Photo-biodegradation of imidacloprid under blue light-emitting diodes with bacteria and co-metabolic regulation

Heatwaves, elevated temperature, and insecticide-induced effects at different trophic levels of a freshwater ecosystem

Heatwaves and increasing average temperatures associated with climate change pose severe stress on nature, including freshwater ecosystems. As these thermal stressors do not act in isolation over temporal or spatial scales, interactions with other stressors, like pesticides, may lead to unpredictable combined effects. Empirical studies investigating multiple stressor effects across different trophic levels are scarce and often lack environmental realism. Here, we performed a multiple stressor experiment using outdoor freshwater mesocosms and realistic pond assemblages including microbes, phytoplankton, macrophytes, and invertebrates. The effects of the pesticide imidacloprid at three dosings (0, 1, 10 μg/L) were examined in combination with three temperature scenarios comprising natural ambient, elevated temperatures (+4 °C), and repeated heatwaves (+8 °C). Our results reveal fast imidacloprid dissipation for all temperature treatments with the lowest average dissipation half-lives (DT50: 6 days) in the heatwave treatment. Imidacloprid induced a series of significant effects on the macroinvertebrate community at 10 μg/L across the temperature treatments. Significant declines in abundance appeared throughout the experiment for the most sensitive taxa Cloeon dipterum, Caenis sp., Chironomini, and Dero sp., whereas significant imidacloprid effects on Tanytarsini, Chironomus, and Gammarus pulex occurred only after each dosing. Only Zygoptera showed an imidacloprid-related increase in abundance, whereas significantly adverse time-cumulative effects on abundance occurred for Asellus aquaticus. The zooplankton community showed imidacloprid tolerance (10 μg/L) with increasing abundances of Chydorus sphaericus, Acroperus harpae, and Ascomorpha. Heatwaves induced significantly meliorating effects on Dero sp. and adverse effects on Caenis sp., Tanytarsini, G. pulex, and A. harpae. The macroinvertebrate community demonstrated faster post-exposure recovery dynamics in the highest imidacloprid treatment when previously exposed to heatwaves and elevated temperatures compared to ambient conditions. Overall, heatwaves amplified the effects of imidacloprid on the invertebrate community, manifesting in manifold effects that adversely impacted multiple trophic levels.

Electrocatalytic coupled biofilter for treating cyclohexanone-containing wastewater: Degradation, mechanism and optimization

Electrocatalytic coupled biofilter (EBF) technology organically integrates the characteristics of electrochemistry and microbial redox, providing ideas for effectively improving biological treatment performance. In this study, an EBF system was developed for enhanced degradation of cyclohexanone in contaminated water. Experimental results show that the system can effectively remove cyclohexanone in contaminated water. Under the optimal parameters, the removal rates of cyclohexanone, TP, NH4+-N and TN were 97.61 ± 1.31%, 76.31 ± 1.67%, 94.14 ± 2.13% and 95.87 ± 1.01% respectively. Degradation kinetics studies found that electrolysis, adsorption, and biodegradation pathways play a major role in the degradation of cyclohexanone. Microbial community analysis indicates that voltage can affect the structure of the microbial community, with the dominant genera shifting from Acidovorax (0 V) to Brevundimonas (0.7 V). Additionally, Acidovorax, Cupriavidus, Ralstonia, and Hydrogenophaga have high abundance in the biofilm and can effectively metabolize cyclohexanone and its intermediates, facilitating the removal of cyclohexanone. In summary, this research can guide the development and construction of highly stable EBF systems and is expected to be used for advanced treatment of industrial wastewater containing cyclohexanone.

