K+) measured in this study, NO3 −, nss-SO4 2−, and NH4 + showed a significant increase in their concentrations during the smoke-haze period together with nss-K+. These observations suggest that the increased atmospheric loading of PM with higher surface area and increased concentrations of optically active secondary inorganic aerosols [(NH4)2SO4 or NH4HSO4 and NH4NO3] resulted in the atmospheric visibility reduction in SEA due to the advection of biomass and peat burning emissions

Seasonal variation characteristics of fungi aerosol tracers in the northern Zhejiang Province

One year-long PM2.5 field sampling was conducted at four representative sites in the Northern Zhejiang Province (NZP) from December 2014 to November 2015. Fungi aerosol tracers such as arabitol and mannitol have been measured by using high performance liquid chromatography (HPLC) -triple quadrupole tandem mass spectrometry (MS/MS). Seasonal variation characteristics and sources of fungal aerosol tracers in NZP area were studied. The annual averaged concentrations of arabitol and mannitol in NZP were (5.6 ± 0.7) and (5.7 ± 1.3) ng·m-3, respectively. The elevated fungal aerosol tracers in summer could be attributed to the intensive local biomass burning and effect of wet and warm weather conditions favorable for the release of fungal spores. The contributions of fungal spores to the organic carbon (OC), estimated using mannitol-based conversion factor, were below 1 % at all sampling sites. The results from principle component analysis (PCA) also showed that fungal spore tracers (arabitol, mannitol) and biomass burning tracers (levoglucosan, mannosan, galactosan, nss-K+) were mostly grouped within the same component contributing to PM2.5 mass during the whole sampling campaign, indicating a continuous influence from biomass burning to the airborne fungal spores in NZP

Could wastewater analysis be a useful tool for China?: a review

Analysing wastewater samples is an innovative approach that overcomes many limitations of traditional surveys to identify and measure a range of chemicals that were consumed by or exposed to people living in a sewer catchment area. First conceptualised in 2001, much progress has been made to make wastewater analysis (WWA) a reliable and robust tool for measuring chemical consumption and/or exposure. At the moment, the most popular application of WWA, sometimes referred as sewage epidemiology, is to monitor the consumption of illicit drugs in communities around the globe, including China. The approach has been largely adopted by law enforcement agencies as a device to monitor the temporal and geographical patterns of drug consumption. In the future, the methodology can be extended to other chemicals including biomarkers of population health (e.g. environmental or oxidative stress biomarkers, lifestyle indicators or medications that are taken by different demographic groups) and pollutants that people are exposed to (e.g. polycyclic aromatic hydrocarbons, perfluorinated chemicals, and toxic pesticides). The extension of WWA to a huge range of chemicals may give rise to a field called sewage chemical-information mining (SCIM) with unexplored potentials. China has many densely populated cities with thousands of sewage treatment plants which are favourable for applying WWA/SCIM in order to help relevant authorities gather information about illicit drug consumption and population health status. However, there are some prerequisites and uncertainties of the methodology that should be addressed for SCIM to reach its full potential in China

Seasonal variation characteristics of fungi aerosol tracers in the northern Zhejiang Province

One year-long PM2.5 field sampling was conducted at four representative sites in the Northern Zhejiang Province (NZP) from December 2014 to November 2015. Fungi aerosol tracers such as arabitol and mannitol have been measured by using high performance liquid chromatography (HPLC) -triple quadrupole tandem mass spectrometry (MS/MS). Seasonal variation characteristics and sources of fungal aerosol tracers in NZP area were studied. The annual averaged concentrations of arabitol and mannitol in NZP were (5.6 ± 0.7) and (5.7 ± 1.3) ng·m-3, respectively. The elevated fungal aerosol tracers in summer could be attributed to the intensive local biomass burning and effect of wet and warm weather conditions favorable for the release of fungal spores. The contributions of fungal spores to the organic carbon (OC), estimated using mannitol-based conversion factor, were below 1 % at all sampling sites. The results from principle component analysis (PCA) also showed that fungal spore tracers (arabitol, mannitol) and biomass burning tracers (levoglucosan, mannosan, galactosan, nss-K+) were mostly grouped within the same component contributing to PM2.5 mass during the whole sampling campaign, indicating a continuous influence from biomass burning to the airborne fungal spores in NZP

Simultaneous measurement of multiple organic tracers in fine aerosols from biomass burning and fungal spores by HPLC-MS/MS

