Composition of dissolved organic matter in urban runoff depends on source and landscape position
Results/Conclusions: Grass clippings and leaves contained similar amounts of leachable DOC (18.94±6.03 mg C/g and 14.56±5.70 mg C/g, respectively; p-value=0.36), but grass clippings had significantly higher leachable TDN as compared to leaves (1.41±0.46 mg N/g and 0.16±0.07 mg N/g, respectively, p-value=0.04). Urban soil contained significantly less leachable DOC and TDN than leaves or grass clippings (0.0676±0.0002 mg C/g, 0.0253±0.0013 mg N/g). We found little variability in CDOM properties within source type (i.e. leaf leachate CDOM properties from different locations were relatively similar, but were distinct from other sources such as road wash runoff, soil leachate, etc.). These results indicate that position within the urban stream continuum determines the relative importance of differences in the source vs. in-system processing for determining the composition of DOM in urban waters. In these highly engineered urban flowpaths, position within the urban stream continuum may be related to residence time, which in turn may partially determine the degree of processing urban DOM undergoes before reaching downstream water bodies including rivers and reservoirs. The amount and type of DOM present can impact the ecosystem services performed by these water bodies, such as drinking water provisioning, nutrient removal, and habitat for aquatic life.