Transport of Conservative and “Smart” Tracers in a First-Order Creek: Role of Transient Storage Type

Alexander Yakirevich,Matthew Stocker,Daniel Shelton,Greg Mccarty,Yakov Pachepsky,Robert Hill,Michael Kuznetsov,Lynda Kiefer,Ryan Blaustein

doi:10.3390/w9070485

Abstract

Using “smart” tracers such as Resazurin (Raz) allows assessment of sediment-water interactions and associated biological activity in streams. We compared two approaches to simulate the effects of transient storage (TS) on the transport of conservative and reactive tracers. The first approach considered TS as composed of metabolically active and metabolically inactive compartments, while the second model approach accounted for the surface transient storage (STS) and hyporheic transient storage (HTS). Experimental data were collected at a perennial first-order creek in Maryland, MD, USA, by injecting the conservative tracer bromide (Br) and the reactive (Raz) tracer and sampling water at two weir stations. The STS–HTS approach led to a more accurate simulation of Br transport and tails of the Raz and its product Rezorufin (Rru) breakthrough curves. Sediments support large microbial communities, and the STS–HTS model in creeks provides additional parameters to characterize the habitats of microbial water-quality indicator organisms.

Highlights

The functioning and ecological services of rivers and streams are of paramount importance for terrestrial environments and human activities
A numerical model of transient water flow and the transportation of Br and Raz-Rru tracers in streams was developed that accounts for the exchange with the surface transient storage (STS) and hyporheic transient storage (HTS)
The modeling results were compared with simulations by conceptually different models that considered transient storage (TS) as being composed of metabolically-active transient storage (MATS) and MITS compartments

Summary

Introduction

The functioning and ecological services of rivers and streams are of paramount importance for terrestrial environments and human activities. In the USA, 55% of all accessed rivers and streams are impaired or threatened [2]. Determining the impairment causes and processes is a necessary component of developing and implementing water quality improvement measures and policies. Most of the water quality degradation is caused by the transport and transformation of dissolved or suspended pollutants to and in streams and rivers. The parameter values of these models cannot be directly measured and must be obtained from inverse modeling before the model can be used for predictive purposes. This is done by calibrating the model to the results of solute tracer experiments conducted in the reach of interest [3].

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Conclusion