Application Of Synchrotron-based X-ray Absorption Near Edge Structure Spectroscopy To The Determination Of Speciation And Concentration Of Chlorine In Typical Environmental Media

Chlorine is a widespread element which is also regarded as one of the mostimportant element among halogen elements. It is abundant in the earth crust,atmosphere, oceans, terrestrial soil and vegetation. Chlorine participates incomplicated biogeochemical cycle in chemical speciation of inorganic chlorine andorganochlorine. To be specific, as one of the essential elements of life, inorganicchlorine exists in nature in forms of chloridion and chlorine salt. Organochlorine isthe chemical creation after one or several hydrogen atoms in aliphatic compound andaromatic compound are replaced by chlorine atoms which can be used to produce rawmaterial for synthetic, intermediate, organic solvents and pesticide. Organochlorine ismass produced and is widely used in different industries including chemical industries,medical industries, agriculture and electronic industries. Most organochlorinecompounds have common characteristics as environmental persistence,bioaccumulation and high toxicity as well as similar significant functions ofteratogenesis, carcinogenesis and mutagenesis. Organochlorine can be released intothe environment through many ways such as emissions of solid waste, waste waterand exhaust gas, utilization of pesticide, combustion of organic product containingchlorine and so on which will result in severe pollution of atmosphere, water and soil.Even worse, it is harmful to humans as organochlorine can accumulate in humansafter being propagated and transferred through food chains.To change relatively insufficient comprehensive researches on chlorineelement’s speciation and content in typical environmental media, the paper makes useof X-ray absorption near edge structure, XANES which can synchronizes radiationand undertakes researches on both nine types of arable soil in China and ultrafineparticles PM0.2in the Shijingshan District of Beijing to study chlorine element’sspeciation and content distribution. It aims to learn conditions and distributions ofthe pollution caused by the chlorine element so as to make further studies on the origin, migration distribution, final destination and pollution effects of pollutants.These findings can provide basic data for further studies on the geochemical cycle ofthe chlorine element. What’s more, they are significant for developing relatedenvironmental standards and establishing environmental management measures.The paper analyzes and measures samples in six different particle sizes which arecollected from nine types of arable soil as well as chlorine element’s speciation andcontent distribution in all soil. It analyzes correlation between the inorganic chlorineand the organochlorine in the soil samples. In the same time, the paper analyzes andmeasures the mass concentration and chlorine element’s speciation and contentdistribution of ultrafine particles PM0.2in the Shijingshan District of Beijing andmakes further discussions on meteorological factors’ influences on them. Mainresearch achievements are summarized as follows:（1）The distribution trend of the total chlorine concentration in nine types ofarable soil is laterite> chestnut soil> paddy soil> boggy soil> cinnamon soil> darkbrown soil> brown soil> red soil> black soil. Only the content of chlorine elementin the chestnut soil and the laterite is a bit higher than the average content of chlorineelement in China. The content of chlorine element in the paddy soil is almost equal tothe average content in our country. While the content of chlorine element in the othersix types of soil is all below the average value. In China, large areas of soil are lack ofchlorine element.（2）The distribution trend of the inorganic chlorine concentration in the studiedarable soil is chestnut soil> cinnamon soil> laterite> paddy soil> boggy soil> darkbrown soil> brown soil> black soil> red soil. All types of soil contain inorganicchlorine with relatively low content excluding the chestnut soil which covers that withhigher content. To improve both the output and the quality of the crop, it is necessaryto supplement the chlorine element by adding appropriate chlorine fertilizers (such asNH4Cl and KCl).（3）The distribution trend of the organochlorine concentration in the studiedarable soil is laterite> chestnut soil>boggy soil> paddy soil> dark brown soil>cinnamon soil> brown soil> red soil> black soil. The organochlorine is the mainspeciation in which the chlorine element exists in the soil with an average content ashigh as61%. The concentration of the organochlorine is one to three times of that ofthe inorganic chlorine. Aliphatic chlorine is the main speciation of organochlorine.（4）With respect to samples collected from above nine types of arable soil, boththe organic chlorine and the inorganic chlorine are inclined to concentrate in micro-aggregate components. The reason may lie in that soil aggregates in smallparticle sizes have bigger specific surface areas and more absorption points whichenable them to contact with objective elements in larger areas. That means higherabsorption probabilities for pollutants.（5）Concentrations of the organochlorine and inorganic chlorine in six differentparticle sizes and contained in all soil samples show a positive correlation. In details,there is apparently positive correlation between them with five different particle sizes(>2mm,2～1mm,1～0.25mm and0.25～0.053mm). And concentrations are highlypositive correlated (R ranges0.71~0.78) in two types of samples with minimumparticle sizes (0.053～0.02mm and <0.02mm).（6）In the process of sampling from June2009to October2013, massconcentration of PM0.2samples collected from the Shijingshan District of Beijingdeclined on the whole. However, the mass concentration of PM0.2is much higher thanthe concentration limit prescribed in Ambient Air Quality Standard which indicatesthat the particulate pollution in the Shijingshan District of Beijing is quite serious.Automobile exhaust and coal burning are the main sources of PM0.2.（7）The chlorine element is mainly existed in the form of inorganic chlorinewhich accounts for83%relative content in the total chlorine concentration. Coalburning is the main source of inorganic chlorine.（8）There is a moderate correlation between the concentration of the aliphaticchlorine and the aromatic chlorine (r=0.493). This indicates that aliphatic chlorineand aromatic chlorine having the similar primary source. Biomass burningsurrounding rural areas in Beijing is the main source of aliphatic chlorine andaromatic chlorine.（9）The total chlorine, the inorganic chlorine, the aliphatic chlorine and thearomatic chlorine gradually decline year by year. The total chlorine concentration inPM0.2is lower than the maximum limit of that in residential areas defined by Ministryof Environmental Protection.（10）The seasonal distribution trends of inorganic chlorine and total chlorine arethe same as winter> autumn> summer> spring, with distributions in autumn andwinter are apparently higher than that in spring and summer. The trend is caused bythe burning of large amount of fossil fuels in autumn and winter. The content ofaromatic chlorine is much higher in summer than in other three seasons. The seasonaldistribution trend of PM0.2’s mass concentration is: spring> summer> winter>autumn. （11）Based on PM0.2’s mass concentration and the relationship betweenspeciation and contents of the chlorine in PM0.2and meteorological factors as well asseasonal distributions, main sources of the atmospheric particulate pollution inBeijing can be deduced as the dust pollution in spring, secondary pollutants insummer and the coal pollution in autumn and winter.（12）Atmospheric pollutions in Beijing have converted from single pollutioncaused by coal burning and blown dust to mixed pollution consist various pollutionsources including coal burning, vehicle exhaust, blown dust, industrial dust and wasteincineration.