Detection Of Pahs In Soil Based On Two-Dimensional Correlation Fluorescence Spectroscopy

The traditional fluorescence spectroscopy has been used for the detection of polycyclic aromatic hydrocarbons (PAHs) in soil. However, due to the complexity of soil system and the diversification and trace of PAHs pollutants, the traditional fluorescence spectroscopy cannot effectively extract the characteristic information of PAHs in soil. In order to solve the above problem, a new detection method of PAHs in soil was proposed and established based on two-dimensional (2D) correlation fluorescence spectroscopy. The typical PAHs pollutants of anthracene and phenanthrene in soil were used as research targets, and 38 mixture samples (the concentration of anthracene and phenanthrene in soil were between 0.000 5 and 0.01 g .g(-1)) were prepared. Three-dimensional (3D) fluorescence spectra of all samples were collected in the excitation wavelength range of 265 similar to 340 nm within an interval of 5 nm and in the emission wavelength range of 350 similar to 500 nm within an interval of 1 nm. And synchronous 2D correlation fluorescence spectra of all samples were calculated based on one-dimensional (1D) fluorescence spectra under the excitation perturbation. The characteristics of 3D fluorescence spectrum and synchronous 2D correlation fluorescence spectrum of the mixture of anthracene and phenanthrene were studied in soil (anthracene: 0.005 g .g(-1), phenanthrene: 0.005 g .g(-1)). In the synchronous 2D correlation fluorescence spectrum, four auto-peaks were observed at 398, 419, 444 and 484 nm along the main diagonal. Among them, the fluorescence peaks of 398 and 484 nm came from the phenanthrene in the soil, and the fluorescence peaks of 419 and 444 nm came from the anthracene in the soil. At the outside of the main diagonal line, there were negative cross peaks between anthracene and phenanthrene fluorescence peaks, which further verified that the sources were different. At the same time, there were two cross peaks at (408, 434) nm and (434, 467) nm, and the peaks at 408 and 434 nm were assigned to phenanthrene and 467 nm was assigned to anthracene in soil. It was pointed out that, compared with traditional 3D fluorescence spectroscopy, 2D correlation fluorescence spectroscopy could not only extract more characteristic information (the characteristic peaks of 408 and 467 nm are not represented in the 3D fluorescence spectrum), but also provide the relationship between fluorescence peaks, and effectively analyse their sources. On the basis of the characteristics of the 2D correlation fluorescence spectra, the N-way partial least squares (N-PLS) models for detecting the contaminants of anthracene and phenanthrene in soil were developed based on synchronous 2D correlation fluorescence spectral matrices (38 x 151 x 151). For anthracene in soil, the correlation coefficients r were 0.986 and 0.985 in calibration and prediction set; the mean square root error of calibration (RMSEC) and the root mean square error of the prediction (RMSEP) were 4.33 x 10(-4) and 5.55 x 10(-4) g . g(-1), respectively. For phenanthrene in soil, the correlation coefficients r were 0.981 and 0.984 in calibration and prediction set; the RMSEC and the RMSEP were 5.20 x 10(-4) and 4.80 x 10(-4) g . g(-1), respectively. In order to compare, the N-PLS models for quantitative analysis of anthracene and phenanthrene in soil were established based on a 3D fluorescence spectral matrices(38 x 16 x 151). For anthracene in soil, the correlation coefficients r were 0.981 and 0.972 in calibration and prediction set; the RMSEC and the RMSEP were 5.09 x 10(-4) and 6.74 x 10(-4) g . g(-1), respectively. For phenanthrene in soil, the correlation coefficients r were 0.957 and 0.956 in calibration and prediction set; the RMSEC and the RMSEP were 7.36 x 10(-4) and 7.77 x 10(-4) g . g(-1), respectively. It was pointed out that, for the detection of-anthracene and phenanthrene in soil, the correlation coefficients r, RMSEC and RMSEP of N-PLS models were better based on 2D correlation fluorescence spectra than 3D fluorescence spectra. The results showed that the direct detection of PAHs contaminants in soil based on 2D correlation fluorescence spectroscopy is not only feasible, but also can provide better analysis results. This study provides a theoretical and experimental basis for direct detection of PAHs in soil by laser induced fluorescence combined with 2D correlation technology, having a good application prospect.