Impacts of land use on phosphorus transport in a river system

Phosphorus (P) is a primary limiting nutrient in freshwater systems, however, excessive P load in the systems cause eutriphication, resulting in algal blooms and oxygen depletion. This study estimated potential exchange of P between water column and sediments by P sorption, and identified P compounds in sediments by 31Phosphorus Nuclear Magnetic Resonance Spectroscopy in the samples collected from the Bronx River, New York City, NY. Similarly, mineralization, as well as enzymatic hydrolysis using native phosphoatases (NPase) and phosphodiesterase (PDEase) showed that land use changes and other anthropogenic factors had effects on the P availability in the river. Distinguished characteristics of P bioavailability appeared at major tributaries of Sprain Brook and Troublesome Brook, boundary between fresh and saline water at East Tremont Ave, and estuary close to Hunts Point Wastewater Treatment Plant. Incidental sewer overflows at Yonkers, oil spill at East Tremont Avenue Bridge, fertilizer application at Westchester’s lawns, and gardens, animal manure from the zoo, combined sewer overflows (CSOs), storm water runoff from Bronx River Parkway, and inputs from East River influenced spatial and temporal variations on P transport in the river. This study provides an overview of impacts of land use on nutrient transport in a river system, which may help to make effective policies to regulate P application in the river watersheds, in turn, improve water quality and ecological restoration of a river.