Chiroptically active copper clusters as platform for enantioselective detection of lysine.

Metal clusters have drawn considerable research attention over the years due to their fascinating optical properties. Owing to their appealing photophysical characteristics, these materials have drawn attention as potential candidates for various application in diverse fields, including disease detection, biosensing, chemical sensing, and the fabrication of light-harvesting materials. Presently, there is an increasing research focus on the use of clusters in biomedical research, both as biodetection platform and as bioimaging agents. Of special interest are chiral clusters, which can selectively interact with chiral biomolecules owing to their optical activity. Herein, we showcase the use of a pair of chiroptically active copper clusters for the enantioselective detection of lysine, an amino acid of vast biological relevance. Two techniques are concurrently employed for the detection of lysine at varying concentrations. Circular dichroism serves as a potent tool for detecting lysine at low concentrations, whereas luminescence is effectively employed as a detection method for high analyte concentrations. The combined electronic impact of clusters and lysine resulted in the emergence of an enhanced enantioselective Cotton effect at specific wavelength.

Comparison of Techniques for the Quantitation of Reductive Aroma Compounds in White Wine: Links to Sensory Analysis and Cu Fractions.

Multiple analytical methodologies allow quantitation of H2S and methanethiol (MeSH) in wine, but confirmation that the determined concentrations are related to perceived off-aromas, or "reductive" faults, is yet to be provided. Fifty white wines underwent sensory evaluation and measurement of free and salt-treated H2S and MeSH concentrations by gas chromatography with sulfur chemiluminescence detection and/or gas detection tubes. The determined concentrations were compared across techniques and different analysis laboratories. Sulfhydryl off-odors in the wines were best described by boiled and rotten egg and natural gas/sewerage/durian aroma attributes. The wines with the highest ratings for both aromas had high concentrations of free H2S, free MeSH, and/or salt-treated MeSH but were unrelated to salt-treated H2S. The free sulfhydryl concentrations and their associated aromas appeared to be suppressed by specific Cu fractions in the wines. This study provides evidence of the relevant measures of reductive aroma compounds and their relation to off-odors and Cu fractions.

Advancing Simultaneous Extraction and Sequential Single-Particle ICP-MS Analysis for Metallic Nanoparticle Mixtures in Plant Tissues.

Engineered nanoparticles (ENPs) have been increasingly used in agricultural operations, leading to an urgent need for robust methods to analyze co-occurring ENPs in plant tissues. In response, this study advanced the simultaneous extraction of coexisting silver, cerium oxide, and copper oxide ENPs in lettuce shoots and roots using macerozyme R-10 and analyzed them by single-particle inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, the standard stock suspensions of the ENPs were stabilized with citrate, and the long-term stability (up to 5 months) was examined for the first time. The method performance results displayed satisfactory accuracies and precisions and achieved low particle concentration and particle size detection limits. Significantly, the oven drying process was proved not to impact the properties of the ENPs; therefore, oven-dried lettuce tissues were used in this study, which markedly expanded the applicability of this method. This robust methodology provides a timely approach to characterize and quantify multiple coexisting ENPs in plants.

Industrial hemp (Cannabis sativa L.) can utilize and remediate soil strongly contaminated with Cu, As, Cd, and Pb by phytoattenuation.

Industrial hemp (Cannabis sativa L.) has great application potential in heavy metal-polluted soils owing to its safe non-food utilization. However, the fate of heavy metals in different varieties of hemp planted in strongly contaminated natural soils remains unknown. Here, we investigated the growth, heavy metal uptake, distribution, and transfer of nine hemp varieties in soils strongly contaminated with Cu, As, Cd, and Pb. Hemp variety and metal type were the main factors affecting the growth and heavy metal uptake in hemp. The nine hemp varieties grew well in the contaminated soils; however, differences existed among the varieties. The biomass of Z3 reached 5669.1 kg hm-1, whereas that of Yunma No. 1 was only 51.8 % of Z3. The plant height, stalk diameter, and stalk bark thickness of Z3 were greater than those of the other varieties, reaching 168 cm, 9.2 mm, and 0.56 mm, respectively. Permanova's analysis revealed that the total effects of Cu, As, Cd, and Pb on the growth of the nine hemp varieties reached 60 %, with leaf As having the greatest effect, reaching 16 %. , Even in strongly contaminated soils, the nine varieties showed poor Cu, As, Cd, and Pb uptake. Most of the Cu, As, Cd, and Pb were retained in the root, reaching 57.7-72.4, 47.6-64.7, 76.0-92.9, and 70.0-87.8 %, respectively. Overall, the Cu, As, Cd, and Pb uptake of Wanma No.1 was the highest among the nine varieties, whereas that of Guangxi Bama was the lowest. These results indicate that hemp is a viable alternative for phytoattenuation in soils contaminated with heavy metals because of its ability to tolerate and accumulate Cu, As, Cd, and Pb in its roots, and Guangxi Bama is superior to the other varieties considering the safe utilization of hemp products.

