Nutrient fluxes from rivers and groundwater into an urban bay of the New York-New Jersey Harbor Estuary.

Surface water and groundwater samples were collected from parts of the New York-New Jersey Harbor Estuary during the summer months of 2018-2022 to investigate water quality and sources of pollution. The Hackensack River exhibited significantly poor water quality compared to the Passaic River and Newark Bay due to sewage effluent from a major sewage treatment plant (STP) of the Bergen County Utilities Authority and freshwater inflow reduced by the Oradell Dam, whereas the effect of sewage effluent from the Passaic Valley Sewerage Commission's STP on the Passaic River's water quality was limited because of greater dilution and flushing by higher river discharge. Nutrients in coastal groundwater along Newark Bay were moderately elevated and were affected by geochemical reactions during discharge to the bay. The annual fluxes of dissolved inorganic nitrogen and phosphorus from the Passaic River, the Hackensack River, groundwater, and other sources into Newark Bay were estimated to be 2218 × 103 and 318 × 103 kg/y, 1004 × 103 and 84 × 103 kg/y, 136 × 103 and 17 × 103 kg/y, and 2242 × 103 and 167 × 103 kg/y, respectively, corresponding to 40 and 54 %, 18 and 14 %, 2 and 3 %, and 40 and 29 %, respectively. This study provides a new insight into hydrological and geochemical processes regulating nutrient fluxes into an urban bay from various point and non-point sources of pollution by field measurements of both surface water and groundwater in an urban estuary. This study highlights the importance of comprehensive water quality and hydrological monitoring of surface water and groundwater for a complete nutrient budget and sustainable estuary management.