RESUMEN
Fractal structures of kaolin and humic flcos by the mass-size method based on the microbalance and free-settling method based on particle image velocimetry technique were investigated. The results showed that kaolin and humic flocs were characterized by fractal structure. The three-dimensional fractal dimensions of Fe flocs with more compact structure ranged from 2.14 to 2.28 are larger than those of alum flocs ranged from 1.75 to 1.83 by the mass-size method. The fractal dimensions of humic flocs are smaller than those of kaolin flocs. The fractal dimension has a close relationship with the settling velocity of flocs. The larger the fractal dimension, the higher the settling velocity. The fractal dimensions by the mass-size method are in good agreement with those by the free-settling method. The measured settling velocities of fractal aggregates do not follow with Stokes' law.
Asunto(s)
Sustancias Húmicas , Caolín , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Floculación , Fractales , Precipitación Fraccionada , Tamaño de la Partícula , Propiedades de SuperficieRESUMEN
Fluorescence fingerprint technique was used to characterize dissolved organic matter (DOM) in river from different sources. The results showed that two types of DOM fluorescence signals were observed in river water: a humic-like fluorescence with three maxima at lambda(ex)/lambda(em) = 250/460 nm(A1), 220/400 nm(A2) and 325/420 nm(C); and a protein-like fluorescence with two maxima at lambda(ex)/lambda(em) = 230/360 nm(T2) and 285/357 nm(T1). The intensity of both of protein-like fluorescence distinctly increased because of the domestic wastewater drainage in the tributary stream. After the tributary converges into the main stream, the Fe3+ concentration in the main stream is 30 times as much as that of tributary stream, and the visible blue-shift of humic-like fluorescence occurred while the others didn't occur. The intensity of all types of fluorescence decreased from source to estuary resulting from different solute chemistry. However, the intensities of humic-like fluorescence C, A1 and protein-like fluorescence T2 at the longer excitation wavelength decreased significantly because of dilution from main river stream and complexation of humic-like with Fe3+, thus the peaks disappeared at the estuary while the fluorescence peaks at the shorter excitation wave-length were relatively stable on which the river solute chemistry had little effect. Therefore, the fluorophores at the shorter excitation wavelength of 220-230 nm area potential tool to determine the sources of DOM in polluted river.