Research On Dust Detention Effect And Optimal Design Of Plant Configuration Types Of The Road Green Belt On PM_2.5 In Guangzhou

With the rapid development of economy,the energy situation and environmental problems are becoming increasingly perilous.The problem of atmospheric pollution is mainly concentrated in economically developed and densely populated areas such as Area of Beijing ferry look forward to,the Yangtze River Delta region and the Pearl River Delta region,and roadside pollution is becoming increasingly serious due to increasing road traffic emissions,so the issue of how to reduce the risk of roadside pedestrians being exposed to high concentrations of pollutants needs to be addressed urgently.Different plant configurations have different effects on pollutant purification,so a reasonable selection and configuration of plants is one of the ways to effectively reduce pollutants.In this study,the relationship between plants and PM_2.5 concentrations in the air was investigated.The results showed that the variation of PM_2.5 concentration on the experimental day was bimodal,with significant correlation with various meteorological factors,including negative correlation with air temperature,wind speed and solar radiation,and positive correlation with relative humidity.The correlation coefficient between PM_2.5 concentrations and the regression analysis of a single meteorological factor is not high,and the measured PM_2.5 concentrations are the result of the combined effect of several meteorological parameters.Secondly,the ENVI-met simulations were used to analyze the degree of influence and contribution of various factors on PM_2.5 dispersion,and found that wind speed has the greatest influence on PM_2.5 concentration,with a maximum contribution of 89%,followed by the street aspect ratio,with a contribution of 8%-9%.Finally,the effect of different planting types on PM_2.5 dust retention in urban streets with different height to width ratios at low and typical wind speeds was analysed.For a street with a height to width ratio of 0.6,the findings are basically the same for both wind velocities,with the best dust retention effect for the roadside green belt with a double layer of plants parallel to the prevailing wind,and a smaller effect on PM_2.5 concentration for the roadside green belt with different plant types.The reduction rate of particulate matter in the roadside green belt is better.For a street with a height to width ratio of 1,the two wind speeds were the same for roads parallel to the prevailing wind,with the largest reduction in PM_2.5 being achieved by the combination of the roadside tree greenbelt planting type and the roadside greenbelt single layer shrub type.For roads perpendicular to the prevailing wind,the presence or absence of herbaceous plants on the windward and leeward sides at low wind speeds had little effect on PM_2.5 dust retention;the reduction rate of plants on the windward side at typical wind speeds was significantly higher than the natural reduction rate,up to 20%,and the PM_2.5concentration after plant reduction was lower than that of the control group,while the PM_2.5concentration after plant reduction on the leeward side was higher than that of the control group.For streets with a height to width ratio of 1.7,the two wind speeds were the same for roads parallel to the prevailing wind,and the best dust retention benefits were achieved by the combination of a double layer of plants in the roadside green belt and a single layer of shrubs in the roadside green belt;the two wind speeds were the same for the leeward side of the road perpendicular to the prevailing wind,and the PM_2.5 concentrations were higher in the leeward side than in the control group after vegetation abatement.For roads perpendicular to the prevailing wind direction,the combination of single-layer tree planting types in the windward side of the roadside green belt and double-layer planting types in the roadside green belt at low wind speed has the best dust retention effect;the more planting types in the roadside green belt and roadside green belt at typical wind speed,the more significant the dust reduction effect.