Study On Time-space Variation Of Air Pollutant Concentration Between Students’ Commuting And Roads

In recent years,there are more and more researches on the concentration of air pollutants,especially on road traffic pollutants.However,most of them are oriented to the road pollution suffered by the working groups,while there is very little research on the road air pollutants in the commuting of students.In order to know more about the concentration of air pollutants in the roads of Urumqi students’commuting to and from school,this paper takes the students in primary school,junior high school and senior high school affiliated to Xinjiang Normal University in Urumqi as the research objects,and randomly distributes questionnaires to find out the students’basic information,commuting characteristics and their perception of air pollutants.The students’commuting behaviors and routes obtained from the survey were screened to provide the basis for the experimental monitoring of pollutants.Taking the typical commuting routes of students in the morning and evening as the experimental monitoring routes,the concentrations of related pollutants PM_2.5,NO₂and CO suffered by students during commuting were monitored based on the mobile monitoring method.Firstly,the characteristics of students’commuting and their perception of air pollutants are analyzed.Secondly,the experimental investigation on the spatial and temporal distribution of pollutants on students’commuting roads is analyzed.Finally,the influencing factors of pollutants in the experimental investigation are discussed.The conclusions are as follows:（1）Analysis of students’commuting characteristics and subjective perception of pollutants.The majority of the questionnaires are female,with age groups ranging from 12 to 15 years old,and the number of students with annual family income ranging from 100,000 to 200,000 is the largest.Students commute in the morning and evening mainly in two periods:08:25-08:50 and 18:40-19:05.Commuting distance is mostly between 1km and 5km,and the commuting time is mainly under 20min and 20-40min.The most commonly used commuting modes are:walking>bus>private car;From the order of importance of factors influencing students’choice of commuting mode,the order is time>distance between residential area and school>safety>air pollution degree.Students think that in the last month’s commute,the air quality in the car or on foot is average and good;The influence of air quality on study and life is mainly general and minor;Allergic rhinitis,chest tightness,shortness of breath and fatigue are the most common physical symptoms.The biggest factors that affect the air quality during commuting to and from school in the morning and evening are automobile exhaust,different vehicles,the number of passengers around and smoking.（2）Experimental investigation on the spatial and temporal distribution of pollutants on students’commuting roads.In different commuting periods of students,the average daily pollutant concentration of PM_2.5and NO₂is higher than that of early commuting and lower than that of late commuting,while the pollutant concentration of CO shows an inconsistent trend in morning and evening commuting.Among the three monitoring routes on different commuting days,the average concentration of PM_2.5and CO is 2>3>1,and the average concentration of NO₂is 1>3>2.The maximum values of PM_2.5and NO₂are found in route 1,and the maximum values of CO are found in route 2.In the spatial analysis of road pollutants on students’commuting routes,the high values of three pollutants are mainly distributed in the middle and south sections of Altay Road,the south section of South Hubei Road and Karamay East Street,while the low values are mainly distributed in Nanhu North Road,Xihong West Road,Kunlun Road and Beijing South Road.The mass concentration of PM_2.5in the north is larger than that in the south,while that of NO₂in the south is larger than that in the north.The high and low values of the concentration distribution cross each other,and the mass concentration of CO in the north is larger than that in the south.The concentrations of pollutants PM_2.5and NO₂in the early commuter road section are lower than those in the late commuter road section,while CO is on the contrary.The concentrations of pollutants in the early commuter road section are higher than those in the late commuter road section.The concentration of PM_2.5in the late commuter sections is high,while that of NO₂in the morning and evening commuter sections is low,and the high and low concentrations of CO are staggered,and the overall concentration is mainly low.（3）Analysis of the relationship between road pollutants and other factors in students’commuting.There are different degrees of correlation among the pollutants in students’commuter roads,between mobile monitoring pollutants and state-controlled fixed monitoring pollutants,and between mobile monitoring pollutants and meteorological factors,which shows that the three pollutants have high homology,mainly from road traffic pollution,and the pollutant concentration is affected by meteorological factors.The pollutants of PM_2.5,NO₂and CO in students’commuting are mainly northwest wind（NW）,west wind（W）and southeast wind（SE）,and the type of wind is mainly soft wind,and the wind speed within 1m/s without wind or soft wind is distributed in each direction;The higher the wind speed,the more it can dilute the concentration of pollutants in students’commuting.