[A case of acute poisoning caused by oral administration of large dose hexazinone].

Hexazinone is a post-emergence herbicide/arboricides, and its acute poisoning has rarely been reported. Hexazinone is low-toxic to humans, but mass intake of hexazinone would still lead to organ impairment. This article analyzes a case of acute hexazinone poisoning from the poisoning treatment center of our hospital, and summarizes the symptoms and treatment effects of hexazinone poisoning, which is aimed at improving the comprehension, diagnosis and treatment of the disease.

Photodegradation and adsorption of hexazinone in aqueous solutions: removal efficiencies, kinetics, and mechanisms.

Hexazinone, a globally applied broad-spectrum triazine herbicide, has not been mechanistically investigated previously under advanced oxidation processes (AOPs) and adsorption on activated carbon. In this study, its fate during UV-based oxidation with/without hydrogen peroxide (H2O2) and adsorption on coconut shell-based granular activated carbon (CSGAC) in water matrices was investigated. A comparison between various irradiation sources (visible, UVA, UVB, and UVC) revealed the highest degradation rate under UVC. More than 98% degradation of hexazinone was observed under 3 J cm-2 UVC fluence in the presence of 0.5 mM H2O2 at pH 7. Moreover, the degradation rate enhanced significantly with an increase in the initial dosage of H2O2, UV fluence, and contact time in the UV/H2O2 process. The rate of degradation was lower using secondary effluent than that of Milli-Q water due to the presence of dissolved organics in wastewater. However, the reactions in both matrices obeyed pseudo-first-order kinetics. The effect of different scavengers, including methanol, potassium iodide (KI), and tert-butyl alcohol (TBA), showed that hydroxyl radicals (•OH) played a dominant role in hexazinone degradation in the UV/H2O2 process. Hexazinone was effectively adsorbed by CSGAC through π-π electron donor-acceptor interactions between hexazinone's triazine ring and CSGAC's surface functional groups. The isotherm and kinetic studies showed that the adsorption followed the Freundlich model and pseudo-second-order reaction, respectively, suggesting chemisorption. This study provided mechanistic insights on the removal of hexazinone at the tertiary stage of wastewater treatment or the advanced treatment of wastewater reuse.

A case of acute poisoning caused by oral administration of large dose hexazinone / 中华劳动卫生职业病杂志

Hexazinone is a post-emergence herbicide/arboricides, and its acute poisoning has rarely been reported. Hexazinone is low-toxic to humans, but mass intake of hexazinone would still lead to organ impairment. This article analyzes a case of acute hexazinone poisoning from the poisoning treatment center of our hospital, and summarizes the symptoms and treatment effects of hexazinone poisoning, which is aimed at improving the comprehension, diagnosis and treatment of the disease.

Accessing biochar's porosity using a new low field NMR approach and its impacts on the retention of highly mobile herbicides.

Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on decay due to diffusion in internal magnetic field (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 µm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha-1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.

Toxicity of Herbicide Mixtures to Tropical Freshwater Microalgae Using a Multispecies Test.

Agriculture within the Great Barrier Reef catchment area has contributed to pesticide contamination of adjacent freshwater ecosystems that flow into the Great Barrier Reef World Heritage Area. A novel multispecies toxicity test was used to assess the toxicity of diuron and hexazinone, 2 herbicides commonly detected within the Great Barrier Reef catchment area, to a community of 3 tropical freshwater microalgae: Monoraphidium arcuatum, Nannochloropsis-like sp., and Pediastrum duplex. Diuron was the most toxic herbicide, with 10% inhibition concentration (IC10) values of 4.3, 7.1, and 29 µg/L for P. duplex, M. arcuatum, and Nannochloropsis-like sp., respectively, followed by hexazinone, with IC10 values of 15, 18, and 450 µg/L, respectively Toxicity testing on 2 commercial formulations (Barrage, 13.2% hexazinone and 48.6% diuron; Diurex, 90% diuron) showed that additives in the commercial formulations did not significantly increase the toxicity of diuron. Direct toxicity assessments were carried out on water samples from the herbicide-contaminated Sandy Creek, which discharges to the Great Barrier Reef lagoon, and a clean reference site, Tully Gorge in the Tully River. Toxicity was observed in several Sandy Creek samples. Artificial herbicide mixtures were assessed in synthetic soft water and natural freshwaters, with toxic responses being observed at environmentally relevant concentrations. The present study successfully applied a novel multispecies tropical microalgal toxicity test, indicating that it is an effective tool for the assessment of herbicide toxicity in both natural and synthetic freshwaters. Environ Toxicol Chem 2021;40:473-486. © 2020 SETAC.

