Thermal and Biological Degradation of Herbicides to Treat Wastewater and Soil Pollution

Abstract

Since their discovery in 1958, atrazine and other members of s-triazine family have been extensively applied in order to control grassy and broadleaf weeds in crops. Although, it was proved by many researchers that atrazine was slow and partially degradable material. These pesticides were widely used to enhance crop quality and yield. Atrazine degradation can be achieved by the effects of air, sun, water, microorganisms and temperature. Thermal degradation plays an important role in agrochemicals elimination; so a better understanding of the role of thermal degradation of atrazine is essential. Quantitative determination of pesticide residues was studied by calculating the amount of herbicide residues left after decomposition using a simple thermo analytical technique (TG, DSC). In this study, we found that all samples undergo the process of melting, evaporation, decomposition and oxidation at a temperature higher than the maximum registered climate temperature which made us conclude that 80–90%wt) of the pesticides stay in the environment without change under 100 °C on different parts of plants like fruits, leaves, and some penetrate into the ground to reach the roots or continue to the groundwater causes toxic problems to their consumers and environmental pollution. This result gave the motivation to find a more effective approach to reduce the harmful effect of these pollutants. In this regard, biological degradation of atrazine by using two legumes roots rhizobium bacteria was investigated. It is found that both rhizobium are able to treat atrazine at moderate temperature (30 °C). In comparison to chickpea rhizobia, bean rhizobia showed a higher performance with a removal efficiency of 43.21% and 57.42% at mild and high atrazine concentrations (5 mg/L and 10 mg/L) respectively. The results from this research offer an elegant way to remove the harmful effect of herbicides through degradation and to bring the safe use of herbicides a step closer to applications.