Determination of reaeration‐rate coefficient by modified tracer gas technique

Abstract

The modified tracer gas technique is used to determine the reaeration coefficient in six different water bodies of the Itajaí River basin, three with rural land use and three in urban areas. Propane was used as the tracer gas and Rhodamine WT as the conservative tracer, providing information on dilution, mixing and dispersion. Liquefied petroleum gas was used instead of high purity propane, aimed at reducing the costs associated with the field trials. Reaeration‐rate coefficients observed in the field ranged from 25.8 to 367.7 d−1. Two data sets could be observed where smaller streams had substantially larger coefficients of between 133.1 and 367.7 d−1, while the larger streams had values ​​ranging from 25.8 to 54.5 d−1. Five empirical equations were evaluated by comparing the values ​​obtained in the field. The equations proposed by Tsivolgou and Wallace and Tsivoglou and Neal showed greater adherence to the values ​​determined in the tests. Reaeration‐rate coefficients obtained in the field were correlated with the hydrodynamic characteristics of the watercourses, thus establishing a mathematical function through which to obtain estimates for future evaluations. The R2 value obtained using this equation was 0.959, indicating a high correlation between the calculated values ​​and those estimated in the field. Copyright © 2012 John Wiley & Sons, Ltd.

Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams

“…Young and Huryn (1999) determined a reaeration rate coefficient varying between 50/day to 250/day at the Powder Creek, depending on the discharge which ranged from 18 to 40 L/s. And Soares et al (2013) found a reaeration rate coefficient between 60/day to 200/day for comparable streams.…”

“…The transfer of k 2 from propane to oxygen is done by multiplication with a factor of 1.39 (Rathbun et al, 1978). This approach of calculating the reaeration rate coefficient has been frequently applied in the past (e.g., Benson et al, 2014;Marzolf et al, 1994;Reid et al, 2007;Soares et al, 2013). We first consider the effect of neglecting the full travel-time distribution.…”

A new method to quantify air–water gas exchanges in streams based on slug injection and semicontinuous measurement

“…This is due to the fact that elevated k values induce a marked difference between the breakthrough curves of the conservative and the volatile tracers. Gas exchange rate coefficients for oxygen at 20°C ( k 2 ), measured in headwater streams by previous studies, were typically comprised between a few tens and a few hundred per day (Wanninkhof et al 1990; Genereux and Hemond 1992; Soares et al 2013; Benson et al 2014; Knapp et al 2019) (Table 2). Figure 2 shows that our method is theoretically valid for this range of gas exchange rate coefficients.…”

“…A gas tracer is often injected together with a conservative tracer, allowing to account for dilution and dispersion. Tracers are released either continuously in the stream until their concentration reaches a stable plateau (Wanninkhof et al 1990; Genereux and Hemond 1992; Tobias et al 2009; Jin et al 2012; Soares et al 2013; Benson et al 2014; Hall and Madinger 2018; Vautier et al 2020), or in the form of a slug injection (Hibbs et al 1998; Jin et al 2012). Continuous injections allow accurate estimates of gas exchange rates, but they are time‐intensive and consume a lot of tracer, which are often costly or even damaging to the environment, as the greenhouse gas SF 6 (Benson et al 2014).…”

Variabilidade espacial e temporal da reaeração superficial em riachos: estimativa por meio dos métodos do traçador gasoso e da sonda solúvel flutuante

“…Este tempo de viagem visou garantir uma mistura efetiva do traçador conservativo no fluxo da água. A montante de cada trecho foi adotada uma distância mínima de mistura lateral e vertical dos traçadores injetados no escoamento da água (SOARES et al, 2013). A estimativa desta distância foi realizada de acordo com o modelo de mistura proposto por Fischer et al (1979) expressado pela Equação 11.…”