The Study Of Heterogeneous Reaction Of NO₂on The Surface Of Black Carbon And Observation Of Carbon-nitrate Internal Mixture Particles

Carbon-containing particles have a crucial influence on the environment, human health and climate change. The extinction effects of carbon-containging particles may lead to the decrease of visibility and the increase of haze days, and their direct radiative forcing may induce the reginal climate perturbation. The heterogeneous reactions of NO2on the surface of black carbon (BC) have been attracted in the past years. This reaction could influence the gas-solid distributions of NO2and NOx, atmospheric oxidation, human healthy and particles’character. Hence, we need to study the correlation between NO2and BC, and the variation of BC character during this reaction on the basis of understanding the reaction mechanism of NO2with BC. Meanwhile, it’ll provide scienctific basis for the atmospheric evolution of BC if we have observations of carbon-nitrate internal mixture(CNIM) particles and their relations with meteorological elements, pollution gases.The heterogeneous reaction of NO2with black carbon has been studied in this paper at room temperature by using atmospheric pressure flow system. The effects of relative humidity and atmospheric age processe on the reaction have been analysed. The results indicate that the heterogeneous reaction can be siginificantly promoted by the increasing humidity, H2O is involved in the reaction of NO2to HONO and may enhance the surface reactivity of BC. HONO yield rapidly increased at first and then went to the saturation as a function of reaction time and NO2concentration. Meanwhile, the higher the relative humility is, the faster the HONO’s initially formation speed will be. Under the age processe experiments, the initial HONO yeild is almost the same with that after30min reaction under different coating situations, which indicate that the surface reactivity of BC might siginificantly decrease during the coating process. There are no obvious differences among different coating materials’effects on reaction.The adsorption capacity of BC with HONO obviously increased.The Carbon-nitrate internal mixture particles’ characterization variations were observed by SPAMS. The particles’number show a strong diurnal variation in the range of350-600/h, with two morning peaks and a mid-afternoon minimum, which is related with human activity, meteorology condition and boundary height. The particles also have an obviously weekend effects. The particles’correlation with visibility is preferably negative. The particles’correlations with CO, SO2are small, preferably positive with NO2, and negative with O3. The Carbon-nitrate internal mixture particles are divided into five categories:K rich particle, Carbon rich particle, K-Na rich particle, Fe rich particle, and Pb rich particle. K rich and K-Na rich particles are mainly from biomass buring process, accounting for66.99%of total CNIM particles. Carbon rich particles are from fossil fuel burning, accounting for29.91%. Fe rich and Pb rich particles are respectively originated from metallurgical and waste incineration processes, accounting for1.31%and0.53%of total CNIM particles respectively.