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Little information is available about the occurrence of neonicotinoid insecticides in surface water and sediment of the metropolitan regions around the rivers in China. Here we investigate the residual level of neonicotinoids in the Guangzhou section of the Pearl River. At least one or two neonicotinoids was detected in each surface water and sediment, and the total amount of neonicotinoids (∑ 5 neonics) in surface water ranged from 92.6 to 321 ng/L with a geometric mean (GM) of 174 ng/L. Imidacloprid, thiamethoxam and acetamiprid were three frequently detected neonicotinoids (100%) from surface water. As for the sediment, total concentration was varied between 0.40 and 2.59 ng/g dw with a GM of 1.12 ng/g dw, and acetamiprid and thiacloprid were the common sediment neonicotinoids. Western and Front river-route of the Guangzhou section of the Pearl River suffered a higher neonicotinoids contamination than the Rear river-route, resulting from more effluents of WWTPs receiving, and intensive commercial and human activities. Level of residual neonicotinoids in surface water was significantly correlated with the water quality (p < 0.01), especially items of pH, DO and ORP, and nitrogen and phosphorus contaminants. Compared with reports about residual neonicotinoids in water and sediment previously, the metropolitan regions of the Guangzhou could be confronted with a moderate contamination and showed serious ecological threats (even heavier than the Pearl Rivers). Our results will provide valuable data for understanding of neonicotinoids contamination in the Pearl River Delta and be helpful for further assessing environmental risk of neonicotinoids. Image 1 • Occurrence of neonicotinoids in the Guangzhou section of the Pearl River is examined. • At least one or two neonicotinoids was detected in each water and sediment sample. • IMI, THM and ACE were frequently detected (100%) neonicotinoids from surface water. • Western- and Front-suffered a higher neonicotinoids contamination than Rear river-route. • The Guangzhou section of the Pearl River could be confronted with a moderate neonicotinoid contamination. This article evaluates the residual level and distribution of neonicotinoids in the Guangzhou section of the Pearl River, South China. It is of great significance to fully understand the migration, transformation, contamination situation and ecological risk of neonicotinoid insecticides. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • This study to assess soil contamination and neonicotinoids degradation investigated by different method. • The neonicotinoids pollution was detected on surface and sub-surface agriculture soil. • Imidacloprid and thiacloprid were abundant in soils, clothianidin and thiamethoxam were lesser. • Degradation of thiacloprid by blue-LEDs with bacteria had greater performance. • Four biotransformation metabolites was identified from thiacloprid photo-biodegradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diverse people groups are confronted with distinct risks of neonicotinoid intake. • Boiling has negligible effect on the elimination of neonicotinoids. • The most frequently detected neonicotinoid was imidacloprid in the tap water. • Human activity and weather play important roles in neonicotinoids in the tap water. • Humans in 9 months –2 years are subjected to the highest drinking neonicotinoids. Neonicotinoids (NEOs) are the most widely used pesticides and have posed a serious threat to human health. However, data on human exposure to NEOs are extremely scarce. To bridge this gap, human exposure potential of NEOs through drinking water consumption and percutaneous penetration was evaluated with the influences of 17 age groups, 4 seasons, 6 regions, and 2 genders. The results showed that drinking water in the present study had an upper middle level of NEO contamination. Anthropogenic activity and weather condition played important roles in the regional distribution of NEOs in tap water. For both children and adults, N EOs intake from d rinking water e xposure (NDE) and p ercutaneous e xposure (NPE) in the south regions of China are significantly higher than those in the north regions, while the order of NDE and NPE by season is summer > spring = autumn > winter. Furthermore, human age and gender also have remarkable impacts on NDE and NPE. The age groups of children subjected to the highest NDE and NPE were 9 months – 2 years old and 9–12 years old, respectively. This study provides insights into the role of seasonal and regional influence, age and gender in the risk of drinking water and percutaneous exposure to NEOs. [ABSTRACT FROM AUTHOR]

