Effect of toxicological interaction of chlorpyrifos, cypermethrin, and arsenic on soil dehydrogenase activity in the terrestrial environment.

Abstract

Soil is the most widespread area for the co-occurrence of two or more numbers of contaminants. Therefore, toxicity assessments based on contaminants mixture are urgently required to assess their combined impacts on soil enzymes. In the present study, the median effect plot and the combination index isobologram were studied to evaluate the dose-response curve for individual and interactive impacts of chlorpyrifos (Chl), cypermethrin (Cyp), and arsenic (As) on soil dehydrogenase, a potential marker of soil health. Along with these methods, a two-way ANOVA was also tested and the results showed significant changes with respect to different treatments. The results also showed that the Dm value increases in the order of As<Cyp<Chl. Another side, the m values for Cyp and As were negative, while positive for Chl. The day-dependent variation analysis revealed maximum inhibition in dehydrogenase activity on days 20 and 30 after treatment. The results also revealed that binary mixtures Chl + Cyp- and Chl + As- induced synergistic and antagonistic impacts over dehydrogenase enzyme at 0.1 fa level on different treatment days, whereas, applied binary and ternary combinations exhibited antagonistic effects at >0.25 fa level. However, Chl + Cyp unveiled a synergistic impact over soil dehydrogenase on day 30th. The overall impact of applied chemicals on dehydrogenase activity was contributed by bioavailability and the nature of toxicological interactions between them. This study would be one of the exclusive studies for the agricultural sector to predict the potential risk associated with the co-existence of these or similar contaminants in the terrestrial environment.