Emissions Of Nitrated Phenols In The Atmosphere From Typical Sources

Nitrated phenols are a kind of nitrogen-containing organic compounds in the atmosphere,which mainly come from the primary emission of human activities and the secondary generation in the environment.Nitrated phenols have significant effects on climate,environment and health.They can significantly affect radiation forcing,regional climate and air quality.In addition,they can also affect plant growth and endanger animal and human health.Therefore,the sources of nitrated phenols in the atmosphere have been widely concerned by researchers.Previous studies have shown that fuel combustion and industrial processes are potential sources of atmospheric nitrated phenols.Up to now,the emission of nitrated phenols caused by biomass combustion has been basically identified,but the emission characteristics,emission coefficient and emission amount of coal combustion,vehicle exhaust and industrial activities are not clear.In order to solve the above scientific problems,this paper carried out the coal simulation combustion experiment,vehicle exhaust collection experiment and industrial exhaust collection experiment.The content,chemical composition and emission coefficient of nitrated phenols in the source samples were determined by high performance liquid chromatography mass spectrometry.The formation mechanism and influencing factors of different emission sources were discussed,and the emission amount of coal combustion source and vehicle emission were estimated.In order to reduce the emission of nitrated phenols in the three emission sources,the control measures were put forward.In this study,10 kinds of coal commonly used in China(2 lignite chunk coal,4 bituminous chunk coal,1 natural coke chunk coal,1 anthracite chunk coal and 2 anthracite honeycomb briquette)were selected and burned in the common coal furnace.The fine particulate matter samples in the flue gas at the early and late stage of coal combustion were collected,the concentration and chemical composition of particulate nitrated phenols were analyzed,and the emission factor and emission rate of nitrated phenols were estimated.The formation mechanism and influencing factors of emission factors of nitrated phenols in coal combustion flue gas were studied.The results showed that:lignite and low maturity bituminous coal(with values of 1 3.0-16.8 and 14.9-16.7?g/m3,respectively)emitted the highest concentration of nitrated phenols,followed by high maturity bituminous coal(4.1-4.9 ?g/m3),natural coke(1.2?g/m3)and anthracite(1.7 ?g/m3).In coal-fired flue gas,the concentrations of nitrated phenols in the early stage of combustion(1.6-28.8 ?g/m3)are generally higher than those in the late stage of combustion(0.7-7.6 ?g/m3),which may be due to the more intense combustion process of coal in the early stage of combustion.Among the 10 nitrated phenols detected in coal combustion flue gas,4NC and MNCs are the highest in most cases(33.1%71.9%),which is similar to the chemical composition of nitrated phenol in biomass combustion flue gas.The emission factors of nitrated phenols in the flue gas of lignite coal,bituminous coal,anthracite coal and anthracite honeycomb briquette combustion are 1 0.1±1.6,2.31±0.4,0.16±0.03 and 0.26±0.04 mg/kg,respectively.Nitrated phenols in coal-fired flue gas may be produced by the reaction of phenolic compounds from coal combustion and nitrogen oxides at high temperature.The emission factor of nitrated phenol decreased significantly with the increase of coal maturity,which may be related to the content of phenolic hydroxyl in coal.Based on the coal consumption of each province,the proportion of different types and forms of coal and the emission factors of nitrated phenols in this study,the total emission of particulate nitrated phenols in the flue gas of residential coal combustion in 30 provinces of China in 2016 is estimated to be 178±24 Mg.Among them,the emission of nitrated phenols from coalfired flue gas in Hebei province exceeds 20%of total emission amount in China.In this study,nine types of vehicles(small gasoline bus,medium gasoline bus,medium diesel bus,large diesel bus,light gasoline truck,light diesel truck,medium diesel truck,heavy diesel truck,taxi fueled with compressed natural gas)in China and urban and suburban roads in Jinan were selected,and the gas pollutants were measured and particulate pollutants were collected during the actual driving process of vehicles.The concentrations and components of nitrated phenols in fine particles were determined.The results show that the concentrations of particulate nitrated phenols in CNG taxis and