Development of a “smart” tracer for the assessment of microbiological activity and sediment‐water interaction in natural waters: The resazurin‐resorufin system

Abstract

[1] A ''smart'' tracer is a tracer that provides, directly or through measurement of its concentration or in combination with another compound, at least one ''bit'' more of information about the environment through which it travels than a conservative tracer. In this study we propose and present the chemical compound resazurin as a smart tracer to assess the coupling between solute transport and microbiological activity in sediment-water interfaces in freshwaters. Resazurin is a weakly fluorescent redox-sensitive dye that undergoes an irreversible reduction to strongly fluorescent resorufin under mildly reducing conditions, most commonly in the presence of living microorganisms. To investigate the suitability of resazurin as a smart tracer, we characterized the decay, sorption, reaction, and transport behavior of resazurin and resorufin in various waters and sediments using laboratory experiments. Results show that resazurin irreversibly and rapidly reacts to resorufin in colonized sediment with pseudo-first-order behavior and a rate coefficient of 1.41 h À1 . This reaction is 3 orders of magnitude faster than that in stream water alone, indicating the tracer is sensitive to microbiological activity and associated sediment-water interactions. The compounds are affected by significant sorption, with an approximately linear isotherm and a K d of 6.63 mL/g for resorufin in sediment with 2.19% organic carbon. The compounds are stable over weeks in natural water, except in the presence of strong light where significant photochemical decay may occur more rapidly.Citation: Haggerty, R., A. Argerich, and E. Martí (2008), Development of a ''smart'' tracer for the assessment of microbiological activity and sediment-water interaction in natural waters: The resazurin-resorufin system, Water Resour. Res., 44, W00D01,

Ecosystem respiration increases with biofilm growth and bed forms: Flume measurements with resazurin

“…The rate during the three experiments was 8.7 ± 4.2 × 10 À4 h À1 based on 2-3 samples in each of the three experiments. This rate is similar in magnitude to unfiltered water column rates observed in samples from Spanish streams [Haggerty et al, 2008]. This rate was~100 times smaller than the Raz-to-Rru reaction rate in the flumes, and so concentrations and reaction rates in the flume were not adjusted for light effects.…”

“…At the laboratory, samples were buffered to pH 8 [Haggerty et al, 2008] before measurement of fluorescence of Raz and Rru on a Hitachi F-7000 spectrofluorometer (Hitachi High Technologies America, USA). Excitation and emission wavelengths for Raz were 602 and 630 nm, respectively, and for Rru were 570 and 583 nm, respectively.…”

“…The test was done with the smart tracer, resazurin. Resazurin (Raz) is a metabolically active compound that reacts irreversibly to resorufin (Rru) [Haggerty et al, 2008[Haggerty et al, , 2009Argerich et al, 2011]. The rate of the Raz-to-Rru reaction provides a measure of net aerobic respiration [González-Pinzón et al, 2012].…”

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

“…Haggerty et al [11] proposed using the "smart tracer" resazurin (Raz) for the assessment of microbiological activity and sediment-water interaction in natural waters. In the presence of mildly reducing conditions, Raz loses an oxygen ion irreversibly to become resorufin (Rru).…”

Exposure times rather than residence times control redox transformation efficiencies in riparian wetlands

“…However, estimation of ET for natural systems is extremely difficult or sometimes even impossible, especially for non-well mixed systems like catchments, because it requires a combined and integrated perspective on how and under what specific circumstances physical controlled transport and (bio)-geochemical reaction occurs in hydrological systems. Modern tracer techniques, such as ''smart tracers" (Haggerty et al, 2008;Liao et al, 2013), that are potentially able to track changes in redox conditions, look promising and may offer a possibility to estimate ET for hydrologic systems in the future.…”