High frequency fluorescence monitoring reveals new insights into organic matter dynamics of an urban river, Birmingham, UK

Research output: Contribution to journalArticle

Abstract

Natural organic matter (NOM) is fundamental to many biogeochemical processes in river ecosystems. Currently,however, we have limited knowledge of NOM dynamics across the spectrum offlow conditions as previous stud-ies have focused largely on storm events. Field deployablefluorescence technology offers new opportunities toexplore both stochastic and predictable diel NOM dynamics atfiner time-steps and for longer periods thanwas hitherto possible, thus yielding new insight into NOM sources, processing, and pathways. Hourlyfluores-cence data (humic-likefluorescence [Peak C] and tryptophan-likefluorescence [Peak T]) and a suite of hydro-climatological variables were collected from an urban river (Birmingham, UK). We explored monthlyconcentration-discharge (C-Q) patterns using segmented regression and assessed hysteretic andflushing behav-iour for Peak C, T and turbidity to infer source zone activation. Diel patterns were assessed during lowflow pe-riods. Wavelet analysis identified strong diurnal variations in Peak C with early morning peaks while no dieldynamics were apparent for Peak T. Using generalised linear modelling relationships between Peak C periodicityand both solar radiation and time since previous storm/scouring event were identified. Breakpoints and positiveslopes for C-Q relationship highlighted chemodynamic behaviour for NOM over most of the monitoring period,with Peak T mobilised more relative to Peak C during high Q. Hysteresis patterns were highly variable butflush-ing behaviour of Peak T and C suggested exhaustion of humic compounds during long duration events and fol-lowing successive rainfall events. Peak Tflushing was correlated with Q magnitude highlighting the potentialfor combined sewer overflows to act as important NOM sources despite significant dilution potential. This re-search highlights the potential of real-time,field deployablefluorescence spectroscopy as a viable method forproviding insight into diel and transport driven NOM dynamics.

Details

Original languageEnglish
Article number135668
JournalScience of the Total Environment
Volume710
Publication statusPublished - 22 Nov 2019