Assessment of the Effects of the Herbicide Aclonifen and Its Soil Metabolites on Soil and Aquatic Environments

Abstract

Aclonifen is an herbicide with a global market that is expected to grow in the period 2021–2027. This study focuses on revealing the effects of both aclonifen and of its soil metabolites on aqueous and soil environments. The soil’s physicochemical parameters and activities of enzymes found in the soil (urease, dehydrogenase, catalase, alkaline phosphatase) were evaluated in laboratory conditions for soil treated with various doses of aclonifen (from half of a normal dose, 2.1 g/ha, to three times the normal dose) every 7 days for a period of 28 days. A computational approach was used to calculate the acute toxicity of aclonifen and of its soil metabolites on aqueous organisms and to evaluate the possible interactions of these compounds with soil enzymes. The results obtained in the experimental study showed a significant inhibitory effect of the herbicide aclonifen on the investigated enzymes; those activities were not recovered after 28 days in the presence of high doses of aclonifen. Statistically significant effects of the herbicide dose and exposure duration on enzymes’ activities were observed using post hoc analysis at the p < 0.001 level. Pearson’s correlations revealed that the investigated enzyme activities were usually strongly (p < 0.001) influenced by the organic matter, available phosphorus content, and nitrogen level. The outcomes of the computational study revealed moderate acute aqueous toxicity of aclonifen and of its metabolites. All metabolites were also able to bind to the investigated enzymes and may have an inhibitory effect on their activities.

The Effects of the Fungicide Myclobutanil on Soil Enzyme Activity

“…This was is agreement with the experimental results, which showed that myclobutanil produced no changes in UA. A similar result was observed for the triticonazole enantiomers [9] and for aclonifen and its metabolites [49] that could not bind to the active site of this enzyme. This was explained by the obtuseness, rigidity and hydrophilicity of the catalytic site of urease [60].…”

“…PA was estimated on the basis of the reaction of ninhydrin with the amino acids that resulted from the hydrolysis of the gelatin used as a substrate, which was the method proposed by Drăgan-Bularda [48]. These methods have previously been applied in order to evaluate the effects on the activity of these enzymes of the herbicides aclonifen [49], S-metolachlor [50] and oxyfluorfen [51], and on the triazole fungicides triticonazole [9] and difenoconazole [52]. The soil treated with myclobutanil at different doses and the control soil were incubated for a period of 28 days under laboratory conditions, and the activity of each enzyme was determined every 7 days.…”

Assessing the Dissipation of Pesticides of Different Polarities in Soil Samples

“…The mechanisms involved in the transformation of herbicides depend on several factors such as their physicochemical properties, soil characteristics, and climatological conditions, and in many cases, they are not completely known [3]. Therefore, monitoring the presence of herbicides in soil is considered crucial, not only to ensure environmental quality, but also to gain knowledge about their persistence, dissipation mechanisms, and final fate [4,5].…”