Benzotriazole and Tolyltriazole as Aquatic Contaminants. 1. Input and Occurrence in Rivers and Lakes † WALTER GIGER,* CHRISTIAN SCHAFFNER, AND HANS-PETER E. KOHLER Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Du ¨ bendorf, Switzerland The complexing agents benzotriazole (BT) and tolyltriazole (TT) are not only widely applied as anticorrosives, e.g., in aircraft deicer and anti-icer fluid (ADAF), but they are also used for so-called silver protection in dishwasher detergents. Due to their low biodegradability and limited sorption tendency, BT and TT are only partly removed in wastewater treatment. Residual concentrations of BT and TT were determined in ambient surface waters in Switzerland including 7 rivers which have distinct water flows and receive treated wastewater effluents at various dilution ratios. A maximum BT concentration of 6.3 μg/L was found in the Glatt River, and a maximum mass flow of 277 kg BT per week was observed in the Rhine River. In most cases, TT was about a factor 5-10 less abundant. During winter 2003/4, BT mass flows at 2 locations in the lower stretch of the Glatt River clearly indicated the input from nearby Zurich airport, where BT was applied as an anticorrosive ADAF component. BT concentrations measured in the three lakes Greifensee, Lake Zurich, and Lake Geneva were approximately 1.2, 0.1-0.4, and 0.2 μg/L, respectively. The observed environmental occurrences indicate that BT and TT are ubiquitous contaminants in the aquatic environment and that they belong to the most abundant individual water pollutants. Introduction The complexing agents benzotriazole (BT) and tolyltriazole (TT, a mixture of the two 4- and 5-methyl isomers with the methyl substituent attached to the benzene ring) are widely used as anticorrosive additives, e.g., in cooling and hydraulic fluids, in antifreezing products, in aircraft deicer and anti- icer fluid (ADAF), and in dishwasher detergents for silver protection. BT and TT are characterized by a high water solubility (28 and 7 g/L, respectively), low vapor pressure, and low octanol water distribution coefficients (log Kow: 1.23 and 1.89, respectively) (1). Because of their application as household detergent additives, these chemicals are very widely used as so-called down-the-drain chemicals, which are discharged in municipal wastewaters. BT and TT are quite resistant to biodegradation. Thus, it must be expected that they widely occur in raw and treated municipal wastewaters and eventually in the receiving, ambient waters. The first reports on the environmental occurrence and on risk assessments of BT and TT were in connection to their application as corrosion inhibitors in ADAFs (2-4). While the glycols as the major ADAF components are rapidly degraded in wastewater treatment, water, and soil environ- ments, BT and TT anticorrosives were detected in the subsurface waters underneath airports. Cancilla and co- workers (2) published concentrations in subsurface water close to an airport: 126 mg/L for BT and 17 mg/L for 4-TT as well as 198 mg/L for total TT. High TT levels have also been determined in a secondary airport runoff outfall (1.67 and 2.16 mg/L for 4- and 5-TT), whereas the concentrations in receiving streams were less than 0.08 mg/L (5). Later, 4- and 5-TTs were detected in snow bank and snowmelt runoffs at an airport (4). Kolpin et al. (6) detected the anticorrosive TT in 17 of 54 samples from U.S. streams above a reporting level of 0.1 μg/L. The maximum and median values were 2.4 and 0.39 μg/L. These authors did not mention the detection of BT. Cancilla et al. noticed that a mixture of BT and TT was the primary cause of toxicity to Vibrio fischeri (Microtox) in one ADAF formulation. Benzotriazole is classified as toxic to aquatic organisms; it can cause long-term adversary effects in the aquatic environment (2-4). Recently, we reported in an abstract publication the development and the quality control of a trace method for BT and TT, as well as preliminary results from aqueous samples (7). Subsequently, the occurrence of BT and TT in municipal wastewaters and their behavior in mechanical- biological wastewater treatment were investigated, and residual concentrations and mass flows of BT and TT were determined in the Glatt River in Switzerland (8). The anticorrosive agents BT and TT occur in all municipal wastewater effluents and are removed only to a small extent in mechanical-biological wastewater treatment because of their high polarity, i.e., high solubility in water, and their resistance to biodegradation. BT and TT concentrations in primary and secondary effluents of municipal wastewater treatment plants varied from below 10 to 100 μg/L. Con- siderable short-term variations of the concentrations and mass flows were observed in untreated sewage (9). The ranges of the concentrations detected in grab samples from the Glatt River were 0.64-3.7 μg/L for BT and 0.12-0.63 μg/L for TT. The corresponding mass flows in g/d were 93-1870 for BT and 18-360 for TT. Generally, the mass flows for all analytes tended to increase along the river longitudinal profile indicating additional incremental inputs and no rapid elimination. However, for a reliable assessment of the elimination behavior of these pollutants in the Glatt River, it would be necessary to perform a more detailed study including all WWTP inputs and aiming at mass flow analyses. A small number of results of wastewater, surface water, and groundwater analyses from the Berlin area were pub- lished by Weiss and Reemtsma (10). In Lake Tegel 0.9 μg/L BT and 0.2 μg/L TT were detected, and in the corresponding bank filtrate 0.2 and 0.05 μg/L were measured for BT and 4-TT. In 2 samples from the Landwehr Canal the average concentrations in μg/L were 0.9 for BT, 0.2 for 4-TT, and 0.1 for 5-TT. The objective of this study was to investigate the envi- ronmental occurrence of BT and TT in Swiss rivers and lakes. In the rivers Glatt, Rhine, Aare, Aabach, and Ustermer Aa weekly composite samples were collected. In the lakes Greifensee, Lake Zurich, and Lake Geneva detailed vertical profiles in the water columns were studied during summer stratification. Based on the measured concentrations and mass flows this investigation aimed at recognizing different input sources, i.e., municipal wastewaters and discharges † This article is part of the Emerging Contaminants Special Issue. * Corresponding author e-mail: giger@eawag.ch. Environ. Sci. Technol. 2006, 40, 7186-7192 7186 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 23, 2006 10.1021/es061565j CCC: $33.50  2006 American Chemical Society Published on Web 11/04/2006