Two {CuI[P4Mo6]2}-Based Coordination Polymers Incorporating In Situ Converted Tetrapyridyl Ligands for Trace Analysis of Nitrofuran Antibiotics.

Nitrofurans are important synthetic broad-spectrum antibacterial drugs with the basic structure of 5-nitrofuran. Due to their toxicity, it is essential to develop a sensitive sensor with strong anti-interference capabilities for their detection. In this work, two {P4Mo6O31}12--based compounds, [H4(HPTTP)]2{CuI[Mo12O24(OH)6(PO4)3(HPO4)(H2PO4)4]}·xH2O (x = 13 for (1), 7 for (2); HPTTP = 4,4',4″,4‴-(1H-pyrrole-2,3,4,5-tetrayl)tetrapyridine), exhibiting similar coordination but distinct stacking modes. Both compounds were synthesized and used for the electrochemical detection of nitrofuran antibiotics. The tetrapyridine-based ligand was generated in situ during assembly, and its potential mechanism was discussed. Composite electrode materials, formed by mixing graphite powder with compounds 1-2 and physically grinding them, proved to be highly effective in the electrochemical trace detection of furazolidone (FZD) and furaltadone hydrochloride (FTD·HCl) under optimal conditions. Besides, the possible electrochemical detection mechanisms of two nitro-antibiotics were studied.

Mobility, bioavailability and distribution of Fe and Cu in mangroves (Avicennia schaueriana and Rhizophora mangle) from a semiarid coast in NE Brazil.

Mangroves buffer metals transfer to coastal areas though strong accumulation in sediments making necessary to investigate metals' bioavailability to plants at the rhizosphere. This work evaluates the effect of mangrove root activity, through iron plaque formation, on the mobility of iron and copper its influence on metals' uptake, and translocation through simultaneous histochemical analysis. The Fe2+ and Fe3+ contents in porewaters ranged from 0.02 to 0.11 µM and 1.0 to 18.3 µg.l-1, respectively, whereas Cu concentrations were below the method's detection limit (<0.1 µM). In sediments, metal concentrations ranged from 12,800 to 39,500 µg.g-1 for total Fe and from 10 to 24 µg.g-1 for Cu. In iron plaques, Cu concentrations ranged from 1.0 to 160 µg.g-1, and from 19.4 to 316 µg.g-1 in roots. Fe concentrations were between 605 to 36,000 µg.g-1 in the iron plaques and from 2,100 to 62,400 µg.g-1 in roots. Histochemical characterization showed Fe3+ predominance at the tip of roots and Fe2+ in more internal tissues. A. schaueriana showed significant amounts of Fe in pneumatophores and evident translocation of this metal to leaves and excretion through salt glands. Iron plaques formation was essential to the Fe and Cu regulation and translocation in tissues of mangrove plants.

Construction of a novel flavonol fluorescent probe for copper (II) ion detection and its application in actual samples.

Copper is an essential trace element in the human body, and its level is directly related to many diseases. While the source of copper in human body is mainly intake from food, then the detection of copper ions (Cu2+) in food becomes crucial. Here, we synthesized a novel probe (E)-3-hydroxy-2-styryl-4H-benzo[h]chromen-4-one (NSHF) and explored the binding ability of NSHF for Cu2+ using nuclear magnetic resonance hydrogen spectroscopy (1H NMR), high-resolution mass spectrometry (HRMS), Job's plot method and density functional theory (DFT). NSHF shows the advantages of fast response time, good selectivity and high sensitivity for Cu2+. The fluorescence intensity ratio (F/F0) of NSHF shows a good linear relationship with the concentration of Cu2+ and the detection limit is 0.061 µM. NSHF was successfully applied to the detection of Cu2+ in real samples. In addition, a simple and convenient Cu2+ detection platform was constructed by combining NSHF with a smartphone and a UV lamp, which can realize the rapid detection of Cu2+. This work provides an effective tool for the real-time detection of Cu2+.

