Continuous fluorescence assessment of organic matter variability on the Bournbrook River, Birmingham, UK

Abstract

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.

Fluorescence index as an indicator of dissolved organic carbon quality in hydrologic flowpaths of forested tropical watersheds

“…Fluorescence characteristics have been demonstrated to be useful for describing DOC precursors and distinguishing between sources of water based on differences in DOC quality (Carstea et al 2009;Cook et al 2009). However, as fluorescence characteristics are quite variable in space and time, care should be taken in characterizing the seasonal patterns in potential source waters if FI is to be used as a tool for hydrologic investigation.…”

“…These differences have enabled researchers to utilize fluorescence spectroscopy as a tool for inferring DOC sources in a diverse range of settings, including sewage outfalls in temperate-zone urbanized watersheds (Carstea et al 2009), tropical mangrove estuaries (Jaffé et al 2004), salmon-bearing streams (Hood et al 2007) and permafrost zones (Balcarczyk et al 2009). DOC fluorescence characteristics have also been used as hydrological tracers for identifying flowpaths contributing water from the landscape to water bodies (Mariot et al 2007), including tracing source water contributions to streams from diverse flowpaths during storm events (Katsuyama and Ohte 2002).…”

Real-time monitoring of nutrients and dissolved organic matter in rivers: Capturing event dynamics, technological opportunities and future directions

“…435 , with TLF peaking either on the rising limb or at peak flow 475 (Figure 5b). This suggests DOM sources are situated close to or in the channel, and probably include 476 dry deposition on impervious surfaces and the breakup of biofilms in the channel, storm drains and 477 combined sewer overflows (Carstea et al, 2009;Khamis et al, 2015). Thus, for this system, suitable 478 triggers for adaptive monitoring would be a combination of river level/discharge and TLF (cf.…”

Fluorescence Spectroscopy as a Potential Tool for In-Situ Monitoring of Dissolved Organic Matter in Surface Water Systems

“…The spectral fingerprints for the major petroleum products that can be present as environmental pollutants (petrol, kerosene, Diesel and engine oil) have been acquired by Patra and Mishra (2002a), Cristescu et al (2009) and Carstea et al (2009a). The authors observed that heavy oil, Diesel and engine oil, show fluorescence maxima in the longer emission wavelength region (420 -550 nm) while lighter oils, petrol and kerosene, present peaks mainly in an intermediate wavelength region (310 -400 nm).…”

“…Riverine samples have been analysed in few occasions, by scientists, in order to identify the peculiarities of a certain water body at temporal and spatial scale (Hudson et al, 2007). Most studies had shown that the humic substances largely dominate the fluorescence spectra, but the protein-like fraction can also be detected, depending on the type, location and inputs of the river Carstea et al, 2009a;Carstea et al, 2009b). It has been shown that riverine DOM presents a seasonal variation (Baker et al, 2003;Carstea unpublished data), but also a subtle daily variation (Spencer et al, 2007).…”