Phosphorus Transport in a Lowland Stream Derived from a Tracer Test with 32P

Abstract

Small streams in urbanized rural areas receive loads of P from various, often episodic, sources. This paper addresses, through a tracer test with 32P, retention and transport of a pulse input of phosphorus in a 2.6 km long stretch of a channelized second-order lowland stream. Tritiated water was introduced alongside the 32P-labelled ortophosphate in order to isolate the influence of the hydrodynamic factors on P behavior. Tracer concentrations in unfiltered water samples were measured by liquid scintillation counting. Four in-stream and five hyporheic breakthrough curves were collected at four points along the stream, two of which encompass a beaver dam impoundment. The overall retention efficiency of 32P along the studied reach was 46%. The transient storage transport model OTIS-P provided reasonable fits for in-stream breakthrough curves (BTCs) but failed at reproducing the hyporheic BTCs. The overall small effect of transient storage on solute transport was higher in the stretch with a more pronounced surface storage. Transient storage and phosphorus retention were not enhanced in the beaver dam impoundment.

Transport of Phosphorus in the Hyporheic Zone

“…(2017) studied the contributions of dissolved phosphorus from hyporheic exchange and groundwater to lake eutrophication. Zieba and Wachniew (2021) found that the overall retention efficiency of 32 P was 46% in a lowland stream in a tracer test. Li et al.…”