| Fine particulate matter(PM2.5)is one of the main pollutants affecting the air quality of urban environment.It has the characteristics of small particle size,large environmental hazards and wide range of influence.With the frequent occurrence of haze weather with PM2.5 as the characteristic pollutant,the problem of particulate matter pollution has aroused widespread concern.Water-soluble ions are one of the most important chemical components of fine particulate matter in the atmosphere.Secondary ions are also an important driving force for haze pollution.Therefore,it is necessary to analyze the source of water-soluble ions in particulate matter.In this dissertation,the typical island city Z was taken as the research object.Particle matter monitoring was carried out in Apr.2016,Jul.2016,Oct.2016 and Jan.2017,and the main pollution sources of Z were sampled as well.At the same time,the emission inventory of main anthropogenic pollutants(SO2,NOx and NH3)in Z was established based on 2016 data.On this basis of sample composition analysis data and emission inventory,combined with numerical analysis and model use,this dissertation analyzed the pollution characteristics,the impact of local pollution sources and the impact of external transport of water-soluble ions.In the analysis of the pollution characteristics of water-soluble ions,based on sample composition analysis data,this dissertation studied the concentration level of particulate matter and water-soluble ions,space-time distribution characteristics,binding forms between water-soluble ions,charge balance and the influencing factors of secondary ions.The results showed that:(1)during the sampling period,the concentration of PM2.5 varied with time,decreasing in the order of spring,winter,summer,and autumn in Z.The secondary ions were the main water-soluble composition in PM2.5,and had consistent seasonal variation characteristics;(2)correlation analysis shows that the fine particulate matter in Z was mainly related to the pollution source of SNA,and there was a strong correlation between SNA;(3)the analysis based on charge balance demonstrated that the aerosol in Z was overall acidic,with the lowest acidity in summer and the highest acidity in autumn;(4)and temperature was the main meteorological factor that affects secondary ion concentration in Z.In the analysis of local pollution source effects,the contribution value and share ratio of secondary inorganic salts to particulate matter were obtained through the CMB model,and the contribution value and share ratio of various pollution sources to secondary ions were further analyzed by combining with the emission inventory.The results of CMB model and source emission inventory showed that ship was the main source of SO42-and NO3-in Z,and its contribution to the two was 6.161 and 1.339?g·m-3,respectively;nitrogen fertilizer application was the main source of NH4+ in Z,and its contribution value was 1.606 ?g·m-3.This conclusion was basically consistent with the research conclusions of the ratio analysis method and multivariate statistical factor analysis.In the analysis of external transmission effects,the seasonal influence analysis was realized by analyzing the thermodynamic properties of land and sea and the data of pollution sources;the pollution source area was analyzed by HYSPLIT backward trajectory mode.The analysis of thermodynamic properties of land and sea,and the relationship between wind speed and the mass concentration of PM2.5 showed that:the particulate matter pollution in spring and winter was mainly affected by local sources,less by external sources;in summer and autumn,in addition to local sources influence,the mass concentration of PM2.5 was also affected by long-distance transport of pollutants.HYSPLIT-4 backward trajectory model was adopted to plot the backward trajectory of air masses that arrived at Z in typical months.According to the result of trajectory clustering analysis,it was inferred that the external source of Z were related to the long-distance transport of ocean air masses from the northern,eastern and southeastern coastal areas of Z in most of the time. |
PDF Full Text Request