Characteristics And Source Analysis Of Dust Pollution In Jinan City

In order to study the characteristics of atmospheric dust pollution in Jinan,this study collected dust samples from 21 points from January to December 2018 in Jinan city and county.The dustfall of each point was counted,and the content of water-soluble ions and inorganic elements in the dust-reducing samples were determined.The temporal and spatial distribution characteristics of water-soluble ions and inorganic elements in the atmospheric dust flux and dustfall in Jinan were studied.Source analysis and acid-base analysis were performed on water-soluble ions.Pollution evaluation and risk assessment of eight heavy metal elements?Cr,Pb,As,Hg,Ni,Zn,Cu and Mn?were carried out.The main conclusions drawn are as follows:1 Spatial and temporal distribution characteristics of atmospheric dust flux in jinanFrom January to December 2018,the monthly dust flux in Jinan City was 4.15¹1.65 t/?km²·30d?,and the annual average dust flux in the city was 7.3±2.9?km²·30d?,which did not exceed the Ministry of Environmental Protection in 2018.The standard issued is 9 t/?km²·30d?.The dust flux is the peak for the whole year in March and April,which are 10.36±2.4 t/?km²·30d?and 12.12±3.7 t/?km²·30d?respectively.In September,the lowest value for the whole year is 4.21±1.1 t/?km²·30d?.The average dust flux in the city of Jinan in spring,summer,autumn and winter is 9.62±3.4 t/?km²·30d?,7.58±2.6 t/?km²·30d?,4.88±1.7 t/?km²·30d?and7.10±1.6 t/?km²·30d?.The order of dustfall flux is spring>summer>winter>autumn.The average annual dust fluxes of residential areas,counties,industrial areas,cultural and educational areas and commercial areas in 2018 are:6.89±2.3 t/?km²·30d?,t/?km²·30d?,8.09±3.9 t/?km²·30d?,7.84±3.3 t/?km²·30d?and 6.37±2.1 t/?km²·30d?.The largest average annual dustfall flux in different functional areas is the industrial area,and the smallest is the commercial area.In 2018,the average distribution of average dust flux in the whole year is west high and low east,and the high dust falling area is roughly elongated in the northeast-southwest direction.2 Distribut ion characteristics of water-soluble ions and inorganic el ements in a tmospheric dust in jinan cityThe concentration of water-soluble ions in atmospheric dustfall in Jinan City ranged from1893 to 54530 mg/kg.The average annual content of the city was:SO₄^2->Ca²⁺>Cl^->Na⁺>NO₃^->K⁺>Mg²⁺>F^->NH₄⁺.The water-soluble ions have the highest concentration of SO₄²and Ca²⁺,and the percentages account for 5.45%and 4.89%of the dust,respectively,which is much higher than the concentration of other water-soluble ions.The average concentration of SO₄²the city is the highest in autumn,the lowest in spring,and the percentages account for8.15%and 2.71%of dust respectively.The average concentration of Ca²⁺in the city is the highest in winter,the lowest in spring,and the percentages account for 4.59%and 3.55%of dustfall,respectively.For the annual average of different ions in different functional zones,F^-and SO₄² have the highest concentrations in the industrial zone;Cl^-?NO₃^-?NH₄⁺?Na⁺and Mg²⁺have the highest concentrations in the commercial zone.The concentration distributions of K⁺and Ca²⁺in different functional areas are basically the same.The comparison between the dustfall of the sampling point of the Shangdongjianzhu University in December 2018 and the water-soluble ion content of PM_2.5 in the ambient air at this point shows that the water-soluble ions in PM_2.5 are mainly secondary ions(NO₃^-?NH₄⁺and SO₄^2-).,accounting for 86%of the total amount of water-soluble ions,and in the dustfall,the highest content of SO₄^2-and Ca²⁺accounted for 45%and 35%of the total amount of water-soluble ions,respectively.Comparing the water-soluble ion content in the dustfall and rainfall in the sampling point of the construction university in Jinan in November,it is found that the dominant water-soluble ions are roughly the same in dustfall and precipitation.However,the difference between the ratios is NH4+.The values of AE/CE in all points of dust reduction in Jinan City are less than 1,indicating that the dust is alkaline.For the city average,the AE/CE value is the largest?0.7?in the fall and the smallest?0.23?in the summer.The larger the particle size,the smaller the value of AE/CE and the greater the alkalinity.The average annual content of