Synergistic optical sensing: Selective colorimetric analysis of copper in environmental and biological samples.

A groundbreaking optical sensing membrane has been engineered for the accurate assessment of copper ions. The pliable poly(vinyl chloride) membrane is formulated through the integration of sodium tetraphenylborate (Na-TPB), 4-(2-hydroxy-4-nitro azobenzene)-2-methyl-quinoline (HNAMQ), and tri-n-octyl phosphine oxide (TOPO), in conjunction with o-nitrophenyl octyl ether (o-NPOE). The sensor membrane undergoes a thorough investigation of its composition to optimize performance, revealing that HNAMQ serves a dual role as both an ionophore and a chromoionophore. Simultaneously, TOPO contributes to enhancing the complexation of HNAMQ with copper ions. Demonstrating a linear range for Cu2+ ions spanning from 5.0 × 10-9 to 7.5 × 10-6 M, the proposed sensor membrane showcases detection and quantification limits of 1.5 × 10-9 and 5.0 × 10-9 M, respectively. Rigorous assessments of potential interferences from other cations and anions revealed no observable disruptions in the detection of Cu2+. With no discernible HNAMQ leaching, the membrane demonstrates rapid response times and excellent durability. The sensor exhibits remarkable selectivity for Cu2+ ions and can be regenerated through exposure to 0.05 M EDTA. Successful application of the sensor in determining the presence of Cu2+ in biological (blood, liver and meat), soil, food (coffee, black tea, sour cherry juice, black currant, and milk powder) and environmental water samples underscores its efficacy.

Simple and sensitive determination of Cr (III), Cu (II) and Pb (II) in tea infusions using AgNPs-modified resin combined with laser-induced breakdown spectroscopy.

The detection of heavy metals in tea infusions is important because of the potential health risks associated with their consumption. Existing highly sensitive detection methods pose challenges because they are complicated and time-consuming. In this study, we developed an innovative and simple method using Ag nanoparticles-modified resin (AgNPs-MR) for pre-enrichment prior to laser-induced breakdown spectroscopy for the simultaneous analysis of Cr (III), Cu (II), and Pb (II) in tea infusions. Signal enhancement using AgNPs-MR resulted in amplification with limits of detection of 0.22 µg L-1 for Cr (III), 0.33 µg L-1 for Cu (II), and 1.25 µg L-1 for Pb (II). Quantitative analyses of these ions in infusions of black tea from various brands yielded recoveries ranging from 83.3% to 114.5%. This method is effective as a direct and highly sensitive technique for precisely quantifying trace concentrations of heavy metals in tea infusions.

CoMnOx Nanoflower-Based Smartphone Sensing Platform and Virtual Reality Display for Colorimetric Detection of Ziram and Cu2.

Transition metal doping is an ideal strategy to construct multifunctional and efficient nanozymes for biosensing. In this work, a metal-doped CoMnOx nanozyme was designed and synthesized by hydrothermal reaction and high-temperature calcination. Based on its oxidase activity, an "on-off-on" smartphone sensing platform was established to detect ziram and Cu2+. The obtained flower-shaped CoMnOx could exhibit oxidase-, catalase-, and laccase-like activities. The oxidase activity mechanism of CoMnOx was deeply explored. O2 molecules adsorbed on the surface of CoMnOx were activated to produce a large amount of O2·-, and then, O2·- could extract acidic hydrogen from TMB to produce blue oxTMB. Meanwhile, TMB was oxidized directly to the blue product oxTMB via the high redox ability of Co species. According to the excellent oxidase-like activity of CoMnOx, a versatile colorimetric detection platform for ziram and Cu2+ was successfully constructed. The linear detection ranges for ziram and Cu2+ were 5~280 µM and 80~360 µM, and the detection limits were 1.475 µM and 3.906 µM, respectively. In addition, a portable smartphone platform for ziram and Cu2+ sensing was established for instant analysis, showing great application promise in the detection of real samples including environmental soil and water.

