## 4 Discussion
### Degradation  
The results from the present study suggest that the degradation of \({}^{14}\)C-metolachlor is enhanced by anaerobic conditions in all the soil types despite the differences in soil properties, as seen from the remaining fraction of the applied parent compound recovered from the soil at the end of the study, as well as their degradation half-life (T\({}_{1/2}\)) values (Table 4). [PERSON] et al. (2017) reported half-lives of metolachlor ranging from 36 to 182 days under aerobic soil conditions, and these are in agreement with the aerobic half-life for the herbicide in the current experiment. [PERSON] and [PERSON] (2018) reported a 62-day half-life for metolachlor in anaerobic sediments, which is on par with the anaerobic T\({}_{1/2}\) values obtained from the present study. Other studies reported fluctuations estimated at 15-132 days in the degradation half-life of metolachlor, depending on the soil type and environmental conditions (2018).  
One of the earliest reports about the impact of soil aeration on the degradation of metolachlor was made by [PERSON] and [PERSON], where a reduction in the half-life of the herbicide in soil was observed after an increase in soil saturation (2018). A similar trend was also reported by [PERSON] et al. (2018), where the first order T\({}_{1/2}\) of metolachlor degradation was substantially shorter for the saturated surface soils compared with that of unsaturated soils. Moreover, [PERSON] et al. (2018) reported a reduction in the half-life of metolachlor in flooded soil (24.1 days) when compared with non-flooded soils (32.2 days). In yet another study, faster degradation of metolachlor was observed in flooded soils with partial anaerobic conditions than in aerobic soils (2018). Conversely, there are also reports of a slight suppression of the degradation of metolachlor under anaerobic or reduced soil conditions (2018).  
Microbial degradation may contribute to the enhanced degradation of metolachlor observed from anaerobic or flooded microcosms, as flooding is characterized by strongly reduced conditions compatible with the activity of strictly anaerobic microorganisms (2018). Such an anoxic environment in the soil creates a conducive habitat for the microorganisms to perform specific reactions, which then leads to the active degradation of metolachlor. [PERSON] and [PERSON] (2018) suggested anaerobic dehalogenation as one such viable microbial mechanism for transforming certain chloroacetanilide herbicides in soils incubated under anaerobic conditions. Additionally, the significant decrease in degradation rates observed in the autoclaved soils reiterates the importance of microbial pathways in the degradation and metabolism of metolachlor in soils of various properties and environmental conditions.  
A negative correlation between the organic matter content of the soil and the degradation half-life of the herbicide was observed in both the aerobic and anaerobic microcosms, indicating metolachlor as being more persistent in soils with low organic matter content. This again emphasizes the importance of organic matter in determining the environmental fate of herbicides regardless of the soil conditions, a statement that has been made by previous studies (2018). This enhanced degradation can be attributed to larger populations of herbicide-degrading microbes, which can often be found in soils rich in organic matter.