Detection of dissolved organic matter in saline-alkali soils using synchronous fluorescence spectroscopy and principal component analysis.

Dissolved organic matter (DOM) is attributed a key role in soil major biogeochemical processes. Its molecular characteristics can reflect both its source and its biogeochemical history. Saline-alkali soil samples were collected from a field in desert and semi-desert region. DOM was analyzed by synchronous fluorescence spectroscopy. Principal Components Analysis (PCA) of synchronous fluorescence spectra was used to detect and describe changes in the DOM in different soil profiles. The analysis of PCA yielded 2 PCs that account for 97% of the variance. DOM is characterized by a dominant tyrosine-like fluorophore in the Region I (PC1>0.9, PC2<0.3), including soils Ke02, Ke03, Ke04, Rh02, Rh03, Rh04, Sa04 and Sc04. The region II including Kf02, Sa01, Yb01, Yzd01 and Yzd02 obtain higher PC2 (>0.9) and lower PC1 (<0.3) loading, which is dominated humic-like fluorophore. Hierarchical cluster analysis (HCA) identified five main clusters. The results of hierarchical cluster analysis (HCA) were consistent with the PCA. The ratio of fluorescence intensity of humic substances at long wavelengths and short wavelengths was used to indicate the humification of organic matter. Two ratios (I(345/318) and I(362/318).) can be used to indicate the humification of DOM. The humification degree of the remaining soils has no systematic trend because of land use, agricultural irrigation, soil erosion and salinization. Soils obtained a relatively high humification degree in the region II and a relatively low humification degree in the region I.

[Denitrification on secondary effluent of acrylic fiber wastewater by tri-stage biofilm advanced reactor].

To resolve the shortage of carbon source during traditional denitrification used to treat secondary effluent of acrylic fiber wastewater, tri-stage biofilm reactor was used, the influence of pH of influent, HRT, and NH4(+) -N concentration in raw water on NH4(+) -N removal was investigated. Efficiency of TN removal was also investigated. It demonstrated that the optimal HRT and pH were 24 hours and 7.8-8.0 respectively. Under these conditions the removal efficiencies of NH4(+) -N and TN were 94. 6% and 53% respectively. And the removal efficiency of NH4(+) -N had no relationship with the concentration of the inflow water. With absence of organic carbon source in the reactor, efficiency of TN removal was obvious, the average and the highest removal efficiencies of TN were 53% and 66% respectively, efficiency of secondary effluent of acrylic fiber wastewater nitrogen removal was obvious when treated with Tri-stage biofilm reactor.

Spectroscopic techniques for quantitative characterization of Cu (II) and Hg (II) complexation by dissolved organic matter from lake sediment in arid and semi-arid region.

Dissolved organic matter (DOM) was extracted from six sediment samples in arid and semi-arid region, which was characterized by fluorescence excitation-emission matrices (EEMs). The results showed that four fluorescent peak, fulvic-like (peak A), humic-like (peak C) and two tryptophan-like (peaks B and D), were identified in lake sediment DOM. Fluorescence quenching titration showed that peaks B and D were quenched gradually by adding additional Cu (II) and Hg (II), whereas humic-like substances had no systematic trend of the change of fluorescence intensity. Increasing fluorescence intensity value of humic-like substances can also be found. The modified Stern-Volmer model was used to calculate conditional stability constants (logK) and the percent of fluorophores (f %) which participate in the complexation between DOM and Cu (II), and Hg (II). The results showed that DOM-Cu (II) and DOM-Hg (II) complexes had higher logK values of 4.21-5.23 and the logK values of DOM-Cu (II) are much larger than the corresponding values for Hg (II). Peak B showed relatively low logK and high f % values than those of peak D. Different pollution sources which are mainly obtained from the upstream industrial wastewater, domestic sewage and return water of farmland irrigation tend to affect the stability constants and complexing capacities of Cu (II) and Hg (II).

[Optimization of acrylic fiber polymerization wastewater treatment condition by three-dimensional electrode].

The research was focus on the influence of experimental conditions to the removal efficiency of contaminant and the change of biodegradability in the treatment of acrylic fiber polymerization wastewater using three-dimensional electrode reactor with granular activated carbon. The anode was Ti/SnO2-Sb2O3 expanded metal sheet electrode. The cathode was Ti expanded metal sheet electrode. The parameters investigated were the reaction time, electrolytic voltage, initial pH value and aeration amount. The results show that the electrolytic voltage and initial pH value had greater impact on the removal efficiency of organic pollutants. Under the optimal experimental condition with electrolytic voltage 15 V, initial pH value 3, aeration amount 400 mL/min, the removal rates of COD, TOC and acrylonitrile were 32.59%, 22.17% and 89.70%, respectively,and the value of BOD5/COD increased from 0.02 to 0.42 within 120 min, which improved the biodegradability greatly and was beneficial for further biological treatment.