Excimer Laser-induced Breakdown Spectroscopy Applied To Climate Inversion Research

Paleoclimatology is a discipline that studies the past climate of the earth.Its purpose is to predict future climate changes and solve problems such as environmental pollution and resource scarcity.By studying the spatial distribution of elements in climate proxies(ice cores,shells,stalagmites,etc.),inferring the evolution of paleo-climate is of great significance to the changes in the natural environment.Element imaging technology based on laser induced breakdown spectroscopy(LIBS)is a new type of atomic spectroscopy analysis technology.After the high-energy pulsed laser is focused,it scans the sample area to be measured in a predetermined order.The spectrometer collects and detects the wavelength and intensity of the plasma emission line,and analyzes the element information qualitatively and quantitatively according to the characteristic line.The element imaging technology based on LIBS can quickly,accurately,in situ and slightly loss analysis of element spatial distribution in large area of complex climate samples,providing a variety of data for climate inversion,and has a broad application prospect in the field of environmental detection.The excimer laser has short wavelength,high peak density,and small fractionation effect.It is suitable as a light source for LIBS element imaging technology to analyze climate agents.Therefore,this article uses 193 nm ArF excimer laser as the excitation source to build an excimer LIBS element imaging system,studies the relevant characteristics of the important parameters of the system,and conducts climate inversion research on typical samples.The main contents include:(1)In this paper,the research progress of element detection technology in climate samples is reviewed,the working principle of laser-induced breakdown spectroscopy is analyzed,and the qualitative and quantitative analysis methods are summarized.(2)Based on the 193 nm ArF excimer laser,a set of excimer LIBS element imaging system suitable for climate agents was designed and built,including cage optical path structure,focusing structure,spectral detection device and coaxial imaging device.(3)The parameters of excimer laser-induced plasma were analyzed,and the plasma temperature and electron number density were calculated according to the theoretical formula to confirm that the system met the local heat balance conditions.At the same time,the ratio of Al/Ca,Fe/Ca,Mg/Ca,Si/Ca in the standard material was detected by using the excimer LIBS element imaging system.The relative standard deviations of the ratios of the four elements are all less than 3%,which can realize stable microscanning analysis.(4)The systematic micro-area imaging technology was used to scan two typical climate samples,and the distribution changes of trace elements Mg/Ca and Sr/Ca in different growth cycles of the samples were studied.The results showed that: The Mg/Ca ratio in the stalactite samples fluctuated significantly,which may be due to the increase of precipitation or temperature in the cave,which accelerated the deposition rate of the stalactite.There were differences in the enrichment areas of Mg and Sr elements between Gastropod and Bivalve shells,but the Mg/Ca and Sr/Ca ratios showed periodic intensity changes,which were inferred to be related to the seasonal change,providing an effective basis for the inversion of the growth environment of shells.