Influence of Cloud/Fog on Atmospheric VOCs in the Free Troposphere: A Case Study at Mount Tai in Eastern China

Abstract

Field measurements of volatile organic compounds (VOCs) were conducted in July of 2015 at Mount Tai, where 63 species of VOCs were measured using GC-MS. In this study, air samples were collected in two different weather conditions: cloud/fog and non-cloud/fog respectively and influences of the cloud/fog on VOCs species were analyzed. The sources of air masses were calculated by back trajectories with HYSPLIT model. Five main kinds of VOCs were analyzed and oxy-VOCs (OVOCs) had the largest contribution (67% on the cloudy/foggy days and 72% on the non-cloudy/foggy days) to total measured VOCs among all of the samples collected at Mount Tai. Acetone was the most abundant compound (18 ppb on the cloudy/foggy days and 15 ppb on the non-cloudy/foggy days) among the VOCs. The concentrations of VOCs collected in cloudy/foggy days were higher than those measured in non-cloudy/foggy days and indicated that cloudy/foggy days favoured the accumulation of atmospheric VOCs. However, the concentrations of most OVOCs in noncloud/fog conditions were higher than those in cloud/fog conditions. Atmospheric photochemical reactions may partly account for this result. Air mass trajectory analysis shows that most air masses from heavily polluted areas results in the increase of atmospheric VOCs. OVOCs and aromatics provided the main contribution to ozone formation potential. Besides cloud and fog, VOC concentration is concerned with integrated factors including temperature, relative humidity, wind speed and direction.

Constraining Emission Estimates of CFC-11 in Eastern China Based on Local Observations at Surface Stations and Mount Tai

“…The ambient mixing ratios of CFC-11 from previous studies in China are pooled together (Figure and Table S3). − ,,,,,− They seemed to show a decreasing trend before 2012 in China’s megacities, including the Pearl River Delta, Shanghai, and Beijing. However, as reported in recent studies in the North China Plain and in this study, the mixing ratios of CFC-11 seemed to increase to higher levels; CFC-11 mixing ratios as high as 307 ± 20 ppt were observed at the same MT site in 2015 .…”

“…CFC-11 had been used primarily as a refrigerant and foam blowing agent and was supposed to be released from banks such as air conditioners or foams only after its complete phase-out. , The emissions of CFC-11 that were far from what was expected from banks , were found to be largely or entirely attributed to the rigid polyurethane (PU) foam industry, , with CFC-11 emission either from the foaming process or from rigid polyurethane foams being a significant portion of the CFC-11 bank . Faced with the CFC-11 crisis in eastern China and the differences in emission estimates of CFC-11 based on observations outside mainland China, we thought it would be better to have local monitoring data to confirm and constrain the estimated emissions, yet data about ambient CFC-11 in mainland China in recent decades are quite sparse, − particularly after 2012 in eastern China. As Shandong and Hebei provinces of China are suggested to be major regions with increased emissions of CFC-11 in eastern mainland China, in this study we present field observation data from five campaigns carried out from 2012 to 2018 in Shandong province and estimate CFC-11 emissions in eastern mainland China on the basis of these observations.…”

Airborne Observations of CFCs Over Hebei Province, China in Spring 2016

“…After 2015, abundant mixing ratios of CFC‐11, CFC‐12, and CFC‐113 above the global background were detected throughout the North China Plain (Gu et al., 2019; Li, Wu, et al., 2016), surrounding waters (Guanlin et al., 2017), and remote areas (F. Yang et al., 2017) and published in peer‐reviewed journals (see Table ), but were not tied to new production or use. These recent (after 2015) studies in urban and background/rural locations documented larger CFC‐11 mixing ratio variability than studies published before the global phaseout.…”

Ozone Formation Potential of Ambient Volatile Organic Compounds at Roadside in Bangkok, Thailand

“…Ozone production is produced by specific hydrocarbon and is dependent on its particular oxidation mechanism. It can be influenced by concentrations of VOCs, and different species have different contributions to the ozone photochemical formation [14]. Each VOC species have different OH loss rates therefore different effects on ozone formation [15].…”