Research On Key Technologies Of Determination Of Elements In Atmospheric Particulate Matter By WDXRF

With the rapid development of economy and society,atmospheric environmental problem has become more and more serious in China.Atmospheric particulate matter is one of the most harmful pollutants with complex composition,and it has become the primary pollutant which has affected many cities' ambient air quality and posed a threat to human health.The damage degree of atmospheric particulate matter to environment and human health is closely related to the composition and content of elements in it.Therefore,the component analysis of atmospheric particulate matter has become a hot issue in environmental research.As the foundation of source apportionment research,the rapid and accurate determination of elements in atmospheric particulate matter has great significance for the study of the pollution status and characteristics,and the real-time and emergency monitoring of atmospheric pollution.At the same time,it can provide scientific basis for taking measures to prevent and control atmospheric pollution,and researching on epidemiology,etc.Supported by National High Technology Research and Development Program of China: high precision spectrum detection instrument development?No.2012AA061803?,and A Project Supported by Scientific Research Fund of Si Chuan Provincial Education Department: research on key technologies of determination of elements in atmospheric particulate matter by wavelength dispersive X-ray fluorescence spectrometry?No.15ZB0075?,and Science and Technology Project of Sichuan Province: application research of the rapid determination of heavy metals in PM_2.5 by X-ray fluorescence spectrometry?No.2016JY0208?,it has accomplished fast,direct,non-destructive,low-cost,accurate multi-element analysis through researching on the theory and key technologies of the determination of elements in atmospheric particulate matter by WDXRF.The main work and achievements are as follows:?1?Based on the physical basis of qualitative and quantitative analysis of elements by WDXRF and Monte Carlo simulation,the judgement standard of critical mass thickness of single element thin samples is put forward in element analysis of atmospheric particulate matter.It is concluded that,under the error requirement of 4.84%,the critical mass thickness of thin samples from Na to I is 83.40¹731.36?g/cm²,and that from Xe to U is 126.63⁴75.58?g/cm².Moreover,under the stricter requirement of error?0.50%?,the critical mass thickness of thin samples for each element will be smaller.It provides the technological support for quantitative analysis of atmospheric particulate matter by WDXRF.?2?The preparation technology and process of sample collection and calibration thin sample are proposed in element analysis of atmospheric particulate matter by WDXRF.A set of preparation technology of calibration thin sample and analysis process which is simple,economical,accurate,reproducible,is formed for element analysis in atmospheric particulate matter,and a series of calibration thin sample which is suitable for element analysis in atmospheric particulate matter by WDXRF are prepared.It provides the technical guarantee for quantitative analysis of atmospheric particulate matter by WDXRF.?3?Based on Axios WDXRF instrument,measurement conditions,working procedure and spectrum processing of multi-element quantitative analysis in atmospheric particulate matter are established.The selection schemes of the analysis line of target element,and the voltage and current of X-ray tube are formulated.Meanwhile reasonable allocation of detector is implemented,and the setup plans of measurement time,analyzer crystal,tube filter,collimator,and so on are proposed.The background and the spectral overlapping interference of target elements in atmospheric particulate matter are corrected.?4?The quality of established method procedure is evaluated.The K value of calibration curve of each target element is between 0.137⁰.478,and the RMS value of that is between 0.249⁰.727,therefore the K value and RMS value of each calibration curve are small.The average relative error of each target element is between 1.12⁷.75%,the precision is between 0.43⁸.53%?n=10?,and the detection limit is between 1.7¹10.5ng/cm².Consequently the established method procedure has good quality.?5?The elements in atmospheric particulate matter in the eastern suburb of Chengdu City are determined by the established method procedure.The concentrations of elements in PM_2.5 are relatively changing during different monitoring cycle of 24 hours,and the concentration of some elements varies a lot.The average concentrations of Na,Mg,Al,Si,S,K and Fe are relatively high,however,the average concentrations of Sc,V,Cr,Co,Ni,Se,Sr,Mo,Pd,Ag,Cd,Sn,Te,W and Hg are relatively low.In most monitoring cycle of 24 hours,the concentrations of Cu and K in PM_2.5 at night are higher than that in the daytime.The average concentrations of Al,Si,K,Cu and Br in PM_2.5 at night are obviously higher than that in the daytime,but the average concentrations of S and Zn in the daytime are distinctly higher than that at night.The enrichment factor calculated by the annual average concentration of each element varies a lot and is even different with several orders of magnitude.The enrichment factor of S,Cu,Zn,As,Br and Pb calculated by the monthly average concentration is high,and the pollution reason of which is related with traffic characteristics,energy structure and industrial distribution in the area of the sampling point.To sum up,the established analysis method obviously improves the accuracy of most target elements,particularly light elements,and reduces the detection limit of most of the elements after the medium atomic number.Wavelength dispersive X-ray fluorescence spectrometry can achieve rapid,non-destructive and accurate multi-element analysis in atmospheric particulate matter.