The high NO_(3)^(−)concentration in fine particulate matters(PM_(2.5))during heavy haze events has attracted much attention,but the formation mechanism of nitrates remains largely uncertain,especially concerning heter...The high NO_(3)^(−)concentration in fine particulate matters(PM_(2.5))during heavy haze events has attracted much attention,but the formation mechanism of nitrates remains largely uncertain,especially concerning heterogeneous uptake of NOX by aqueous phase.In this work,the heterogeneous uptake of NO_(2) by sodium acetate(NaAc)droplets with different NO_(2) concentrations and relative humidity(RH)conditions is investigated by microscopic Fourier transform infrared spectrometer(micro-FTIR).The IR feature changes of aqueous droplets indicate the acetate depletion and nitrite formation in humid environment.This implies that acetate droplets can provide the alkaline aqueous circumstances caused by acetate hydrolysis and acetic acid(HAc)volatilization for nitrite formation during the NO_(2) heterogeneous uptake.Meanwhile,the nitrite formation will exhibit a pH neutralizing effect on acetate hydrolysis,further facilitating HAc volatilization and acetate depletion.The heterogeneous uptake coefficient increases from 5.2×10^(−6) to 1.27×10^(−5) as RH decreases from 90%to 60%due to the enhanced HAc volatilization.Furthermore,no obvious change in uptake coefficient with different NO_(2) concentrations is observed.This work may provide a new pathway for atmospheric nitrogen cycling and secondary nitrite aerosol formation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91644101 and 42127806).
文摘The high NO_(3)^(−)concentration in fine particulate matters(PM_(2.5))during heavy haze events has attracted much attention,but the formation mechanism of nitrates remains largely uncertain,especially concerning heterogeneous uptake of NOX by aqueous phase.In this work,the heterogeneous uptake of NO_(2) by sodium acetate(NaAc)droplets with different NO_(2) concentrations and relative humidity(RH)conditions is investigated by microscopic Fourier transform infrared spectrometer(micro-FTIR).The IR feature changes of aqueous droplets indicate the acetate depletion and nitrite formation in humid environment.This implies that acetate droplets can provide the alkaline aqueous circumstances caused by acetate hydrolysis and acetic acid(HAc)volatilization for nitrite formation during the NO_(2) heterogeneous uptake.Meanwhile,the nitrite formation will exhibit a pH neutralizing effect on acetate hydrolysis,further facilitating HAc volatilization and acetate depletion.The heterogeneous uptake coefficient increases from 5.2×10^(−6) to 1.27×10^(−5) as RH decreases from 90%to 60%due to the enhanced HAc volatilization.Furthermore,no obvious change in uptake coefficient with different NO_(2) concentrations is observed.This work may provide a new pathway for atmospheric nitrogen cycling and secondary nitrite aerosol formation.
