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The use of plant tissue analysis as a tool for attaining low cyanogenic glucoside levels in cassava roots, has hardly been investigated. Just as the quality of crops is improved through the use of plant tissue analysis, the same can probably be done to consistently attain the lowest possible cyanogenic glucoside levels in cassava roots. High levels of cyanogenic glucosides in consumed fresh cassava roots or in their products have the potential of causing cyanide intoxication, hence the need to lower them. An experiment was thus conducted to assess the occurrence of meaningful relationships between plant nutritional status and cyanogenic glucoside production in cassava roots. Total hydrogen cyanide (HCN) levels in cassava roots were used to assess cyanogenic glucoside production. Using NPK fertiliser application to induce changes in plant nutritional status, the main objective of the study was investigated using the following sub-objectives; (1) to determine the effects of increased NPK fertiliser application on cassava root HCN levels; (2) and to show the occurrence of relationships between changes in nutrient levels in plant 'indicator tissue' and HCN levels in cassava roots. The study was a field experiment laid out as a split-plot in a randomized complete block design with three replicates. It was repeated in two consecutive years, with soil nutrient deficiencies only being corrected in the second year. The varieties Salanga, Kalinda, Supa and Kiroba were used in the experiment, while the NPK fertiliser treatments included; a control with no fertiliser applied; a moderate NPK treatment (50 kg N + 10 kg P + 50 kg K /ha); and a high NPK treatment (100 kg N + 25 kg P + 100 kg K /ha). A potassium only treatment (50 kg K/ha) was also included, but mainly for comparison. The root HCN levels of Salanga, Kalinda and Kiroba were significantly influenced by NPK fertiliser application in at least one of the two field experiments, while those of Supa remained uninfluenced. Changes in plant nutritional status in response to fertiliser application were thus shown to influence cyanogenic glucoside production. The results of the multiple linear regression analysis for the first field experiment, generally showed that the root HCN levels of some cassava varieties could have been 'reduced' by decreasing concentrations of nitrogen, potassium and magnesium in plants, or by improving plant calcium concentrations along with NPK fertiliser application. However, in the second field experiment (with corrected soil nutrient deficiencies) the regression analysis generally showed that the root HCN levels of some cassava varieties could have been 'reduced' by improving either one or a combination of the nutrients phosphorous, zinc and potassium in plants along with NPK fertiliser application. Although the results obtained in the two experiments had been contradicting due to slight differences in how they were conducted, the study had nonetheless demonstrated the occurrence of meaningful relationships between plant nutritional status and cyanogenic glucoside production; confirming the possible use of plant tissue analysis in predicting fertiliser needs for the consistent attainment of low cyanogenic glucosides in cassava roots.

Determination of free cyanide (fCN) is required for various industrial, environmental, food, and clinical samples. Enzymatic methods are not widely used in this field despite their selectivity and mild conditions. Therefore, we present here a proof of concept for new spectrophotometric enzymatic assays of fCN. These are based on the hydrolysis of fCN affording the readily detectable NADH. fCN is hydrolyzed either in one step by cyanide dihydratase (CynD) or in two steps by cyanide hydratase (CynH) and formamidase (AmiF). An advantage of the latter route is the higher activity of CynH and AmiF compared to CynD. In both cases, the resulting formate is then transformed by an NAD-dependent formate dehydrogenase (FDH). The NADH thus formed is quantified colorimetrically using a known method based on a reduction of a tetrazolium salt (WST-8) with NADH. The developed assays of fCN are selective except for formic acid interference, proceed under mild conditions, and, moreover, fCN is detoxified during the reactions. The assays proceeded in a microtiter plate format. The limit of detection (LOD) and the limit of quantification (LOQ) were lower for the three-enzyme (CynH-AmiF-FDH) method (7.00 and 21.2 µmol/L, respectively) than for the two-enzyme (CynD-FDH) method (10.7 and 32.4 µmol/L, respectively). In conclusion, the new fCN assays presented in this work are selective, high-throughput, do not require harsh conditions, and use only small amounts of chemicals and enzymes. Graphical Abstract

This work describes the synthesis and characterization of new quinolone–benzothiazole hybrids, the study of their aggregation-induced emission (AIE) properties, and the use of these systems as efficient fluorescent probes for cyanide ions. These conjugated derivatives are linked through a double bond favoring electronic communication, and together with their planar geometry, can strongly aggregate under solvophobic environments, leading to aggregation and exhibiting significant AIE behavior. The double bond between electroactive units is prone to nucleophilic addition reactions by cyanide ions, selectively, conducive to turning off the fluorescence properties, making this hybrid system an efficient probe for cyanide ions. These studies were theoretically explained using DFT and TD-DFT calculations.

