Dissolved organic matter signatures in urban surface waters: spatio-temporal patterns and drivers

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.