Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), 75007, Uppsala, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), 75007, Uppsala, Sweden; Department of Ecology and Genetics/Limnology, Uppsala University, 75236, Uppsala, Sweden.
Water Res. 2015 Nov 15;85:286-94. doi: 10.1016/j.watres.2015.08.024. Epub 2015 Aug 28.
Absorbance, 3D fluorescence and ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) were used to explain patterns in the removal of chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) at the molecular level during drinking water production at four large drinking water treatment plants in Sweden. When dissolved organic carbon (DOC) removal was low, shifts in the dissolved organic matter (DOM) composition could not be detected with commonly used DOC-normalized parameters (e.g. specific UV254 absorbance - SUVA), but was clearly observed by using differential absorbance and fluorescence or ESI-FT-ICR-MS. In addition, we took a novel approach by identifying how optical parameters were correlated to the elemental composition of DOM by using rank correlation to connect optical properties to chemical formulas assigned to mass peaks from FT-ICR-MS analyses. Coagulation treatment selectively removed FDOM at longer emission wavelengths (450-600 nm), which significantly correlated with chemical formulas containing oxidized carbon (average carbon oxidation state ≥ 0), low hydrogen to carbon ratios (H/C: average ± SD = 0.83 ± 0.13), and abundant oxygen-containing functional groups (O/C = 0.62 ± 0.10). Slow sand filtration was less efficient in removing DOM, yet selectively targeted FDOM at shorter emission wavelengths (between 300 and 450 nm), which commonly represents algal rather than terrestrial sources. This shorter wavelength FDOM correlated with chemical formulas containing reduced carbon (average carbon oxidation state ≤ 0), with relatively few carbon-carbon double bonds (H/C = 1.32 ± 0.16) and less oxygen per carbon (O/C = 0.43 ± 0.10) than those removed during coagulation. By coupling optical approaches with FT-ICR-MS to characterize DOM, we were for the first time able to confirm the molecular composition of absorbing and fluorescing DOM selectively targeted during drinking water treatment.
采用吸光度、三维荧光和超高分辨率电喷雾电离傅里叶变换离子回旋共振质谱（ESI-FT-ICR-MS）技术，从分子水平上解释了在瑞典四个大型饮用水处理厂的饮用水生产过程中，有色和荧光溶解有机物（CDOM 和 FDOM）的去除模式。当溶解有机碳（DOC）去除率较低时，通常使用的 DOC 归一化参数（如比紫外吸光度 - SUVA）无法检测到 DOM 组成的变化，但通过使用差分吸光度和荧光或 ESI-FT-ICR-MS 则可以清楚地观察到。此外，我们还采用了一种新方法，通过使用秩相关将光学参数与 DOM 的元素组成相关联，从而将光学特性与 FT-ICR-MS 分析中分配给质荷峰的化学公式联系起来，以此来识别光学参数与 DOM 元素组成的相关性。混凝处理选择性地去除了更长发射波长（450-600nm）的 FDOM，这与含有氧化碳（平均碳氧化态≥0）、低氢碳比（H/C：平均±SD=0.83±0.13）和丰富含氧官能团（O/C=0.62±0.10）的化学公式显著相关。慢砂过滤在去除 DOM 方面效率较低，但选择性地针对较短发射波长（300-450nm）的 FDOM，这通常代表藻类而不是陆地来源。这种较短波长的 FDOM 与含有还原碳（平均碳氧化态≤0）的化学公式相关，与那些在混凝过程中去除的化学公式相比，其碳碳双键相对较少（H/C=1.32±0.16），每个碳原子的氧含量也较少（O/C=0.43±0.10）。通过将光学方法与 FT-ICR-MS 相结合来表征 DOM，我们首次能够确认在饮用水处理过程中选择性去除的吸收和荧光 DOM 的分子组成。
