Temporal concentration changes of DEET, TCEP, terbutryn, and nonylphenols in freshwater streams of Hesse, Germany: possible influence of mandatory regulations and voluntary environmental agreements

Abstract

Background, aim, and scope: The present study focuses on the temporal concentration changes of four common organic pollutants in small freshwater streams of Hesse, Germany. The substances (tris(2-chloroethyl)phosphate (TCEP), the technical isomer mixture of 4-nonylphenol (NP), 2-(t-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine (terbutryn), and N,N-diethyl-m-toluamide (DEET)) are subject to differing regulations. Whereas the use of NP and the related nonylphenolethoxylates (NPEOs) are almost completely banned under EU directive 2003/53/EC, the herbicide terbutryn is only restricted for use as a herbicide in the majority of member states of the European Union (EU). In contrast, TCEP and DEET are not regulated by legislation, but have been replaced in some products through consumer pressure. The impact of regulation on the environmental concentrations of these pollutants is discussed.

Materials and methods: The substances were monitored in small freshwater streams in the Hessisches Ried region, Germany, during the period September 2003 to September 2006. The samples were extracted with solid phase extraction (SPE) and analyzed by coupled gas chromatography-mass spectrometry (GC-MS).

Results: All target compounds were detected frequently within the fresh water streams of the study area. Monitoring in the study area revealed a significant concentration decrease only for NP. For the other three compounds, no significant concentration decrease was observed. Terbutryn concentrations and loads showed a seasonal trend with higher levels in summer and autumn, but were also present in winter and spring. Concentrations of TCEP and DEET were in the range of prior investigations.

Discussion: The decrease of NP concentrations and loads during the sampling period indicates that the regulation of NP and NP ethoxylates has led to a significant improvement in reducing the occurrence of this compound in the aquatic environment. Furthermore, the ban on agricultural use of terbutryn at the end of 2003 had no discernable influence on terbutryn concentrations in the following years.

Conclusions: The benefits of national bans or self-regulations by manufacturers on several chemicals appear to be limited. In contrast, the European-wide ban (of NP) revealed to be effective in preventing the substance from entering the aquatic environment on a large scale and reduced the NP concentration to an acceptable level (i.e., below the PNEC).

Recommendations and perspectives: Further research is needed to investigate diffuse sources and point sources of terbutryn not related to agriculture. Further research is required to find an explanation for the ongoing high concentration of TCEP in river water despite of the supposed replacement of TCEP by TCPP already in the 1990s.