Three monosaccharide anhydrides (MAs: levoglucosan, mannosan, and galactosan) and sugar alcohols (arabitol and mannitol) are widely used as organic tracers for source identification of aerosols emitted from biomass burning and fungal spores, respectively. In the past, these two types of organic tracer have been measured separately or conjointly using different analytical techniques, with which a number of disadvantages have been experienced during the application to environmental aerosol samples, including organic solvent involved extraction, time-consuming derivatization, or poor separation efficiency due to overlapping peaks, etc. Hence, in this study a more environment-friendly, effective and integrated extraction and analytical method has been developed for simultaneous determination of the above mentioned organic tracers in the same aerosol sample using ultrasonication and high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The ultrasonication assisted extraction process using ultrapure water can achieve satisfactory recoveries in the range of 100.3 ± 1.3% to 108.4 ± 1.6% for these tracers. All the parameters related to LC and MS/MS have been optimized to ensure good identification and pronounced intensity for each compound. A series of rigorous validation steps have been conducted. This newly developed analytical method using ultrasonication and HPLC-MS/MS has been successfully applied to environmental aerosol samples of different pollution levels for the simultaneous measurement of the above mentioned five organic tracers from biomass burning and fungal spores

Sources and processes of iron aerosols in a megacity in Eastern China

Iron (Fe) in aerosol particles is a major external source of micronutrients for marine ecosystems and poses a potential threat to human health. To understand the impacts of aerosol Fe, it is essential to quantify the sources of dissolved Fe and total Fe. In this study, we applied receptor modeling for the first time to apportion the sources of dissolved Fe and total Fe in fine particles collected under five different weather conditions in the Hangzhou megacity of Eastern China, which is upwind of the East Asian outflow. Results showed that Fe solubility (dissolved Fe to total Fe) was the largest on fog days (6.7 ± 3.0 %), followed by haze (4.8 ± 1.9 %), dust (2.1 ± 0.7 %), clear (1.9 ± 1.0 %), and rain (0.9 ± 0.5 %) days. Positive matrix factorization (PMF) analysis suggested that industrial emissions were the largest contributor to dissolved Fe (44.5 %–72.4 %) and total Fe (39.1 %–55.0 %, except for dust days) during haze, fog, dust, and clear days. Transmission electron microscopy analysis of individual particles showed that > 75 % of Fe-containing particles were internally mixed with acidic secondary aerosol species on haze, fog, dust, and clear days. Furthermore, Fe solubility showed significant positive correlations with aerosol acidity/total Fe and liquid water content. These results indicated that the wet surface of aerosol particles promotes heterogeneous reactions between acidic species and Fe aerosols, contributing to a high Fe solubility

Atmospheric conditions and composition that influence PM2.5 oxidative potential in Beijing, China

Epidemiological studies have consistently linked exposure to PM2.5 with adverse health effects. The oxidative potential (OP) of aerosol particles has been widely suggested as a measure of their potential toxicity. Several acellular chemical assays are now readily employed to measure OP; however, uncertainty remains regarding the atmospheric conditions and specific chemical components of PM2.5 that drive OP. A limited number of studies have simultaneously utilised multiple OP assays with a wide range of concurrent measurements and investigated the seasonality of PM2.5 OP. In this work, filter samples were collected in winter 2016 and summer 2017 during the atmospheric pollution and human health in a Chinese megacity campaign (APHH-Beijing), and PM2.5 OP was analysed using four acellular methods: ascorbic acid (AA), dithiothreitol (DTT), 2,7-dichlorofluorescin/hydrogen peroxidase (DCFH) and electron paramagnetic resonance spectroscopy (EPR). Each assay reflects different oxidising properties of PM2.5, including particle-bound reactive oxygen species (DCFH), superoxide radical production (EPR) and catalytic redox chemistry (DTT/AA), and a combination of these four assays provided a detailed overall picture of the oxidising properties of PM2.5 at a central site in Beijing. Positive correlations of OP (normalised per volume of air) of all four assays with overall PM2.5 mass were observed, with stronger correlations in winter compared to summer. In contrast, when OP assay values were normalised for particle mass, days with higher PM2.5 mass concentrations (µgm−3) were found to have lower mass-normalised OP values as measured by AA and DTT. This finding supports that total PM2.5 mass concentrations alone may not always be the best indicator for particle toxicity. Univariate analysis of OP values and an extensive range of additional measurements, 107 in total, including PM2.5 composition, gas-phase composition and meteorological data, provided detailed insight into the chemical components and atmospheric processes that determine PM2.5 OP variability. Multivariate statistical analyses highlighted associations of OP assay responses with varying chemical components in PM2.5 for both mass- and volume-normalised data. AA and DTT assays were well predicted by a small set of measurements in multiple linear regression (MLR) models and indicated fossil fuel combustion, vehicle emissions and biogenic secondary organic aerosol (SOA) as influential particle sources in the assay response. Mass MLR models of OP associated with compositional source profiles predicted OP almost as well as volume MLR models, illustrating the influence of mass composition on both particle-level OP and total volume OP. Univariate and multivariate analysis showed that different assays cover different chemical spaces, and through comparison of mass- and volume-normalised data we demonstrate that mass-normalised OP provides a more nuanced picture of compositional drivers and sources of OP compared to volume-normalised analysis. This study constitutes one of the most extensive and comprehensive composition datasets currently available and provides a unique opportunity to explore chemical variations in PM2.5 and how they affect both PM2.5 OP and the concentrations of particle-bound reactive oxygen species

