No abstract

The extensive and random application of major organic pollutants, mainly pesticides, threatens ecosystems and human health. The present study was conducted to isolate and identify microorganisms from some water resources contaminated with pesticides. We investigated the ability of the identified microbes to grow in water spiked with dimethoate and methomyl. We also evaluated the potential effect of the identified microbial isolates on dimethoate and methomyl biodegradation in water. In addition, the total detoxification of dimethoate and methomyl residues in water after treatment with the most effective microbial isolates was confirmed using toxicity tests and analyzing biochemical parameters and histopathological changes in the kidney and liver of treated rats. The microbial isolates were identified as Xanthomonas campestris pv. Translucens and Aspergillus fumigates. Results showed that X. campestris pv. Translucens and A. fumigatus grow in media supplemented with dimethoate and methomyl faster than in other media without both pesticides. About 97.8% and 91.2% of dimethoate and 95% and 87.8% of methomyl (initial concentration of both 5 mg L−1) were biodegraded within 32 days of incubation with X. campestris pv. Translucens and A. fumigatus, respectively. There was no remaining toxicity in rats treated with dimethoate- and methomyl-contaminated water with respect to biochemical parameters and histopathological changes. Collectively, the identified bacterial isolate showed high potential for the complete degradation of dimethoate and methomyl residues in water.

The present study was performed to fabricate a titanium dioxide (TiO2) nanocatalyst with proper characteristics for the removal of some insecticides (dimethoate and methomyl) from aqueous media. A TiO2 catalyst of regular (TiO2—commercial—/H2O2/UV) or nano (TiO2—synthesized—/H2O2/UV) size was employed as an advanced oxidation process by combining it with H2O2 under light. Moreover, the total detoxification of insecticides after treatment with the most effective system (TiO2(s)/H2O2/UV) was also investigated through exploring the biochemical alterations and histopathological changes in the liver and kidneys of the treated rats. Interestingly, the present study reported that degradation rates of the examined insecticides were faster using the TiO2 catalyst of nano size. Complete degradation of the tested insecticides (100%) was achieved under the TiO2(s)/H2O2/UV system after 320 min of irradiation. The half-life values of the tested insecticides under H2O2/TiO2(c)/UV were 43.86 and 36.28 for dimethoate and methomyl, respectively, whereas under the H2O2/TiO2(c)/UV system, the half-life values were 27.72 and 19.52 min for dimethoate and methomyl, respectively. On the other hand, no significant changes were observed in the biochemical and histopathological parameters of rats administrated with water treated with TiO2(s)/H2O2/UV compared to the control, indicating low toxicity of the TiO2 nanocatalyst-. Altogether, the advanced oxidation processes using TiO2 nanocatalyst can be considered as a promising and effective remediation technology for the complete detoxification of methomyl and dimethoate in water. However, further future research is needed to identify the possible breakdown products and to verify the safety of the used nanomaterials.

Pesticides are among the major organic pollutants, and their random extensive applications threaten human health and ecosystems. Clearly, detoxification of toxic insecticides from the aquatic system remains a global priority. In the present study, a zinc oxide nanocatalyst was synthesized with suitable properties to achieve complete degradation of some insecticides (dimethoate and methomyl) from aqueous media. The ZnO catalyst was used in normal and in nano-size as a part of an advanced oxidation process in the presence of H2O2 and UV rays. The complete detoxification of the tested pesticides after treatment with the most effective process (ZnO(s)/H2O2/UV) was then examined by exploring the biochemical and histopathological changes in the liver and kidneys of treated rats compared to the control. The effect of water treatment by ZnO (nano)/H2O2/UV on the water quality parameters of treated water was also investigated. Interestingly, the present study reported that the degradation rates of the investigated insecticides were faster using the nano-sized ZnO catalyst than the regular ZnO catalyst. In this respect, complete decomposition of the tested insecticides (100%) under the ZnO(s)/H2O2/UV system was achieved after 320 min of irradiation. The half-lives of the tested insecticides under ZnO(c)/H2O2/UV were 43.86 and 36.28 for dimethoate and methomyl, respectively, while under the ZnO(c)/H2O2/UV system, the half-live values were 27.72 and 19.52 min for dimethoate and methomyl, respectively. On the other hand, there were no significant changes in the biochemical and histological parameters of rats treated with remediated water when compared to the control group. The treatment of water by zinc oxide nanocatalyst improved the quality of water parameters. Collectively, advanced oxidation processes using ZnO nanocatalyst can be considered as a promising treatment technology for the complete detoxification of methomyl and dimethoate in water. However, further research is warranted for the identification of the potential breakdown products.