Volatile Organic Compound Emissions From The Oilfield In The Yellow River Delta Region,Northern China And Their Impact On Regional Ozone Pollution

The world's consumption of energy is increasing while the consumption of coal is declining.In 2017,the ratio of oil and gas consumption in China grew to 26%.SINOPEC SHENGLI Oilfield,the fifth largest oilfield in China(2017),is located in Shandong Province,whose energy consumption ability ranks second in China,2017.Reserve of oil and gas in the Yellow River Delta region is rich and extraction is ongoing both on and off land.Volatile organic compounds(VOCs)are main pollutants from oil and gas extraction and they are essential precursors of ozone.With ozone pollution getting worse,VOCs from oilfield have attracted much attention.Based on data of six national observational sites and the Yellow River Delta Ecology Research Station of Coastal Wetland,we analyze ozone pollution trends and characteristics in the Yellow River Delta region.We also build up an oilfield VOCs emission inventory using VOCs source profile data,which helps to revise MEIC(Multi-resolution Emission Inventory for China).After the emission update,we use the WRF-Chem model to quantify the impacts of oilfield VOCs emissions on regional ozone pollution.Ozone concentration in the Yellow River Delta region has been increasing since 2015.The maximum summer ozone concentration reached 166 ppb in 2018 with an increasing rate of 6.87 ppb/yr.Differences of ozone concentrations at different sites in the Yellow River Delta Region are small,indicating ozone pollution is more of a regional problem.Ozone concentrations are higher in summer and autumn than in winter and spring.Main factors that lead to ozone pollution are solar radiation,emissions and unfavorable meteorological conditions(such as low wind speed and high pressure).Background ozone concentrations also vary,with the lowest and highest values before sunrise and after noontime,respectively.VOCs in the Yellow River Delta region are mainly from extractions of oil and gas.In 2017,emission of VOCs reached 31,000 tons,of which alkanes accounted for 90%and alkenes accounted the least.MEIC(2016)underestimates VOCs emissions by about 23%.Influences of oilfield on VOCs vary by season and species,with the largest least on summer alkanes and winter alkenes,respectively.VOCs levels in the YelRD region and the northeastern coastal area are most influenced by the oilfield.The impact of oilfield VOCs emissions on MDA8-O3 is larger in summer(8 ppb)than in winter(3 ppb).Moreover,meteorological conditions favorable for ozone production can enhance the impact of oilfield VOCs.The influenced area is mainly the northwestern sea and varies by the meteorological condition.The most influenced areas include the southern part of Liaoning Province,the Jing-Jin-Ji region and the northern coastal area of Shandong Province.We built up a regional oilfield emission inventory of VOCs and found out its impact on regional ozone pollution.The research is helpful for related researches afterwards.It can also provide scientific evidence for regional ozone control.