Cassava cyanide effluent arising from cassava processing contaminate soil, leading to increased concentration of cyanide in soil and water, posing a risk to plant, aquatic life, and human health. Hence, the aim of this study is to investigate the impact of abattoir sludge on cyanide concentration of cassava effluent and soils receiving cassava effluent. In this study, soil samples were carried out following standard protocol. The concentration of nutrients after treatment revealed increase in nutrients level in 28 days of treatment as the weight of sludge dosage rises from 0 to 30%. However, as the remediation period progresses from 28 to 56 days, nutrients level of effluent and soil begins to drop, though nutrients level after the treatment period falls within the permissible range of habitat and agricultural soil after remediation period. The level of cyanide after treatment revealed a drop in concentration of effluent/soil as the dosage of sludge rises. In the same vein, concentration of effluent/soil cyanide also drop as the period of incubation increases from 28 to 56 days. The decrease in the level of cyanide is more pronounced in the 42nd and 56th days of treatment. The level of cyanide after the treatment is within the recommended range of soil used for habitat and agricultural soil. Therefore, abattoir sludge shows a promising greener biomass of choice for soil revitalizations and remediation of cyanide. Graphical Abstract

Understanding the behavior of cyanide in rivers is of utmost importance as it has a direct impact on the health of people who depend on these water sources. Cyanide contamination from gold mining activities poses a significant environmental threat to river ecosystems, particularly in southern Ecuador. This study aimed to investigate the behavior of cyanide when it enters contact with other metals in these rivers. Simulations were conducted to determine the speciation of cyanide, mercury, arsenic, lead, and manganese in a study area, taking into account the water temperature and pH at four locations. The findings revealed that CN − and HCN (aq) species were present in the research area. Additionally, mercury-cyanide (Hg(CN) 2(aq) , Hg(CN) 3 − ), and manganese-cyanide (MnCN + ) complexes were identified 3 km downriver from the site where the mining activity is higher. These metal-cyanide complexes tend to dissociate quickly under weak acidic conditions, making them hazardous to the environment. This research is crucial, not only for the environment but also for human health, as it allows to predict toxicity risks for people supplied with this water source, emphasizing the potential harm to human health. This study highlights the importance of stringent regulations and effective monitoring practices to mitigate cyanide contamination and safeguard environmental and occupational health.

The purpose of this study is to summarize the current knowledge of the enzymes which are involved in the hydrolysis of cyanide, i.e., cyanide hydratases (CHTs; EC 4.2.1.66) and cyanide dihydratases (CynD; EC 3.5.5.1). CHTs are probably exclusively produced by filamentous fungi and widely occur in these organisms; in contrast, CynDs were only found in a few bacterial genera. CHTs differ from CynDs in their reaction products (formamide vs. formic acid and ammonia, respectively). Several CHTs were also found to transform nitriles but with lower relative activities compared to HCN. Mutants of CynDs and CHTs were constructed to study the structure-activity relationships in these enzymes or to improve their catalytic properties. The effect of the C-terminal part of the protein on the enzyme activity was determined by constructing the corresponding deletion mutants. CynDs are less active at alkaline pH than CHTs. To improve its bioremediation potential, CynD from Bacillus pumilus was engineered by directed evolution combined with site-directed mutagenesis, and its operation at pH 10 was thus enabled. Some of the enzymes have been tested for their potential to eliminate cyanide from cyanide-containing wastewaters. CynDs were also used to construct cyanide biosensors.

Artisanal and small-scale gold mining (ASGM) in Burkina Faso increasingly relies on cyanide, intensifying concerns about environmental contamination and human exposure. This study assessed free cyanide levels in water and soil across three ASGM sites—Zougnazagmiline, Guido, and Galgouli. Water samples (surface and groundwater) and topsoil (0–20 cm) were analyzed using the pyridine–pyrazolone method. Data were statistically and spatially processed using SPSS version 29.0 and the Google Earth Engine in conjunction with QGIS version 3.34, respectively. A site conceptual model (SCM) was also developed, based on the literature review, field observations, and validation by multidisciplinary experts in public health, toxicology, ecotoxicology, environmental engineering, and the mining sector, through a semi-structured survey. The results showed that 9.26% of the water samples exceeded the WHO guideline (0.07 mg/L), with peaks of 1.084 mg/L in Guido and 2.42 mg/L in Galgouli. At Zougnazagmiline, the water type differences were significant (F = 64.13; p < 0.001), unlike the other sites. In the soil, 29.36% of the samples exceeded 0.5 mg/kg, with concentrations reaching 9.79 mg/kg in Galgouli. A spatial analysis revealed pollution concentrated near the mining areas but spreading to residential and agricultural zones. The validated SCM integrates pollution sources, transport mechanisms, exposure routes, and vulnerable populations, offering a structured tool for environmental monitoring and health risk assessment in cyanide-impacted mining regions.

In Côte d’Ivoire, despite an intense development of artisanal and small-scale gold mining (ASGM) activities in thelast two decades, the environmental impacts of this activity are poorly documented. This study aimed to documentthe concentrations of geogenic and exogenous contaminants potentially released by ASGM (metals and cyanides) indifferent sources (ore, mining wastes) and environmental compartments (soils, surface and ground waters, sediments) inthe Kokumbo area, part of the Au-rich Birimian greenstone belt. Alluvial ore material is enriched in various metal(oid)s (As, Co, Cu, Cr, Fe, Mn, Ni, Sb, and V) compared to the average composition of the upper continental crust whileother metals (Cd, Pb, Ti, Zn) show no geochemical anomalies. High Hg concentrations were found in cyanidationresidues (up to 8.32 mg/kg) and sediments (up to 20.4 mg/kg) compared to unprocessed alluvial ores (0.06 ± 0.01 mg/kg) indicating that Hg used in amalgamation is the source of Hg contamination. Cyanidation residues contain up to100 mg/kg of total cyanides but generally less than 3% are in the form of free cyanides, the most mobile and toxicform. Arsenic concentrations in water are low (< 2.5 μg/L) despite its relatively high content in sediments and soils(76 ± 54 mg/kg), showing a low mobility of As, likely due to its adsorption on iron oxy(hydr)oxides. Apart from Mn,metals have low dissolved concentrations in water except in a stream draining a cyanidation site suggesting that thecyanidation effluent discharge may contribute to metal dispersion in rivers.

The present study explored the feasibility of using graphite electrodes for the electrochemical oxidation of cyanide, thiocyanate, phenol and aniline with hydrogen peroxide. The dosing effects of hydrogen peroxide and current density were examined in the pre-treated coke oven wastewater. It was found that 0.025 M hydrogen peroxide and 13.63 mA/cm2 of current density were more favorable for the removal of 100%, 90%, 71% and 40% cyanide, thiocyanate, phenol and aniline respectively. The increased removal of phenol in the coke oven wastewater was attributed to the pre-treatment of wastewater. Initially, 28% phenol was converted to phenolate ion by air stripping process, which increased the removal rate of phenol by the electro-oxidation process as the removal of phenolate is quite easy compared to phenol. The advanced oxidation process degrades the more toxic cyanide into less toxic intermediate cyanate ions (CNO─), which further cut down into nontoxic end products such as N2, HCO3 and CO2. The experimental results show that the primary mechanisms in the oxidation of cyanide and phenol are mediated electro-oxidation by hydroxyl radicals and hypochlorite ions. The operating cost under the optimized conditions for the removal of 100% cyanide and 71% phenol was estimated to be 616.95 INR/m3.

A real electroplating wastewater, containing 51,190 mg/L of free cyanide (CNf), 4899 mg/L of Ni and 1904 mg/L of Cu, was treated with calcium alginate hydrogel beads (CAB), pure or impregnated with biodegraded grape marc (EBGM) or activated carbon (EAC) in order to reduce the elevated load of toxic pollutants below the regulatory limits. It was evaluated the effect of increasing the amount of bioadsorbent as well as the influence of two successive adsorption cycles in the removal efficiency of pollutants. The most favourable sorption conditions onto CAB provided removal percentages of 85.02% for CNf and between 93.40–98.21% for heavy metals regarding the raw wastewater. The adsorption capacity of each pollutant onto CAB was considerably increased during the first 30 min of contact time, but after achieving the equilibrium, the following sorption capacities were obtained: 1177, 107.3, 39.5 and 1.52 mg/g for CNf, Ni, Cu and Zn, respectively. The kinetic adsorption of pollutants onto the CAB was adjusted to different kinetic models, observing that kinetic data agreed with the pseudo-second-order model. The information about intraparticle diffusion mechanisms in the bioadsorption process was also interpreted.