Thienopyrimidine-derived multifunctional fluorescence sensor for the detection of Cu2+, Fe3+, and PPi in different solvents.

Hydrazine substituted thienopyrimidine, a new fluorophore, was used to synthesize a novel Schiff base R1 as a chemosensor via the condensation with p-formyltriphenylamine, and the structure was confirmed using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) analysis. When treated with Cu2+ in dimethylsulfoxide (DMSO)/H2O buffer, R1 showed a phenomenon of fluorescence quenching, which was reversible with the action of ethylenediaminetetraacetic acid (EDTA). When treated with Fe3+ in dimethylformamide (DMF)/H2O buffer, R1 exhibited the same phenomenon, but fluorescence was recovered with inorganic pyrophosphate (PPi) quantitatively. The complexation ratios for R1-Cu2+ and R1-Fe3+ were both 1:2, which were manifested by MS titrations and corresponding Job's plots. The limits of detection of R1 for Cu2+ and Fe3+ were 3.11 × 10-8 and 1.24 × 10-7 M, respectively. The sensing mechanism of R1 toward Cu2+ and Fe3+ was confirmed using density functional theory calculations and electrostatic potential analysis. Test strips of R1 were fabricated successfully for on-site detection of Cu2+ and Fe3+. In addition, R1 was applied to recognize Cu2+ and Fe3+ in actual water samples with satisfactory recovery.

Semi-quantitative and visual detection of Cu2+ and glyphosate in real samples and living cells using fluorescent and colorimetric dual-signals peptide-based probe.

The excessive emission of copper ions (Cu2+) and the abuse of glyphosate (Glyp) have caused serious harm to the ecological environment and human health, so it is important to develop a fast and convenient method for the analysis of Cu2+ and glyphosate to ensure environmental and food safety. Herein, a dual-signals peptide-based probe (FASRH) with fluorescent and colorimetric was prepared using 5-carboxyl fluorescein modified tetrapeptide (Ala-Ser-Arg-His-NH2). FASRH was successfully used to recognize Cu2+ as a fluorescence "on-off" probe, forming the FASRH-Cu2+ complex with non-fluorescence. As a new promising cascade probe, FASRH-Cu2+ complex probe has high selectivity (only Glyp), good sensitivity (50.2 nM), good anti-interference ability and wide pH range (7.0-11.0) for the detection of glyphosate by ligand replacement method. In addition, the recognizable color changed markedly under 365 nm UV light and natural light. Notably, FASRH not only achieved accurate monitoring of Cu2+ and glyphosate in two real water samples, but also successfully applied to detect Cu2+ and glyphosate in live Hacat cells based on low cytotoxicity. Moreover, it is worth noting that FASRH-impregnated test strips exhibited significant fluorescence and colorimetric color changes for Cu2+ and glyphosate via naked eye. Furthermore, smartphone-assisted FASRH was used for the portable detection of Cu2+ and glyphosate based on the advantages of simplicity, low cost and fast response.

The highly selective and sensitive fluorescence probe for detection of copper (II) ions and its bioimaging in vitro and vivo.

We designed and developed the probe W-3 for detection of Cu2+. The results showed probe can selectively detect Cu2+, accompanied by noticeable color change. The probe can detect the Cu2+ in water samples and drinks based on absorption detection. In addition, the combination of portable test paper and the smartphone platform obtained great convenience for on-site and visual detection of Cu2+, with satisfactory sensitivity and reliability. More importantly, the fluorescence probe W-3 can be used for the detection of Cu2+ in cells and mice. Therefore, the W-3 provided potential chemical tools for detecting Cu2+ in vitro and vivo.

Commercially available mouthguards: Unearthing trace elements for the first time.

The use of mouthguards is advocated by the American Dental Association for orofacial injury prevention and teeth protection. However, the chemical environment in the mouth may cause harmful substances within the mouthguard's polymer material to leach out and be absorbed by the user. Considering this, the present study for the first time analyzed commercially available mouthguards and disclosed the presence of trace elements. Specifically, an analytical method was developed based on closed-vessel microwave-assisted digestion and plasma-based atomic spectrometry for determining toxic trace elements in mouthguard samples. Initially, 75 elements were assessed and, thereafter, quantified cadmium (Cd), copper (Cu) and lead (Pb) in each sample by inductively coupled plasma mass spectrometry (ICP-MS). Method validation was carried out by analyzing a certified reference material of Low-Density Polyethylene, and by addition and recovery experiments. Results for copper were further validated by ICP optical emission spectrometry (ICP-OES). While most samples exhibited elemental levels beneath the method's limit of quantification, Cd, Cu and Pb were detected in four samples. Remarkably, one sample had Cu levels exceeding safe limits by 109 times, highlighting potential toxicity risks. This initial research underscores the need for stricter contamination control in mouthguard materials to minimize potentially health hazards.

Heterocyclic fluorescent Schiff base chemosensors for the detection of Fe(III) and Cu(II) ions.

Two new Schiff bases were synthesized from 1-(2,4-dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV-Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6-31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation-recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4-(1-(pyridin-4-ylimino)ethyl)benzene-1,3-diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4'-((pyridine-2,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)-chelation-enhanced fluorescence (CHEF) effect and chelation-enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 × 10-6 and 2.16 × 10-7 M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 × 10-4 M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells.

A Water-Soluble Wavy Coordination Polymer of Cu(II) as a Turn-On Luminescent Probe for Histidine and Histidine-Rich Proteins/Peptides.

Histidine plays an essential role in most biological systems. Changes in the homeostasis of histidine and histidine-rich proteins are connected to several diseases. Herein, we report a water-soluble Cu(II) coordination polymer, labeled CuCP, for the fluorimetric detection of histidine and histidine-rich proteins and peptides. Single-crystal structure determination of CuCP revealed a two-dimensional wavy network structure in which a carboxylate group connects the individual Cu(II) dimer unit in a syn-anti conformation. The weakly luminescent and water-soluble CuCP shows turn-on blue emission in the presence of histidine and histidine-rich peptides and proteins. The polymer can also stain histidine-rich proteins via gel electrophoresis. The limits of quantifications for histidine, glycine-histidine, serine-histidine, human serum albumin (HSA), bovine serum albumin, pepsin, trypsin, and lysozyme were found to be 300, 160, 600, 300, 600, 800, 120, and 290 nM, respectively. Utilizing the fluorescence turn-on property of CuCP, we measured HSA quantitatively in the urine samples. We also validated the present urinary HSA measurement assay with existing analytical techniques. Job's plot, 1H NMR, high-resolution mass spectrometry (HRMS), electron paramagnetic resonance (EPR), fluorescence, and UV-vis studies confirmed the ligand displacement from CuCP in the presence of histidine.

Enzyme-integrated metal-organic framework platform for cascade detection of α-amylase.

As one of the most important industrial enzymes, α-amylase is widely used in food processing, such as starch sugar and fermentation, bringing high added value to industry of more than a trillion dollars. We developed a multi-enzyme system (Glu&Gox@Cu-MOF-74) prepared by embedding α-glucosidase (Glu) and glucose oxidase (Gox) into the biomimetic metal-organic framework Cu-MOF-74 using in situ encapsulation within 15 min at room temperature for efficient and sensitive detection of α-amylase activity. Benefitting from the remarkable peroxidase-mimicking property and rigid skeleton of Cu-MOF-74, the biocatalytic platform exhibited excellent cascade activity and tolerance in various extremely harsh environments compared to natural enzymes. On this basis, a cascade biocatalytic platform was constructed for the detection of α-amylase activity with wide linear range (5-100 U/L) and low limit of detection (1.45 U/L). The colorimetric cascade scheme is important for the sensitive and selective determination of α-amylase in complex fermentation samples, and the detection time is short (∼0.5 h). This work provides new ideas for the detection of α-amylase based on the cascade amplification method.

A water-soluble colorimetric chemosensor for sequential probing of Cu2+ and S2- and its practical applications to test strips, reversible test, and water samples.

A water-soluble colorimetric chemosensor NHOP ((E)-1-(2-(2-(2-hydroxy-5-nitrobenzylidene)hydrazineyl)-2-oxoethyl)pyridin-1-ium) chloride) was developed for the sequential probing of Cu2+ and S2-. NHOP underwent a color change from pale yellow to colorless in the presence of Cu2+ in pure water. The binding ratio between NHOP and Cu2+ was confirmed to be 1:1 by the Job plot and ESI-MS (electrospray ionization mass spectrometry). The detection limit of NHOP for Cu2+ was calculated as 0.15 µM, which was far below the EPA (Environmental Protection Agency) standard (20 µM). The NHOP-coated test strip was able to easily monitor Cu2+ in real-time. Meanwhile, the NHOP-Cu2+ complex reverted from colorless to pale yellow in the presence of S2- through the demetallation. The stoichiometric ratio between NHOP-Cu2+ and S2- was determined to be 1:1 by analyzing the Job plot and ESI-MS. The detection limit of NHOP-Cu2+ for S2- was calculated as 0.29 µM, which was very below the WHO (World Health Organization) guideline (14.7 µM). NHOP successfully achieved the quantification for Cu2+ and S2- in water samples. NHOP could work as a sequential probe for Cu2+ and S2- at the biological pH range (7.0-8.4). Moreover, NHOP could successively probe Cu2+ and S2- at least three cycles because of its reversible property. The detection mechanisms of NHOP for Cu2+ and NHOP-Cu2+ for S2- were demonstrated with Job plot, ESI-MS, and DFT (density functional theory) calculations. Therefore, NHOP could work as an efficient sequential probe for Cu2+ and S2- in environmental systems.

High-efficiency combination washing agents with eco-friendliness simultaneously removing Cd, Cu and Ni from soil of e-waste recycling site: A lab-scale experiment.

Soil washing technology plays an important role in the removal of heavy metals, and the efficacy of this process depends on the washing agent used. Due to the difficulty in treating soils contaminated by multiple heavy metals, there is still a need for further exploration of efficient washing agents with low environmental impact. Although single washing agents, such as chelators, can also effectively remove heavy metals from soil, combining efficient washing agents and determining their optimal washing conditions can effectively improve their removal efficiency for multiple heavy metals in soil simultaneously. Based on the previous research, the present study was carried out to combine different types of washing agents to remediate contaminated soils at a commonly e-waste recycling site. The objectives were to investigate their efficient washing conditions and assess the impact of the washing process on the speciation distribution and pollution level associated with heavy metals in soil. The results showed that the combination of HEDP (1-hydroxyethylidene-1,1-diphosphonic acid) and FeCl3 at a ratio of 6:4 exhibited the most effective removal of Cd, Cu and Ni from the contaminated soil at an e-waste recycling site. Under optimal washing conditions, with a soil-to-liquid ratio of 1:20 and a washing time of 48 h, the removal rates of Cd, Cu and Ni were 96.72%, 69.91% and 76.08%, respectively. It needed to be emphasized that the combination washing agents were able to remove most of the acid-soluble, reducible and oxidizable fractions of heavy metals, and even the removal rates of the stable residual fraction (e.g., of Cd) was at a relatively high level. In addition, the washing process significantly reduced the pollution level associated with heavy metals in soil. This study aid in the development of combined efficient washing agents and explores optimal washing strategies for the remediation of Cd, Cu, and Ni-contaminated soil at e-waste recycling sites. The findings may play a role in enhancing the remediation capabilities for soils contaminated with multiple heavy metals, due to its characteristics of and high-efficiency and environmental friendliness.

Prediction models for bioavailability of Cu and Zn during composting: Insights into machine learning.

Bioavailability assessment of heavy metals in compost products is crucial for evaluating associated environmental risks. However, existing experimental methods are time-consuming and inefficient. The machine learning (ML) method has demonstrated excellent performance in predicting heavy metal fractions. In this study, based on the conventional physicochemical properties of 260 compost samples, including compost time, temperature, electrical conductivity (EC), pH, organic matter (OM), total phosphorus (TP), total nitrogen, and total heavy metal contents, back propagation neural network, gradient boosting regression, and random forest (RF) models were used to predict the dynamic changes in bioavailable fractions of Cu and Zn during composting. All three models could be used for effective prediction of the variation trend in bioavailable fractions of Cu and Zn; the RF model showed the best prediction performance, with the prediction level higher than that reported in related studies. Although the key factors affecting changes among fractions were different, OM, EC, and TP were important for the accurate prediction of bioavailable fractions of Cu and Zn. This study provides simple and efficient ML models for predicting bioavailable fractions of Cu and Zn during composting, and offers a rapid evaluation method for the safe application of compost products.