Residue levels of organochlorine pesticides in some ecosystem components of Manzala Lake

To evaluate the organochlorine pesticide (OCP) contamination of Manzala Lake, its ecosystem was investigated during the winter season (December to March). The studied ecosystem components were water, sediment, aquatic weeds, and fishes in four locations. The samples were analyzed by gas chromatography with electron capture detector. Pollutant levels of total OCPs showed significantly high levels in the water areas of Round road (46.253 ng/ml), Port-Said Damietta road (19.301 ng/ml), followed by Bughas El-Rasoah (5.539 ng/ml), then Ashtoum El Gamel (natural reserve area now) (0.289 ng/ml). Organochlorines were detected in sediment only in Round road (3.359 μg/kg) and Port-Said Damietta road (0.171 μg/kg) by significant order while they were undetectable in Ashtoum El Gamel and Bughas El-Rasoah. Total OCPs in aquatic weeds ranged between 0.194 μg/kg in Port-Said Damietta and 0.026 μg/kg in Ashtoum El Gamel. While OCPs were 0.160 and 0.153 μg/kg in Round road and Bughas El-Rasoah, respectively. Concerning fish muscles OCPs were significantly higher in the Round road area (0.397 μg/kg) followed by the Port-Said Damietta road (0.258 μg/kg), and finally, Ashtoum El Gamel samples (0.126 μg/kg). The results revealed the direct relation for the accumulation of OCPs between studied ecosystem parameters at the Manzala Lake during the winter season. Results also demonstrated that fish samples collected from the Manzala Lake in the studied areas were contaminated with levels of organochlorines, not higher than the maximum permissible level recorded by FAO/WHO, and that the public is not at risk with fish consumption.     

Engineering the metabolism of the phenylurea herbicide chlortoluron in genetically modified Arabidopsis thaliana plants expressing the mammalian cytochrome P450 enzyme CYP1A2

Transgenic Arabidopsis thaliana plants were generated by introduction of the human P450 CYP1A2 gene, which metabolizes a number of herbicides, insecticides and industrial chemicals. Transgenic A. thaliana plants expressing CYP1A2 gene showed remarkable resistance to the phenylurea herbicide chlortoluron (CTU) supplemented either in plant growth medium or sprayed on foliar parts of the plants. HPLC analyses showed a strong reduction in CTU accumulation in planta supporting the tolerance of transgenic lines to high concentrations of CTU. Besides increased herbicide tolerance, expression of CYP1A2 resulted in no other visible phenotype in transgenic plants. Our data indicate that CYP1A2 can be used as a selectable marker for plant transformation, allowing efficient selection of transgenic lines in growth medium and/or in soil-grown plants. Moreover, these transgenic plants appear to be useful for herbicide resistance as well as phytoremediation of environmental contaminants.     

Synthesis of high-quality graphene sheets via decomposition of non-condensable gases from pyrolysis of polypropylene waste using unsupported Fe,Co, and Fe–Co catalysts

Producing high-quality graphene sheets from plastic waste is regarded as a significant economic and environmental challenge. In the present study, unsupported Fe, Co, and Fe–Co oxide catalysts were prepared by the combustion method and examined for the production of graphene via a dual-stage process using polypropylene (PP) waste as a source of carbon. The prepared catalysts and the as-produced graphene sheets were fully characterized by several techniques, including XRD, H₂-TPR, FT-IR, FESEM, TEM, and Raman spectroscopy. XRD, TPR, and FT-IR analyses revealed the formation of high purity and crystallinity of Fe₂O₃ and Co₃O₄ nanoparticles as well as cobalt ferrite (CoFe₂O₄) species after calcining Fe, Co, and Fe–Co catalysts, respectively. The Fe–Co catalyst was completely changed into Fe–Co alloy after pre-reduction at 800 °C for 1 h. TEM and XRD results revealed the formation of multi-layered graphene sheets on the surface of all catalysts. Raman spectra of the as-deposited carbon showed the appearance of D, G, and 2D bands at 1350, 1580, and 2700 cm⁻¹, respectively, confirming the formation of graphene sheets. Fe, Co, and Fe–Co catalysts produced quasi-identical graphene yields of 2.8, 3.04, and 2.17 g_C/g_cat, respectively. The graphene yield in terms of mass PP was found to be 9.3, 10.1, and 7.2 g_C/100g_PP with the same order of catalysts. Monometallic Fe and Co catalysts produced a mix of small and large-area graphene nanosheets, whereas the bimetallic Fe–Co catalyst yielded exclusively large-area graphene sheets with remarkable quality. The higher stability of Fe–Co alloy and its carbide phase during the growth reaction compared to the Fe and Co catalysts was the primary reason for the generation of extra-large graphene sheets with relatively low yield. In contrast, the segregation of some metallic Fe or Co particles through the growth time was responsible for the growth small-area graphene sheets.