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

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