The optical signature of chromophoric dissolved organic matter (CDOM) has been related to sources and composition of dissolved organic matter (DOM) in surface waters, but the spatial scope of previous research has been limited to single cities with no studies exploring patterns across gradients of development/industrialization or latitude. Using EEM (excitation emission matrix) techniques, a study was conducted to examine optical properties of CDOM in urban waters along a gradient of urban development (developed and undeveloped cities) and industries (primary, secondary, tertiary). The optical properties of CDOM were measured in 436 water samples collected from urbanized waterbodies spanning 93 cities across China. Results showed marked differences of DOM composition for different level of urban development and for different types of dominant industries. The mean aCDOM(254) for developed cities (14.31m-1) was significantly lower (p<0.05) than that of undeveloped cities (18.01m-1). The intensity of the tryptophan-like component (Q2) of CDOM was significantly higher for developed cities (0.98*1010 nm) than for undeveloped cities (4.6*109 nm), whereas the humic-like component (Q5) intensity was significantly lower for undeveloped cities (19.80*1010 nm) than for developed cities (16.26*1010 nm). Regression analysis showed that the Q5 component was mainly (and positively) influenced by secondary industries, while Q2 was mainly affected by both tertiary and secondary industries. The proportion of allochthonous CDOM increased significantly with latitude from south to north with the minimum increased percentage of 67% for humification index (HIX) within different urban development degrees. These findings indicate that changes in urban development, human activities and industrial structure could alter DOM sources and composition in urbanized waterbodies. These findings are relevant to the management of urban water resources in regions experiencing rapid urban and industrial expansion, and add to our understanding of carbon cycling in urbanized freshwater ecosystems.

The optical signature of chromophoric dissolved organic matter (CDOM) has been related to sources and composition of dissolved organic matter (DOM) in surface waters, but the spatial scope of previous research has been limited to single cities with no studies exploring patterns across gradients of development/industrialization or latitude. Using EEM (excitation emission matrix) techniques, a study was conducted to examine optical properties of CDOM in urban waters along a gradient of urban development (developed and undeveloped cities) and industries (primary, secondary, tertiary). The optical properties of CDOM were measured in 436 water samples collected from urbanized waterbodies spanning 93 cities across China. Results showed marked differences of DOM composition for different level of urban development and for different types of dominant industries. The mean aCDOM(254) for developed cities (14.31m-1) was significantly lower (p<0.05) than that of undeveloped cities (18.01m-1). The intensity of the tryptophan-like component (Q2) of CDOM was significantly higher for developed cities (0.98*1010 nm) than for undeveloped cities (4.6*109 nm), whereas the humic-like component (Q5) intensity was significantly lower for undeveloped cities (19.80*1010 nm) than for developed cities (16.26*1010 nm). Regression analysis showed that the Q5 component was mainly (and positively) influenced by secondary industries, while Q2 was mainly affected by both tertiary and secondary industries. The proportion of allochthonous CDOM increased significantly with latitude from south to north with the minimum increased percentage of 67% for humification index (HIX) within different urban development degrees. These findings indicate that changes in urban development, human activities and industrial structure could alter DOM sources and composition in urbanized waterbodies. These findings are relevant to the management of urban water resources in regions experiencing rapid urban and industrial expansion, and add to our understanding of carbon cycling in urbanized freshwater ecosystems.