Formation of biogenic non-extractable residues from pesticides: metabolic and environmental conditions and their potential implications for risk assessment (FormNER)

• Applicant: Dr. Karolina Malgorzata Nowak
• Subject Area: Soil Sciences
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 369055934

Results of a previous DFG project show that non-extractable residues (NER) formed from easily biodegradable pesticides (2,4-D, glyphosate and metamitron) mainly contain biogenic NER (bioNER). BioNER can be a result of a direct assimilation of C (N) from the pesticide or indirect incorporation of C via CO2 fixation and assimilation of mineralised N into the microbial biomass ultimately stabilised in the organic matter (OM) of soil or sediments. The pesticide turnover and bioNER formation is presumably controlled by external environmental conditions, soil characteristics or internal microbial metabolic pathways depending on the nutritional status of the organisms; however, the variability of these processes in different soils particularly from different climates were not analysed yet. In addition, similar turnover processes may also occur in plants, but they have not been investigated in detail so far.The overall goal of the present project is thus to investigate the turnover of pesticides under different metabolic and environmental conditions and in different soils including the bioNER formation and the fixation of labelled CO2. The impact of environmental conditions (temperature, pH, OM) or soil type on the degradation of two globally best-selling pesticides (2,4-D and glyphosate) will be investigated in German (temperate climate) and Colombian (tropical climate) soils for comparison. The impact of metabolic conditions (starvation versus growth conditions) on bioNER formation will be determined by the calculation of the ratios of amino acids to amino sugars and by identification of proteins from the active degraders. Indirect formation of bioNER via CO2 fixation from the highly oxidised carbon atoms relevant for several pesticide classes (e.g. triazines or triazinones) will be studied and related to N uptake. Similar processes of NER formation and turnover routes of pesticides as in the soil and sediment are expected in the plant cells; these processes are thus also relevant for pesticide residues in food. In this context, the metabolisation and bioNER formation of several pesticides will be investigated in plant cell suspension cultures as a first approach. The project will therefore provide a first step towards an integrated assessment of pesticide fate including transformation in soils and in plant cells and thus of environmental risk and toxicological hazard of food crops.

• DFG Programme: Research Grants