University of Oulu

Danny Croghan, Kieran Khamis, Chris Bradley, Anne F. Van Loon, Jon Sadler, David M. Hannah, Combining in-situ fluorometry and distributed rainfall data provides new insights into natural organic matter transport dynamics in an urban river, Science of The Total Environment, Volume 755, Part 1, 2021, 142731, ISSN 0048-9697,

Combining in-situ fluorometry and distributed rainfall data provides new insights into natural organic matter transport dynamics in an urban river

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Author: Croghan, Danny1,2; Khamis, Kieran1; Bradley, Chris1;
Organizations: 1School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom of Great Britain and Northern Ireland
2Water Resources and Environmental Engineering, University of Oulu, Oulu, FI-90014, Finland
3Institute for Environmental Studies, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, Netherlands
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.8 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2022-02-01


Urbanization alters the quality and quantity of Dissolved Organic Matter (DOM) fluxes to rivers potentially leading to water quality problems and impaired ecosystem function. Traditional synoptic and point sampling approaches are generally inadequate for monitoring DOM source dynamics. To identify links between spatial heterogeneity in precipitation and DOM dynamics, we used a unique approach combining high spatial and temporal resolution precipitation datasets featuring point, catchment, and land-cover weighted precipitation to characterise catchment transport dynamics. These datasets were linked to fluorescence records from an urban stream (Bourn Brook, Birmingham, UK). Humic-like fluorescence (HLF: Ex. 365 nm, Em. 490 nm) and Tryptophan-like fluorescence (TLF: Ex. 285 nm, Em. 340 nm) were measured, (plus river flow and turbidity) at 5 min intervals for 10 weeks during Autumn 2017. The relationship between discharge (Q) and concentration (C) for TLF and HLF were strongly chemodynamic at low Q (<Q50) but TLF was chemostatic when Q exceeded this threshold. Figure of eight hysteresis was the most common response type for both HLF and TLF, indicating that DOM sources shift within and between events. Key drivers of DOM dynamics were identified using regression analysis and model outputs using point, catchment-averaged, and land-use weighted precipitation were compared. Antecedent rainfall was identified as the most important predictor (negative relationship) of TLF and HLF change suggesting DOM source exhaustion. Precipitation weighted by land cover showed that urbanization metrics were linked to increased TLF:HLF ratios and changes in hysteresis index. This study presents a novel approach of using land-cover weighted rainfall to enhance mechanistic understanding of DOM controls and sources. In contrast, catchment-average rainfall data have the potential to yield stronger understanding of TLF dynamics. This technique could be integrated with existing high resolution in-situ datasets to enhance our understanding of DOM dynamics in urban rivers.

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Series: Science of the total environment
ISSN: 0048-9697
ISSN-E: 1879-1026
ISSN-L: 0048-9697
Volume: 755
Issue: 1
Article number: 142731
DOI: 10.1016/j.scitotenv.2020.142731
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Funding: This research was supported by an Engineering and Physical Sciences Research Council studentship grant awarded to Danny Croghan (grant number: 1673769).
Dataset Reference: Supplementary data to this article can be found online at
Copyright information: © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (