Identifying Plant Stress Responses to Roxarsone in Soybean Root Exudates: New Insights from Two-Dimensional Correlation Spectroscopy

Rapid identification of the aging time of Liupao tea using AI-multimodal fusion sensing technology combined with analysis of tea polysaccharide conjugates

Identifying the aging time of Liupao Tea (LPT) presents a persistent challenge. We utilized an AI-Multimodal fusion method combining FTIR, E-nose, and E-tongue to discern LPT's aging years. Compared to single-source and two-source fusion methods, the three-source fusion significantly enhanced identifying accuracy across all four machine learning algorithms (Decision tree, Random forest, K-nearest neighbor, and Partial least squares Discriminant Analysis), achieving optimal accuracy of 98-100 %. Physicochemical analysis revealed monotonic variations in tea polysaccharide (TPS) conjugates with aging, observed through SEM imaging as a transition from lamellar to granular TPS conjugate structures. These quality changes were reflected in FTIR spectral characteristics. Two-dimensional correlation spectroscopy (2D-COS) identified sensitive wavelength regions of FTIR from LPT and TPS conjugates, indicating a high similarity in spectral changes between TPS conjugates and LPT with aging years, highlighting the significant role of TPS conjugates variation in LPT quality. Additionally, we established an index for evaluating quality of aging, which is sum of three fingerprint peaks (1029 cm-1, 1635 cm-1, 2920 cm-1) intensities. The index could effectively signify the changes in aging years on macro-scale (R2 = 0.94) and micro-scale (R2 = 0.88). These findings demonstrate FTIR's effectiveness in identifying aging time, providing robust evidence for quality assessment.

Climate warming inhibits neonicotinoid photodegradation on vegetable leaves: Important role of the olefin group in leaf wax

Neonicotinoid photodegradation is seldom considered in different vegetable leaves after spraying under climate warming. This study investigated the effect of elevated cultivated temperature from 15/10 °C to 21/16 °C on the photodegradation of dinotefuran, thiamethoxam, acetamiprid, and thiacloprid on four vegetable leaves under simulated sunlight irradiation. The photodegradation rates of neonicotinoids on spinach leaves were 1.1-1.6, 1.1-2.0, and 1.4-2.4 times higher than those on pak choi, Chinese cabbage, and radish leaves, respectively. The higher production concentrations of hydroxyl radicals (•OH) and superoxide radicals in spinach leaf wax may contribute to the fastest photodegradation among four vegetables. When the cultivated temperature increased from 15/10 °C to 21/16 °C, neonicotinoid photodegradation rates decreased by 1.4-2.8 times on the four vegetables. Elevated cultivated temperature decreased the polarity of wax, which reduced the contact probability of neonicotinoids with reactive species on vegetable leaves and photodegradation rates. A positive linear correlation was found between the content of CHCH groups in wax determining •OH generation and the neonicotinoid photodegradation rates on four vegetable leaves cultivated at three temperatures (R² = 0.67-0.94). Insights into neonicotinoid photodegradation on edible vegetables under climate warming are of great significance for better evaluating human exposure to neonicotinoids through the dietary pathway.

Environmental Behavior and Remediation Methods of Roxarsone

Roxarsone (ROX) is used extensively in the broiler chicken industry, and most is excreted in poultry litter. ROX degradation produces inorganic arsenic, which causes arsenic contamination of soil and aquatic environment. Furthermore, elevated arsenic concentrations are found in livers of chickens fed ROX. Microorganisms, light, and ions are the main factors that promote ROX degradation in the environment. The adsorption of ROX on different substances and its influencing factors have also been studied extensively. Additionally, the remediation method, combining adsorption and degradation, can effectively restore ROX contamination. Based on this, the review reports the ecological hazards, discussed the transformation and adsorption of ROX in environmental systems, documents the biological response to ROX, and summarizes the remediation methods of ROX contamination. Most previous studies of ROX have been focused on identifying the mechanisms involved under theoretical conditions, but more attention should be paid to the behavior of ROX under real environmental conditions, including the fate and transport of ROX in the real environment. ROX remediation methods at real contaminated sites should also be assessed and verified. The summary of previous studies on the environmental behavior and remediation methods of ROX is helpful for further research in the future.

