Formation of biogenic non-extractable residues from pesticides: metabolic and environmental conditions and their potential implications for risk assessment (FormNER)
Final Report Abstract
The results showed that environmental conditions like temperature and a soil parameter variation (pH or total organic carbon [TOC] content), soil type as well as different history of agricultural use of soils influenced the transformation of pesticides to biogenic non-extractable residues (biogenic NERs). We investigated the combined effect of the soil property (TOC or pH) and of the temperature (10°C, 20°C or 30°C) variation on turnover of two best-selling pesticides 13C315N-glyphosate (13C315N-GLP) and 13C6-dichlorophenoxyacetic acid (13C6-2,4-D) in two reference soils, a haplic Chernozem (from Germany) and a humic Cambisol (from Colombia). Two levels of TOC (haplic Chernozem: 3% and 4%; humic Cambisol: 4% and 5%) and two levels of pH (haplic Chernozem: 6.0 and 5.5; humic Cambisol: 6.5 and 5.5) were tested. Temperature was the major factor controlling mineralisation of two pesticides as well as amounts of extractable pesticide residues in two soils. With increasing incubation temperature, the mineralisation of the pesticides increased, whereas the extractable pesticide residues decreased. An enhanced TOC (3% and 4%) promoted the transformation of 13C315N-GLP to 13C-biogenic NERs in two soils, whereas both temperature and TOC influenced the amounts of 13C-biogenic NERs from 13C6-2,4-D. The contents of 13C-biogenic NERs were in the range of 10-40% of the initially added 13C for both 13C3-GLP and 13C6-2,4-D. However, the 13C-biogenic NERs from 13C6-2,4-D comprised a lower portion of the total 13C-NERs (12-60% of the 13C-NERs) than that of from 13C3-GLP (38-88% of the 13C-NERs). The amounts of 15N-biogenic NERs (5-30% of the initially added 15N) and the contribution of 15N-biogenic NERs to the 15N-NERs (< 30% of 15N-NERs) from 15N-GLP were lower than that of 13C3-GLP. A different history of agricultural use of soils also affected biodegradation of 13C3-GLP in humic Cambisol, and 13C3-GLP mineralisation was highest for soil with > 30 years (38% of the initially added 13C) and lowest for soil without agricultural use (3% of the initially added 13C). The amounts of 13C-biogenic NERs from 13C3-atrazine (13C3-ATR) were much lower (5.1% of the initially added 13C) than 15N-biogenic NERs from 15N3-ATR (18% of the initially added 15N). This divergence can be explained by a different metabolic assimilation of 13C and 15N into microbial biomass. The 13C atoms from 13C3-ATR are released from the triazine ring of ATR as a 13CO2 and the 13CO2 is assimilated into microbial biomass via heterotrophic CO2 fixation. In contrast, the 15N atoms from the triazine ring of ATR can be directly assimilated into microbial biomass. Overall, the results showed that multiple environmental factors, soil conditions and metabolic assimilation of elements into microbial biomass can affect the extent of biogenic NER formation and this effect may vary for different pesticides. Therefore, it is difficult to elucidate the key environmental or metabolic factor favouring the formation of non-toxic biogenic NERs or potentially hazardous xenobiotic NERs. Therefore, a new approach simplifying the NER speciation using a deuterium (D) isotope was developed. In this approach, an integration of D into biogenic NERs from easily biodegradable D-labelled substrates was low. For instance, the amounts of 13C-biogenic NERs from 13C6-2,4-D were five times higher (15% of the initially added 13C) than that of D-biogenic NERs from D3-2,4-D (3% of the initially added D).
Publications
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2018. Prediction of the formation of biogenic non-extractable residues during degradation of environmental chemicals from biomass yields. Environ. Sci. Technol. 52, 663-672
Trapp, S.; Brock, A.L.; Nowak, K.M.; Kästner, M.
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2018. Unraveling microbial turnover and non-extractable residues of bromoxynil in soil microcosms with 13C-isotope probing. Environ. Pollut. 242, 769-77
Nowak, K.M., Telscher, M.; Seidel, E.; Miltner, A.
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2019. Effect of temperature, pH and total organic carbon variations on microbial turnover of 13C3 15N-glyphosate in agricultural soil. Sci. Total Environ. 658, 697-707
Muskus, A.M.; Krauss, M.; Miltner, A.; Hamer, U.; Nowak, K.M.
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2019. Microbial turnover of glyphosate to biomass: utilization as nutrient source, formation of AMPA and biogenic NER in an OECD 308 test. Environ. Sci. Technol. 53, 10, 5838-5847
Brock, A.L.; Rein, A.; Polesel, F.; Nowak, K.M.; Kästner, M.; Trapp, S.
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2020. Degradation of glyphosate in a Colombian soil is influenced by temperature, total organic carbon content and pH. Environ. Pollut. 259:113767
Muskus, A.M.; Krauss, M.; Miltner, A.; Hamer, U.; Nowak, K.M.
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2020. Plant litter enhances degradation of the herbicide MCPA and increases formation of biogenic non‐extractable residues in soil. Environ. Int. 142, September 2020, 105867
Nowak, K.M.; Miltner, A.; Poll, C.; Kandeler, E.; Streck, T.; Pagel, H.
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2021. Microbial activity and metamitron degrading microbial communities differ between soil and water-sediment systems. J. Hazardous Mat.
Wang, S.; Miltner, A.; Muskus, A.; Nowak, K.M.
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2022. Microbial community composition and glyphosate degraders of two soils under the influence of temperature, total organic carbon and pH. Env. Pollut. 15;297:118790
Muskus, A.M.; Miltner, A.; Hamer, U.; Nowak, K.M.
