Study On Emission Characteristics Of Road Dust In Shijiazhuang City During Summer And Winter Based On Dustfall Method

In order to understand the dust emission characteristics of pavement roads in Shijiazhuang during summer and winter,road dust samples were collected from 1.5m and2.5m high of four types of roads in urban area by dust tank.Inorganic elements,carbon components and water-soluble ions in PM_2.5.5 and PM₁₀0 were detected.The substances analyzed were as follows:K,Cr,Co,Ni,Cu,Zn,As,Cd,Pb,Mg,Ca,Fe,Si,OC and EC,Ca²⁺,Mg²⁺,Na⁺,K⁺,NH₄⁺,SO₄^2-,Cl^-,NO₃^-,NO₂^-and F^-.Results were as follows:1)The orders of element concentration of road dust in summer and winter were Si>Ca,Fe>Mg>K,Cr>Cu,Zn,Pb>Ni,As>Co,Cd.The highest concentration of 13elements in summer occurred at main roads,while at main road and branch road in winter.Crust elements enriched at 1.5m high,while man-made pollution elements enriched at2.5m high;The enrichment factors of Cd and Cr in both seasons were all more than 40,and the enrichment degree was extremely strong.The enrichment of Pb and Zn in summer was also extremely strong,but crust elements such as K,Mg and Fe were not significant enrichment.The results of geoaccumulation index were similar to the enrichment factors,the contamination degree of Cd,Cr,Pb,Zn and Cu is very strong in summer,Cr was very strong in winter,and Cd,Pb,Zn and Cu are strong in winter.The main factor analysis showed that the pollution in both seasons mainly came from motor vehicles（exhaust gas,parts wear,fuel）,road dust and coal combustion emission also contributed a little.2)The mass concentration of OC and EC varied greatly in different seasons,and it was obviously higher in winter than that in summer.concentration of OC on expressway was higher than that on other types of roads,and the regularity of EC is not obvious.Both OC and EC were higher concentration at 1.5m than that at 2.5m high.The correlation between OC and EC indicates that the sources of OC and EC were similar.The value of OC/EC showed that the carbon of road dust mainly came from the sedimentation of coal and biomass combustion.3)The order of the concentration of ionic mass concerntration in both seasons was Ca²⁺>SO₄^2->Cl^->NO₃^->NO₂^->Na⁺>NH₄⁺>Mg²⁺>K⁺>F^-.The proportion of SO₄^2-in total ions was obviously larger in winter,it can be seen that coal pollution was relatively heavy.In summer,the ion concentration was the highest in expressway and secondary trunk road,in addition to SO₄^2-,the ion concentration was relatively larger in branch roads and secondary trunk roads in winter.The results of anion-cation balance equation showed that the cations were excessive in urban area,the whole particles were alkaline.