Emissions of pesticides from agricultural fields are threatening water quality of aquatic systems in large parts of the world. After their application, pesticides are to some extent retained and degraded in the environment, depending on the specific compound properties and application they are used for. However, a share is often incompletely mineralized resulting in transformation products (TPs). TPs are generated by biological and chemical processes in the environment and water treatment. The important parameters governing their properties, behavior and toxicity are often unknown. In contrast to the parent compounds (PCs), fate and effects of the single TPs as well as in mixture with PCs is poorly investigated. Even small fractions can be harmful to aquatic organisms, by long-term exposure at low concentrations and/or acute exposure at high peak concentrations, e.g. after a heavy rain event. The generation and presence of such TPs have increasingly gained interest in the aquatic cycle (incl. drinking water) only recently.


The research issue was to analyze the behavior of TP’s compared to its PC. Therefore, mecoprop (methylchlorophenoxypropionic acid) was chosen due to its widespread application in agricultural as well as in urban areas. Photolysis of mecoprop was simulated by exposure to a xenon arc lamp which represents the solar radiation. The biological breakdown was analyzed for both PC and photolytic TP-mixture (8 hour irradiation). The primary elimination of the pesticides was measured by HPLC-DAD/UV-Vis. The structural identification of transformation products was performed with LC-MS (Esquire Iontrap). Furthermore, the acute and chronic toxicity of both was investigated.


Mecoprop was degraded rapidly by exposure to a xenon arc lamp with a half-life of 0.6 hours. Five transformation products were detected. They were of higher polarity than the PC. Most TP’s were not eliminated during the photolytic treatment, which implies that they are persistent to photolytic transformation. In most cases a dehalogenation and hydroxylation of aromatic carbons of mecoprop took place. The potential of biological degradation of the total photolytic mixture compared to the initial substance increases by 30 percent. Likewise, there is an increase in acute and chronic toxicity to of the photolytic mixture by 20 percent.


The findings point out that the properties of mecoprop-TPs differ from the PC. Accordingly, these TPs have a changed behavior in the aquatic environment such as sorptivity and solubility and therefore to its temporal and spatial distribution in agricultural and urban catchments. This research demonstrates that new insights on the fate and behavior of TPs in aquatic environments are necessary for the development of water pollution control measures addressing the aims of SDG 6.3.