Vegetable Residues Research Articles

Mono e codigestão anaeróbia de resíduos de frutas e vegetais: Efeitos no rendimento de biogás e no biofertilizante

ABSTRACT The proper disposal of fruit and vegetable waste is essential to promote environmental sustainability, reduce the carbon footprint, improve soil quality, and contribute to the transition to a circular economy. This study examined the impact of incorporating dairy cattle wastewater (DCWW) into anaerobic co-digestion with fruit and vegetable residues and utilization of the resulting biofertilizer as a diluent in the anaerobic mono-digestion of fruit and vegetable residues (recycle). The specific biogas and methane production and the agronomic quality of the biofertilizer were evaluated in a semi-continuous trial. Two startup strategies were employed: initially, the reactors were entirely fed with inoculum (biofertilizer derived from DCWW), and fruit and vegetable residue feedstock was gradually introduced. Anaerobic co-digestion of fruit and vegetable residues with DCWW yielded the highest specific production of biogas and methane at 720 and 436 L kg-1 of volatile solids (VS), respectively. The addition of DCWW increases fruit and vegetable residue alkalinity by 249% and reduces the volatile acidity by 83.4%. Anaerobic mono-digestion of fruit and vegetable residues enhances macronutrient recovery in the biofertilizer through recycle. Logistically, directing fruit and vegetable residues to rural areas for anaerobic co-digestion with DCWW promotes agricultural biofertilizer use.

Smartphone-based colorimetric paper chip sensor using single-atom nanozyme for the detection of carbofuran pesticide residues in vegetables

Smartphone-based colorimetric paper chip sensor using single-atom nanozyme for the detection of carbofuran pesticide residues in vegetables

Traffic signal-inspired fluorescence lateral flow immunoassay utilizing self-assembled AIENP@Ni/EC for simultaneous multi-pesticide residue detection

The presence of multiple pesticide residues in fruits and vegetables poses a serious threat to human health. Conventional gold nanoparticles (AuNPs) used in multiplex lateral flow immunoassays (M−LFIA) often exhibit poor sensitivity and potential for misidentification. This study introduces a traffic signal-inspired fluorescent LFIA (T-FLFIA) designed for the simultaneous quantitative detection of chlorothalonil (CTN), paclobutrazol (PBZ), and fipronil (FIP) in cowpea and apple samples. Utilizing the hydrophobic interactions of aggregation-induced emission luminogens (AIEgens) and the coordination of epicatechin (EC) with Ni2+, we developed a novel nanostructure-aggregation-induced emission nanoparticle (AIENP) coated with a metal-polyphenol network of Ni/EC (AIENP@Ni/EC) via a self-assembly method and employed it as fluorescence probe in T-FLFIA. Three distinct colors of AIENP@Ni/EC featuring green, yellow, and red fluorescence were successfully synthesized by coating various AIEgens. This multicolor fluorescence capability facilitates more precise and expedited discrimination among multiple detection targets. High-performance AIE fluorescence probes were fabricated by directly coupling AIENP@Ni/EC with different antibodies through electrostatic interactions, leveraging the exceptional biocompatibility of Ni/EC. The T-FLFIA exhibited sensitive detection of CTN, PBZ, and FIP at concentrations as low as 0.038 ng/mL, 0.025 ng/mL, and 0.046 ng/mL, respectively, with high qualitative accuracy (92.5 %) within a rapid timeframe (5 s). This exceptional performance can be attributed to its outstanding optical properties and distinguishable colors. This approach demonstrated enhanced sensitivity and accuracy, reduced consumption of antibodies and immunoprobes, and a broader detection range compared to single-color AuNPs-M−LFIA. This study introduces a novel, practical, and cost-effective tool for rapid screening of diverse pesticide residues in field settings

Highly sensitive time-resolved fluorescent microspheres lateral flow immunoassay for the quantitative detection of triadimefon and its metabolite residues in fruits and vegetables.