Imidacloprid (IMI) is existence in the soil environment with a half-life habitually more than hundred days. This study targets to determine, identify and characterize photo-biodegradation bacteria from neonicotinoids (NEOs) contaminated agricultural field soils. The sub-surface soil had a higher level contamination of NEOs, in specifically greater concentration of IMI (3445.2 ± 0.09 μg/g) and thiacloprid (4084.4 ± 0.09 μg/g) has been found. Three bacteria Ralstonia pickettii (PBMS-2), Bacillus cereus (PBMS-3) and Shinella zoogloeoides (PBMS-4) was identified from soil-free stable enrichment cultures. The biodegradability of IMI (50 mg L−1) by three bacteria under different colors of light-emitting diodes (LEDs) with a constant 12 V power supply was tested and found that the blue-LEDs had greatest efficiency in supporting biodegradation of IMI which is called photo-biodegradation. In specific, the rate of photo-biodegradation of IMI by Ralstonia pickettii (87%), Bacillus cereus (80%) and Shinella zoogloeoides (80%) was measured. Besides this study also tested the effect of aeration (rpm), pH, and temperature on photo-biodegradation of IMI. There were seven intermediate metabolites were measured as biodegradation products of IMI under photo-biodegradation conditions and they are; IMI-urea, IMI-desnitro, 6-chloronicotinic acid, 6-hydroxy nicotinic acid, IMI- aminoguanidine, IMI-nitrosoguanidine and 4,5-hydroxy IMI, these metabolites are may non-toxic to the environment. • Neonicotinoids insecticide such as imidacloprid in the soil environment had greater half-life. • The agricultural field sub-surface soil had a higher concentration of IMI (3445.2 ± 0.09 μg/g). • Photo-biodegradation performance is greater than separate photo degradation and biodegradation. • The bacteria of Ralstonia pickettii with blue-LEDs enhanced IMI degradation rate. [ABSTRACT FROM AUTHOR]

• At least one neonicotinoid was detected in all soil, water and sediment samples. • Transport of raw agricultural products could be a source of NEOs in urban areas. • Pollution of NEOs in rural areas was significantly higher than that in urban areas. • Correlation and migration of NEOs residue in soil-water-sediment systems were studied. • Exposure to the current NEOs residue level of Guangzhou suggests a serious threat to sensitive non-target invertebrates. Residues and distribution of neonicotinoid insecticides (NEOs) in soil-water-sediment systems of the urban and rural areas of Guangzhou, South China were investigated. A total of 104 soil samples from 7 different functional zones and 29 water/sediment samples from creeks were collected. The results showed that at least one neonicotinoid insecticide was detected in all samples. The summed levels of five target neonicotinoids (∑ 5 neonics) were in the range of 0.003–229 ng/g dw for soil samples, 7.94–636 ng/L for water samples, and 0.017–31.3 ng/g dw for sediment samples, with a geometric mean of 0.59 ng/g dw, 153 ng/L and 1.11 ng/g dw, respectively. Soils from agricultural areas contained the highest residual NEOs, followed by commercial, traffic, residential, industrial, educational zones and parks. Among the seven different functional zones studied, imidacloprid was the most dominant NEO in the agricultural areas and commercial zones, whereas acetamiprid was dominant in the other five functional zones with different land-use types. Thiamethoxam and acetamiprid were the main NEOs in water and sediment samples collected from 29 creeks. The pollution of NEOs in soils, water and sediments from rural areas was higher than that in the counterparts from urban areas. Residual concentration of NEOs detected in soils, water and sediments showed significant correlations with each other. The distribution of NEOs in soil-water-sediment systems indicated that NEOs tended to concentrate in water, followed by sediments and soils, especially in urban areas. An evaluation of the exposure to the current level of the ∑ 5 NEOs in Guangzhou suggests a significant risk for aquatic and soil organisms, particularly under chronic exposures. The results of the present study offer valuable data to better understand the contamination and ecological risks of neonicotinoid insecticides in the rapidly developing urbanized region of South China. [ABSTRACT FROM AUTHOR]

Abstract Occurrence and distribution of five neonicotinoids (NEOs) in surface water and sediment were studied in the Pearl Rivers, including three trunk streams, Dongjiang, Beijiang, Xijiang River (DR, BR and XR), South China. At least one neonicotinoid was detected in surface water and sediment of the Pearl Rivers, with imidacloprid (IMI) and thiamethoxam (THM) being the frequently detected NEOs. Total amount of NEOs (∑ 5 neonics) in surface water and sediment ranged from 24.0 to 322 ng/L, and from 0.11 to 11.6 ng/g dw, respectively. Moreover, the order of contamination level of NEOs in the Pearl Rivers was as follows: XR > DR > BR for surface water, and BR > DR > XR for sediment. Local agricultural activities and effluents of wastewater treatment plants (WWTPs) could be major sources of NEOs in the Pearl Rivers. Solubilization and dilution of NEOs between surface water and sediment during different seasons (spring and summer) could be attributed to rainfall intensities or climate of the Pearl River Delta. An ecological risk assessment of the exposure to current environmental concentration of imidacloprid and ∑ 5 NEOs suggests a threat to sensitive non-target invertebrates, including aquatic invertebrates. Results would provide a better understanding of NEOs contamination in the Pearl Rivers, as well as being a reliable dataset for decision-making in contamination control and environmental protection. Graphical abstract Image 1 Highlights • At least one NEO was detected in water and sediment of the Pearl Rivers. • Imidacloprid and thiamethoxam were the most frequently detected NEOs. • Local agricultural runoff and effluents of WWTPs could be the main sources. • Seasonal differences of NEOs contamination could be attributed to rainfall intensities. • Exposure to current level would pose a potential threat to sensitive non-target invertebrates. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1T-MoS 2 /PMS oxidation process was successfully established for IMI degradation. • The nano-scale 1T-MoS 2 exhibited good catalytic activity for PMS oxidation process. • The activation mechanism of PMS by 1T-MoS 2 was revealed. • The degradation pathway of IMI by 1T-MoS 2 /PMS oxidation process was proposed. Imidacloprid (IMI) which has been widely detected in the natural water environment is potentially genotoxic to humans and should be effectively eliminated. Persulfate-based advanced oxidation processes are considered to be reliable means aiming at organic pollutants degradation, while an efficient catalyst is urgently needed for the activation of the reaction. As a two-dimensional material, 1T-MoS 2 is expected to be applied for the activation of persulfates due to its abundant active sites and good electrical conductivity. Therefore, in this study, 1T-MoS 2 was synthesized by a simple and safe two-step solvothermal reaction and proposed as an emerging activator of peroxymonosulfate (PMS) for the degradation of IMI. It was found that 1T-MoS 2 has significantly better catalytic performance on PMS than 2H-MoS 2 and Bulk-MoS 2 , reaching. 76.4 % at pH = 3. The degradation rate of IMI reduced under alkaline conditions due to the inhibition of catalytic processes. Among the different coexisting anions, H C O 3 - had the greatest degree of interference and inhibition to the degradation process, resulting in the lowest IMI degradation rate for only 42.45 %. Quenching experiments and EPR analysis showed that S O 4 - ∙ and OH were the main reactive oxygen species in the 1T-MoS 2 /PMS process. In addition, the IMI degradation pathways analyzed by UPLC-Q-TOF-MS/MS included dehydrogenation, electrophilic addition, heterocyclic ring breakage and intramolecular rearrangement. This study promotes the application of 1T-MoS 2 and is expected to provide a novel persulfate-based advanced oxidation process catalyzed by 1T-MoS 2 for IMI elimination in the aqueous environment. [ABSTRACT FROM AUTHOR]

Imidacloprid (IMI), as the most-consumed pesticide, has posed a severe threat to the water ecosystem due to its recalcitrance and inefficient elimination in the traditional wastewater treatment. Herein, a heterogeneous electro–Fenton (EF) system coupled with 3D–MoO 2 –porous biochar (PBC) cocatalytic electrodes, abbreviated as 3D–MPE–EF, is initially applied to promote the elimination of IMI in the agrochemical wastewater from pesticide production. The elimination rate of IMI by 3D–MPE–EF system is 18.15 times higher than that by traditional EF system at pH 7.0. The utilization of 3D–MoO 2 –PBC electrodes sufficiently compensates for inherent deficiencies of traditional EF system. The circular utilization of Fe is also addressed by 3D–MoO 2 –PBC cocatalytic electrodes to reduce the consumption of Fe2+ and the deposition of iron mud. Through comparison, MoO 2 is considered the most appropriate cocatalyst in terms of the reutilization of Fe and degradation of IMI. Eight mechanisms are identified in the degradation pathways of IMI by UPLC–Q–TOF–MS. The ecotoxicities of IMI are remarkably attenuated in the 3D–MPE–EF system. This study provides insights into the roles of 3D–MoO 2 –PBC cocatalytic electrodes in the enhanced elimination of IMI in heterogeneous EF system. [Display omitted] • The IMI removal by EF system is greatly enhanced by 3D–MoO 2 –PBC electrodes. • The alkaline elimination of IMI is promoted by 3D–MoO 2 –PBC electrodes. • The reutilization of Fe is addressed by MoO 2 to reduce the deposition of iron mud. • Eight plausible degradation mechanisms of IMI were identified in 3D–MPE–EF. • The ecotoxicity of IMI were progressively attenuated in the 3D–MPE–EF system. [ABSTRACT FROM AUTHOR]