Efficient degradation of imidacloprid by surface discharge cold plasma: Mechanism of interaction between ROS and molecular structure and evaluation of residual toxicity

Incorrect use of neonicotinoid pesticides poses a serious threat to human and pollinator health, as these substances are commonly present in bee products and even drinking water. To combat this threat, the study developed a new method of degrading the pesticide imidacloprid using surface discharge cold plasma oxidation technology. The study showed that this method achieved a very high efficiency of imidacloprid degradation of 91.4%. The main reactive oxygen species (H2O2, O3, ·OH, O2-, 1O2) effectively participated in the decomposition reaction of imidacloprid. Reactive oxygen species were more sensitive to the structure of the nitroimine group. Density functional theory (DFT) further explored the sites of reactive oxygen species attack on imidacloprid and revealed the process of energy change of attacking imidacloprid. In addition, a degradation pathway for imidacloprid was proposed, mainly involving reactive oxygen species chemisorption, a ring-opening intermediate, and complete cleavage of the nitroimine group structure. Model predictions indicated that acute oral and developmental toxicity were significantly reduced after cold plasma treatment, as confirmed by insect experiments. Animal experiments have shown that plasma treatment reduces imidacloprid damage to mice hippocampal tissue structure and inhibits the reduction of brain-derived neurotrophic factor content, thus revealing the detoxification mechanism of the body.

Ovarian antral follicles metabolize imidacloprid in vitro

Neonicotinoid insecticides are synthetic nicotine derivatives that have high affinity for invertebrate nicotine receptors and low affinity for mammalian nicotine receptors. However, imidacloprid (IMI), the most commonly used neonicotinoid, can be bioactivated by the liver in mammals to desnitro-imidacloprid, an intermediate metabolite that effectively binds and activates mammalian receptors. However, it is not known if other tissues such as the ovaries can metabolize IMI. Thus, the present study tested the hypothesis that ovarian antral follicles metabolize and bioactivate IMI. Antral follicles were dissected from the ovaries of CD-1 mice and cultured in media containing dimethyl sulfoxide or IMI (0.2-200 µg/ml) for 48 and 96 h. Media were subjected to liquid chromatography-mass spectrometry for detection of phase I IMI metabolites. Follicles from the cultures were used for gene expression analysis of metabolic enzymes associated with IMI metabolism. All IMI metabolites were detected at 48 and 96 h. Oxidized IMI intermediates were detected in media from cultured follicles, but not environmental controls. Reduced IMI intermediates were detected in media from cultured follicles and the environmental controls. At 48 h, IMI did not affect expression of any metabolic enzymes compared with control. At 96 h, IMI induced Cyp2e1 and Cyp4f18 compared with control. These data indicate that mouse ovarian follicles metabolize IMI and that IMI induces ovarian Cyp expression over time.

Performance and microbial metabolic mechanism of imidacloprid removal in a microbial electrolysis cell-integrated adsorption biological coupling system

Coke used as a filler to treat imidacloprid (IMI) wastewater by both adsorption biological coupling and microbial electrolysis cells (MEC)-adsorption biological coupling technologies, the removal efficiencies on pollutions in wastewater containing IMI were investigated, and the key functional genes related to IMI degradation pathways were also revealed. Results showed that the removal rates of COD, ammonia nitrogen, TP, and IMI under the adsorption biological coupling treatment and MEC-adsorption biological coupling treatment were 94.61-95.54%, 93.37-95.79%, 73.69-83.80%, and 100%, respectively. MEC increased the relative abundance of Proteobacteria by 9.01% and transformed the dominant bacteria from Lysobacter and Reyranella to Brevundimonas and Aquincola. Moreover, MEC up-regulated the abundance of the coding genes PK (9.30%), narG (2.26%), pstS (3.63%), and phnD (1.32%), and converted the IMI degradation products to smaller molecular weight C6H8N2 and C6H6ClNO. This study provided an important reference information for efficient treatment of IMI wastewater using the MEC-adsorption biological coupling technology.

Detection of Neonicotinoids in agriculture soil and degradation of thiacloprid through photo degradation, biodegradation and photo-biodegradation