Ageneral one-step lateral flow immunochromatographic assay (LFIA) for the quantitative detection of triadimefon (TDF) and triadimenol(TDN) in fruit and vegetable samples was developedusing time-resolved fluorescence microspheres (TRFM) as labels. A specific anti-triadimefon monoclonal antibody (mAb) was conjugated with TRFM to fabricate LFIA test strips. A time-resolved fluorometer as an LFIA reader was applied to obtain quantitative results and assess risk ranges for the LFIA test strips. Under the optimized experimental conditions, the limits of detection (LODs) in buffer/cucumbers/tomatoes/oranges were 0.046ng/mL, 0.135µg/kg, 1.047µg/kg, and 5.811µg/kg, respectively, which are ca. 1000 times lower than that of colloidal gold-labeled strips. The recovery in cucumber/tomato/orange samples was 109.4-116.7%, 87.7-110.9%, and 88.0-111.9%, respectively, indicating that the test strips had good reliability. Coupled with the easily customizable pretreatment procedures for various samples, the LFIA results were obtained within 18min without the need for professional personnel or complicated equipment. TRFM-LFIA for TDF and TDN also shows remarkable specificity and precision. The test strips were also low-cost, portable, and convenientto use. These results indicate the test strips could be utilized as a novel strategy for on-site detection of TDF and TDN, which has the potential to expand and detect other pesticide or insecticide residues in food.

Levels of chlorpyrifos, ethion, lambda-cyhalothrin, pendimethlin and triazophos pesticide residues in vegetables

Keeping in view the adverse effects of pesticides, due to their excessive uses in crops and storages, a representative study was conducted to evaluate the presence of pesticide residues in vegetables for most frequently used pesticides in the state of Haryana in India. In all, a variety of vegetables were collected as samples from farmers as well as markets located in twenty one districts of Haryana, India for the period of eight years. The extraction of pesticides from vegetable samples was done using QuEChERS method and analysis for commonly used pesticides was done using Gas chromatography–mass spectrometry (GCMS). The analysis of samples showed that approximately one-third of samples were found with detectable presence of pesticide residues. More importantly, the presence of some banned or withdrawn pesticides such as DDT isomers, endosulphan. Furthermore, approximately 40 % of the analyzed samples contained pesticide residues at or below maximum residue level (MRLs) and 16 % of analyzed samples contained pesticide residues above MRLs in terms of commodity groups. Furthermore, residues of Chlorpyrifos were found most often exceeding the Food Safety and Standards Authority of India (FSSAI). Ethion, lambda-cyhalothrin, pendimethlin and triazophos were other pesticides with detected value higher than specified MRL values. Pesticides occurrence in large number of samples need to be "alarming and forcing matter to take appropriate action" to the cause of public health. This study may provide new directions for the application, management and control of pesticides used by farmers.

Assessing the multifaceted repercussions of chemical insecticides on vegetable yield and human population: A modeling study

Vegetables stand out as invaluable reservoirs of essential vitamins, minerals, antioxidants, and vital dietary elements, yet their production faces a considerable threat due to insects. To tackle this challenge, farmers spray chemical insecticides to enhance vegetable yields by controlling the insect population. Nevertheless, the presence of insecticide residues in vegetables stands as a primary contributor to acute illnesses and chronic health conditions in humans. In the present research work, we formulate a novel nonlinear mathematical model meticulously designed to scrutinize the multifaceted repercussions of chemical insecticides on vegetable yield and the human population. In our model formulation, we adopt a dynamic approach where insecticide application on vegetables in agricultural fields correlates with the insect population. However, we acknowledge the consequential impact of insecticide usage on human health, which in turn reduces the growth rate of the human population. This study determines the critical value of the spraying rate of insecticide at which the human population reaches its maximum, ensuring that human needs for vegetables are met while minimizing the adverse effects of insecticide. Since various species of insects attack vegetables in the field and different insect species have different natural mortality rates, therefore we also identify the range of natural mortality rates of insects for which vegetable yield is minimal and fluctuates with time. Further, our research reveals that if the natural mortality rate of insects in a certain crop field lies within this identified range, then farmers should increase the insecticide spraying rate to avoid this upheaval situation and stabilize vegetable yield at a higher level.

