Analysis Of Influence Factors Of Green Plant Retention Black Carbon During Dry Deposition Process

Black carbon aerosol is a kind of carbon particle formed by incomplete combustion.It has the function of changing climate characteristics,harming human health,affecting atmospheric chemical reaction process and reducing visibility.It has become a hot topic in atmospheric environmental science research in recent years.In the city,the main problem of environmental air pollution has gradually evolved into particulate matter pollution in the air.In order to reduce the concentration of particulate matter,the most widely used technology is air pollution control technology to reduce the degree of air pollution.Besides,we can also improve the air pollution by means of the natural clearing system.Urban green plants are effective ways to mitigate the pollution of urban particulate matter.Plants retention particles through leaf stagnation,sorption or adhesion,can effectively reduce the concentration of particles in the air so that the main influencing factors of green plants retention characteristics,to reduce the concentration of atmospheric particulate matter in the city and improve air quality is of great significance.In this paper,ten main parks in Wuhan are selected as sampling points.FromJuly 2015 to June 2016,the content of black carbon in the soil dust-gas system is collected and analyzed.From January 2017 to November 2017,acquisition of arbor,shrub and herb species in three types of foliar dust has 30 species,and record the sampling of real-time meteorological data(temperature,atmospheric pressure,wind speed).The black carbon and leaf dust samples were measured and analyzed by chemical analysis,mass difference method,correlation analysis,one-way ANOVA analysis.An attempt to understand the main factors affecting the characteristics of plant truncation during the dry dust reduction of black carbon aerosols in Wuhan.A systematic understanding of the quality distribution of black carbon in each link from a systematic view of material migration,and further understanding the ability of plants to remove black carbon particles.The main factors that affect the characteristics of the green plant are analyzed in combination with the characteristics of plant leaf surface,the concentration of particulate matter in the air,the distance of the dust source and the meteorological factors.The main conclusions of this paper include:(1)The space-time law of the distribution of black carbon dry settlement.The results show that with the vertical settlement process,the content of black carbon decreases in the gas-dust-soil system.Black carbon is gradually diluted in the process of sedimentation from the atmosphere to the surface of the plant to the surface dust to the soil.In Wuhan central district,the average value of the Detained black carbon ratio of the leaf is 23%,the rate of the surface dust is 16%,the rate of the surface soil is 7%,and the ratio of the leaf surface is the highest in the whole year.The content of black carbon in aerosol is highly positively correlated with the concentration of fine particles in air(r=0.86).As the concentration of fine particles in the atmosphere increases,the content of black carbon in aerosols is also increasing.(2)The ability of trees,shrubs and herbs to intercept black carbon particles is significantly different,Herbs>trees>shrubs.The difference of black carbon content between different tree species is large,and the black carbon content of the same tree at different sampling points is also different.From the seasonal variation,the black carbon content of the three plant types plants in summer is smaller than that in summer.The tree plants and herbaceous plants have the highest black carbon content in autumn,and the shrub plants have the highest black carbon content in winter.In the three plant types,herbaceous plants fluctuated the most in autumn,followed by arboreal plants with an average delay in black carbon and the largest fluctuation in autumn,the average amount of black carbon in shrub plants is the largest in winter.According to the law of space change,the dust accumulation of plants in different locations is distinct,and the concentration of fine particles in the atmosphere is high,while most of the greening plants in the same place are characterized by higher spring and autumn season and lower in summer.(3)The single factor variance analysis showed that different foliar characteristics of plants between the unit of a plant leaf area were highly significant difference(P<0.01).The Taraxacum mongolicum Hand-Mazz.unit of a plant leaf area is the largest,1.36 mg/dm2,Platycladus orientalis(L.)Franco of 1.09 mg/dm2,Cedrus deodara(Roxb.)G.Don in third,1.08 mg/dm2.The bark with thick cuticle,leathery and cilia has strong ability to capture black carbon.(4)The concentration of fine particles in air significantly affects the size of black carbon captured by plants.The correlation between the black carbon content of the unit leaf area of green plants and the concentration of fine particles in the air in the day of sampling was analyzed.The results showed that the black carbon content of the same tree at different sampling points was positively correlated with the air quality index of each sampling point.The correlation coefficient of black carbon content and particle concentration is 0.88,the correlation coefficient of shrub plant and particle concentration is 0.34,and the correlation coefficient of herbaceous plant and particle concentration is 0.54.Compared with the three distance gradients of dust sources,the black carbon content of plants is decreasing.With the increase of distance from pollution sources,the amount of black carbon captured per unit area is decreasing.This indicates that the farther away the plant is from the source,the faster the black carbon will decrease.This indicates that the farther away the plant is from the pollution source,the smaller the black carbon that the plant will intercept.(5)Among the three meteorological factors,the wind speed has a significant influence on the difference of black carbon size by plant,and the air pressure and temperature have little effect on the difference of green plant’s cross-sectional black carbon.There is a strong negative correlation between wind speed and black carbon content,r=-0.61,to moderate significant level,the correlation coefficient between the air temperature and the black carbon content is negative,r=-0.11,the degree of correlation is weak,basically unrelated.The correlation coefficient between atmospheric pressure and intercepting black carbon is 0.14,which is positively correlated,and the degree of correlation is weak.