Embryonic toxicity of Imidacloprid: Impact on hatchability, survivability, swimming speed and cardiac function of catfish, Clarias gariepinus

Combined neurotoxicity of aged microplastics and thiamethoxam in the early developmental stages of zebrafish (Daniorerio)

Microplastics (MPs) pollution, together with its consequential effect on aquatic biota, represent a burgeoning environmental concern that has garnered significant scholarly attention. Thiamethoxam (TMX), a prevalently utilized neonicotinoid insecticide, is renowned for its neurotoxic impact and selective action against targeted pests. The aquatic environment serves as a receptacle for numerous pollutants, such as MPs and neonicotinoid insecticides. However, there is currently a lack of comprehensive understanding regarding the toxic effects of co-exposure to aged MPs and neonicotinoid insecticides in aquatic organisms. Therefore, we endeavor to elucidate the deleterious impacts of aged polystyrene (PS) and TMX on zebrafish (Danio rerio) larvae when present at environmentally relevant concentrations, and to reveal the underlying molecular mechanisms driving these effects. Our study showed that exposure to aged PS, TMX, or their combination notably inhibited the heart rate and locomotion of zebrafish larvae, with a pronounced effect observed under combined exposure. Aged PS and TMX were found to diminish the activity of antioxidative enzymes (SOD, CAT, and GST), elevate MDA levels, and disrupt neurotransmitter homeostasis (5-HT, GABA and ACh). Notably, the mixtures exhibited synergistic effects. Moreover, gene expression related to oxidative stress (e.g., gstr1, gpx1a, sod1, cat1, p38a, ho-1, and nrf2b) and neurotransmission (e.g., ache, ChAT, gat1, gabra1, 5ht1b, and 5ht1aa) was significantly altered upon co-exposure to aged PS and TMX in larval zebrafish. In summary, our findings support the harmful effects of aged MPs and the neonicotinoid insecticides they carry on aquatic organisms. Results from this study enhance our understanding of the biological risks of MPs and insecticides, as well as help fill existing knowledge gaps on neonicotinoid insecticides and MPs coexistence toxicity in aquatic environment.

Photocatalytic removal of imidacloprid pesticide from wastewater using CdS QDs passivated by CQDs containing thiol groups

Over the past decade, CdS QDs have become versatile semiconductors. Surface modification of CdS QDs has become an interesting case study, as it can eliminate surface defects and improve their photochemical properties. In this study, we report a new strategy of using carbon quantum dots containing a large number of thiol groups (CQDs-SH) as a passivating agent for the stabilization of CdS quantum dots (QDs). Various characterization techniques have clearly revealed that the CdS QDs have been successfully passivated by CQDs-SH. The photocatalytic performance of CQDs-SH/CdS QDs was investigated for the degradation of the insecticide imidacloprid from an aqueous solution. Parameters affecting the photodegradation process, including the light source, photocatalyst amount, initial concentration of the pollutant, radiation time, pH, oxidizing agent, and temperature, were investigated. Furthermore, the HPLC technique was applied to quantitatively analyze imidacloprid and its degradation products. The results of the HPLC analysis revealed that under simulated visible light at pH 9, imidacloprid scarcely existed after 90 min of irradiation (90.13% degradation). The LC-MS method was also used to detect the degradation products and investigate the mechanism of photodegradation of the pesticide. The results showed that the CQDs-SH/CdS QDs composite was a promising photocatalyst for the degradation of imidacloprid in wastewater.