Multi-confinement structured carbon dots with long room temperature phosphorescence lifetime and efficiency for sensing thiram residues assisted by copper ions.

Room temperature phosphorescent carbon dots(NCCDs@SiO2) were obtained by encapsulating hydrothermally synthesized CDs in a dense Si-O network structure after high-temperature calcination using silica as the matrix. Thiscan avoid the quenching effect of dissolved oxygen in water and has a phosphorescence lifetime of up to 2.41 s. Using the phosphorescence property of NCCDs@SiO2, a phosphorescence quenching sensor was developed for the sensitive and selective detection of thiram with the assistance of Cu2+. Cu2+-thiram complexesled to a rapid phosphorescence quenching of NCCDs@SiO2 within 30 s through the inner filter effect. The linear range of phosphorescence for thiram was 0.5-100 µM with a detection limit of 0.121 µM. Theproposed method was able to detect thiram in real samples and was validated by high-performance liquid chromatography (HPLC) confirmingthe potential of this phosphorescence sensing method for thiram detection. This work opens up a new avenue for the detection of thiram residues in fruits and vegetables and also provides a new idea for the design of a rapid detection platform using other room temperature phosphorescent materials.

Monitoring and Risk Assessment of Multi-Pesticide Residues in Apples: A Focus on Consumer Safety

Pesticide residues in human diets pose significant health hazards, particularly for vulnerable populations such as infants and children. This study aimed to determine pesticide residues in apples and to assess the cumulatively chronic risk posed to adult and child consumers from simultaneous exposure to multiple residues. During the 2022–2023 harvest seasons, 100 apple samples from Turkey were analyzed for the presence of 225 different pesticide residues. Pesticide extraction was performed using the QuEChERS method, followed by detection through liquid chromatography coupled with tandem mass spectrometry. Fifteen distinct pesticides (ten insecticides and five fungicides) were detected in 64 out of the 100 apple samples analyzed. Eleven samples contained pesticide residues that exceeded the maximum residue limit (MRL) set by the Turkish Food Codex and the European Union. Thiophanate-methyl was the most frequently detected pesticide (34%) in apples, with concentrations ranging from 0.012 to 0.108 mg kg−1, all of which were well below the MRL of 0.5 mg kg−1. Other commonly detected residues included chlorantraniliprole (28%), acetamiprid (24%), sulfoxaflor (22%), bifenazate (18%), indoxacarb (13%), diflubenzuron (12%), and carbendazim (10%). Under a worst-case scenario, the hazard index (HI) values for adults and children were 0.85% and 2.60%, respectively, indicating that these values remain significantly below the risk threshold of 100%, suggesting no associated health risks from apple consumption. However, regular monitoring of pesticide residues in fresh fruits and vegetables remains critically important.

Specific and enzyme-free monitoring of propiconazole pesticide residues in vegetables with a portable nanozyme-based paper sensor

The nanozyme-based colorimetric sensor shows promise for rapid pesticide detection but struggles with non-specific enzyme inhibition. This study developed a portable paper-based sensor for detecting the propiconazole (PC) pesticide using Fe@PCN-224 nanocubes (NCs). Characterization confirmed the successful synthesis of Fe@PCN-224 NCs, which displayed peroxidase-like activity. The specific interaction between PC's triazole ring and the Fe active site inhibited their activity, enabling selective detection with a limit of 8 × 10−9 mol L−1 and a linear range of 0.03 × 10−6 to 0.90 × 10−6 mol L−1. Kinetic studies revealed a Michaelis-Menten constants (Km) of 0.68 × 10−3 mol L−1 for TMB, indicating higher affinity in Fe@PCN-224 NCs. The electron paramagnetic resonance (EPR) analysis revealed the production of •OH, 1O2, O2•− during the catalytic reactions. By integrating smartphone technology, this portable sensor achieved recoveries from vegetable samples between 94.6 % and 109.2 %, demonstrating its potential as an accurate, cost-effective analytical tool for food safety and advancing nanozyme applications.

The rapid detection of pesticide residues in fruits and vegetables using electrochemical methods

To meet global demand, pesticides play a very important role in the control of pests that damage agricultural products. However, overuse of pesticides threatens ecosystems and human health. In recent years, gas chromatography, liquid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, capillary chromatography and capillary electrophoresis have been used in the determination of pesticides. Although these methods are highly specific, highly selective and sensitive, the high value of sophisticated laboratory equipment and tools is a complex and time-consuming process. Because of this, electrochemical sensors and biosensor platforms have become good analytical methods for detecting pesticides due to a number of advantages, including ease of detection of system manufacturing processes, high sensitivity and selectivity. This article describes the methods of manufacturing portable electrochemical sensors for detecting pesticide residues in fruits and vegetables on site, that is, the achievements in recent years in the field of cyclic voltammetry, square wave voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. In addition, detailed information is provided on the basic mechanism and electrochemical sensitivity of these methods. The development of electrochemical methods and real-time monitoring of smartphone technologies, as well as their integration with detection platforms, are discussed. For readers with a scientific and technological focus, this article will provide additional valuable information for understanding the creation of portable electrochemical devices, rapid detection of pesticides, the role of electrochemical sensitive methods and contributing to their further development.

Development of an advanced analytical technique for detecting multiple pesticide residues in vegetables through liquid chromatography tandem mass spectroscopy (LC-MS/MS)

A comprehensive LC-MS/MS method, which employs Positive Electrospray Ionization (PEI) and Multiple Reaction Monitoring (MRM) was developed for the simultaneous determination of 35 pesticides belonging to various chemical classes in tomato, brinjal, chili, and okra samples. Extraction was facilitated using a modified QuEChERS method, which allows efficient sample analysis in a single run. Calibration curves for each pesticide exhibited linearity within the concentration range of 0.0025 to 0.1 µg mL−1, with correlation coefficients ranging from 0.993 to 0.999. Mean recoveries at five fortification levels (0.01 to 0.5 µg kg−1) ranged from 80 to 90%, demonstrating satisfactory precision (RSD < 20%). The matrix effects, mitigated through an optimized cleanup process, were observed within the range of 6.42% to 19.52%. The developed method having the limit of quantification of 0.01 mg kg−1 for all 35 pesticides, proved to be highly sensitive and rapid for multi-residue estimation in diverse vegetable samples. Subsequently, the method was used to analyze the market samples from Varanasi, India, which revealed the presence of pesticides like Chlorpyrifos, Chlorantraniliproleand Indoxacarb in tomato, brinjal, chili and okra. Therefore, the method could be considered as a robust tool for monitoring pesticide residues in vegetables, aiding in quality assessment and regulatory compliance in the agriculture sector.

NiCoFeS/rGO nanozyme-mediated multifunctional homogeneous sensing system for ultrasensitive electrochemical assay of pesticides residues in fruits and vegetables

In this work, a homogeneous sensing platform was constructed for ultrasensitive electrochemical organophosphate pesticides (OPs) detection based on nano-enzyme NiCoFeS/rGO with high peroxidase-like activity. In the presence of H2O2, NiCoFeS/rGO catalyst oxidized o-phenylenediamine (OPD) to produce yellow OPDox with strong absorbance and reduction peak current. This activity could be inhibited by thiocholine (TCh) produced by acetylcholinesterase (AChE). However, presence of organophosphates (OPs) could inhibit AChE and reduce TCh production, enabling protect the peroxidase-like activity of NiCoFeS/rGO. So, according to the increased signal of OPDox, the content of OPs could be measured by colorimetric or electrochemical mode. Using electrochemical analysis mode and optimizing experimental conditions, the detection limit was low (9.74fg mL−1) and the linear range was wide (12.5fg mL−1-1.25 ng mL−1). The selectivity, stability reproducibility and practicability of the method were investigated. At the same time, the analysis results of colorimetric and electrochemical method for AChE and colorimetric method for OPs were preliminarily determined, respectively.

Emulsifying properties of cellulose nanocrystals with different structures and morphologies from various solanaceous vegetable residues

The stems of solanaceous vegetables with attractive source of cellulose, have caused severe environmental problems as agricultural residues. For the reutilization of the residues, this study isolated cellulose nanocrystals (CNs) from the stems of tomato, eggplant, and pepper to explore their applications in Pickering emulsions. Detailed analyses of the crystalline structure and morphology revealed differences in their emulsifying properties. Tomato stem CNs had higher crystallinity of 82.1 % and a short, straight rod-like shape with a low aspect ratio of 8.0, while eggplant and pepper CNs were long, curved whisker-like fibers with lower crystallinities of 75.3 % and 75.4 %, respectively. Tomato stem CNs exhibited the best emulsifying properties, attributed to their relatively higher crystallinity and larger crystal brick size enhancing amphiphilicity, along with their lower aspect ratio improving interface coverage, which resulted in stable emulsions across different temperatures, pH levels, and ionic strengths. This study enhances our understanding of how the structure and morphology of CNs influence their emulsifying properties, thereby contributing to the promotion of agricultural waste reutilization.

The Valorization of Fruit and Vegetable Wastes Using an Anaerobic Fixed Biofilm Reactor: A Case of Discarded Tomatoes from a Traditional Market

Tomato waste, characterized by high organic matter and moisture content, offers a promising substrate for anaerobic digestion, though rapid acidification can inhibit methanogenic activity. This study investigated the performance of a 10.25 L anaerobic fixed biofilm reactor for biogas production using liquid tomato waste, processed through grinding and filtration, at high organic loading rates, without external pH control or co-digestion. Four scouring pads were vertically installed as a fixed bed within a fiberglass structure. Reactor performance and buffering capacity were assessed over three stages with progressively increasing organic loading rates (3.2, 4.35, and 6.26 gCOD/L·d). Methane yields of 0.419 LCH4/gCOD and 0.563 LCH4/g VS were achieved during the kinetic study following stabilization. Biogas production rates reached 1586 mL/h, 1804 mL/h, and 4117 mL/h across the three stages, with methane contents of 69%, 65%, and 72.3%, respectively. Partial alkalinity fluctuated, starting above 1500 mg CaCO3/L in Stage 1, dropping below 500 mg CaCO3/L in Stage 2, and surpassing 3000 mg CaCO3/L in Stage 3. Despite periods of forced acidification, the system demonstrated significant resilience and high buffering capacity, maintaining stability through hydraulic retention time adjustments without the need for external pH regulation. The key stability indicators identified include partial alkalinity, effluent chemical oxygen demand, pH, and one-day cumulative biogas. This study highlights the effectiveness of anaerobic fixed biofilm reactors in treating tomato waste and similar fruit and vegetable residues for sustainable biogas production.

Neonicotinoid residues in fruits and vegetables in Shenzhen: Assessing human exposure and health risks

The extensive use of neonicotinoids (NEOs) in agricultural production has led to their pervasive presence in various environmental matrices, including human samples. Given the central role of fruits and vegetables in daily human diets, it is crucial to evaluate the levels of NEOs residues and their potential health risks. In this study, 3104 vegetable samples and 1567 fruit samples from the Shenzhen city were analyzed. Using the relative potency factor (RPF) method, the residue levels of six representative neonicotinoids, including imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (THM), dinotefuran (DIN), clothianidin (CLO), thiacloprid (THI), were systematically evaluated. The estimated daily intake (EDI), hazard quotient (HQ), and hazard index (HI) for both children and adults were calculated to gauge the prevalence and potential health risks of NEOs in fruits and vegetables. Acetamiprid (ACE) was the most frequently detected NEO in vegetables (69.4%) and fruits (73.9%), making it the predominant contributor to total residues. Further analyses indicated notably higher levels of imidacloprid-equivalent total neonicotinoids (IMIRPF) in root and tuber vegetables (3025 μg/kg) and other fruits (243 μg/kg). A significant strong positive correlation (r = 0.748, P < 0.05) was observed between thiamethoxam (THM) and clothianidin (CLO), possibly due to their shared metabolic pathways. Although the mean HI values for adults and children from daily fruit (adults: 0.02, children: 0.01) and vegetable (adults: 0.02, children: 0.03) intake were generally below safety thresholds, some maximum HI values exceeded these limits, indicating that the potential health risks associated with NEOs exposure should not be overlooked.

A Fungicide, Fludioxonil, Formed the Polyploid Giant Cancer Cells and Induced Metastasis and Stemness in MDA-MB-231 Triple-Negative Breast Cancer Cells.

Fludioxonil, an antifungal agent used as a pesticide, leaves a measurable residue in fruits and vegetables. It has been identified to cause endocrine disruption, interrupt normal development, and cause various diseases such as cancers. In this study, fludioxonil was examined for its effects on the development and metastasis of breast cancer cells. On fludioxonil exposure (10-5 M) for 72 h, mutant p53 (mutp53) MDA-MB-231 triple-negative breast cancer (TNBC) cells significantly inhibited cell viability and developed into polyploid giant cancer cells (PGCCs), with an increase in the number of nuclei and expansion in the cell body size. Fludioxonil exposure disrupted the normal cell cycle phase ratio, resulting in a new peak. In addition, PGCCs showed greater motility than the control and were resistant to anticancer drugs, i.e., doxorubicin, cisplatin, and 5-fluorouracil. Cyclin E1, nuclear factor kappa B (NF-κB), and p53 expressions were remarkably increased, and the expression of cell cycle-, epithelial-mesenchymal-transition (EMT)-, and cancer stemness-related proteins were increased in the PGCCs. The daughter cells obtained from PGCCs had the single nucleus but maintained their enlarged cell size and showed greater cell migration ability and resistance to the anticancer agents. Consequently, fludioxonil accumulated Cyclin E1 and promoted the inflammatory cytokine-enriched microenvironment through the up-regulation of TNF and NF-κB which led to the transformation to PGCCs via abnormal cell cycles such as mitotic delay and mitotic slippage in mutp53 TNBC MDA-MB-231 cells. PGCCs and their daughter cells exhibited significant migration ability, chemo-resistance, and cancer stemness. These results strongly suggest that fludioxonil, as an inducer of potential genotoxicity, may induce the formation of PGCCs, leading to the formation of metastatic and stem cell-like breast cancer cells.

Biodegradation of Cyromazine by Mycobacterium sp. M15: Performance, Degradation Pathways, and Key Enzymes.

Cyromazine, a triazine insecticide, raises food safety concerns due to residues in vegetables like cowpeas. Microbial metabolism is key for pesticide elimination, but bacteria efficient in cyromazine degradation are limited, with uncharacterized enzymes. This study isolated a highly efficient cyromazine-degrading bacterium, Mycobacterium sp. M15, from a cowpea field. M15 utilized cyromazine as the sole carbon source for its growth and completely degraded 0.5 mM cyromazine within 24 h. The degradation pathway involved hydrolyzing cyromazine to N-cyclopropylammeline and further to N-cyclopropylammelide, with amino groups removed sequentially. The cyclopropylamine group in N-cyclopropionamide continued to hydrolyze to cyanuric acid. A protein, CriA, identified as an aminohydrolase in M15, degraded cyromazine to N-cyclopropylammeline. Using CriA reduced cyromazine residues on cowpea surfaces and completely degraded them in immersion solutions. These findings offer insights into cyromazine's microbial degradation mechanism and highlight the potential of cyromazine-degrading enzymes in enhancing food safety.

Determination of hexachlorophene residue in fruits and vegetables by ultra-high performance liquid chromatography-tandem mass spectrometry.

A modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) -LC-MS/MS method was developed for the determination of hexachlorophene in fruits and vegetables. Samples were extracted by acetonitrile and then salted with an acetate buffer system. Extractants neutral alumina (Al-N), strong cation exchange silica gel bonded adsorbent (SCX) and graphitized carbon black (GCB) were used for sample purification. The method demonstrates excellent accuracy and reproducibility. Under optimized conditions, the correlation coefficients of hexachlorophene were higher than 0.995 in the range of 0.5-20 ng/mL. The limit of quantification (LOQ) was 2.0 μg/kg. The average recoveries, assessed at three spiked levels (2.0, 4.0, and 20.0μg/kg) across various matrices including cabbage, celery, tomato, eggplant, potato, radish, cowpea, chives, apple, peach, grape, citrus, bitter melon, banana and hami melon ranged from 72.0 to 100.5% with relative standard deviations from 3.2 to 9.8% (n = 6).

Easily overlooked petiole traits are key factors that affect soil carbon sequestration in plantations in karst areas

Vegetation restoration in karst areas has shifted from expanding planting areas to the collective enhancement of various ecological functions, especially carbon sequestration. Identifying and regulating key plant functional traits involved in the carbon cycle is an effective approach to increase carbon sequestration. However, reports on the significant contribution of petiole traits to the carbon cycle are scarce. Eucalyptus globulus and Bauhinia purpurea plantations in Liujiang river basin were investigated in this study. Petiole traits, understory characteristics, and soil organic carbon have been measured. The aim is to explore key effect of petiole traits for increasing soil carbon sequestration and to provide scientific evidence for the high-quality development of plantations in karst areas. The results indicate that in Eucalyptus globulus plantations, when the understory vegetation coverage is below 50 %, petioles tend to elongate rather than thicken, leading to an increase in specific petiole length. In Bauhinia purpurea plantations, petioles consistently tend to increase diameter. However, when specific leaf area decreases, specific petiole length increases. In both plantations, an increase in specific petiole length accelerates leaf shedding. It leads to increased litter accumulation so that soil carbon content increases. In Eucalyptus globulus plantations, to enhance soil carbon sequestration as an ecological goal, it is recommended to keep the soil total nitrogen below 1.20 mg/g, to control understory vegetation coverage below 50 %, and to limit the extension of Bidens pilosa. In Bauhinia purpurea plantations, within 100 m of altitude, the soil total nitrogen can be controlled below 1.00 mg/g to increase soil organic carbon from large leaf shedding due to the increase of specific petiole length. At lower altitudes, increasing soil total nitrogen can enhance understory vegetation coverage, allowing soil organic carbon to originate from both leaf shedding and understory vegetation residues.

Synthesis of metal framework-modified carbon dots with super large stokes shift using Hami melon as a green precursor for detecting thiophanate-methyl residue in leafy vegetables

Consuming leafy vegetables with excessive thiophanate-methyl (TM) residue poses serious risks to human health. To realize rapidly and sensitively detecting TM in leafy vegetables, we developed a fluorescent probe based on zeolitic imidazolate framework-8-modified carbon dots using Hami melon as the green precursor (HM-CDs@ZIF-8). Meanwhile, the mechanism of HM-CDs@ZIF-8 for detecting TM was investigated and explained. The results of the performance tests showed that the prepared HM-CDs@ZIF-8 exhibited high sensitivity, excellent selectivity, robust anti-interference capability, reliable reproducibility and repeatability, and long-term stability. After optimization experiments, the fluorescence intensity of HM-CDs@ZIF-8 showed a strong linear correlation with the concentration of TM (0.00171–3.4239 mol/L) with a detection limit of 2.025 μmol/L. The HM-CDs@ZIF-8 was successfully applied to determine TM in spiked leafy vegetables with satisfactory recoveries of 96–105%. The relative standard deviations were in the range of 0.26–2.55%. The sensor has a promising application for detecting TM in leafy vegetables.