Abstract:Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high-temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short-term variations in chemical and ecological function. The authors report a 2-week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub-daily variations in both organic matter concentration and characteristics. In particular, after relatively high-magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic-like and tryptophan-like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation <2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation >2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic-like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer-derived 'old' organic matter at low-rainfall amounts and a mixed signal at high-precipitation amounts where 'event' surface runoff-derived organic matter dominate during storm sewer and combined sewer overflow routed DOM.

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We intend to prepare periodic multilayered structures for photonic applications. With this goal we have performed a study of some characteristics of SiO x -P 2 O 5 films deposited by the sol-gel method on glass and ITO (InSnO x )-coated glass. The as prepared films were annealed to different temperatures (150 and 200 • C). The chemical composition of the samples was determined by X-ray Photoelectron Spectroscopy (XPS). The XPS results revealed the presence of P in the as-deposited films. The structural an optical properties were examined by Fourier Transform Infrared Spectroscopy (FTIR), Spectroellipsometry (SE) and UV Transmission Spectroscopy. IR spectra of the deposited films attest the interaction of an amorphous SiO 2 with the H 3 PO 4 used as a P-precursor. Refractive indices for individual SiO x -P 2 O 5 determined from SE measurements show a densification of the layer structure with the increasing temperature in the thermal treatment. The UV transmission spectra revealed a lower transmission for the sol-gel SiO x -P 2 O 5 films as compared to ITO/glass substrate. AFM images proved the densification of the films with annealing in agreement with the ellipsometric results.The work was originally presented at "Physics of Photonic Crystals and Metamaterials (PPCM)" Workshop, Brussels, 12-15 June, 2006.

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