Sources of pesticides in surface waters in Switzerland: pesticide load through waste water treatment plants––current situation and reduction potential Andreas C. Gerecke a , Michael Sch€ arer a , Heinz P. Singer a , Stephan R. M€ uller a, * , Ren e P. Schwarzenbach a , Martin S€ agesser b , Ueli Ochsenbein b , Gabriel Popow c a Swiss Federal Institute for Environmental Science and Technology (EAWAG) and Swiss Federal Institute of Technology (ETH), P.O. Box 601, Ueberlandstrasse 133, CH-8600 D€ ubendorf, Switzerland b Amt f€ ur Gew€ asserschutz und Abfallwirtschaft (GSA) des Kantons Bern, Gew€ asser- und Bodenschutzlabor, Schermenweg 11, 3014 Bern, Switzerland c Kantonale Zentralstelle f€ ur pflanzenschutz, Strickhof 8315-Lindau, Switzerland Received 24 July 2001; received in revised form 19 December 2001; accepted 5 February 2002 Abstract Concentrations of pesticides in Swiss rivers and lakes frequently exceed the Swiss quality goal of 0.1 lg/l for surface waters. In this study, concentrations of various pesticides (e.g., atrazine, diuron, mecoprop) were continuously mea- sured in the effluents of waste water treatment plants and in two rivers during a period of four months. These mea- surements revealed that in the catchment of Lake Greifensee, farmers who did not perfectly comply with ‘good agricultural practice’ caused at least 14% of the measured agricultural herbicide load into surface waters. Pesticides, used for additional purposes in urban areas (i.e. protection of materials, conservation, etc.), entered surface waters up to 75% through waste water treatment plants. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Herbicides; Point source; Diffuse sources; Waste water treatment plant; Water quality; Material protection 1. Introduction In Switzerland 1500 t of pesticides per year are used for agricultural purposes (SGCI, 1999). In addition, an unknown amount of identical and other pesticides are used for non-agricultural purposes, such as herbicides on lawns (e.g. mecoprop, Ahrens, 1994), as algicides in paints and coatings (e.g. diuron, Paulus, 1993) or as root protection agents in flat roof sealings (e.g. mecoprop, Bucheli et al., 1998). The three mentioned applications are only illustrative examples. In fact, the actual number of compounds and applications is much higher and broader (Paulus, 1993). In Switzerland, as everywhere in the world, a detailed survey of the annual consumption and the number of different applications of pesticides in urban areas is not available. The Swiss quality goal for pesticides in surface waters is <0.1 lg/l (Anonymous, 1998). The concentrations of herbicides such as atrazine, metolachlor, isoproturon, and mecoprop, however frequently exceed this quality goal (Ulrich et al., 1994; Corvi and Khim-Heang, 1997; M€ uller et al., 1997). Therefore, efforts have to be made to reduce the pesticide load into surface waters. An ef- ficient reduction of these elevated concentrations is only possible if the sources of pesticides (e.g., handling of pesticides before its application, the application itself) and the pesticide pathways into surface waters (e.g., through waste water treatment plants, WWTP) are known. The different possibilities are illustrated in Fig. 1 and discussed (i) for pesticides used in agriculture and Chemosphere 48 (2002) 307–315 www.elsevier.com/locate/chemosphere * Corresponding author. Fax: +41-1-8235471. E-mail address: stephan.mueller@eawag.ch (S.R. M€ uller). 0045-6535/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0045-6535(02)00080-2