Study on effects of airborne Pb pollution on quality indicators and accumulation in tea plants using Vis-NIR spectroscopy coupled with radial basis function neural network

Tea plants that have a large leaf area mainly suffer from heavy metal accumulation in the above-ground parts through foliar uptake. With the world rapid industrialization, this pollution in tea is considered a crucial challenge due to its potential health risks. The present study proposes an innovative approach based on visible and near-infrared (Vis-NIR) spectroscopy coupled with chemometrics for the characterization of tea chemical indicators under airborne lead stress, which can be performed fast and in situ. The effects of lead stress on chemical indicators and accumulation in leaves of the two tea varieties at different time intervals and levels of treatment were investigated. In addition, changes in cell structure and leaf stomata were monitored during foliar uptake of aerosol particles by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The spectral variation was able to classify the tea samples into the Pb treatment groups through the linear discriminant analysis (LDA) model. Two machine learning techniques, namely, partial least squares (PLS) and radial basis function neural network (RBFNN), were evaluated and compared for building the quantitative determination models. The RBFNN models combined with correlation-based feature selection (CFS) and PLS data compression methods were used to optimize the prediction performance. The results demonstrated that the PLS-RBFNN as a non-linear model outperformed the PLS model and provided the R-value of 0.944, 0.952, 0.881, 0.937, and 0.930 for prediction of MDA, starch, sucrose, fructose, glucose, respectively. It can be concluded that the proposed approach has strong application potential in monitoring the quality and safety of plants under airborne heavy metal stress.

Effects of extracellular polymeric substances on silver nanoparticle bioaccumulation and toxicity to Triticum aestivum L

The potential effects of extracellular polymeric substances (EPS) on the behavior and toxicity of silver nanoparticle (Ag-NPs) and silver sulfide nanoparticle (Ag₂S-NPs) remains ambiguous. The interaction of EPS from Bacillus subtilis with Ag₂S-NPs, metallic Ag-NPs, or ionic Ag, and the associated plant safety had been examined in this study. The biological impacts of Ag-NPs and Ag₂S-NPs were Ag form-dependent and highly influenced by microbial EPS. Compared with metallic Ag-NPs, Ag₂S-NPs exert inert biological impacts, as revealed by 3.44 times lower Ag bioaccumulation in wheat (Triticum aestivum L.) seedlings and nearly reduce plant biomass when wheat was subjected to 1.0 mg-Ag L^-1 of Ag-NPs and Ag₂S-NPs with the transfer factors of 151.56-930.87 vs. 12.52-131.81, respectively. These observations were coincident with the low dissolved Ag ([Ag]_diss) in the Ag₂S-NPs treatment than the Ag-NPs treatment (114.0 vs. 0.0791, μg L^-1). Compared with the enhanced toxicity of Ag₂S-NPs to wheat, Bacillus subtilis EPS significantly alleviate the phytotoxicity of Ag-NPs, as revealed by the relative root elongation (7.15-45.40% decrease vs. 2.39-11.75% increase), and malondialdehyde (1.47-83.22% increase vs. 8.57-25.25% decrease) and H₂O₂ (11.27-71.78% increase vs. 5.16-36.67% decrease) contents. These constrasting plant responses of B. subtilis EPS are mainly caused by their complexation property with toxic Ag⁺ and nutrient elements for wheat stressed by Ag-NPs and Ag₂S-NPs, respectively. Our findings highlight the importance of rhizospheric EPS in affecting the biogeochemistry and ecotoxicity of metal nanoparticles including Ag-NPs and Ag₂S-NPs in agricultural systems.

Interaction and coexistence characteristics of dissolved organic matter with toxic metals and pesticides in shallow groundwater

The long-term and large-scale utilization of fertilizers and pesticides in facility agriculture leads to groundwater pollution. However, the coexistence and interactions between organic fertilizers (i.e., organic matter), toxic metals, and pesticides in shallow groundwater have seldom been studied. Thus, the study sought to characterize said interactions via fluorescence, ultraviolet-visible spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy and chemometric techniques. The results indicated that groundwater DOM was comprised of protein-, polysaccharide-, and lignin-like substances derived from organic fertilizers. Protein-like substances accounted for the binding of Co, Ni, and Fe, while polysaccharide- and lignin-like substances were mainly responsible for Cr and Mo complexation. Moreover, lignin- and polysaccharide-like substances played a key role in the binding of pesticides (i.e., dichlorodiphenyltrichloroethane [DDT], endosulfan, γ-hexachlorocyclohexane [γ-HCH], monocrotophos, chlorpyrifos, and chlorfenvinphos), rendering the conversion of γ-HCH to β-hexachlorocyclohexane (β-HCH) and the degradation of DDT to dichlorobenzene dichloroethylene (DDE) ineffective. However, the presence of protein-like substances in groundwater benefited the degradation and conversion of γ-HCH and α-endosulfan. Redundancy analyses showed that lignin- and polysaccharide-like matter had the most impacts on the coexistence of DOM with toxic metals and pesticides.

Interactions between Imidacloprid and Thiamethoxam and Dissolved Organic Matter Characterized by Two-Dimensional Correlation Spectroscopy Analysis, Molecular Modeling, and Density Functional Theory Calculations

The heavy application of neonicotinoid insecticides in agricultural production has burdened the environment. In the present study, interactions of two neonicotinoid insecticides imidacloprid and thiamethoxam with dissolved organic matter (DOM) were investigated by spectroscopic techniques, molecular modeling, and density functional theory (DFT) calculations. The static mechanism of imidacloprid and thiamethoxam quenching the endogenous fluorescence of DOM was assessed through time-resolved analyses. During the binding process, a protein-like substance binds imidacloprid and thiamethoxam later than a humic-like substance, as analyzed by two-dimensional correlation spectroscopy, but more strongly than the humic-like substance, as suggested by molecular modeling and DFT calculations. The conformational changes of DOM are attributed to imidacloprid and thiamethoxam, as assessed with three-dimensional spectra. Fourier transform infrared spectroscopy indicated that DOM binds imidacloprid and thiamethoxam by hydroxyl, aliphatic C-H, amide I, and carboxyl to form stable DOM-imidacloprid and DOM-thiamethoxam complexes. Understanding the changes in the structural conformation of humic-like and protein-like substances with imidacloprid and thiamethoxam helps further understand the fate of the neonicotinoids in the environment.

Arsanilic acid contributes more to total arsenic than roxarsone in chicken meat from Chinese markets

Organoarsenicals have been used in poultry production for years, however, studies focused on roxarsone (ROX), with little attention to p-arsanilic acid (ASA). We assessed arsenic (As) concentration and speciation in chicken meat collected from 10 cities in China. The geometric mean for total As in 249 paired raw and cooked samples was 4.85 and 7.27 μg kg^-1 fw, respectively. Among 81 paired raw and cooked samples, ASA and ROX were detected in >90% samples, suggesting the prevalence of organoarsenical use in China. ASA contributed the most (45% on average) to total As in cooked samples, followed by As(V), DMA, As(III), and ROX (7.2-22%). ASA was found to contribute more to total As in chicken meat compared to ROX for the first time. Arsenic in chicken meat showed considerable geographic variation, with higher inorganic arsenic (iAs) being detected from cities with higher ROX and ASA, indicating that organoarsenical use increased iAs concentration in chicken meat. When health risk was estimated, dietary exposure to iAs would result in an increase of 3.2 bladder and lung cancer cases per 100,000 adults. The result supports the removal of organoarsenicals in poultry production from Chinese market and further supports its removal from the global markets.

Contributions of root cell wall polysaccharides to Cu sequestration in castor (Ricinus communis L.) exposed to different Cu stresses

Cell wall polysaccharides play a vital role in binding with toxic metals such as copper (Cu) ions. However, it is still unclear whether the major binding site of Cu in the cell wall varies with different degrees of Cu stresses. Moreover, the contribution of each cell wall polysaccharide fraction to Cu sequestration with different degrees of Cu stresses also remains to be verified. The distribution of Cu in cell wall polysaccharide fractions of castor (Ricinus communis L.) root was investigated with various Cu concentrations in the hydroponic experiment. The results showed that the hemicellulose1 (HC1) fraction fixed 44.9%-67.8% of the total cell wall Cu under Cu stress. In addition, the pectin fraction and hemicelluloses2 (HC2) fraction also contributed to the Cu binding in root cell wall, accounting for 11.0%-25.9% and 14.1%-26.6% of the total cell wall Cu under Cu treatments, respectively. When the Cu levels were ≤25 μmol/L, pectin and HC2 contributed equally to Cu storage in root cell wall. However, when the Cu level was higher than 25 μmol/L, the ability of the pectin to bind Cu was easy to reach saturation. Much more Cu ions were bound on HC1 and HC2 fractions, and the HC2 played a much more important role in Cu binding than pectin. Combining fourier transform infrared (FT-IR) and two-dimensional correlation analysis (2D-COS) techniques, the hemicellulose components were showed not only to accumulate most of Cu in cell wall, but also respond fastest to Cu stress.