Agricultural pesticide land budget and river discharge to oceans.

Pesticides are ubiquitous environmental pollutants negatively affecting ecosystem and human health1,2. About 3 Tg of pesticides are used annually in agriculture to protect crops3. How much of these pesticides remain on land and reach the aquifer or the ocean is uncertain. Monitoring their environmental fate is challenging, and a detailed picture of their mobility in time and space is largely missing4. Here, we develop a process-based model accounting for the hydrology and biogeochemistry of the 92 most used agricultural pesticide active substances to assess their pathways through the principal catchments of the world and draw a near-present picture of the global land and river budgets, including discharge to oceans. Of the 0.94 Tg net annual pesticide input in 2015 used in this study, 82% is biologically degraded, 10% remains as residue in soil and 7.2% leaches below the root zone. Rivers receive 0.73 Gg of pesticides from their drainage at a rate of 10 to more than 100 kg yr-1 km-1. By contrast to their fate in soil, only 1.1% of pesticides entering rivers are degraded along streams, exceeding safety levels (concentrations >1 µg l-1) in more than 13,000 km of river length, with 0.71 Gg of pesticide active ingredients released to oceans every year. Herbicides represent the prevalent pesticide residue on both land (72%) and river outlets (62%).

Dual-Mode Fluorescent/Intelligent Lateral Flow Immunoassay Based on Machine Learning Algorithm for Ultrasensitive Analysis of Chloroacetamide Herbicides.

Given the harmful effect of pesticide residues, it is essential to develop portable and accurate biosensors for the analysis of pesticides in agricultural products. In this paper, we demonstrated a dual-mode fluorescent/intelligent (DM-f/DM-i) lateral flow immunoassay (LFIA) for chloroacetamide herbicides, which utilized horseradish peroxidase-IgG conjugated time-resolved fluorescent nanoparticle probes as both a signal label and amplification tool. With the newly developed LFIA in the DM-f mode, the limits of detection (LODs) were 0.08 ng/mL of acetochlor, 0.29 ng/mL of metolachlor, 0.51 ng/mL of Propisochlor, and 0.13 ng/mL of their mixture. In the DM-i mode, machine learning (ML) algorithms were used for image segmentation, feature extraction, and correlation analysis to obtain multivariate fitted equations, which had high reliability in the regression model with R2 of 0.95 in the range of 2 × 102-2 × 105 pg/mL. Importantly, the practical applicability was successfully validated by determining chloroacetamide herbicides in the corn sample with good recovery rates (85.4 to 109.3%) that correlate well with the regression model. The newly developed dual-mode LFIA with reduced detection time (12 min) holds great potential for pesticide monitoring in equipment-limited environments using a portable test strip reader and laboratory conditions using ML algorithms.

Portable and Flexible Hydrogel Sensor for On-Site Atrazine Assay on Agricultural Products.

There is growing attention focused toward the problems of ecological sustainability and food safety raised from the abuse of herbicides, which underscores the need for the development of a portable and reliable sensor for simple, rapid, and user-friendly on-site analysis of herbicide residues. Herein, a novel multifunctional hydrogel composite is explored to serve as a portable and flexible sensor for the facile and efficient analysis of atrazine (ATZ) residues. The hydrogel electrode is fabricated by doping graphite-phase carbon nitride (g-C3N4) into the aramid nanofiber reinforced poly(vinyl alcohol) hydrogel via a simple solution-casting procedure. Benefiting from the excellent electroactivity and large specific surface area of the solid nanoscale component, the prepared hydrogel sensor is capable of simple, rapid, and sensitive detection of ATZ with a detection limit down to 0.002 ng/mL and per test time less than 1 min. After combination with a smartphone-controlled portable electrochemical analyzer, the flexible sensor exhibited satisfactory analytical performance for the ATZ assay. We further demonstrated the applications of the sensor in the evaluation of the ATZ residues in real water and soil samples as well as the user-friendly on-site point-of-need detection of ATZ residues on various agricultural products. We envision that this flexible and portable sensor will open a new avenue on the development of next-generation analytical tools for herbicide monitoring in the environment and agricultural products.

A lateral strip assay for ultrasensitive detection of glyphosate in soybeans and corn.

Glyphosate (GLY) is widely applied in agriculture and horticulture as a herbicide. The development of genetically modified plants has caused abuse of GLY, with excessive residues potentially causing harm to human health. Consequently, a novel method needs to be built to detect GLY in soybeans and corn. Computer simulation was used to design an excellent hapten which was used to produce an anti-GLY monoclonal antibody (mAb) with outstanding sensitivity and affinity, and its 50%-inhibitory concentration (IC50) was 128.59 ng mL-1. Afterwards, an immunochromatographic assay strip was developed based on the mAb. In soybeans and corn, the visual detection limits were 1 mg kg-1 and 0.2 mg kg-1, while the cut-off values were 50 mg kg-1 and 5 mg kg-1, respectively. The reliability of the strips was proved by the existing methods. Thus, a rapid method to detect GLY residues on-site in soybeans and corn was established.

Advances, limitations, and considerations on the use of vibrational spectroscopy towards the development of management decision tools in food safety.

Food safety and food security are two of the main concerns for the modern food manufacturing industry. Disruptions in the food supply and value chains have created the need to develop agile screening tools that will allow the detection of food pathogens, spoilage microorganisms, microbial contaminants, toxins, herbicides, and pesticides in agricultural commodities, natural products, and food ingredients. Most of the current routine analytical methods used to detect and identify microorganisms, herbicides, and pesticides in food ingredients and products are based on the use of reliable and robust immunological, microbiological, and biochemical techniques (e.g. antigen-antibody interactions, extraction and analysis of DNA) and chemical methods (e.g. chromatography). However, the food manufacturing industries are demanding agile and affordable analytical methods. The objective of this review is to highlight the advantages and limitations of the use of vibrational spectroscopy combined with chemometrics as proxy to evaluate and quantify herbicides, pesticides, and toxins in foods.

Development and validation of two analytical strategies for the determination of glucosides of acidic herbicides in cereals and oilseed matrices.

The aim of the present research was the development and validation of a selective and reliable method for the indirect and direct determination of acidic herbicide glucosides. Enzymatic deconjugation was investigated as a mild alternative to harsh alkaline hydrolysis. Various enzymatic options for deconjugation were exploited. One out of nine tested specific enzymes proved to be practical and repeatable for different matrices and concentration ranges, leading to the complete deconjugation of the glucosides. The method was validated according to the SANTE/11312/2021 guideline for cereals and oilseeds and for a rice-based infant formula. Additionally, for four acidic herbicide glucosides available on the market, a quantitative method for direct determination of the intact glucosides was optimized and validated. In both methods, the average recoveries were within 70-120%. The limits of quantification (LOQ) achieved were 10 µg kg-1 and 2.5 µg kg-1 for the intact glucosides and the free acids in cereal and oilseeds. For the rice-based infant formula, the LOQ was 1 µg kg-1 (3 µg kg-1 for dichlorprop). To confirm its applicability, the deconjugation approach was tested for fifteen samples (cereals, oilseeds, and citrus) with incurred residues. Comparisons were made between the method without deconjugation, and two methods with deconjugation, the here proposed enzymatic deconjugation and the more commonly used alkaline hydrolysis. The inclusion of enzymatic deconjugation during sample preparation led to an increase up to 2.7-fold compared to analysis without deconjugation. Enzymatic deconjugation resulted in comparable results to alkaline hydrolysis for 13 out of 15 samples.

Low-background interference detection of glyphosate, glufosinate, and AMPA in foods using UPLC-MS/MS without derivatization.

The abuse of herbicides has emerged as a great threat to food security. Herein, a low-background interference detection method based on UPLC-MS was developed for the simultaneous determination of glufosinate, glyphosate, and its metabolite aminomethylphosphonic acid (AMPA) in foods. Initially, this study proposed a simple and rapid pretreatment method, utilizing water extraction and PRiME HLB purification to isolate glyphosate, glufosinate, and AMPA from food samples. After the optimization of pretreatment conditions, the processed samples are then analyzed directly by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) without pre-column derivatization. The method can effectively reduce interference from by-products of pre-column derivatization and background substrates of food sample, showing low matrix effects (ME) ranging from - 24.83 to 32.10%. Subsequently, the method has been validated by 13 kinds of food samples. The recoveries of the three herbicides in the food samples range from 84.2 to 115.6%. The limit of detection (LOD) is lower to 0.073 mg/kg, 0.017 mg/kg, and 0.037 mg/kg, respectively. Moreover, the method shows an excellent reproducibility with relative standard deviations (RSD) within 16.9%. Thus, the method can provide high trueness, reproducibility, sensitivity, and interference-free detection to ensure human health safety.

Resistance-gene-directed discovery of a natural-product herbicide with a new mode of action.

Bioactive natural products have evolved to inhibit specific cellular targets and have served as lead molecules for health and agricultural applications for the past century1-3. The post-genomics era has brought a renaissance in the discovery of natural products using synthetic-biology tools4-6. However, compared to traditional bioactivity-guided approaches, genome mining of natural products with specific and potent biological activities remains challenging4. Here we present the discovery and validation of a potent herbicide that targets a critical metabolic enzyme that is required for plant survival. Our approach is based on the co-clustering of a self-resistance gene in the natural-product biosynthesis gene cluster7-9, which provides insight into the potential biological activity of the encoded compound. We targeted dihydroxy-acid dehydratase in the branched-chain amino acid biosynthetic pathway in plants; the last step in this pathway is often targeted for herbicide development10. We show that the fungal sesquiterpenoid aspterric acid, which was discovered using the method described above, is a sub-micromolar inhibitor of dihydroxy-acid dehydratase that is effective as a herbicide in spray applications. The self-resistance gene astD was validated to be insensitive to aspterric acid and was deployed as a transgene in the establishment of plants that are resistant to aspterric acid. This herbicide-resistance gene combination complements the urgent ongoing efforts to overcome weed resistance11. Our discovery demonstrates the potential of using a resistance-gene-directed approach in the discovery of bioactive natural products.

Comparative studies of knapsack, boom, and drone sprayers for weed management in soybean (Glycine max L.).

The study titled, "Comparative Evaluation of Knapsack, Boom, and Drone Sprayers for Weed Management in Soybean (Glycine max L.)" was carried out during the Kharif season 2021-22 at an experimental farm affiliated with the Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. The primary objective was to evaluate the comparative efficacy of various sprayers in controlling weeds in soybeans and their work efficiency. The Randomized Block Design (RBD) included ten treatments of pre-emergence (PE) and post-emergence (POE) herbicides applied by knapsack, boom, and drone sprayers. Pendimethalin 30% EC @ 750 g a.i ha-1 was used for pre-emergence herbicide application, and Imazamox 35% EC + Imazethapyr 35% WG @ 70 g a.i ha-1 were used for post-emergence. These treatments were tested on soybean Monocot and Dicot weed count, weed dry weight, weed index, and weed control efficiency. The sprayers were compared for time, water, labor, herbicide, and overall work efficiency. A knapsack sprayer showed the best results for pre- and post-emergence herbicide application, with the lowest weed count, dry weight, control efficiency, and weed index. Boom and drone sprayers followed in effectiveness. Herbicide application was faster with the drone sprayer than with hand weeding, cultural practices, boom sprayer, and knapsack sprayer. Compared to knapsack and boom sprayers, the drone sprayer used less water and labour. Drone sprayers work most efficiently, followed by boom and knapsack sprayers. This study focuses on the prevalence of herbicides and their impact on non-target ecosystems. It aims to develop mitigation strategies by optimizing spraying efficiency and reducing herbicide usage during pre and post emergence. The dissemination of efficient weed management practices that reduce environmental impacts and increase the efficiency of soybean cultivation is consistent with Sustainable Development Goal 15: life on land.

Herbicide detection: A review of enzyme- and cell-based biosensors.

Herbicides are the most widely used class of pesticides in the world. Their intensive use raises the question of their harmfulness to the environment and human health. These pollutants need to be detected at low concentrations, especially in water samples. Commonly accepted analytical techniques (HPLC-MS, GC-MS, ELISA tests) are available, but these highly sensitive and time-consuming techniques suffer from high cost and from the need for bulky equipment, user training and sample pre-treatment. Biosensors can be used as complementary early-warning systems that are less sensitive and less selective. On the other hand, they are rapid, inexpensive, easy-to-handle and allow direct detection of the sample, on-site, without any further step other than dilution. This review focuses on enzyme- and cell- (or subcellular elements) based biosensors. Different enzymes (such as tyrosinase or peroxidase) whose activity is inhibited by herbicides are presented. Photosynthetic cells such as algae or cyanobacteria are also reported, as well as subcellular elements (thylakoids, chloroplasts). Atrazine, diuron, 2,4-D and glyphosate appear as the most frequently detected herbicides, using amperometry or optical transduction (mainly based on chlorophyll fluorescence). The recent new WSSA/HRAC classification of herbicides is also included in the review.

Recent technologies for glyphosate removal from aqueous environment: A critical review.

The growing demand for food has led to an increase in the use of herbicides and pesticides over the years. One of the most widely used herbicides is glyphosate (GLY). It has been used extensively since 1974 for weed control and is currently classified by the World Health Organization (WHO) as a Group 2A substance, probably carcinogenic to humans. The industry and academia have some disagreements regarding GLY toxicity in humans and its effects on the environment. Even though this herbicide is not mentioned in the WHO water guidelines, some countries have decided to set maximum acceptable concentrations in tap water, while others have decided to ban its use in crop production completely. Researchers around the world have employed different technologies to remove or degrade GLY, mostly at the laboratory scale. Water treatment plants combine different technologies to remove it alongside other water pollutants, in some cases achieving acceptable removal efficiencies. Certainly, there are many challenges in upscaling purification technologies due to the costs and lack of factual information about their adverse effects. This review presents different technologies that have been used to remove GLY from water since 2012 to date, its detection and removal methods, challenges, and future perspectives.

How do glyphosate and AMPA alter the microbial community structure and phosphorus cycle in rice-crayfish systems?

Glyphosate, a commonly used organophosphorus herbicide in rice-crayfish cropping regions, may alter regional phosphorus cycle processes while affecting the structure of microbial communities. However, the effects of glyphosate residues on rice-crayfish systems remain unclear. In this study, we assessed the spatial and temporal distribution characteristics of glyphosate and its primary degradation products, as well as the impact mechanisms of glyphosate on microbial communities and the phosphorus cycle in rice-crayfish systems such as paddy fields, breeding ditches and recharge rivers. The detection rates of glyphosate and aminomethylphosphonic acid (AMPA) were 100% in rice-crayfish systems. Concentrations of glyphosate in the water phase and soil/sediment were as high as 0.012 µg/L and 7.480 µg/kg, respectively, and concentrations of AMPA were as high as 17.435 µg/L and 13.200 µg/kg, respectively. Glyphosate concentrations were not affected by rainfall or sampling site, but concentrations of AMPA in the water phase of recharge rivers were affected by rainfall. The glyphosate concentration was significantly and positively correlated with RBG-16-58-14 abundance, and the AMPA concentration was significantly and positively correlated with Actinobacteria and Lysobacter abundance, and negatively correlated with Cyanobacteria abundance (P < 0.05). The highest abundances of phoD, phnK, and ppx genes were found in all soils/sediments. Glyphosate concentration in soil/sediment was significantly and positively correlated with the abundance of phoD gene encoding an organophosphorus-degrading enzyme and ppx gene encoding poly inorganic phosphate (Pi) hydrolase (P < 0.05). In addition, the glyphosate concentration was significantly and positively correlated with the Ca-bonded Pi content (P < 0.05). This implies that glyphosate may promote the production of stable Pi in rice-crayfish systems by increasing the abundance of phoD and ppx genes. The results of this study reveal the impact mechanism of glyphosate on the phosphorus cycle in rice-crayfish systems and provide a basis for the risk assessment of glyphosate.

Porous poly(bismaleimide-co-divinylbenzene) microspheres as dispersive solid-phase extraction adsorbent coupled to high-performance liquid chromatography for the determination of triazine herbicide residues in vegetable samples.

In this work, monodisperse and nano-porous poly(bismaleimide-co-divinylbenzene) microspheres with large specific surface area (427.6 m2 /g) and rich pore structure were prepared by one-pot self-stable precipitation polymerization of 2,2'-bis[4-(4-maleimidophenoxy) phenyl] propane and divinylbenzene. The prepared poly(bismaleimide-co-divinylbenzene) microspheres were employed as dispersive solid-phase extraction (DSPE) adsorbent for the extraction of triazine herbicides. Under optimized conditions, good linearities were obtained between the peak area and the concentration of triazine herbicides in the range of 1-400 µg/L (R2 ≥ 0.9987) with the limits of detection of 0.12-0.31 µg/L. Triazine herbicides were detected using the described approach in vegetable samples (i.e., cucumber, tomato, and maize) with recoveries of 93.6%-117.3% and relative standard deviations of 0.4%-3.5%. In addition, the recoveries of triazine herbicides remained above 80.7% after being used for nine DSPE cycles, showing excellent reusability of poly(bismaleimide-co-divinylbenzene) microspheres. The adsorption of poly(bismaleimide-co-divinylbenzene) microspheres toward triazine herbicides was a monolayer and chemical adsorption. The adsorption mechanism between triazine herbicides and adsorbents might be a combination of hydrogen bonding, electrostatic interaction, and π-π conjugation. The results confirmed the potential use of the poly(bismaleimide-co-divinylbenzene) microspheres-based DSPE coupled to the high-performance liquid chromatography method for the detection of triazine herbicide residues in vegetable samples.

Evaluation of phosphate insecticides and common herbicides: monitoring and risk assessment in water treatment plant, distribution networks, and underground water wells.

Despite the negative effects that the use of pesticides (such as herbicides and insecticides) have on human health and water resources, a significant portion of the world's agricultural production depends on them. The purpose of this study was to determine selected residual concentrations of pesticides (diazinon, ethion, malathion, alachlor, methyl-parathion, trifluralin, atrazine, chlorpyrifos, and azinphos-methyl) in samples from Shiraz potable water sources. For this purpose, water treatment plant, groundwater wells, treated surface water, and a mixture of groundwater and treated surface water were taken. In addition, statistical and risk analyses (carcinogenic and non-carcinogenic) were used. According to the results, chlorpyrifos with 84.4% had the highest removal efficiency and methyl-parathion with 10% had the lowest removal rate in the Shiraz water treatment plant process. The highest mean concentration was related to azinphos-methyl (1.5 µg/L) and chlorpyrifos (0.59 µg/L) in the groundwater samples. All measured compounds in water source samples were below standard levels, except for chlorpyrifos and azinphos-methyl, which were reported in groundwater above the limit recommended by the Environmental Protection Agency (EPA). The results showed that while the selected pesticides measured had a low non-carcinogenic risk for both adults and children, malathion and trifluralin posed a high carcinogenic risk for adults.

Biomonitoring of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide: A global view.

We conducted a literature review of urinary 2,4-D in populations not associated with a herbicide application. Of the 33 studies identified, the median/mean concentrations were similar for children, adults, and pregnant women regardless of geography. Individuals with highest concentrations may have had opportunities to directly contact 2,4-D outside of an application. Most studies were conducted in populations in North America and did not examine potential sources of 2,4-D, or what factors might influence higher or lower urinary 2,4-D concentrations. In the future, prioritizing the examination of 2,4-D biomonitoring in other regions and collecting information on sources and factors influencing exposures would better our understanding of 2,4-D exposures globally. In all the studies reviewed the concentrations of urinary 2,4-D observed were orders of magnitude below the US regulatory endpoints, suggesting that people are not being exposed to 2,4-D at levels high enough to result in adverse health effects.

Sorption and mobility assessment of tembotrione in soils of upper, trans and middle Gangetic plain zones of India.

The presence of undesired agrochemicals residues in soil and water poses risks to both human health and the environment. The behavior of pesticides in soil depends both on the physico-chemical properties of pesticides and soil type. This study examined the adsorption-desorption and leaching behavior of the maize herbicide tembotrione in soils of the upper (UGPZ), trans (TGPZ) and middle Gangetic plain zones of India. Soil samples were extracted using acetone followed by partitioning with dichloromethane, whereas liquid-liquid extraction using dichloromethane was used for aqueous samples. Residues of tembotrione and its metabolite TCMBA, {2-chloro-4-(methylsulfonyl)-3-[(2,2,2-trifluoroethoxy) methyl] benzoic acid}, were quantified using liquid chromatography-tandem mass spectrometry. The data revealed that tembotrione adsorption decreased with increasing pH and dissolved organic matter but increased with salinity. The maximum adsorption occurred at pH 4, 0.01 m sodium citrate and 4 g/L NaCl, with corresponding Freundlich constants of 1.83, 2.28 and 3.32, respectively. The hysteresis index <1 indicated faster adsorption than desorption. Leaching studies under different flow conditions revealed least mobility in UGPZ soil and high mobility in TGPZ soil, consistent with groundwater ubiquity scores of 4.27 and 4.81, respectively. Soil amendments decreased tembotrione mobility in the order: unamended > wheat straw ash > wheat straw > farm yard manure > compost. The transformation of tembotrione to TCMBA and its mobility in soil columns were also assessed.

Assessing global-warming induced soil organic matter and iron oxides depletion: Empirical insights into sorption and uptake of atrazine by plants.

Recent pesticide use is alarmingly high and unregulated in several parts of the world. Pesticide fate in soil is controlled by sorption processes which affect the subsequent transport and chemical reactivity in the environment, as well as uptake by plants. Sorption processes are dependent on soil composition and properties, but these are beginning to be affected by global warming-linked factors leading to soil depletion. Thus, it is vital to decipher soils' response, especially in the sub-Sahara (SS), to the depletion of some inherent components in the presence of pesticides. This was ascertained by monitoring a model pesticide (atrazine) sorption and desorption on whole SS soil (WS), and the same soil whose organic matter (OMR) and iron oxides (IOR) were substantially depleted, as well as studying atrazine uptake from these soils by fast-growing vegetables. Organic matter depletion enhanced equilibrium in OMR. Sorption was enhanced at lower ambient pH, higher initial atrazine concentration, and higher temperature. Hysteresis was low resulting in high desorption. Overall, atrazine desorption of ≥65 % was observed; it was higher in OMR (≥95 %) since SOM enhanced hysteresis. Though sub-Saharan soils are rich in iron oxides, SOM played a significantly higher role in sorption than iron oxides in this soil. This result suggests a high potential for atrazine to leach into the aquifer in the sub-Saharan. Atrazine uptake experiment by waterleaf and spinach showed that it could be detected in soil after 63 d, and its presence significantly affected the growth of both vegetables especially in soils with depleted SOM and iron oxides, and at high (100 µg/kg) atrazine spiking. Spinach may be a higher atrazine accumulator than waterleaf. It may be concluded that waterleaf and spinach grown on atrazine-contaminated soils, especially on SOM/iron oxide-depleted soils, are likely to accumulate atrazine.

Dissipation behaviours, residues, and health risk of six herbicides in sugar beets under field conditions.

This study established a residue detection method based on the QuEChERS pre-treatment method and combined it with high-performance liquid chromatography-tandem mass spectrometry to test six herbicides (metamitron, clopyralid, desmedipham, phenmedipham, ethofumesate, and haloxyfop-p-methyl) in sugar beet plants, soil, and roots. The degradation dynamics and terminal residues of each herbicide in sugar beets were analysed. Finally, the dietary risks of various herbicides in sugar beets were evaluated based on the dietary structure of Chinese people, and the risk quotient values were below 100%. Using this detection method, all reagents exhibited good linearity (0.9724 ≤ R2 ≤ 0.9998), The limit of quantification (LOQ) ranged from 0.01 to 0.05 mg/L, the matrix effect ranged from -1.2% to -50%, the addition recovery rate ranged from 77.00% to 103.48%, and the relative standard deviation ranged from 1.61% to 16.17%; therefore, all indicators of this method met the residue detection standards. Under field conditions, the half-lives (t1/2) ranged about 0.65 ∼ 2.96 d and 0.38 ∼ 27.59 d in sugar beet plants and soil, respectively. All herbicides were easily degraded in sugar beet plants and soil (t1/2 < 30 d). The terminal residue amounts in the beet plants, soil, and roots ranged from < LOQ to 0.243 mg/kg. The dietary risk assessment of each pesticide was conducted based on the residual median of the terminal residues and the highest residual values on the edible part of the beetroot. The chronic exposure risk quotient (RQc) and acute exposure risk quotient (RQa) values were < 100%, indicating that the residue of each pesticide in beetroot posed low risks to consumers in China at the recommended dosage.

Adsorption-desorption behavior of florpyrauxifen-benzyl on three microplastics in aqueous environment as well as its mechanism and various influencing factors.

Microplastics (MPs) and pesticides are two categories contaminants with proposed negative impacts to aqueous ecosystems, and adsorption of pesticides on MPs may result in their long-range transport and compound combination effects. Florpyrauxifen-benzyl, a novel pyridine-2-carboxylate auxin herbicide has been widely used to control weeds in paddy field, but the insights of which are extremely limited. Therefore, adsorption and desorption behaviors of florpyrauxifen-benzyl on polyvinyl chloride (PVC), polyethylene (PE) and disposable face masks (DFMs) in five water environment were investigated. The impacts of various environmental factors on adsorption capacity were evaluated, as well as adsorption mechanisms. The results revealed significant variations in adsorption capacity of florpyrauxifen-benzyl on three MPs, with approximately order of DFMs > PE > PVC. The discrepancy can be attributed to differences in structural and physicochemical properties, as evidenced by various characterization analysis. The kinetics and isotherm of florpyrauxifen-benzyl on three MPs were suitable for different models, wherein physical force predominantly governed adsorption process. Thermodynamic analysis revealed that both high and low temperatures weakened PE and DFMs adsorption, whereas temperature exhibited negligible impact on PVC adsorption. The adsorption capacity was significantly influenced by most environmental factors, particularly pH, cations and coexisting herbicide. This study provides valuable insights into the fate of florpyrauxifen-benzyl in presence of MPs, suggesting that PVC, PE and DFMs can serve as carriers of florpyrauxifen-benzyl in aquatic environment.

Long-term herbicide residues affect soil multifunctionality and the soil microbial community.

Residues of herbicides with the extensive applications may impact the soil ecosystem and ultimately threaten agricultural sustainability. However, the effects of long-term herbicide residues on soil multifunctionality and the soil microbial community remain poorly understood. Here, we evaluated relationships between soil multifunctionality and soil microbial communities with residual herbicide concentrations by surveying and analyzing 62 black soil samples collected from an agricultural area in northeastern China. Total residual herbicide concentrations varied from 35 to 568 µg/kg in the soil samples. The response of soil multifunctionality to increasing residual herbicide concentrations exhibited an inverted U-shaped relationship with a peak at approximately 310 µg/kg, with net mineralized organic nitrogen (Nm) and total nitrogen (TN) exhibiting the same trend. Microbial community richness was significantly lower in soil samples with high residual herbicide concentrations (> 310 µg/kg, HG) compared to low residual herbicide concentrations (< 310 µg/kg, LG). In addition, the relative abundances of specific keystone microbial genera differed significantly between LG and HG: norank_f_Acetobacteraceae, norank_f_Caldilineaceae, Candidatus_Alysiosphaera, and Gonytrichum. The relative abundances of these genera were also significantly correlated with soil multifunctionality. Structural equation models (SEMs) further showed that herbicide residues influenced soil multifunctionality by affecting these specific keystone genera. Our study demonstrates that long-term herbicide residues significantly impact the multifunctionality of agricultural black soil, where low concentrations stimulate while high concentrations inhibit, underscoring the need for reasonable application of herbicides to maintain soil ecosystem health.