Analog and Digital Bipolar Resistive Switching in Co-Al-Layered Double Hydroxide Memristor.

We demonstrate a nonvolatile memristor based on Co-Al-layered double hydroxide (Co-Al LDH). We also introduce a memristor that has a hexazinone-adsorbing Co-Al LDH composite active layer. Memristor characteristics could be modulated by adsorbing hexazinone with Co-Al LDHs in the active layer. While different, Co-Al LDH-based memory devices show gradual current changes, and the memory device with small molecules of adsorbed hexazinone undergo abrupt changes. Both devices demonstrate programmable memory peculiarities. In particular, both memristors show rewritable resistive switching with electrical bistability (>105 s). This research manifests the promising potential of 2D nanocomposite materials for adsorbing electroactive small molecules and rectifying resistive switching properties for memristors, paving a way for design of promising 2D nanocomposite memristors for advanced device applications.

Simultaneous analysis of betrixaban and hexazinone using liquid chromatography/tandem mass spectrometry in aqueous solutions.

A new analytical method has been developed, optimised, and validated for simultaneous detection and identification of betrixaban, an oral anticoagulant drug approved recently by food and drug administration (FDA), and hexazinone, a broad-spectrum triazine herbicide, in aqueous media by liquid chromatography/tandem mass spectrometry (LC-MS/MS) using multiple reaction monitoring (MRM). The method was validated by the limit of detection (LOD), the limit of quantification (LOQ), linearity, matrix effect, recovery, precision, and accuracy. The recovery experiments were carried out on raw wastewater samples, spiked with these two compounds, using solid phase extraction (SPE). It is the first time that betrixaban has been analysed for environmental samples. The developed analytical method can be applied for more in-depth studies on the fate and occurrence of these compounds in the engineered and natural aquatic environment. The key benefits of the method described here are: •It is highly suitable for betrixaban and hexazinone detection and quantification in aqueous samples.•It can be successfully applied for understanding the fate of betrixaban and hexazinone in real-world water samples.•Method validation revealed that the method is repeatable, robust, and accurate and can be expanded to include detection of other pharmaceuticals and pesticides in aqueous media.

Electrochemical degradation of insecticide hexazinone with Bi-doped PbO2 electrode: Influencing factors, intermediates and degradation mechanism.

Electrochemical degradation of hexazinone in aqueous solution using Bi-doped PbO2 electrodes as anodes was investigated. The main influencing parameters on the electrocatalytic degradation of hexazinone were analyzed as function of initial hexazinone concentration, current density, initial pH value and Na2SO4 concentration. The experiment results showed that the electrochemical oxidization reaction of hexazinone fitted pseudo-first-order kinetics model. 99.9% of hexazinone can be decontaminated using Bi-doped PbO2 electrode as anode for 120 min. Comparing with pure PbO2 electrode, the Bi-doped PbO2 electrodes possess higher hexazinone and COD removal ratio, higher ICE and lower energy consumption in the electrocatalytic degradation process. The results revealed that electrochemical oxidation using Bi-doped PbO2 anodes was an efficient method for the elimination of hexazinone in aqueous solution. The electrocatalytic oxidization mechanism of hexazinone with Bi-doped PbO2 anode was discussed, then the possible degradation pathway of hexazinone with two parallel sub-routes was elucidated according to 15 intermediates identified using HPLC-MS.

