Photocatalytic degradation of four insecticides and their main generated transformation products in soil and pepper crop irrigated with reclaimed agro-wastewater under natural sunlight

Thiamethoxam dynamics in pepper plants: Deciphering deposition and dissipation pattern across diverse planting modes and regions

To reduce the application dosage of thiamethoxam (TMX), we investigated the deposition and dissipation patterns in a pepper-planted ecosystem under different planting modes across four regions in China, namely Hainan (HN), Zhejiang (ZJ), Anhui (AH) and Hebei (HB). This study focused on the deposition and dissipation of TMX at concentrations of 63.00, 47.25, 31.50, 23.63 and 15.75 g a.i.hm-2. As the application dose increased, the deposition amount of TMX initially increased in the plants and cultivated soil, showing obvious geographic differences in four cultivation areas. Surprisingly, the initial amount of TMX deposited the pepper-cultivated greenhouse of ZJ and AH was 1.1-2.1-fold and 1.0-3.6-fold higher than that in the open field system at the same application dose, respectively. In pepper leaves, stems, fruits and soil, the dissipation exhibited rapid growth and then slowed. However, the residual concentration showed an increasing trend, followed by a subsequent decrease in the pepper roots. In different planting regions, the dissipation rate of TMX followed the order HN > ZJ > AH > HB in pepper plants and cultivated soil. In comparison to the open field, the total TMX retention rate in greenhouse was higher, indicating overall greater persistence in the greenhouse conditions. These findings reveal the deposition and dissipation characteristics of TMX within the pepper-field ecosystem, offering a significant contribution to the risk assessment of pesticides.

Risk characteristics of resistome coalescence in irrigated soils and effect of natural storage of irrigation materials on risk mitigation

Irrigation and fertilization are the routinely agricultural practices but also cause resistome coalescence, by which the entire microbiomes from irrigation materials invade soil microbial community, to transfer antibiotic resistance genes (ARGs) in the coalesced soils. Although studies have reported the effect of irrigation or fertilization on the prevalence and spread of ARGs in soils, risk characteristics of resistome coalescence in irrigation system remain to be demonstrated and few has shown whether natural storage of irrigation materials will reduce resistance risks. To fill the gaps, two microscopic experiments were conducted for deeply exploring resistance risks in the soils irrigated with wastewater and manure fertilizer from a perspective of community coalescence by metagenomic analysis, and to reveal the effect of natural storage of irrigation materials on the reduction of resistance risks in the coalesced soils. Results showed irrigation and coalescence significantly increased the abundance and diversity of ARGs in the soils, and introduced some emerging resistance genes into the coalesced community, including mcr-type, tetX, qacB, and an array of genes conferring resistance to carbapenem. Procrustes analysis demonstrated microbial community was significantly correlated with the ARGs in coalesced soils, and variance partitioning analysis quantified its dominant role on shaping resistome profile in the environment. Besides ARGs, abundant and diverse mobile genetic elements (MGEs) were also identified in the coalesced soils and co-existed on the ARG-carrying contigs, implying potential transfer risk of ARGs in the irrigation system. Further, the analysis of metagenome-assembled genomes (MAGs) confirmed the risk by recovering 358 ARGs-carrying MAGs and identifying the resistant bacteria that co-carried multiple ARGs and MGEs. As expected, the natural storage of irrigation water and manure fertilizer reduced about 27%-54% of ARGs, MGEs and virulence factors in the coalesced soils, thus caused the soils to move towards lower resistance risks to a certain extent.

Recent advances in structural engineering of photocatalysts for environmental remediation

Photocatalysis appears to be an appealing approach for environmental remediation including pollutants degradation in water, air, and/or soil, due to the utilization of renewable and sustainable source of energy, i.e., solar energy. However, their broad applications remain lagging due to the challenges in pollutant degradation efficiency, large-scale catalyst production, and stability. In recent decades, massive efforts have been devoted to advance the photocatalysis technology for improved environmental remediation. In this review, the latest progress in this aspect is overviewed, particularly, the strategies for improved light sensitivity, charge separation, and hybrid approaches. We also emphasize the low efficiency and poor stability issues with the current photocatalytic systems. Finally, we provide future suggestions to further enhance the photocatalyst performance and lower its large-scale production cost. This review aims to provide valuable insights into the fundamental science and technical engineering of photocatalysis in environmental remediation.

The dissipation, processing factors, metabolites, and risk assessment of pesticides in honeysuckle from field to table

Globally, honeysuckle is consumed as a food and administered as a medicinal agent. However, pesticide residues in honeysuckle limit its application and development of the honeysuckle industry, affecting food safety and endangering human health. Here, the degradation kinetics of 11 typical pesticides, including insecticides, fungicides, and an acaricide, in honeysuckle were investigated. The half-lives of pesticides in Henan and Liaoning fields were 1.90-4.33 and 2.05-4.62 d, respectively. The processing factors (PFs) of these pesticides after oven, sun, and shade drying ranged from 3.52 to 11.2. After decocting, the PFs of the pesticides were <1. Twenty degradation products were identified using ultra high performance liquid chromatography-quadrupole time-of-flight mass spectrometry, and pathways were proposed based on drying and decoction. The ecotoxicities of the degradation products were evaluated using the Toxicity Estimation Software Tool. Finally, the acute hazard indices of these pesticides, as determined via dietary exposure assessment combined with the PFs, were 0.227 and 0.911 for adults and children, respectively. Thus, special populations, such as children, require particularly careful risk control in terms of dietary exposure.

