Aqueous fluorescence fingerprint characteristics of printing and dyeing wastewater and their influencing factors

The textile and dyeing industry in the Yangtze River Delta region is highly concentrated and generates a large amount of wastewater, which increases the risk of illegal discharges. Therefore, accurately tracing the source of the dyeing wastewater has become an urgent need in the field of water environment governance and ecological protection. Aqueous fluorescence fingerprint technology enables rapid identification of the suspected pollution source by comparing the fingerprints of contaminated water samples with those of known pollution sources in the database. Its application potential in the field of water environment supervision is enormous. Taking the wastewater from two typical dyeing enterprises in the Yangtze River Delta region (dyeing wastewater 1 and 2) and the dye dispersant MF as the research objects, the aqueous fluorescence fingerprint patterns were determined, and the influence of environmental factors (pH and ${\mathrm{N}\mathrm{O}}_3^{-}$) on the aqueous fluorescence fingerprint characteristics was investigated. The results show that in the aqueous fluorescence fingerprints of each sample, there are two fluorescence peaks, peak 1 and peak 2, whose [excitation wavelength, emission wavelength] positions are respectively located near [280, 320] nm and [230, 340] nm. In the three-dimensional fluorescence spectra of the dyeing wastewater 1 and 2, the C1 and C2 components may originate from the dispersant MF. The fluorescence intensity of peak 2 for wastewater 1 is more affected by pH and ${\mathrm{N}\mathrm{O}}_3^{-}$ than that of the dispersant MF. This suggests that it may contain other fluorescent organic substances that are more sensitive to changes in environmental factors. The normal pH levels in surface water and the typical concentrations of ${\mathrm{N}\mathrm{O}}_3^{-}$ in centralized surface water sources for drinking water have a relatively minor impact on the position of the fluorescence peaks, and do not affect the identification of the pollution source type. When the mass concentration of ${\mathrm{N}\mathrm{O}}_3^{-}$ was 40 mg/L, the fluorescence intensity of peak 2 in the dyeing wastewater samples 1 and 2 decreased by 32.52% and 24.79%, respectively, compared to the case without adjusting the ${\mathrm{N}\mathrm{O}}_3^{-}$ concentration, which might lead to an underestimation of the degree of pollution.