基于硅漂移探测系统的实验室光源X射线发射光谱仪的研制及在铬价态识别中的应用OA

The toxicity of chromium is strongly dependent on its chemical speciation,and the rapid and accurate identification of hexavalent chromium(Cr(Ⅵ))in the environment is the key to environmental risk assessment.Conventional chemical analytical methods involve cumbersome sample pretreatment and may cause valence state distortion,while energy-dispersive X-ray fluorescence(EDXRF)fails to resolve the subtle spectral differences caused by chromium valence variations due to insufficient spectral resolution.Although X-ray emission spectroscopy(XES)is highly sensitive to valence states and requires no chemical pretreatment,its application has long been limited by the reliance on synchrotron radiation sources.In this study,a laboratory-based XES spectrometer was developed utilizing a low-power X-ray tube,a Si(333)cylindrically bent crystal,and a silicon drift detector(SDD).The developed instrument achieved an energy resolution of 2.74 eV,which was 47.8 times higher than that of EDXRF,effectively eliminating the spectral overlap interference of Mn Kα on Cr Kβ.Meanwhile,its peak-to-background ratio in the Cr Kβ1,3 spectral region was 5.7 times superior to EDXRF.Reliable identification of Cr(Ⅵ)valence state was realized based on the Cr Kβ1,3 peak shift induced by valence variation,with a peak difference of(0.59±0.15)eV between Cr(0)and Cr(Ⅵ).The instrument was applied to analysis of soil sample collected from a chromium residue-contaminated site.Without any chemical pretreatment,the proportion of Cr(Ⅵ)in the sample was determined to be approximately 35.0％,corresponding to a concentration of 4.0×103 mg/kg(calculated as Cr).This result was significantly higher than that obtained by the alkaline extraction combined with inductively coupled plasma optical emission spectrometry(ICP-OES)(1.87×103 mg/kg),which was consistent with the previously reported incomplete extraction phenomenon of conventional chemical methods.The research results indicated that conventional chemical extraction methods had a potential risk of underestimating Cr(Ⅵ)concentrations in contaminated soil.Furthermore,this study demonstrated that the laboratory-scale XES spectrometer served as an accurate,non-destructive,rapid and effective analytical technique for determination of both chemically extractable and non-extractable Cr(Ⅵ)in contaminated soil.