Overby Meyer (dashdrug46)

To study the composition characteristics and sources of volatile organic compounds (VOCs) in Shijiazhuang City, three national control points were selected to conduct VOCs sampling and analysis from March 2017 to January 2018. The correlation of VOCs through combination with meteorological and ground-level O3 data, and the sources of VOCs were analyzed by positive matrix factorization (PMF). To quantify the pollution period of O3 in summer, its temporal sequence characteristics were studied by wavelet analysis. During the sampling period, the average concentration of ambient total VOCs (TVOCs) was (137.23±64.62) μg·m-3. Haloalkanes were the most dominant VOC compounds, accounting for 31.77% of total VOCs mass, followed by aromatic (30.97%) and oxygenated VOCs (OVOCs, 23.76%). The seasonal variation in VOC concentration followed the trend in winter (187.7 μg·m-3) > autumn (146.8 μg·m-3) > spring (133.24 μg·m-3) > summer (107.1 μg·m-3); the concentration of VOCs shows a trend of increasing gradient from west to east. The O3 concentration correlated negatively with VOCs and NO2, and positively with temperature, sunshine duration, wind speed, and visibility. Changes in meteorological elements were concerned before the occurrence of ozone pollution in summer, especially in 4-5 days in June and 7-8 days during July to August after the occurrence of increasing temperature. Finally six potential sources of VOCs were quantified by the PMF model, including from gasoline emissions (24.78%), diesel vehicle emissions (24.69%), solvent usage (18.64%), the chemical industry (11.87%), regional background (10.84%), and the pharmaceutical industry (9.17%). Ozone formation potential (OFP) contribution of emission sources of gasoline and diesel vehicles (54.98%) was over half of the total contribution. Meanwhile, these findings illustrated that control of vehicle emissions and industrial sources would be an important way to reduce VOCs concentrations and improve air quality in Shijiazhuang.In the research, volatile organic compounds (VOCs) were observed online in urban areas of Chengdu to study VOC concentration level, change characteristics, ozone generation contribution (OFP), and source contribution from June to September 2019. The results showed that the average concentration of TVOCs (total volatile organic compounds) was 112.66 μg·m-3, with alkanes (29.51%) and halogenated hydrocarbons (23.23%) forming the main components. The diurnal peak in VOCs mainly occurred from 1000 am to 1100 am, which is affected by urban motor vehicles, oil or gas volatilization, and industrial emissions. For OFP contribution of VOCs in summer, the contribution rate of aromatic hydrocarbons (42.7%) was the highest, followed by alkenes (27.4%). The key active species were m/p-xylene, ethylene, propylene, o-xylene, isopentane, cyclopentane, and acrolein. According to the source analysis by the PMF model, mobile sources are the main contributors of VOCs in summer in Chengdu, contributing 34% to TVOCs, followed by industrial sources (17%), volatile oil and gas (14%), and solvent use and natural sources contributing 11% and 13%. Therefore, motor vehicle and industrial emissions are the key control sources of VOCs in Chengdu, although control of pollution sources such as solvent use and oil or gas volatilization cannot be ignored.The ambient concentration of 122 volatile organic compound (VOC) species were continuously measured in urban Hangzhou, China from May 2018 to April 2019. The average mixing ratio of VOCs was (59.4±23.6)×10-9 and the oxygenated VOCs (OVOC) were the largest component. There was no clear "weekend effect" in urban Hangzhou, while the concentration of VOCs had a sharp decrease during long holidays. The concentration of VOCs had a positive correlation with air quality index (AQI) and reached the highest level when the primary pollutant was PM2.5. The assessment results of atmospheric chemical reactivity with·OH radical loss rate (L·OH) and