Influence of Landscape Patterns on Nitrate and Particulate Organic Nitrogen Inputs to Urban Stormwater Runoff

The landscape pattern of permeable/impermeable patches or areas significantly influences nitrogen transport in urban stormwater runoff. Therefore, the optimal landscape pattern of permeable/impermeable patches in urban catchments can contribute to alleviating stormwater nitrogen pollution. This study investigated the effect of the landscape pattern of permeable/impermeable patches on NO3--N and particulate organic nitrogen (PON) concentrations during stormwater runoff transport and their source contributions. Six landscape pattern indices, namely the mean proximity index (MPI), largest patch index (LPI), mean shape index (MSI), landscape shape index (LSI), connect index (CONNECT), and splitting index (SPLIT), were selected to reflect the fragmentation, complexity, and connectivity of permeable patches in urban catchments. The results show that lower fragmentation, higher complexity, and greater connectivity can reduce NO3--N concentrations in road runoff and drainage flow (ie., the flow in the stormwater drainage network), as well as PON concentrations in road runoff. Low impact development (LID) can also be incoporated with the landscape pattern of permeable/impermeable patches to mitigate nitrogen pollution in urban stormwater at the catchment scale by optimizing its spatial arrangement