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Autori: E.M. Carstea, A. Baker, I. Boomer, G.Pavelescu
Editorial: Hydrological processes, 23, p.1937-1946, 2009.
Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability a 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.
Cuvinte cheie: dissolved organic matter; fluorescence; absorbance; isotope hydrology; urban rivers