Impact of stream pH changes on re-mobilization of phosphorus stored in streambed sediments

Shuyang Wang, James W. Roy, Clare E. Robinson

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: Streambed sediments can temporarily store P acting as a legacy source that can be re-mobilized and released to a stream via groundwater discharge as stream water chemistry changes. pH is a key factor that controls the retention-remobilization of P from sediments, including streambed sediments, with P release increasing as the pH increases above near-neutral conditions. pH in streams varies over multiple time scales including diurnal, seasonal, and long-term scales as well as between baseflow to event stream flow conditions. For instance, pH in streams may vary between baseflow and high flow conditions as the fraction of stream water derived from groundwater compared to surface overland flow varies. Further, long-term pH changes have been observed in streams across North America as a result of acid rain control programs implemented in the 1970s. It remains unclear how these pH variations may affect P retention-remobilization from streambeds. This study aims to investigate how stream pH changes that occur on multiple time scales may contribute to the release of legacy P storage from streambeds. This will be achieved by combining analyses of historical and current stream pH time series data with laboratory experiments. For the laboratory experiments, streambed sediment will be collected from rural streams in Ontario to characterize the P content and mineralogy, and conduct P desorption equilibrium experiments at different pH. Preliminary analysis of the historical pH data in streams across Ontario indicates the annual mean pH in streams has changed from 7.4 to 8.3 over the last 40 years. Combining this will the laboratory experiment data suggests that this pH change may be associated with substantial P release. The study will provide new findings regarding the role of stream pH in controlling streambed sediment P re-mobilization and its potential contribution to P stream loads.

Please include this code when submitting a data update: GEO2021_356

Retrouver cet article:
Les membres de la Société canadienne de géotechnique peuvent accéder à cet article, ainsi qu'à tous les autres articles de la Conférence Géotechnique Canadienne, dans le Espace membre. Les comptes rendus d'articles sont également disponibles dans de nombreuses bibliothèques.

Citer cet article: