Superabsorbent hydrogel as a formulation to promote mineralization and accelerate degradation of acetochlor in soils

Far-UVC direct photolysis of iohexol and acetochlor: an experimental and mechanism study

Recently, the emission of 222 nm Far-UVC krypton chloride (KrCl*) excimer lamps, has gained widespread attention in the field of water treatment. This study compared the degradation kinetics of IOX and ACE under UV222 and UV254 irradiation. The results demonstrated that UV222 irradiation exhibited higher efficiency, increasing the removal rates of IOX and ACE from 72.46% and 19.31% to 100%, respectively. Probe experiments and electron paramagnetic resonance (EPR) spectroscopy were used to identify the major active species generated during UV222 irradiation ([HO•]ss = 2.74 × 10-13 M). In addition, the effect of pH, pollutant concentration, anions, and natural organic matter (NOM) on the photolysis of IOX and ACE was investigated. The results indicated that IOX and ACE exhibited minimal dependence on pH, and IOX showed low sensitivity to water matrix components. Finally, the electrical energy consumption of the IOX and ACE photolysis by UV222 and UV254 irradiation was evaluated. The results revealed that UV222 irradiation demonstrated superior economic benefits (EE/OUV222/IOX = 0.59951 KWh/L, EE/OUV222/ACE = 0.25443 KWh/L), effectively reducing treatment costs. This study elucidated the photolysis characteristics of IOX and ACE under Far-UVC irradiation, providing a reference for the selection of process conditions in practical applications.

Carbon-14 labeled transformation of atrazine in soils: Comparison of superabsorbent hydrogel coating and technical material

Atrazine exhibits adverse effects on diverse organisms in both terrestrial and aquatic environments, even though it effectively targets specific organisms. This study employed superabsorbent hydrogels to coat 14C-atrazine coupled with a four-compartment model to determine the fate of this herbicide in three oxic soils over a 100-day incubation period. Mineralization of atrazine was limited in all soils, with rates remaining below 3.5 %. The encapsulation treatment reduced mineralization of atrazine in soil A and soil B. Bound residues ranged from 26.1 to 43.6 % at 100 d. The encapsulation treatment enhanced the degradation of atrazine and reduced the content of deethylatrazine in soil A, but significantly increased the content of deisopropylatrazine in soil A and hydroxyatrazine in soil C. Using the obtained data, we also constructed a four-compartment model to clarify the relationships among the parent compound, degradation products, bound residues, and mineralization. This model accurately fits the fate of atrazine in the present work. Additionally, the correlation study suggested that both soil parameters and superabsorbent hydrogels played significant roles in influencing atrazine transformation. These findings serve as a reference for evaluating the environmental impact of superabsorbent hydrogels in atrazine pollution reduction and offer a foundational model approach for a comprehensive understanding of organic pollutants.

Impact of superabsorbent hydrogels on microbial community and atrazine fate in soils by 14C-labeling techniques

The accumulation of atrazine in soils can create environmental challenges, potentially posing risks to human health. Superabsorbent hydrogel (SH)-based formulations offer an eco-friendly approach to accelerate herbicide degradation. However, the impact of SHs on soil microbial community structure, and thus on the fate of atrazine, remains uncertain. In this study, a radioactive tracer was employed to investigate the influence of SHs on microbial communities and atrazine transformation in soils. The results revealed that the mineralization of atrazine in active soils was considerably greater than that in sterilized soils. Atrazine degradation proceeded rapidly under SH treatment, indicating the potential of SH to accelerate atrazine degradation. Furthermore, SH addition did not alter the atrazine degradation pathway in soils, which included dealkylation, dechlorination and hydroxylation. The relative abundance of dominant microbial population was influenced by the presence of SHs in the soil. Additionally, SH application led to an increased relative abundance of Lysobacter, suggesting its potential involvement in atrazine degradation. These findings reveal the significance of soil microorganisms and SH in atrazine degradation, offering crucial insights for the development of effective strategies for atrazine remediation and environmental sustainability.

