Interactions with freshwater biofilms cause rapid removal of common herbicides through degradation – evidence from microcosm studies,Environmental Science: Processes & Impacts

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Interactions with freshwater biofilms cause rapid removal of common herbicides through degradation – evidence from microcosm studies
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2020-12-14 , DOI: 10.1039/d0em00394h
Maria Alexandra Bighiu _{1,

2,

3,

4} , Willem Goedkoop _{1,

2,

3,

4}

Affiliation

We investigated the role of periphyton biofilms for the fate of three common herbicides, i.e. bentazone, metazachlor and metribuzin, at low, environmental levels and 100 times higher, during a 16 days laboratory experiment. We found that herbicide water concentrations were stable during the first 8 days, whereas substantial declines (>78%) occurred between days 8–16 for all three herbicides. These rapid declines were explained only to a small extent (<8% of the total herbicide loss) by biofilm sorption. As herbicide concentrations in light and dark treatments without biofilms were similar, and the applied light regimen did not cover the UV-spectrum, herbicide photolysis was ruled out as a possible explanation for the observed declines. Furthermore, based on the compounds' characteristics, also volatilization was judged negligible. Therefore, we conjecture that the observed declines in herbicides were due to biodegradation and subsequent evasion of ¹⁴CO₂ that was driven by enzymatic action from heterotrophic microbes. We reason that heterotrophic microbes used herbicide molecules as labile organic C-sources during C-limitation. Future studies should identify the microbial communities and genes involved in biodegradation in order to understand better the role of biofilms for the self-purification of surface waters.

中文翻译：

与淡水生物膜的相互作用导致通过降解迅速去除常见除草剂–微观研究的证据

我们调查了周生生物膜对三种常见除草剂的命运的作用，即在为期16天的实验室实验中，低浓度，环境水平和高100倍的苯达松，偏甲草胺和甲硝唑的含量。我们发现除草剂中的水浓度在前8天保持稳定，而所有三种除草剂在第8-16天之间均出现了大幅下降（> 78％）。这些快速下降仅在很小程度上（小于除草剂总损失的8％）通过生物膜吸附来解释。由于在没有生物膜的明暗处理中，除草剂的浓度相似，并且所应用的光照方案未涵盖紫外线光谱，因此排除了除草剂的光解作用，可作为观察到的下降的可能原因。此外，根据化合物的特性，挥发度也可以忽略不计。因此，¹⁴ CO₂是由异养微生物的酶促作用驱动的。我们认为异养微生物在C限制期间使用除草剂分子作为不稳定的有机C源。未来的研究应确定参与生物降解的微生物群落和基因，以便更好地了解生物膜对地表水自净的作用。

更新日期：2020-12-16

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