The social and ecological influence of Neonicotinoids (NEOs) usage in agriculture sector is progressively higher. There are seven NEOs insecticides widely used for the insects control. Among the NEOs, thiacloprid (THD) was extensively used for insect control during crop cultivation. This study targets to analyse the contamination levels of NEOs in agricultural soil and identify photo-biodegradation of THD degradation using pure isolates and mixed consortium. The photo degradation (PD), biodegradation (BD) and photo-biodegradation (PBD) of THD were compared. The corn field agricultural soils were polluted by four NEOs, among them THD had greater contamination level (surface soil: 3901.2 ± 0.04 μg/g) and (sub-surface soil: 3988.6 ± 0.05 μg/g). Three soil free enriched bacterial strains following Bacillus atrophaeus (PB-2), Priestia megaterium (PB-3) (formerly known as Bacillus megaterium), and Peribacillus simplex (PB-4) (formerly known as Bacillus simplex) were identified by microbiological and molecular 16s rRNA gene sequencing. The PD, BD and PBD of THD were conducted and degradation rate was detected by instrument UPLC-MS-MS. The PBD process with blue-LEDs showed better THD degradation efficiency than PD and BD, where the specific THD degradation rate was 85 ± 0.2%, 87 ± 0.5%, and 89 ± 0.3%, respectively for PB-2, PB-3 and PB-4. Then, the photo-biodegradation performance is greater at 150, 175, 200 rpm, pH 7.0-9.0, and temperature 30-35 °C. After the PBD system deliver four intermediate metabolites, the THD degradation process maybe through nitro reduction, hydroxylation and oxidative cleavage pathway.

Designing NAZO@BC electrodes for enhanced elimination of hydrophilic organic pollutants in heterogeneous electro-Fenton system: Insights into the detoxification mediated by 1O2 and •OH

Hydrophilic organic pollutants (HLOPs) in effluents of wastewater treatment plants are more prevalent than hydrophobic counterparts, therefore development of upstream processes that can effectively enhance the removal of HLOPs can substantially enhance overall treatment performance. To bridge this gap, 3D electrodes made of biochar-supported Al-ZnO nanoparticles (NAZO@BC) applied in heterogeneous electro-Fenton (EF) system, abbreviated as NBE-EF system, is rationally designed for enhanced elimination of HLOPs in wastewater. Our analysis indicates the NBE-EF system results in an efficient THM elimination, 42.4 times greater than that of conventional EF system. MoS₂ as an efficient cocatalyst plays an important role in the conversion from Fe(III) to Fe(II). Singlet oxygen (¹O₂) and hydroxyl radical (•OH) are identified as the primary reactive oxygen species (ROS) in the NBE-EF system. NAZO@BC electrodes could concentrate HLOPs on their surface and degrade it effectively, achieving also a self-cleaning effect. Effective elimination of four HLOPs, i.e., thiamethoxam (THM), dinotefuran (DIN), nitenpyram (NIT), and acetamiprid (ACE), demonstrated the high degradation performance of the NBE-EF system, even at neutral and alkaline conditions. This study provides a new approach for enhanced elimination of HLOPs in wastewater treatment and mechanical insights into degradation pathways and toxicity attenuation.

Accurate prediction and further dissection of neonicotinoid elimination in the water treatment by CTS@AgBC using multihead attention-based convolutional neural network combined with the time-dependent Cox regression model

Imidacloprid (IMI), as the most widely used neonicotinoid insecticide, poses a serious threat to the water ecosystem due to the inefficient elimination in the traditional water treatment. Chitosan (CTS)-stabilized biochar (BC)-supported Ag nanoparticles (CTS@AgBC) are applied to eliminate the IMI in the water treatment effectively. Batch experiments depict that the modification of BC by CTS and Ag nanoparticles remarkably improve its adsorption performance. The pseudo-second-order and Elovich models have good performance in simulating the adsorption processes of CTS@AgBC and BC. This indicates that the chemical adsorption on real surfaces plays the dominant role in the adsorption of IMI by CTS@AgBC and BC. In addition, the multihead attention (MHA)-based convolutional neural network (CNN) combined with the time-dependent Cox regression model are initially applied to predict and dissect the adsorption elimination processes of IMI by CTS@AgBC. The proposed MHA-CNN model achieves more accurate concentration prediction of IMI than traditional models. According to influence weights by MHA module, biochar category, pH, and treatment temperature are considered the three dominant environmental variables to determine the IMI elimination processes. This study provides insights into roles of environmental variables in the elimination of IMI by CTS@AgBC and the accurate prediction of IMI concentration.