Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Advances in analytical chemistry have facilitated the characterization of dissolved organic matter (DOM), which has improved understanding of DOM sources and transformations in surface waters. For urban waters, however, where DOM diversity is likely to be high, the interpretation of DOM signatures is hampered by a lack of information on the influence of land cover and anthropogenic factors such as nutrient enrichment and release of organic contaminants. Here we explored the spatio-temporal variation in DOM composition in contrasting urban water bodies, based on spectrophotometry and fluorometry, size-exclusion chromatography, and ultrahigh-resolution mass spectrometry, to identify linkages between DOM signatures and potential drivers. The highly diverse DOM we observed distinguished lakes and ponds, which are characterized by a high proportion of autochthonous DOM, from rivers and streams where allochthonous DOM is more prevalent. Seasonal variation in DOM composition was apparent in all types of water bodies, apparently due to interactions between phenology and urban influences, such as nutrient supply, the percentage of green space surrounding the water bodies and point source pollution. Optical DOM properties also revealed the influence of effluents from wastewater treatment plants, suggesting that simple optical measurements can be useful in water quality assessment and monitoring, providing information about processes both within water bodies and in their catchments.

Highlights

  • 30 Urban freshwaters typically receive high loads of organic carbon, nutrients and micropollutants, ranging from pharmaceuticals and personal care products to industrial chemicals and more (Schwarzenbach et al, 2006)

  • We followed a three-step approach to analyze the spatio-temporal patterns of dissolved organic matter (DOM) composition: First we identified major axes of variation in DOM composition by a principal component analysis (PCA) based on quantitative indicators of DOM, analytically accessible fractions thereof or quantitative proxies: dissolved organic carbon (DOC) concentration, all absorbance and fluorescence data, absolute 175 component-specific fluorescence intensities from parallel factor analysis (PARAFAC), and the results from size-exclusion chromatography

  • The composition of DOM collected in a suite of contrasting water bodies in a large metropolitan area, the city of Berlin in Germany, is diverse. varying widely in molecular size and other features related to the degree of allochthonous inputs and conveying a distinct urban character

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Summary

Introduction

30 Urban freshwaters typically receive high loads of organic carbon, nutrients and micropollutants, ranging from pharmaceuticals and personal care products to industrial chemicals and more (Schwarzenbach et al, 2006). This includes the lateral and vertical disconnection from floodplains and aquifers and results in large impacts on the extent and complexity of riverine habitat (White and Walsh, 2020). The disruption of connectivity limits the self-purification capacity of urban surface waters (D'arcy et al, 2007), which can lead to turbid water and visually unpleasant and potentially harmful algal blooms (Carpenter et al, 1998). This and the resulting failure of citizens to recognize urban freshwaters as providers of ecosystem services (Huser et al., 40 2016) calls for improved water management strategies that consider ecological in addition to hygienic and chemical criteria (Gessner et al, 2014)

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