Ozone (O3) pollution is becoming increasingly severe in China. In addition, our limited understanding of the relationship between O3 and volatile organic compounds (VOCs), is an obstacle to improving air quality. By developing an improved source-oriented speciated VOC emission inventory in 2013, we estimated the ozone formation potential (OFP) and investigated its characteristics in China. Besides, a comparison was made between our estimates and space-based observations from the ozone monitoring instrument (OMI) on the National Aeronautics and Space Administration (NASA)’s Aura satellite. According to our estimates, m-/p-xylene, ethylene, formaldehyde, toluene, and propene were the five species that had the largest potential to form ozone, and on-road vehicles, industrial processes, biofuel combustion, and surface coating were the key contributing sectors. Among different regions of China, the North China Plain, Yangtze River Delta, and Pearl River Delta had the highest OFP values. Our results suggest that O3formation is VOC-limited in major urban areas of China. Additionally, considering the different photochemical reactivities of various VOC species and the disparate energy and industry structures in the different regions of China, more efficient OFP-based and localized VOC control measures should be implemented, instead of the current mass-based and nationally uniform policies.

Chongqing, the largest megacity in southwest China, faces serious aerosol pollution but lacks information on particle characteristics and its sources. Official data released by Chongqing Environmental Protection Bureau demonstrated that urban PM10 concentrations decreased remarkably from 150 μg m− 3 in 2000 to 90 μg m− 3 in 2012. However, only several peer-reviewed studies paid attention to local fine particle (PM2.5) pollution. In the study, PM2.5 samples were obtained and subjected to chemical analysis in an urban site of the city during 2012 to 2013. The annual mean PM10 and PM2.5 concentrations in urban Chongqing were 103.9 ± 52.5 and 75.4 ± 42.2 μg m− 3, respectively. PM2.5 showed a distinct seasonality of high concentration in winter and similar levels in other seasons. The average OC/EC (organic carbon/element carbon) ratio was 3.7 with more high-OC/EC ratio sources contribution in autumn and winter. The varying sources and formation mechanisms resulted in SO42 − and NH4+ peaks in both summer and winter, whereas high nitrate concentration was only observed in winter. In the average mass closure, PM2.5 was composed of 23.0% SO42 −, 11.7% NO3−, 10.9% NH4+, 30.8% OM (organic matter), 5.2% EC, 8.2% mineral dust, 0.6% TEO (trace elements), 1.0% Cl− and 1.1% K+, while exhibiting large seasonal variability. Using positive matrix factorization (PMF), six sources were apportioned in PM2.5: secondary inorganic aerosols, coal combustion, other industrial pollution, soil dust, vehicular emission, and metallurgical industry. The annual mean contribution of above sources to PM2.5 was 37.5, 22.0, 17.5, 11.0, 9.8 and 2.2%, respectively. Coal combustion was identified by As tracer and dominated the primary sources of PM2.5, while the two different industrial sources were characterized by Cr and Mo, Co, Ni, and Se, respectively. The study is of great importance in characterizing the historical trends, current chemical characteristics and sources of fine particles in urban Chongqing.

Bibliometric analysis was applied to identify global patterns and trends in the research of biogenic volatile organic compounds (BVOCs), which are important to atmospheric ozone formation and secondary organic aerosol formation. Yearly publications, mainstream subject categories and journals, leading countries and institutions, research emphases and trends were identified. Number of publications and times of citation were used as indicators to evaluate publication performances. A summary of the most frequently used keywords obtained from author keywords and KeyWords Plus provided clues for research emphases in different periods. A network of keywords was drawn to visualize the cross-relationship of keywords. Results indicated that annual output of the related scientific papers increased notably during 1991–2014. Atmospheric Sciences, Environmental Sciences & Ecology, Environmental Sciences & Engineering, and Chemistry were the main subject categories. Journal of Geophysical Research-Atmospheres was the most competitive journal in productivity and academic impact. The USA and the National Center for Atmospheric Research (NCAR) were, respectively, the leading country and leading institution in BVOC research. “Emissions,” “isoprene,” and “model” were the leading research emphases in BVOC field in terms of word frequencies and centrality driven from the network structure. The three leading research hotspots cross-fields, emissions-isoprene, emissions-model, and isoprene-model showed substantial growth in scientific outputs during the study period. These trends were evidenced by the evolution of research contents in various studies.