gasoline vehicles are similar(with values of 0.17 and 0.17-0.23?g/m3,respectively),which are less than those in diesel vehicles(2.30-10.73 ?g/m3).In vehicle exhaust,the chemical composition of nitrophenols varies with vehicle type,vehicle size and fuel type.In most cases,4NP and MNPs are the most important species,accounting for 38.4%-68.0%.The emission factors of nitrated phenols were 0.68 ± 0.08?1.02±0.79 and 58.62±48.06 ?g/km in CNG taxi,gasoline vehicle and diesel vehicle exhaust,respectively.Nitrated phenols in vehicle exhaust are mainly produced by the reaction of aromatic hydrocarbons in fuel and nitrogen oxides at high temperature.Comparative analysis shows that the higher emission factors of nitrated phenols is due to more nitrogen oxides emitted by diesel vehicles during driving.Besides,exhaust emission standard and vehicle mileage can significantly affect the emission factors of nitrated phenols in vehicle exhaust.In 2017,the total amount of nitrated phenols emitted by motor vehicles in 28 provinces of China is expected to reach 58.9 Mg(within the 95%confidence interval,the uncertainty range is-86%-85%).According to the emission inventory,the proportion of nitrated phenols emission in the exhaust gas of diesel trucks reached 86.6%,and mainly light diesel trucks and heavy diesel trucks.In this study,16 factories from 8 industrial sectors(pharmaceutical production,dyestuff production,pesticide production,explosive production,spraying industry,phenolic resin production,pulp production and polystyrene foam production)were collected,and particulate samples and semi volatile samples were collected downwind of these factories.The concentration and composition of nitrated phenols in the samples were determined.The concentration level,gas-solid distribution,diurnal variation and chemical composition of nitrated phenols in waste gases from different factories were analyzed.The formation mechanism of nitrated phenols in industrial waste gas was discussed.The emission ratios of particulate and gaseous nitrated phenols relative to fine particles in different factories and industries were calculated.The industrial control strategies were put forward effective measures for nitrated phenol emission.The total concentrations of nitrated phenol in the particulate and gaseous phase in the industrial waste gas are in the range of 272.3-540.4 ng/m3 ng/m3,which are much higher than the concentrations in the background environmental samples(272.3-540.4 ng/m3),indicating that industrial activities significantly affect the content of nitrated phenol in the atmosphere,and lead to the increase of nitrated phenols in the downwind area.Compared with the background air,more nitrated phenols are enriched in the gas phase,which may be due to the higher temperature in industrial production process.In dye production and pesticide production industry,the concentration of particulate nitrated phenols at night is much higher than that in daytime.In the industrial waste gas,4NP,NSAs and 4M-2,6-DNP were the dominant species in the particulate and gas phase,and the sum proportions of them in the particulate phase and gas phase are 47.9%-72.3%and 63.1%-70.3%,respectively.The proportion of nitrated phenol in industrial waste gas is significantly different from biomass combustion source,coal combustion source and vehicle exhaust source,indicating that nitrated phenols have different formation mechanism in different emission sources.In industrial production activities,nitrated phenols mainly come from the volatilization of nitroaromatic hydrocarbon raw materials or the chemical reaction of aromatic hydrocarbon raw materials with nitrogen oxides and oxidants under high temperature production conditions.In industrial waste gases,the emission ratios of nitrated phenols in the particle and gas phase were in the range of 0.5‰-4.3‰ and 1.5‰-4.8‰,which were significantly higher than those of other industrial sources.This research indicated that industrial emission is an important primary emission source of nitrated phenols in the atmosphere,and effective measures should be taken to control the emission of nitrated phenols in gas phase and particulate phase at the same time.This study strongly proved that coal combustion,vehicle exhaust and industrial activities will emit a large number of nitrophenols,and discussed the formation mechanism and influencing factors of nitrated phenols in the three typical sources.This study can provide important basic data for the establishment of emission inventory and related atmospheric chemical models,and provide scientific basis for the control of pollutant emissions from emission sources.