[Determination of Hexazinone and Its Major Metabolites in Livestock Products by LC-MS/MS].

A method for the determination of hexazinone and three metabolites (hexazinone metabolite B, hexazinone metabolite C, hexazinone metabolite F) in livestock products by LC-MS/MS was developed. Hexazinone and the three metabolites were extracted from a sample with acetonitrile in the presence of n-hexane, and lipid was removed by acetonitrile/n-hexane partition. The acetonitrile extract was cleaned up using a SAX/PSA cartridge column. Average recoveries (n=5) of hexazinone and the three metabolites from cattle meat, fat, liver and milk spiked at the maximum residue limits (MRLs) or at 0.0025 mg/kg ranged from 85.6 to 96.0%, and the relative standard deviations ranged from 0.8 to 4.9%.

Ecotoxicity thresholds for ametryn, diuron, hexazinone and simazine in fresh and marine waters.

Triazine and urea herbicides are two groups of photosystem II inhibiting herbicides frequently detected in surface, ground and marine waters. Yet, there are few water quality guidelines for herbicides. Ecotoxicity thresholds (ETs) for ametryn, hexazinone and simazine (triazine herbicides) and diuron (a urea herbicide) were calculated using the Australian and New Zealand method for deriving guideline values to protect fresh and marine ecosystems. Four ETs were derived for each chemical and ecosystem that should theoretically protect 99, 95, 90 and 80% of species (i.e. PC99, PC95, PC90 and PC80, respectively). For all four herbicides, the phototrophic species were significantly more sensitive than non-phototrophic species, and therefore, only the former data were used to calculate the ETs. Comparison of the ET values to measured concentrations in 2606 samples from 15 waterways that discharge to the Great Barrier Reef (2011-2015) found three exceedances of the simazine PC99, regular exceedances (up to 30%) of the PC99 in a limited number of rivers for ametryn and hexazinone and frequent (> 40%) exceedances of the PC99 and PC95 ETs in at least four waterways for diuron. There were no exceedances of the marine ETs in inshore reef areas. Further, ecotoxicity data are required for ametryn and hexazinone to fresh and marine phototrophic species, for simazine to marine phototrophic species, for tropical phototrophic species, repeated pulse exposures and long-term (2 to 12 months) exposures to environmentally relevant concentrations.

Herbicide effects on the growth and photosynthetic efficiency of Cassiopea maremetens.

Herbicides from agricultural run-off have been measured in coastal systems of the Great Barrier Reef over many years. Non-target herbicide exposure, especially photosystem II herbicides has the potential to affect seagrasses and other marine species. The symbiotic benthic jellyfish Cassiopea maremetens is present in tropical/sub-tropical estuarine and marine environments. Jellyfish (n = 8 per treatment) were exposed to four separate concentrations of agricultural formulations of diuron or hexazinone to determine their sensitivity and potential for recovery to pulsed herbicide exposure. Jellyfish growth, symbiont photosynthetic activity and zooxanthellae density were analysed for herbicide-induced changes for 7 days followed by a 7 day recovery period. Both the jellyfish and endosymbiont were more sensitive to diuron than hexazinone. The 7-day EC50 for jellyfish growth was 0.35 µg L-1 for Diuron and 17.5 µg L-1 for Hexazinone respectively. Diuron exposure caused a significant decrease (p < 0.05) in jellyfish growth at 0.1 µg L-1, a level that is below the regional Great Barrier Reef guideline value. Jellyfish recovery was rapid with growth rates similar to control animals following removal from herbicide exposure. Both diuron and hexazinone caused significant decreases in photosynthetic efficiency (effective quantum yield) in all treatment concentrations (0.1 µg L-1 and above) and this effect continued in the post-exposure period. As this species is frequently found in near-shore environments, they may be particularly vulnerable to herbicide run-off.