inorganic elements in the dust reduction in Jinan City is:Si>Ca>Na>Fe>Al>Mg>K>Zn>Mn>Ti>Cr>Ba>B>Sr>Cu>Pb>Ni>V>Hg>As.The highest content of inorganic elements is Si,followed by Ca,and the concentrations are:95626±6344mg/kg and 65135±3889 mg/kg,respectively.For the city's annual average of major heavy metals,the concentrations of Cr,Ni,Zn,Mn,As,Pb,Cu,and Hg were:48.87±16.21 mg/kg,57.74±21.60 mg/kg,and 527.07±146.29 mg,respectively./kg,444.52±105.19 mg/kg,5.55±2.61mg/kg,75.72±23.66 mg/kg,74.37±20.79 mg/kg and 0.31±0.22 mg/kg,the order of concentration of various heavy metals is:Zn>Mn>Pb>Cu>Ni>Cr>As>Hg.Ni,Zn,Pb,Cu and Hg were higher than soil background values of 1.94,7.16,2,2 and 7.28 times,respectively.Among them,Cr exceeds the screening value of the soil pollution risk management and control standard for soil environmental quality construction land by 7.6 times,and other heavy metals are lower than the screening value in the standard.Comparing the content of inorganic elements in the dustfall and rainfall at the sampling point of the construction university in Jinan in November,it was found that the contents of Ca,K,Mg and Na were higher in the precipitation.In the dustfall,the higher content is the crust elements Ca,Fe,Mg,Al and Ni.3 Morphological analysis and bioavailability evaluation of heavy metal elements in dustfall in Jinan CityIn the dustfall of different functional areas,Zn and Cd mainly exist in the form of extractable acetic acid.Hg and Cu are mainly present in an oxidizable state.As and Cr mainly exist in a residual state.Studies on the bioavailability of heavy metals show that Hg has the highest bioavailability in counties and the lowest in residential areas.The bioavailability of As is the highest in industrial areas and the lowest in cultural and educational areas.Cu has the highest bioavailability in residential areas and the lowest in counties.Pb had the highest bioavailability in residential areas and the lowest in cultural and educational areas.Zn has the highest bioavailability in industrial areas and the lowest in cultural and educational areas.Cd has the highest bioavailability in the business district and the lowest in the county.The bioavailability of Cr was the highest in industrial areas and the lowest in county areas.Ni has the highest bioavailability in the industrial area and the lowest in the commercial area.4 Pollution level assessment and potential ecological risk assessment of heavy metal elements in dustfall in Jinan CityThe evaluation of heavy metal pollution degree in atmospheric precipitation by land accumulation index shows that Cr,Mn and As in precipitation of different functional areas do not cause pollution.The pollution degree caused by Zn is moderate toxic pollution-severe pollution.The degree of pollution caused by Hg is moderate toxic pollution-severe pollution.The pollution caused by Cu and Pb was mild.The average potential risk index?E_i?of heavy metals in Jinan City is Hg>Cu>Pb>Ni>Zn>As>Cr>Ni.The potential ecological risk caused by Hg reaches a high degree of risk.The potential risk factors of heavy metals Cr,Ni,Zn,Mn,As,Pb and Cu are all at a slight ecological risk.The comprehensive potential risk index RI of Jinan City is at a medium risk level.The order of the comprehensive risk index RI of different functional areas is:suburb>industrial area>commercial area>cultural and educational area>residential area.5 Source analysis of atmospheric dust in jinanThe sampling PMF was used to analyze the source of water-soluble ions and inorganic elements in the dust,and the results showed that water-soluble ions in the dust mainly came from soil and construction dust,industrial and coal-burning sources,biomass combustion sources,motor vehicle sources,secondary sources and other sources.In the spring,the contribution of water-soluble ions is 29.5%of soil and construction dust.In summer,the contribution of soil and construction dust is 26.3%.In autumn,the largest contribution of water-soluble ions was from motor vehicles?26.5%?.In winter,soil and construction dust contributed the most to water-soluble ions at 28%.By analyzing the source of inorganic elements in dust,it is determined that the contribution of inorganic elements in dust mainly comes from soil dust,industrial mixed source,mobile source,biomass combustion source and other sources,among which the contribution rate of soil dust is 39.2%.