Characterisation and assessment of spatiotemporal variations in nutrient concentrations and fluxes in an urban watershed: Passaic River basin, New Jersey, USA

This study investigated the spatial and temporal variations in total inorganic nitrogen (TIN) and total phosphorus (TP) and examined the relationship between water quality and urbanisation in the Passaic River watershed. The results indicate that: 1) the mean TIN and TP concentrations and fluxes showed a relatively steadily decreasing trend in last two decades; 2) TIN and TP concentrations in summer and autumn were higher than those in spring and winter, but the fluxes were lower than those in spring and winter. At the same time, TIN and TP concentrations in normal flow condition were also higher than those in storm flow condition, but the fluxes were lower than those in storm flow condition; 3) spatially, water quality in upper reaches of the rivers was better than that of middle and lower reaches, and the nutrient concentrations in water management area (WMA) 4 were the highest, followed by WMA 6 and WMA 3. Land use change, population growth, urbanisation and environmental protection investment were the main factors that influence the change of environment in the Passaic River Basin.