Potentials of photolytic rhodamine WT as a large-scale water tracer assessed in a long-term experiment in the Loosdrecht lakes

Abstract

The dispersal of 0.13 kg of water-tracer rhodamine WT in the Loosdrecht lakes was surveyed during 19 months. Solid-phase extraction and liquid chromatography were used to measure the very low concentrations of rhodamine WT in the experiment. The detection limit was -2 x lo-l1 kg m-3. The photolysis constant of rhodamine WT was measured in a laboratory experiment. A numerical model for hindcasting the dilution of a photolytic tracer in the lake system was developed. Model results compare well with observations showing that rhodamine WT is well suited for tracer experiments on large time and space scales, provided that photolysis is taken into account.

Dying to find the source – the use of rhodamine WT as a proxy for soluble point source pollutants in closed pipe surface drainage networks

“…The potential for turbidity to impact upon our field study was assessed by measuring a range of RWT solutions prepared using water from our field site, and no significant deviation from expected fluorescence was observed hence any possible effects of turbulence on RWT fluorescence measurements were ignored for the remainder of the study. A number of studies have also demonstrated that the use of RWT in quantitative studies may be compromised by photochemical decay of RWT over time (Smart and Laidlaw, 1977;Tai and Rathbun, 1988;Suijlen and Buyse, 1994;Upstill-Godard et al, 2001;Dierburg and C. H. Mines et al: Use of rhodamine WT as proxy for point source pollutants DeBusk, 2005) and loss of RWT due to adsorption (Smart and Laidlaw, 1977;Wilson et al, 1986;Sabatini and Austin, 1991;Shiau et al, 1993;Di Fazio and Vurro, 1994;Soerens et al, 1994;Kasnavia et al, 1999;Close et al, 2002;Keefe et al, 2004;Kung et al, 2000;Vasudevan et al, 2001;Lin et al, 2003;Pang et al, 2003;Richardson et al, 2004;Dierburg and DeBusk, 2005) but as the work described here focused on the use of RWT within a closed pipe surface water drainage network these potential losses were deemed insignificant and not re-examined. Given this range of potential compromising factors, the inconsistent nature of field results concerning RWT fate and transport (Tai and Rathbun, 1988;Jones and Jung, 1990;Suijlen and Buyse, 1994;Ptak and Schmid, 1996;Kung et al, 2000;Upstill-Godard et al, 2001;Close et al, 2002;Lin et al, 2003) is unsurprising.…”

The use of photolytic rhodamines WT and sulpho G as conservative tracers of dispersion in surface waters

“…Distilled water blank values never exceeded these thresholds. Although such detection limits were fully acceptable for our current purpose, much lower thresholds are routinely possible in other applications of this technique (Suijlen et al 1994). …”

“…For rhodamine analysis, we used a slightly modified version of the procedure described by Suijlen et al (1994). Full details of the modified method are given elsewhere (Den Das et al 1997).…”

“…Rhodamine WT (WT) and sulpho rhodamine G (SG) are superior candidates for such work because of their low octanol/water partition coefficients (Benoit-Guyod et al 1979). Rhodamine WT has been successfully used in a lake (Suijlen and Buyse 1994), and WT and SG have been codeployed in the North Sea (Suijlen 1995).…”

“…They were used with high precision to correct for the tidal dispersion of volatile tracers released simultaneously. Because WT and SG are both degraded by sunlight (Abood et al 1969;Suijlen 1995), their photolytic losses were compensated for by use of a novel method first described by Suijlen and Buyse (1994). This is based on measuring the concentration ratio of the two rhodamines by improved high-performance liquid chromatography (HPLC) at the high dilution encountered.…”