| With the gradual deepening of China's urbanization process,various problems have emerged in the urban environment,and the problems of heat island and air quality are particularly prominent.Pollution particles in the air can enter the body through the respiratory system of the human body,thereby damaging human physiology and psychology.Furthermore,high concentrations of pollutants will reduce visibility of the city atmosphere,and thus cause harm to traffic travel.The emergence of urban heat island effect will exacerbate atmospheric pollution and create favorable conditions for the spread of disease,which further endangers human survival.Heat island effect and air pollution not only have adverse effects on human daily life,but also restrict the development of urban economy.Therefore,it is of great significance to study the heat island effect and air quality in Xi'an.This study was based on the meteorological and air pollutant data of different monitoring sites in urban and suburban areas of Xi'an in 2016.First analyzed the time variation characteristics of PM2.5 concentration in urban and suburban areas and the relationship between different meteorological parameters and particle concentration,Secondly,analyzed the changes of temperature and heat island intensity with time in Xi'an city and the influence of different meteorological parameters on the intensity of the heat island,and analyzed the relationship between meteorological parameters and particle concentration under different meteorological conditions.Finally,this paper established different prediction models of particle concentration by multiple linear regression method,and puts forward reasonable suggestions for Xi'an to improve heat island effect and air pollution.The main conclusions of this study are as follows:?1?The trend of temperature change in urban and suburban areas of Xi'an is the same.There is no significant difference in the temperature between the two areas in the daytime period.At night,the temperature difference between the two areas is larger,and the maximum temperature difference reaches 2?.The daily variation of heat island intensity is more intense.During the day,the minimum value reaches-2.5?,while the maximum value at night reaches 3.7?.The mean value of heat island varies from-0.08?to 1.69?.The trend of the intensity of the heat island in the four seasons is similar.The intensity of the heat island is greater between 10p.m.and 2a.m.The cold island effect usually occurs during the summer and autumn day periods,and occurs less frequently.?2?Through the study of the relationship between meteorological parameters and heat island intensity,wind speed,pressure and relative humidity have certain influence on the intensity of heat island,and all are negatively correlated,and the influence of wind speed is the most significant.Based on further analysis of wind speed and direction,it is found that wind speed is negatively correlated with heat island intensity,that is,as the wind speed increases,the urban heat island effect will gradually weaken.The wind direction has a significant influence on the intensity of different azimuth heat island,especially in the direction parallel to the wind direction.?3?The diurnal variation of PM2.5 concentration in urban and suburban areas showed the double crest variation,and the change of PM2.5 concentration was"U"distribution throughout the year.The concentrations of pollutants in winter and spring are significantly higher than those in summer and autumn.The concentration of PM2.5.5 in urban and suburban areas varies in a week,but on the whole,the working day is higher than the weekend.There are obvious differences in air pollution in different months.Particulate matter monitoring in urban areas(PM2.5)annual average concentration is 74g/m3,which exceeding the national ambient air quality secondary standard?35g/m3?about 1.05 times.At the same time,the average concentration of suburban monitored by the 66.97g/m3,more than the national ambient air quality secondary standard about 0.9times,which means that Xi'an's air pollution problem is still not optimistic.?4?Through the study of the relationship between meteorological parameters and particle concentration,it is found that there are some differences between urban and suburban areas in different seasons and different meteorological parameters.The mass concentration of PM2.5 in the urban and suburban areas was negatively correlated with the temperature in spring.In summer,there is a significant positive correlation between the mass concentration of PM2.5 and the wind speed in the urban area,while the mass concentration of PM2.5 in the suburb was not related to the above meteorological factors.In autumn,the mass concentration of PM2.5 in the urban area is only positively correlated with the temperature,and the mass concentration of PM2.5 in the suburb is negatively correlated with the temperature,pressure and wind speed.In winter,the correlation between mass concentration of PM2.5 and meteorological factors is similar in suburb and urban area,which is negatively correlated with pressure and wind speed,and has a significant positive correlation with relative humidity.Throughout the year,urban and suburban areas have a positive correlation with atmospheric pressure and relative humidity,which are negatively related to temperature and wind speed.?5?When the PM2.5 concentration is predicted,the prediction and regression of the particle mass concentration is improved when the intensity of the heat island is taken as an independent variable.?6?In the study of the relationship between the intensity of heat island and the concentration of pollutants under different conditions,it is found that heat island intensity is positively correlated with particulate matter concentration,and the correlation between daily mean heat island intensity and particulate matter concentration is lower than that of maximum hour heat island intensity and particulate matter concentration.For the seasons,the correlation between the intensity of heat island and the concentration of particulate matter in the season with low temperature is stronger than the higher temperature season.During the day,the correlation between the intensity of the heat island and the concentration of particles at night time is greater than that in the daytime period.Based on different weather conditions,the relationship between the intensity of heat island and the concentration of pollutants will change.Specifically,compared to the low wind speed conditions,the correlation between the two will be weakened under the high wind speed,wind speed increases will weaken the degree of correlation;low relative humidity?RH<40%?or high relative humidity?RH?70%?under the two correlation is stronger than that in the middle of the relative humidity?40%?RH40%<70%?.?7?Relieving the heat island effect and air pollution can be used as an entry point from the rational layout of urban construction patterns,control of heat sources and pollution sources,and increase of greening volume. |
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