NO3-对二级出水DOM与Cu2+络合作用的光谱特性影响

利用三维荧光光谱法和紫外分光光度法，研究NO₃^-对二级出水DOM与Cu²⁺络合作用的光谱特性和络合能力的影响.随投加NO₃^-浓度增加，二级出水DOM与Cu²⁺络合作用后代表类蛋白质（类色氨酸）物质荧光峰消失，紫外吸收峰右侧红移.投加NO₃^-浓度与二级出水DOM和Cu²⁺络合作用后的HIX、α₃₀₀、α₂₅₀/α₃₆₅、E₃/E₄和UV₂₅₃/UV₂₀₃值呈显著正相关，与BIX显著负相关（r为-0.958~-0.719），与S_240-400和S_275-295值分别呈指数增加和指数减少关系（R²分别为0.9678~0.9952和0.9965~0.9978），对FI、α₃₅₀、α₃₅₅和S_350-400值影响较小.二级出水DOM中的紫外光类腐殖质、可见光类腐殖质和高激发波长类色氨酸物质与Cu²⁺作用后的条件稳定常数lgK分别为2.08~2.46，1.84~2.51，2.27~2.57L/mmol，配位荧光官能团比例分别为19.5%~36.5%、22.5%~33.3%和24.4%~29.2%.二级出水DOM中类腐殖质和类蛋白质与Cu²⁺的络合反应强度相差不大，且样品中NO₃^-浓度不同时，用部分荧光参数（HIX）和紫外参数（α₃₀₀、α₂₅₀/α₃₆₅、E₃/E₄、S_240-400和S_275-295）表示DOM的含量、分子性质存在一定的不确定性.

Effect of NO3- on spectral characteristic of the complexation of DOM and Cu2+ from secondary effluent

The effects of nitrate on the spectral characteristics and complexation ability of DOM with Cu²⁺ in the secondary effluent of municipal wastewater were investigated by using three-dimensional fluorescence and UV spectrophotometry. The fluorescence peak representing the protein-like (tryptophan-like) produced by complexation of DOM and Cu²⁺ disappeared with the increase of NO₃^- concentration, and the right side of the UV absorption peak occurred red-shift. The concentration of NO₃^- was significantly positively correlated with the values of HIX, α₃₀₀, α₂₅₀/α₃₆₅, E₃/E₄ and UV₂₅₃/UV₂₀₃ after complexation of DOM with Cu²⁺, while negatively correlated with BIX (r with -0.958~-0.719). It had an exponential increase with S_240-400 (R² with 0.9678~0.9952) and an exponential decrease with S_275-295 (R² with 0.9965~0.9978), but had little effect on the values of FI, α₃₅₀, α₃₅₅ and S_350-400. The conditional stability constant lgK of ultraviolet humus-like, visible humus-like and high excitation wavelength tryptophan-like in the secondary effluent of DOM with Cu²⁺ were 2.08~2.46L/mmol, 1.84~2.51L/mmol and 2.27~2.57L/mmol, respectively; and the proportion of coordination fluorescent functional groups were 19.5%~36.5%, 22.5%~33.3% and 24.4%~29.2%, respectively. In summary, there was not significant difference in the intensity of the complexation reaction between Cu²⁺ and humus-like or protein-like from DOM of the secondary effluent. When the NO₃^- concentration in the samples was different, there were some uncertainties in expressing the content of DOM and molecular properties with partial fluorescence (HIX) and ultraviolet parameters (α₃₀₀, α₂₅₀/α₃₆₅, E₃/E₄, S_240-400 and S_275-295).