Impact of HO2 aerosol uptake on radical levels and O3 production during summertime in Beijing

The impact of heterogeneous uptake of HO2 on aerosol surfaces on radical concentrations and the O3 production regime in Beijing in summertime was investigated. The uptake coefficient of HO2 onto aerosol surfaces, γHO2 , was calculated for the AIRPRO campaign in Beijing, in summer 2017, as a function of measured aerosol soluble copper concentration, [Cu2+]eff, aerosol liquid water content, [ALWC], and particulate matter concentration, [PM]. An average γHO2 across the entire campaign of 0.070 ± 0.035 was calculated, with values ranging from 0.002 to 0.15, and found to be significantly lower than the value of γHO2 = 0.2, commonly used in modelling studies. Using the calculated γHO2 values for the summer AIRPRO campaign, OH, HO2 and RO2 radical concentrations were modelled using a box model incorporating the Master Chemical Mechanism (v3.3.1), with and without the addition of γHO2 , and compared to the measured radical concentrations. The rate of destruction analysis showed the dominant HO2 loss pathway to be HO2 + NO for all NO concentrations across the summer Beijing campaign, with HO2 uptake contributing < 0.3 % to the total loss of HO2 on average. This result for Beijing summertime would suggest that under most conditions encountered, HO2 uptake onto aerosol surfaces is not important to consider when investigating increasing O3 production with decreasing [PM] across the North China Plain. At low [NO], however, i.e. < 0.1 ppb, which was often encountered in the afternoons, up to 29 % of modelled HO2 loss was due to HO2 uptake on aerosols when calculated γHO2 was included, even with the much lower γHO2 values compared to γHO2 = 0.2, a result which agrees with the aerosol-inhibited O3 regime recently proposed by Ivatt et al. (2022). As such it can be concluded that in cleaner environments, away from polluted urban centres where HO2 loss chemistry is not dominated by NO but where aerosol surface area is high still, changes in PM concentration and hence aerosol surface area could still have a significant effect on both overall HO2 concentration and the O3 production regime. Using modelled radical concentrations, the absolute O3 sensitivity to NOx and volatile organic compounds (VOCs) showed that, on average across the summer AIRPRO campaign, the O3 production regime remained VOC-limited, with the exception of a few days in the afternoon when the NO mixing ratio dropped low enough for the O3 regime to shift towards being NOx -limited. The O3 sensitivity to VOCs, the dominant regime during the summer AIRPRO campaign, was observed to decrease and shift towards a NOx -sensitive regime both when NO mixing ratio decreased and with the addition of aerosol uptake. This suggests that if [NOx ] continues to decrease in the future, ozone reduction policies focussing solely on NOx reductions may not be as efficient as expected if [PM] and, hence, HO2 uptake to aerosol surfaces continue to decrease. The addition of aerosol uptake into the model, for both the γHO2 calculated from measured data and when using a fixed value of γHO2 = 0.2, did not have a significant effect on the overall O3 production regime across the campaign. While not important for this campaign, aerosol uptake could be important for areas of lower NO concentration that are already in a NOx -sensitive regime

Atmospheric pollution and human health in a Chinese megacity (APHH-Beijing) programme. Final report

In 2016, over 150 UK and Chinese scientists joined forces to understand the causes and impacts - emission sources, atmospheric processes and health effects - of air pollution in Beijing, with the ultimate aim of informing air pollution solutions and thus improving public health. The Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) research programme succeeded in delivering its objectives and significant additional science, through a large-scale, coordinated multidisciplinary collaboration. In this report are highlighted some of the research outcomes that have potential implications for policymaking