Characteristics And Sources Of Halogenated Hydrocarbons In The Yellow River Delta Region

Halocarbons are important air pollutants in the atmosphere.They are compounds in which one or more hydrogen atoms are substituted by halogens.Their lifetimes are between decades to hundreds of years.Thus,they can be transported to the stratosphere and pose a threat to the ozone layer.Some of the halocarbons have a global warming effect owing to their high Global Warming Potential(GWP).The Yellow River Delta(YelRD)region is an important area that connects the Beijing-Tianjin-Hebei region and Shandong province.It is located in the northeast of Shandong province,near the Bohai Sea,and is about 300 kilometers far from Qingdao.To better understand the characteristics and sources of halocarbons in the YelRD region,an important oil extraction and petrochemical industrial area in northern China,a two-phased(winter-spring and summer)intensive campaign was conducted between February to April and June to July of 2017.A total of 133 VOCs samples were sampled and analyzed.The concentrations of Montreal Protocol(MP)regulated species(CFCs,Halons and CH3CCl3)in this region were at the same level with the Northern Hemispheric(NH)background except CH3Br and CCl4 which showed 130%and 30%higher levels than NH background,respectively.The concentrations of MP under control species(HCFCs and HFC-134a)were 30%-70%larger than NH background.Other Chlorine and Bromine-containing halocarbons are much higher than NH background(22%-75%)because they are not regulated.Concentrations of MP regulated species were of the same level in summer and winter-spring period.,their seasonality and diurnal variation are not obvious.Historical trends of these halocarbons in the YelRD region also exhibited declining trends.Results above indicate good implementation of the MP in China for most MP regulated species.But we should still be cautious to these MP regulated species,because some species,like CCl4 and CH3Br,still have strong regional sources.We also conducted same analysis to MP under control and unregulated species,and they showed their own characteristics.Wind combined pollutants levels analysis showed that halocarbons in this site were influenced by sources of urban area of Dongying,Kenli,Huanghekou in the southwest and the Bohai Sea in the southeast.In addition,we compared the halocarbons levels in the oil fields and the site,the results showed that oil fields have a negligible influence on ambient halocarbons in this region.The back-trajectory analysis showed that of all three clusters from the North China Plain(34%),Siberia(53%)and central Asia(12%)that influenced the area in winter and spring,and clusters from the North China Plain contributed most to local halocarbon concentrations.While in summer,of all four clusters from the East China(60%),Northeast China(26%)Siberia(26%)and the South China Sea(9%)that influenced the area,and clusters from East China contributed most to local halocarbon concentrations.Source apportionment of halocarbons was carried out by positive matrix factorization(PMF).Model results indicated that biomass burning(37%),marine(23%),refrigerants and foam blowing(15%),solvent usage(15%)and leakage of CFCs banks(10%)were the most important sources.The analysis of the characteristics and sources of halocarbons in the YelRD regional provides the latest information of halocarbons levels in China,demonstrating effective implementation of the MP in China.In addition,the study can provide scientific guides for decision-makers.