Current insights into environmental acetochlor toxicity and remediation strategies

Acetochlor is a selective pre-emergent herbicide that is widely used to control annual grass and broadleaf weeds. However, due to its stable chemical structure, only a small portion of acetochlor exerts herbicidal activity in agricultural applications, while most of the excess remains on the surfaces of plants or enters ecosystems, such as soil and water bodies, causing harm to the environment and human health. In recent years, researchers have become increasingly focused on the repair of acetochlor residues. Compared with traditional physical and chemical remediation methods, microorganisms are the most effective way to remediate chemical pesticide pollution, such as acetochlor, because of their rich species, wide distribution, and diverse metabolic pathways. To date, researchers have isolated and identified many high-efficiency acetochlor-degrading strains, such as Pseudomonas oleovorans, Klebsiella variicola, Bacillus subtilus, Rhodococcus, and Methylobacillus, among others. The microbial degradation pathways of acetochlor include dechlorination, hydroxylation, N-dealkylation, C-dealkylation, and dehydrogenation. In addition, the microbial enzymes, including hydrolase (ChlH), debutoxylase (Dbo), and monooxygenase (MeaXY), responsible for acetochlor biodegradation are also being investigated. In this paper, we review the migration law of acetochlor in the environment, its toxicity to nontarget organisms, and the main metabolic methods. Moreover, we summarize the latest progress in the research on the microbial catabolism of acetochlor, including the efficient degradation of microbial resources, biodegradation metabolic pathways, and key enzymes for acetochlor degradation. At the end of the article, we highlight the existing problems in the current research on acetochlor biodegradation, provide new ideas for the remediation of acetochlor pollution in the environment, and propose future research directions.

Determination of acetochlor by UPLC-MS3 in cells and its application to a cellular pharmacokinetic study

The aim of this work was to develop a fast, simple, and reliable UPLC-MS3 method for the sensitive detection of acetochlor in biological samples. In MS3 mode, the ion transition m/z 270.1 → 224.1→148.1 was chosen for quantification with butachlor as the internal standard. In the UPLC system, separation was performed on a UPLC column (2.1 × 50 mm ID, 1.7 μm) with 0.1 % FA in water and acetonitrile as mobile phases. After simple protein precipitation via acetonitrile, the method was well validated with good linearity (0.5-20 ng/mL, r > 0.995), accuracy (-3.70 %-2.98 %), and precision (<15 %). The selectivity and sensitivity were improved obviously in MS3 mode than that in MRM mode. The developed UPLC-MS3 method was successfully applied to the cellular pharmacokinetics study of acetochlor in MCF-7 cells.

Occurrence, multiphase partitioning, drivers, and ecological risks of current-use herbicides in a river basin dominated by rice-vegetable rotations in tropical China

Rice-vegetable rotation practices prevail in subtropical and tropical agriculture worldwide, with applications of current-use herbicides (CUHs) vital for nontarget plant control. After application, CUHs migrate to environmental compartments, where the occurrence, fate, and ecological risks have not been well characterized. To further understand the occurrence and multiphase partitioning, as well as to evaluate potential drivers and mixture risks in environmental compartments, we analyzed 11 CUHs in 576 samples from 36 rice-vegetable rotations in Nandu River basin, Hainan, China. Samples included soil, water, suspended particulate matter, and sediment collected during both rice and vegetable planting periods. The CUH concentrations varied across environmental compartments, but with high levels of glyphosate and aminomethylphosphonic acid organophosphorus herbicides (OPHs) frequently detected, accounting for 82.3 % to 99.0 % in environmental compartments. Phenoxy acid (PAA) and chloroacetanilide (ANH) herbicides were detected at lower frequencies. Spatiotemporal variation was significantly different among OPHs, ANHs, and PAAs, with geographic and crop-related patterns most evident for CUHs rather than OPHs. Structural equation model, redundancy, and boosted regression tree analyses indicated environmental compartment properties (pH, organic matter, and Fe/Al oxides), crop type, and wet/dry climate were important drivers of spatiotemporal patterns. Fugacity ratios indicated multiphase partitioning and transport of CUHs differed in rice and vegetable planting periods. A new assessment framework based on species-sensitive distributions and environmental compartment weight index indicated unacceptable risks of CUHs (risk quotient >1 in >50 % of sites), with most risks from OPHs (10.5 % to 98.0 %) and butachlor, acetochlor, and 2,4-dichlorophenoxyacetic acid. Risk hot spots were identified as the soil, the central region, and the vegetable planting period, potentially threatening nontarget organisms (e.g., Lemna minor, Glomus intraradices, and Apis mellifera). This study provides a new risk assessment framework and demonstrates the domination of OPHs in CUH contamination and risks in the tropics, thus helping guide policymakers and stakeholders on herbicide management.