Predição da performance de carvão ativado granular para remoção de herbicidas com ensaios em coluna de escala reduzida / Prediction of granular activated carbon performance in removing herbicides with rapid small-scale column tests

RESUMO: Na região de Ribeirão Preto está localizado um dos polos produtores da cana-de-açúcar, com vasta área cultivada e uso intensivo de herbicidas, tais como o diuron e a hexazinona, os quais possuem elevado potencial de contaminação em águas superficiais e subterrâneas. Diversas tecnologias podem ser utilizadas para remover esses microcontaminantes da água, em função de, neste caso, não ser eficiente a técnica de tratamento em ciclo completo (ou convencional). Neste trabalho, estudou-se o desempenho do carvão ativado granular na remoção destes herbicidas. A água de estudo foi preparada em laboratório e fortificada com diuron e hexazinona. Foi construída e operada uma instalação piloto com colunas de adsorção em carvão ativado granular, cujos resultados obtidos mostraram que a difusividade intrapartícula predominante entre o carvão e os herbicidas diuron e hexazinona pode ser considerada constante, em relação ao tamanho do grão de carvão ativado. Eles também possibilitaram a validação do método de ensaios rápidos em coluna de carvão ativado em escala reduzida, com vista à predição do tempo para ruptura de um filtro de carvão ativado granular em escala real.

ABSTRACT: Ribeirão Preto has one of the producer poles of sugarcane, with a vast sugarcane plantation area and intensive use of herbicides, especially diuron and hexazinone, which have high potential of contaminating surface waters and groundwater. Several technologies can be used to remove these micro-contaminants from water, since the conventional treatment in complete cycle is not an efficient technique for this case. In the present study, the performance of the granular activated carbon in removing these herbicides was evaluated. The water sample was prepared in a laboratory and supplemented with diuron and hexazinone. A pilot granular activated carbon column was built and operated, and the results showed that the prevailing intra-particle diffusivity between carbon and diuron and hexazinone herbicides could be considered constant, with regard to the size of the activated carbon grain. The results obtained also enabled the validation of the rapid small-scale column test method to predict the full scale breakthrough time of a granular activated carbon filter.

Washoff of Residual Photosystem II Herbicides from Sugar Cane Trash under a Rainfall Simulator.

Herbicides are often applied to crop residues, but their fate has not been well studied. We measured herbicide washoff from sugar cane trash during simulated rainfall, at 1, 8, and 40 days after spraying (DAS), to provide insight into herbicide fate and for use in modeling. Herbicides included are commonly used in the sugar industry, either in Australia or in Brazil. Concentrations of all herbicides and applied Br tracer in washoff declined exponentially over time. The rate of washoff during rainfall declined with increasing DAS. Cumulative washoff as a function of rainfall was similar for most herbicides, although the most soluble herbicides did have more rapid washoff. Some but not all herbicides became more resistant to washoff with increasing DAS. Of the total mass washed off, 80% washed off in the first 30 mm (∼40 min) of rainfall for most herbicides. Little herbicide remained on the trash after rainfall, implying nearly complete washoff.

Performance of herbicides in sugarcane straw / Dinâmica de herbicidas em palha de cana-de-açúcar

The process of mechanical harvesting of sugarcane generates a large deposition of straw on the soil surface, providing a coverage that several studies have found important for reducing the weed population. Although such coverage reduces weed infestations, additional management, including chemical control, is still needed. Thus, this study aimed to evaluate the leaching of atrazine, pendimethalin, metribuzin, clomazone, diuron and hexazinone in sugarcane straw. The experiment was conducted at the School of Agronomic Engineering at UNESP (Sao Paulo State University) - Botucatu/SP. The sugarcane straw was collected in the field, cut and placed in quantities of 10t ha-1 in the capsules used as experimental units. The experimental design was completely randomized, using six herbicide treatments and four replications. Within 24 hours after the herbicides were applied in capsules with straw, five different rainfalls (5, 10, 20, 50 and 100mm) were simulated. The leached water was collected for chromatographic analysis. The herbicide percentages that crossed the straw layer were statistically correlated with the rainfall amount by the Mitscherlich model that compares the facility of herbicide removal from sugarcane straw. In summary, pendimethalin did not present quantified transposition of the product by sugarcane straw even with a rain simulation of 100 mm. Furthermore, two different profiles of facility to transpose the herbicides in straw were found: one for metribuzin and hexazinone that crossed quickly through the straw layer and another for atrazine, diuron and clomazone that required more rainfall to be leached from coverage to the soil according to the maximum removable amount of each herbicide.

