The Investigation Of The Six Metal Elements And Their Chemical Species In Dust In Chongqing Main City

Dust is an important aerosol,it could produce a great effection on ecosystem and material exchange of soil and atmosphere.Dust is actually a primary source of fine soil and edaphic salinity,and could profoundly change the component and property of soil.The heavy-metals in the dust could endanger human and ecosphere when they enter into soil and hydrosphere,so it's important guidance-signification that we study concentration and chemical species of heavy metal in the dust.We have researched actual levels of the heavy-metals in dust in Chongqing main city, and study the distribution characteristics of the toxic-heavy-metals and chemical-species to estimate the harm to the environment,which could provide Municipal Government with some appropriate theory and data to strongly control and improve the dust pollution.In order to highlight the dust charicateristic in different zones,while we researched the dust quantity at every administrative region,the main city were also divided into different "Function Areas" such as tourist district,campus area,sowntown,building site,highway,industrial park,and we comprehensive analysised influencing-factors and space-time distribution of the six important toxic heavey-metals(Pb,Zn,Cu,Ni,Cd,Cr)and their four chemical-species,and study the source-characteristic(human-factors source or natural source)of the six metals in the dust in the especial "Function Areas" by the enrichment-factor method.In the studding of dust-quantity,The samples of dustfall were collected from 2006 to 2007 at Yuzhong,Jingbei,Nanan,Shangbingba,Yubei,Dadukou,Jiulongpo,Banan,Beibei etc.the 9 sections of Chongqing urban and Jinyunshan site for compared and analyzed the spatio-temporal distributing characteristics of dustfall in the city zones.In order to ensure that the representative sample were collected,the study-area were divided into many the same-size grids and random selected a few grids as sampling-location.The samples were taken back every one month and the total sampling-time was two years.The collection-method was wet-collection,we collected the samples by dust-gather jar and measured the weight of dust on GB/T15264—94 method.In 2007,we focused on collecting and studing the dust samples at some main especial function zones.In this working,we still use the wet-collection method, but the samples were taken back every three months and the total sampling-time was one year, because we only want to research the distribution characteristic of dust in four seasons.According to plenty of acid rain in Chongqing and the theory that Tessier divided the chemical-espeies of heavy-metal in solid matters in nature,in studing heavy-metals,we mainly divided the heavy-metals into four chemical-espeies such as acid-soluble state,Fe-Mn oxide-bound state,organic-combination state,residue crystal-lattice state.According to GB/T15264—94,before weighting dust sample,the dust sample would be heated to a higher temperature to remove a lot of water,while chemical-especies of the metals could be changed in the heating process,the result would be affected,so,in this studing item,we measured the weight of dust on GB11901—89 method which is used to weight the nonfiltered residues——suspending material in water.The dust samples were deal with step by step according the "four-step extraction" program of EU "Measurement and Testing Program" (Tessier step by step extraction program)to ensure good extraction to every chemical form, and the supernate of every class pre-treatment sample was filtered and concentrated to 25ml, and then we could measure metals concentration by FAAS or GFAAS.According to researching and analysising,the result showed that Chongqing main city were heavily polluted by dust and heavy-metals in the dust,and we gained the main conclusion as follows:a.After "blue sky" action was carried out in the city zone of Chongqing from 2005,the dustfall of Chongqing city zone was tremendous down,but it was still more 40%than standard-value,so the dust-pollution of Chongqing city zone was still heavy,dust-quantity descending order was as follow:highway＞building site＞industrial park＞campus area＞sowntown＞tourist district(background area)。b.Except for nickel,the five other elements in dust were great enriched.Both plumbum and cadmium were supreme artificially enriched so that plumbum's enrichment factor was up to125 and cadmium's was up to 689,while chromium was mainly natural-enrichment,zinc and cuprum'enrichment were both artificial and natural.It had a total of about 691.1 tons Cd, Pb,Cu,Zn and Cr landing while the dust were sedimentation in the main city,2007,and the amout is very big.c.The first three chemical-species of the five enriched elements in dust account for a large proportion in a body in the six "function areas",especially plumburn,cadmium and zinc. According to the study about concentration and activity of the five elements,the most dangerous elements were Pb,Zn,Cd,followed by Cu,Cr was relatively small dangerous.d.Pollutants from human-factors source,such as industrial production,fuel combustion, etc.are very important factors leading to both enrichment of heavy metals in the dust and enhanced elements activity.e.It reflected that the region were heavily polluted near the source.Among the six especial "function area",According to the dust-quantity,concentration and activity of heavy-metals,the study shown that the heavily polluted area were industrial park,highway and building site,while sowntown,campus area and tourist district were relatively less pollution.f.The dust pollution has obvious seasonal features,while the different regions have own law.It was the decending order that the six especial "function area" were polluted by dust in four seasons,2007:in tourist district,spring＞summer＞autumn＞winter;in campus area, spring＞summer＞winter＞autumn;in sowntown,summer＞spring＞autumn＞winter;in building site,spring＞autumn≈winter＞summer;near highway,winter＞spring＞summer＞autumn;in industrial park,spring＞winter≈autumn＞summer.There was some difference that the main source resgions were heavier pollution in spring and winter,and others in spring and summer, so spring was a period of the heaviest dust-pollution in the main city.The heavier pollution was due to weather condition such as diffusing in winter,and the lightest pollution was in summer.g.Climatic characteristics are also important influencing fators on dust and enrichment of heavy-metals in dust.In Chongqing main city,because of higher temperature-inversion frequency(60%-80%)and calm-air ratio(30%-40%),plentiful rain,the poor self-purification ability of air make fine particulates suspend in the atmosphere for long time,and compronents in the particulates would be enriched in the process,so pollution of dust and metals in the dust was so heavy in spring and winter,2007;Plentiful rainfall could remove the particulates in the atmosphere,wash the road,and increase the difficulty of metal-enrichment,which is very prominent that rainfall purify atmosphere,so pollution of dust and metals in the dust was lower in spring and winter,2007.