Observation Constrained Aromatic Emissions in Shanghai, China

Abstract

Aromatics in the atmosphere are a large contributor to ozone and secondary organic aerosol formation and have an adverse impact on human health. Observation‐based emissions are urgently needed for air quality management and decision making due to the large uncertainties in the emissions inventories. Atmospheric aromatics were continuously observed at one urban site in Shanghai of China in 2015, which were compared with the simulations of the Community Multiscale Air Quality (CMAQ) model. Large differences were found in the temporal variations between the model and measurements, corroborating with previous studies that the current bottom‐up emission inventories are highly biased. We corrected the aromatic emissions biases of the emission inventories using the observations with the CMAQ simulations, with the assumption that the response relationship of the emissions input and aromatic concentrations was reasonable on a monthly basis in CMAQ simulations, suggesting that the results are dependent on the model performance. The resulting aromatic emissions exhibited clear monthly variations, increasing from 5.5 ± 2.1 Gg month−1 in February to 17.4 ± 7.7 Gg month−1 in July, being different from the flat monthly pattern in the current bottom‐up emissions inventory. Toluene, xylenes, and ethylbenzene dominated aromatic emissions, accounting for ~74% on average but with considerable monthly variations, which was different from the nearly uniform value of 77% throughout the whole year in the emissions inventory. These highly temporally resolved and speciated in situ aromatics measurements provide observation‐based constraints on aromatic emissions, which cannot be obtained from satellite measurements. This study proposes a top‐down emission estimation method constrained by ambient measurements.

Driving Forces of Changes in Air Quality during the COVID-19 Lockdown Period in the Yangtze River Delta Region, China

“…The PM 2.5 composition and VOCs measurements were made at the SAES site, and the measurement methods have been described in previous studies and references therein. 22 − 25 …”

Secondary organic aerosol formation from monocyclic aromatic hydrocarbons: insights from laboratory studies

“…The maximum emission in July was (17.4 AE 7.7) Gg per month, which was approximately 3.2 times higher than the emission in February ((5.5 AE 2.1) Gg per month). 40 More recently, Han et al also reported obvious seasonal variations of BTEX at a regional background site in Fig. 1 Global overview of aromatic SOA.…”

“…38 MAHs accounted for a substantial fraction of the total VOCs in urban and industrial areas. 39,40 Even in suburban regions, high concentrations of MAHs have been observed. 41 The implementation of control policies for VOCs has led to an overall decline in the annual average mass concentrations of MAHs in China from 2001 to 2016.…”

“…39,43,44 MAH emissions could be estimated and validated by a combination of ground or satellite observations and model simulations. 40 Recently, Cabrera-Perez et al simulated the global budget and distribution of common MAHs with an atmospheric chemistry general circulation model. 43 The results showed global emissions of 7.8 Tg per year benzene, 7.9 Tg per year toluene, 0.8 Tg per year ethylbenzene, 5.9 Tg per year xylene, 1.4 Tg per year trimethylbenzene and 0.8 Tg per year of styrene (Table 1).…”

“…Wang et al performed continuous measurements of 17 aromatic hydrocarbons for a year at an urban site of Shanghai, China, the results of which were compared with those from the Community Multiscale Air Quality model. 40 They showed that the monthly variations in aromatic hydrocarbon emissions were obvious. The maximum emission in July was (17.4 AE 7.7) Gg per month, which was approximately 3.2 times higher than the emission in February ((5.5 AE 2.1) Gg per month).…”