Plaza César, Brunetti Gennaro, Senesi Nicola, Polo Alfredo
Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano 115 dpdo., 28006 Madrid, Spain.
Environ Sci Technol. 2006 Feb 1;40(3):917-23. doi: 10.1021/es051687w.
Humic acids (HAs) isolated from sewage sludge (SS) and control and SS-amended soils were characterized by fluorescence spectroscopy. The main feature of fluorescence spectra was a broad band with the maximum centered at excitation/emission wavelengths that were much shorter for SS-HA (340/438 nm) than for any soil HA (440/510 nm). Titration with Cu(II), Zn(II), Cd(II), and Pb(II) ions decreased fluorescence intensities of HAs. Titration data were fitted to a single-site fluorescence quenching model, and metal ion complexing capacities of each HA sample and stability constants of metal ion-HA complexes were calculated. The binding capacities of HAs and strengths of metal ion-HA complexes followed the order Pb(II) > Cu(II) > Cd(II) > Zn(II). With respect to the control soil HA, SS-HA, which showed the smallest contents of acidic functional groups and the lowest humification degree, was characterized by much smaller binding capacities and stability constants. The binding capacities and affinities of SS-amended soil HA were intermediate between those of native soil HA and SS-HA but closer to the former, thus suggesting a partial incorporation of HA fractions of SS into native soil HAs. These effects are expected to have a great impact on the behavior of metals in SS-amended soils.
采用荧光光谱法对从污水污泥（SS）以及对照土壤和添加了SS的土壤中分离出的腐殖酸（HA）进行了表征。荧光光谱的主要特征是一个宽带，其最大值位于激发/发射波长处，对于污泥腐殖酸（SS-HA，340/438 nm）而言，该波长比任何土壤腐殖酸（440/510 nm）的波长要短得多。用铜（II）、锌（II）、镉（II）和铅（II）离子进行滴定会降低腐殖酸的荧光强度。将滴定数据拟合到单点位荧光猝灭模型，并计算了每个腐殖酸样品的金属离子络合能力以及金属离子-腐殖酸络合物的稳定常数。腐殖酸的结合能力和金属离子-腐殖酸络合物的强度顺序为：铅（II）＞铜（II）＞镉（II）＞锌（II）。与对照土壤腐殖酸相比，污泥腐殖酸的酸性官能团含量最低，腐殖化程度也最低，其结合能力和稳定常数要小得多。添加了污泥的土壤腐殖酸的结合能力和亲和力介于天然土壤腐殖酸和污泥腐殖酸之间，但更接近前者，这表明污泥中的腐殖酸部分掺入了天然土壤腐殖酸中。预计这些效应会对添加了污泥的土壤中金属的行为产生重大影响。