Preparation of fast-swelling porous superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking

Superabsorbent hydrogels have wide applications in many fields because of their unique water absorbing performance. In spite of decades of research about superabsorbent hydrogels, high water absorbency under pressure and fast-swelling are still challenging and highly desired for their applications in hygienic products and others. Here, we report preparation of fast-swelling porous starch-g-poly(acrylic acid)/poly(vinyl alcohol) superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking. 2,2'-Azobis(2-amidinopropane) dihydrochloride (AIBA) was used as a new porogen instead of conventional porogens like NaHCO3. Post surface crosslinking of the hydrogel was achieved using glycerol via the esterification reaction. AIBA is a better porogen than NaHCO3 regarding porosity and swelling performance of the hydrogels, and its content has great influences on structure and swelling performance of the hydrogels including water absorbency and swelling rate. Also, the surface crosslinking using glycerol can significantly enhance the saline water absorbency under pressure (2 kPa) but at the sacrifice of the swelling rate. Consequently, the hydrogels show high water absorbencies for deionized water (560 g/g), 0.9 wt% NaCl solution (58 g/g), 0.9 wt% NaCl solution under 2 kPa pressure (28 g/g) and fast-swelling (31 s to achieve a highly swelling state).

Insights into the metabolic pathways and biodegradation mechanisms of chloroacetamide herbicides

Chloroacetamide herbicides are widely used around the world due to their high efficiency, resulting in increasing levels of their residues in the environment. Residual chloroacetamides and their metabolites have been frequently detected in soil, water and organisms and shown to have toxic effects on non-target organisms, posing a serious threat to the ecosystem. As such, rapid and efficient techniques that eliminate chloroacetamide residues from the ecosystem are urgently needed. Degradation of these herbicides in the environment mainly occurs through microbial metabolism. Microbial strains such as Acinetobacter baumannii DT, Bacillus altitudinis A16, Pseudomonas aeruginosa JD115, Sphingobium baderi DE-13, Catellibacterium caeni DCA-1, Stenotrophomonas acidaminiphila JS-1, Klebsiella variicola B2, and Paecilomyces marquandii can effectively degrade chloroacetamide herbicides. The degradation pathway of chloroacetamide herbicides in aerobic bacteria is mainly initiated by an N/C-dealkylation reaction, followed by aromatic ring hydroxylation and cleavage processes, whereas dechlorination is the initial reaction in anaerobic bacteria. The molecular mechanisms associated with bacterial degradation of chloroacetamide herbicides have been explored, with amidase, hydrolase, reductase, ferredoxin and cytochrome P450 oxygenase currently known to play a pivotal role in the catabolic pathways of chloroacetamides. The fungal pathway for the degradation of these herbicides is more complex with more diversified products, and the degradation enzymes and genes involved remain to be discovered. However, there are few reviews specifically summarizing the microbial degrading species and biochemical mechanisms of chloroacetamide herbicides. Here, we briefly summarize the latest progress resulting from research on microbial strain resources and enzymes involved in degradation of these herbicides and their corresponding genes. Furthermore, we explore the biochemical pathways and molecular mechanisms for biodegradation of chloroacetamide herbicides in depth, thereby providing a reference for further research on the bioremediation of such herbicides.