Phosphorus Export from Headwater Streams in the Lake Erie Basin: Storms, Snow-Melt and Speciation

Session: 42. - Multi-Watershed Nutrient Study: Establishing a Monitoring Network in Agricultural Regions

Chris Parsons, University of Waterloo, [email protected]
Philippe Van Cappellen, University of Waterloo, [email protected]
Mohamed Mohamed, Ontario Ministry of the Environment and Climate Change, [email protected]

Abstract

Non-point source phosphorus (P) contributions from agriculturally dominated landscapes constitute the largest P export to the lower Great Lakes. The highest P concentrations in streams and the greatest P export from the landscape occur during periods of high flow due to snow-melt or rain storms. However, the timing, magnitude and speciation of P exported from agriculturally dominated watersheds during high flow events are poorly characterized due to the logistical difficulties of sampling during such events. This study utilized the Multi-Watershed Nutrient Study (MWNS) network established by the Ontario Ministry of Environment and Climate Change (MOECC) to analyse the timing, speciation and seasonality of P export during high flow events from three small agriculturally dominated headwater catchments in the watersheds of the Thames and Ausable rivers during all seasons. The exported dissolved and suspended P was characterized using a combination of total and sequential extractions, 31P NMR spectroscopy, electron microscopy, X-ray diffraction and aqueous phosphorus analyses during 37 high flow events in 2015 and 2016. The results were used to evaluate changes to P loading and P bioavailability during events based on season, hydrology and watershed characteristics. Concentration-discharge hysteresis relationships across the hydrograph were also analyzed to elucidate P mobilization

1. Keyword
phosphorus

2. Keyword
nutrients

3. Keyword
sediment transport