Assessment of Soil Dehydrogenase and Phosphatase Activities after Exposure to Certain Pesticides as Biomarkers for Pesticide Pollution

Abstract

Soil enzymes play a critical role in the biogeochemical cycles of essential nutrients and protect soil against the accumulation of harmful organic compounds. However, there is limited information on the effect of pesticides on enzyme activities in both old and newly reclaimed Egyptian soils. Laboratory studies were conducted to determine the effects of two nematicides (carbofuran and oxamyl) and two herbicides (ametryn and bentazone) on dehydrogenase and phosphatase activities in alluvial soil (clay soil) and calcareous soil (sandy soil) at concentrations of 25 and 100 µg/g soil over eight weeks. The results showed that dehydrogenase and phosphatase activities were generally enhanced in both clay and sandy soils treated with all tested pesticides. However, oxamyl had the lowest effect on dehydrogenase and phosphatase activities in both soil types compared to the other pesticides used in this study. Dehydrogenase and phosphatase activities in treated or untreated clay soil were higher than those in sandy soil. Additionally, the highest enhancement of dehydrogenase activity was observed at low concentrations of carbofuran and oxamyl, while a high concentration of ametryn and bentazone had a similar effect in both soil types. The highest stimulation of phosphatase activity was achieved at low pesticide concentration in clay soil, whereas high concentration was more effective in sandy soil. Based on the results obtained, it can be stated that the pesticide concentration, the soil type, and the incubation time are important factors affecting the pesticide-soil enzyme relationship. Accordingly, such a study can be used, which indicates the induction of such important enzymes in the soil, which can be used as an indicator to measure pesticide contamination in the soil within 60 days of exposure to pesticides.