Application Study On Fluorescence Measurement Technology Of Petroleum Hydrocarbon Pollutants In Soil

Soil petroleum hydrocarbon pollutants pose a huge threat to environmental safety,industrial and agricultural production and human health.The development of rapid on-site detection techniques of soil petroleum hydrocarbon pollutants was of great significance to site pollution investigation,treatment and emergency monitoring.Laser induced fluorescence technology had the characteristics of fast detection,high sensitivity,and on-site detection,which provided a new method for the rapid detection of soil petroleum hydrocarbon pollutants on site.The thesis carried out Application Study on Fluorescence Measurement Technology of Petroleum Hydrocarbon Pollutants in Soil to provided methods and data support for further development of rapid monitoring equipment for soil organic pollutants.The main research work of the thesis was as follows:(1)A laser-induced fluorescence experiment system for soil petroleum hydrocarbon pollutants was built,parameters were optimized,and the fluorescence spectrum characteristics of soil petroleum hydrocarbon pollutants under different physical properties were analyzed.The characteristics of the excitation and emission spectra of soil petroleum hydrocarbons were studied,and the excitation wavelength and fluorescence spectrum range of soil petroleum hydrocarbons were determined.A 4-fold frequency Nd:YAG laser and optical fiber spectrometer were selected to construct a soil petroleum hydrocarbon fluorescence spectrum detection experimental system.The experiment analyzed the fluorescence spectrum characteristics and stability of soil petroleum hydrocarbon pollutants under different laser pulse energy,repetition frequency and spectrum accumulation times,and determines the optimal experimental parameters.The laser pulse energy density range was 2mJ/cm2-4mJ/cm2.The repetition frequency was 10 Hz,the number of spectral accumulation times was 40,and the single measurement time of the sample was only 4s.The experiment analyzes the influence of soil looseness,particle size and humidity on the fluorescence emission characteristics of petroleum hydrocarbon pollutants.Among them,soil moisture has the greatest influence on the fluorescence intensity,and with the increase of humidity,the fluorescence intensity shows a trend of rapid increase and decline.The degrees of looseness and particle size had little effect on the intensity and stability of the fluorescence spectrum.(2)The identification methods of soil petroleum hydrocarbon pollutant components,humidity correction and quantitative detection were studied.Based on the iterative approximation algorithm and the interception characteristic spectrum method,the spectrum of soil mixed petroleum hydrocarbons was decentralized,the contribution rate of motor oil and diesel oil was calculated,and the fluorescence spectrum was reconstructed,and the error from the original spectrum was less than 5%.The identification method of soil petroleum hydrocarbon components based on principal component analysis and support vector machine was studied.The recognition rate of petroleum hydrocarbons such as engine oil,diesel oil and lubricating oil is 100%,and the recognition accuracy of petroleum hydrocarbons with different labels of the same type was low.The three-dimensional fluorescence spectrum identification method of soil petroleum hydrocarbon pollutants was studied,and the identification characteristics were established with parameters such as average value,standard deviation,center of gravity horizontal and vertical coordinates,correlation coefficient,long-axis slope,skewness,kurtosis and long-axis slope.Using principal component analysis and BP-ANN classification and recognition algorithm,the comprehensive recognition rate of different types of petroleum hydrocarbon classification reached 95.62%;research and comparison of calibration curve method,3DEEM parallel factor method and RBF-NN algorithm and other quantitative methods,the results showed that the use of The improved RBF model had the best effect,the measurement error was about 5.5%,and it cloud correct the measurement error introduced by soil moisture.(3)The three-dimensional pollution distribution law of petroleum hydrocarbons in soil was studied.Taking diesel as an example,the RBF-NN model was used to calculate the lateral diffusion width and vertical vertical penetration depth of the soil diesel under different humidity,and a three-dimensional penetration model of diesel under different soil humidity was established.The results showed that with the increase of soil moisture,the lateral spread of diesel oil on the soil surface gradually increases,and the vertical and vertical penetration depth gradually decreases,that was the increase of soil moisture helps the horizontal diffusion of petrol and diesel,hinders the vertical penetration of diesel.When the soil moisture is 0%,5%and 10%,the total amount of diesel oil was retrieved using the established soil red diesel three-dimensional penetration model,and the relative errors were 6.22%,8.30%and 9.10%in order.The diffusion rule of crude oil under different soil moisture was studied,and the applicability of the three-dimensional diffusion model of petroleum hydrocarbons was verified,that was,the water content in the soil generally contributed to the diffusion of petroleum hydrocarbons,and the application of LIF spectroscopy to the three-dimensional pollution of petroleum hydrocarbons was verified.The research can provide a theoretical basis for the accurate evaluation and scientific remediation of oil contaminated soil.It provided an effective means for the on-site monitoring of the total amount of petroleum hydrocarbons in the soil,and provides a theoretical basis for the accurate evaluation of oil-contaminated soil,emergency monitoring of leakage,and efficient remediation.(4)Field experiments were conducted on soil contaminated with petroleum hydrocarbons.Based on the spectral characteristics of actual soil petroleum hydrocarbons,a quantitative algorithm for soil mixed petroleum hydrocarbons was proposed to achieve rapid quantitative detection of soil mixed petroleum hydrocarbon pollution.Firstly,under laboratory conditions,the measurement error of total petroleum hydrocarbon with a concentration of 0%-10%in soil with a humidity of 5%is analyzed,and the measurement error is within 15%.On-site measurement of 40 soil samples was carried out on a 1-hectare site near an automobile repair plant in Hefei,and the test results were corrected and analyzed.The test results showed that the total petroleum hydrocarbon concentration in the area around the automobile repair plant was about 0.6%.LIF technology could be used for rapid detection and screening of petroleum hydrocarbon contaminants on contaminated sites.The research in this paper provided data supported and method support for the further development of on-site rapid monitoring methods of soil petroleum hydrocarbon pollutants.