Biomass burning (BB) is an important source of primary organic aerosols (POA). These POA contain a significant fraction of semivolatile organic compounds, and can release them into the gas phase during the dilution process in transport. Such evaporated compounds were termed secondarily evaporated BB organic gases (SBB-OGs) to distinguish them from the more studied primary emissions. SBB-OGs contribute to the formation of secondary organic aerosols (SOA) through reactions with atmospheric oxidants, and thus may influence human health and the Earth's radiation budget. In this study, tar materials collected from wood pyrolysis were taken as proxies for POA from smoldering-phase BB and were used to release SBB-OGs constantly in the lab. OH-initiated oxidation of the SBB-OGs in the absence of NOx was investigated using an oxidation flow reactor, and the chemical, optical, and toxicological properties of SOA were comprehensively characterized. Carbonyl compounds were the most abundant species in identified SOA species. Human lung epithelial cells exposed to an environmentally relevant dose of the most aged SOA did not exhibit detectable cell mortality. The oxidative potential of SOA was characterized with the dithiothreitol (DTT) assay, and its DTT consumption rate was 15.5 +/- 0.5 pmol min 1 mu g(-1). The SOA present comparable light scattering to BB-POA, but have lower light absorption with imaginary refractive index less than 0.01 within the wavelength range of 360-600 nm. Calculations based on Mie theory show that pure airborne SOA with atmospherically relevant sizes of 50-400 nm have a cooling effect; when acting as the coating materials, these SOA can counteract the warming effect brought by airborne black carbon aerosol.

This study applies the nested-grid version of Goddard Earth Observing System (GEOS) chemical transport model (GEOS-Chem) to examine future changes (2000-2050) in SOA concentration and associated direct radiative forcing (DRF) over China under the Representative Concentration Pathways (RCPs). The projected changes in SOA concentrations over 2010-2050 generally follow future changes in emissions of toluene and xylene. On an annual mean basis, the largest increase in SOA over eastern China is simulated to be 25.1% in 2020 under RCP2.6, 20.4% in 2020 under RCP4.5, 56.3% in 2050 under RCP6.0, and 44.6% in 2030 under RCP8.5. The role of SOA in PM2.5 increases with each decade in 2010-2050 under RCP2.6, RCP4.5, and RCPS.5, with a maximum ratio of concentration of SOA to that of PM2.5 of 16.3% in 2050 under RCP4.5 as averaged over eastern China (20 degrees-45 degrees N, 100 degrees-125 degrees E). Concentrations of SOA are projected to be able to exceed those of sulfate, ammonium, and black carbon (BC) in the future. The future changes in SOA levels over eastern China are simulated to lead to domain-averaged (20 degrees-45 degrees N, 100 degrees-125 degrees E) DRI's of +0.19 W m(-2), +0.12 W m(-2), -0.28 W m(-2), and -0.17 W m(-2) in 2050 relative to 2000 under RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. Model results indicate that future changes in SOA owing to future changes in anthropogenic precursor emissions are important for future air quality planning and climate mitigation measures. (C) 2018 Elsevier B.V. All rights reserved.

Secondary organic aerosol (SOA) nearly always exists as an internal mixture, and the distribution of this mixture depends on the formation mechanism of SOA. A model is developed to examine the influence of using an internal mixing state based on the mechanism of formation and to estimate the radiative forcing of SOA in the future. For the present day, 66% of SOA is internally mixed with sulfate, while 34% is internally mixed with primary soot. Compared with using an external mixture, the direct effect of SOA is decreased due to the decrease in total aerosol surface area and the increase of absorption efficiency. Aerosol number concentrations are sharply reduced, and this is responsible for a large decrease in the cloud albedo effect. Internal mixing decreases the radiative effect of SOA by a factor of >4 compared with treating SOA as an external mixture. The future SOA burden increases by 24% due to CO2 increases and climate change, leading to a total (direct plus cloud albedo) radiative forcing of -0.05 W m(-2). When the combined effects of changes in climate, anthropogenic emissions, and land use are included, the SOA forcing is -0.07 W m(-2), even though the SOA burden only increases by 6.8%. This is caused by the substantial increase of SOA associated with sulfate in the Aitken mode. The Aitken mode increase contributes to the enhancement of first indirect radiative forcing, which dominates the total radiative forcing.

Isoangustone A是一种来源于甘草的异戊烯基化黄酮类化合物,具有抗菌、抗氧化、抗炎、抗肿瘤等活性。为了增加其结构多样性,本文利用丝状真菌冻土毛霉(Mucor hiemalis CGMCC 3.14114)对该化合物进行微生物转化,共分离得到3个新化合物。通过NMR和MS谱学分析,其结构分别鉴定为isoangustone A 7-O-glucoside(2),isoangustone A 7-O-glucoside-4'-O-sulfate(3),以及isoangustone A 7,3'-di-O-glucoside(4)。主要转化反应为C-7位糖基化反应。此外,硫酸酯化反应是较为罕见的微生物转化反应。

Ambient organic carbon (OC) to elemental carbon (EC) ratios are strongly associated with not only the radiative forcing due to aerosols but also the extent of secondary organic aerosol (SOA) formation. An inter-comparison study was conducted based on fine particulate matter samples collected during summer in Beijing to investigate the influence of the thermal-optical temperature protocol on the OC to EC ratio. Five temperature protocols were used such that the NIOSH (National Institute for Occupational Safety and Health) and EUSAAR (European Supersites for Atmospheric Aerosol Research) protocols were run by the Sunset carbon analyzer while the IMPROVE (the Interagency Monitoring of Protected Visual Environments network)-A protocol and two alternative protocols designed based on NIOSH and EUSAAR were run by the DRI analyzer. The optical attenuation measured by the Sunset carbon analyzer was more easily biased by the shadowing effect, whereas total carbon agreed well between the Sunset and DRI analyzers. The ECIMPROVE-A (EC measured by the IMPROVE-A protocol; similar hereinafter) to ECNIOSH ratio and the ECIMPROVE-A to ECEUSAAR ratio averaged 1.36 +/- 0.21 and 0.91 +/- 0.10, respectively, both of which exhibited little dependence on the biomass burning contribution. Though the temperature protocol had substantial influence on the DC to EC ratio, the contributions of secondary organic carbon (SOC) to OC, which were predicted by the EC-tracer method, did not differ significantly among the five protocols. Moreover, the SOC contributions obtained in this study were comparable with previous results based on field observation (typically between 45 and 65%), but were substantially higher than the estimation provided by an air quality model (only 18%). The comparison of SOC and WSOC suggests that when using the transmittance charring correction, all of the three common protocols (i.e., IMPROVE-A, NIOSH and EUSAAR) could be reliable for the estimation of SOC by the EC-tracer method. (C) 2013 Elsevier B.V. All rights reserved.