Organochlorine pesticides and other pesticides in peanut oil: Residue level, source, household processing factor and risk assessment

Peanut oil, edible vegetable oil largely consumed in China, may be polluted with pesticides during both peanut cultivation and processing. In this study, we analyzed organochlorine pesticides, five currently used pesticides and two degradation products, in soils, seeds, peanuts, oil and dregs and systematically tracked variations of their levels in field soils and during the pressing process. The results showed that the application of metolachlor, pirimicarb and quizalofop-p-ethyl pesticides during peanut cultivation caused their concentrations in peanuts to increase. In most samples, the concentration of 3-phenoxybenzoic acid was higher than that of λ-cyhalothrin, and the variation trends of λ-cyhalothrin and 3-phenoxybenzoic acid in soil samples were similar, which indicate that after application, most λ-cyhalothrin may rapidly be degraded to 3-phenoxybenzoic acid. Regarding the pressing process of peanut oil, the sum of mass of oil and shells was less than the mass of the corresponding raw peanut. Compared with that in peanuts, the total mass of most pesticides in oil and shells was lower, while that of two degradation products was higher, an indication that the degradation products were still generated during the pressing process. Finally, the assessment of health risk of different age groups consuming the studied peanuts and peanut oil showed that the risk was very low.

Recent progress of silver-containing photocatalysts for water disinfection under visible light irradiation: A review

Photocatalysis has emerged as an environmentally friendly approach for microbial disinfection. The development of visible-light-driven (VLD) photocatalysts for water pollution remediation is imperative, considering that visible light constitutes a substantial fraction of the solar spectrum. The modification of photocatalysts by Ag/AgX (X = Cl, Br, I) deposition can be used to improve photocatalytic efficiencies. This is achieved by preventing photogenerated electron-hole pairs recombination through electron trapping mechanisms. With the introduction of silver NPs, visible light absorption can also be increased through its SPR enhancement. Silver also possesses excellent antimicrobial properties. Consequently, a novel class of Ag/AgX-containing hybrid materials has recently emerged as a promising candidate for water disinfection. This review summarizes the latest advances in the synthesis of Ag/AgX-containing photocatalysts using various synthetic methods. The microbial disinfection efficiencies of the as-prepared materials, the main reactive oxygen species and disinfection mechanisms are also reviewed in detail. Finally, some areas that need to be improved are discussed along with new insights as perspectives for future developments in this field.

Assessment of reclaimed agro-wastewater polluted with insecticide residues for irrigation of growing lettuce (Lactuca sativa L) using solar photocatalytic technology

Scientific literature is full of works studying the removal of different pollutants from water through different Advanced Oxidation Processes (AOPs). Many of them only suggest it is reused for agricultural purposes or for small crops in pots. This study is based on the reuse of reclaimed agricultural wastewater contaminated with four insecticides (chlorantraniliprole, imidacloprid, pirimicarb and thiamethoxam) for growing lettuce in field conditions. First, solar photocatalysis with TiO2/Na2S2O8 was used on a pilot plant in a sunny area (Murcia, SE of Spain) as an environmentally friendly technology to remove insecticide residues and their main reaction intermediates from contaminated water. The necessary fluence (H, kJ m-2) to accomplish 90% removal (H90) ranged from 0.12 to 1212 kJ m-2 for pirimicarb and chlorantraniliprole, respectively. Only six (derived from imidacloprid, pirimicarb and thiametoxam) of 18 transformation intermediate products studied were detected in reclaimed water during the photoperiod (2000 kJ m-2 of accumulated UVA radiation) although all of them were totally photodegraded after a fluence of 1250 kJ m-2. Secondly, reclaimed agro-wastewater was used to irrigate two lettuce crops grown under greenhouse conditions and under agricultural field conditions. In no cases, insecticide residues nor their TIPs were noticed above their respective LOQs (limits of quantification) in soil and lettuce samples (between 0.03 and 0.04 μg kg-1 for pirimicarb and 2.49 and 2.23 μg kg-1 for thiamethoxam, respectively) when they were irrigated with reclaimed water, while residues of the four insecticides and some of their intermediates were found in soil and lettuce by the end of cultivation when they were irrigated with non-reclaimed contaminated water. According to the results, this technology can be applied in a sustainable way, mainly in areas with water scarcity and high solar radiation, contributing to water utilisation in drought areas and the use of renewable energy.

Photocatalytic Oxidation of Chlorantraniliprole, Imidacloprid, Pirimicarb, Thiamethoxam and Their Main Photoreaction InterMediates as Impacted by Water Matrix Composition under UVA-LED Exposure

Processes on wastewater treatment plants (WWTP) are not always efficient for pollutant removal. A new, low-cost, and effective technology is needed. In this work, the photocatalytic degradation of four insecticides, chlorantraniliprole, imidacloprid, pirimicarb, and thiamethoxam, has been examined in different water matrices (irrigation water, leaching waters, and WWTP effluent). Lab experiments were conducted with TiO2 and ZnO, as photocatalysts, with and without Na2S2O8 as an oxidant, exposed to UVA irradiation with LED lamps. Previously, different loadings of TiO2 and ZnO were assessed on the disappearance kinetics of the different insecticides to know the optimal efficiency. The effect of water matrices, susceptible to being contaminated with the target insecticides, was discussed when the photocatalytic system TiO2/Na2S2O8 was applied. The abatement of their main transformation products (TPs) was also monitored during the studied photoperiods. A total of 13 TPs were detected in the different water matrices studied. All of them were formed and eliminated during the photoperiod, except thiamethoxam urea which was present from the beginning of the experiments due to its hydrolysis in water. In conclusion, UVA-LED lamps are a good source to carry out heterogeneous photocatalysis in WWTP, since its high efficiency, low-cost, long lifetime, and effectiveness on pollutant removal.