O processo de colheita mecanizada de cana-de-açúcar gera uma grande quantidade de palhada depositada na superfície do solo e vários trabalhos destacam a importância da manutenção dessas coberturas em sistemas de cana crua, com destaque na redução da população de plantas daninhas. Mas, apesar de a cobertura vegetal reduzir a infestação das plantas daninhas, medidas complementares, como o controle químico, ainda são necessárias. Dessa forma, o objetivo deste estudo foi avaliar a transposição dos herbicidas atrazine, pendimethalin, metribuzin, clomazone, diuron e hexazinone em palha de cana-de-açúcar. O experimento foi desenvolvido na Faculdade de Ciências Agronômicas da UNESP - Botucatu/SP. A palha da cana-de-açúcar foi coletada em campo, cortada e colocada em quantidades de 10t ha-1 em recipientes plásticos utilizados como unidades experimentais. O delineamento experimental foi inteiramente casualisado, e foram testados seis tratamentos (atrazine, pendimethalin, metribuzin, clomazone, diuron e hexazinone) e quatro repetições. Nas cápsulas com palha e pulverizadas, foi realizado, no período de 24 horas após a aplicação, a simulação de diferentes lâminas de chuva (5, 10, 20, 50 e 100mm) e coletada a água lixiviada para posterior quantificação cromatográfica. Como análise estatística, os herbicidas foram correlacionados com as lâminas de chuva e foi usado o modelo de Mitscherlich para ajuste dos dados, que permitiu comparar a facilidade de remoção dos herbicidas pela palha. Em síntese, para o pendimethalin, não se observou transposição quantificada do produto pela palha de cana-de-açúcar, mesmo com uma lâmina de 100mm de chuva. Foram encontrados dois perfis diferentes de facilidade de transposição dos herbicidas em palha: um para o metribuzin e hexazinone, que passaram rapidamente pela camada de palha, e outro para atrazine, clomazone e diuron, que precisaram de uma quantidade superior de chuva para serem lixiviados da cobertura vegetal, em função da quantidade máxima removível dos herbicidas.

Pré-oxidação e adsorção em carvão ativado granular para remoção dos herbicidas Diuron e Hexazinona de água subterrânea / Preoxidation and adsorption in granular activated carbon for the removal of Diuron and Hexazinone from groundwater

O cultivo da cana-de-açúcar exige a utilização de herbicidas, destacando-se o Diuron e a Hexazinona. Alguns dos poços de abastecimento de Ribeirão Preto (SP) construídos no Aquífero Guarani estão situados em pontos de recarga, e a presença de solo de textura arenosa nessas áreas aumenta a vulnerabilidade da água subterrânea à contaminação por herbicidas. Neste trabalho foram monitorados alguns poços localizados na área de recarga e estudou-se a remoção de Diuron e Hexazinona por meio da adsorção em carvão ativado granular (CAG) e da pré-oxidação com cloro e dióxido de cloro em uma instalação piloto de escoamento contínuo. Verificou-se que o tempo de saturação do CAG no ensaio com a pré-oxidação foi inferior ao obtido no ensaio sem a pré-oxidação com ambos os oxidantes, possivelmente pela formação de subprodutos que competiram com a adsorção dos herbicidas.

The cultivation of sugarcane demands the use of herbicides such as Diuron and Hexazinone. Some supply wells from Ribeirão Preto, SP, Brazil, built in the Guarani Aquifer are located in recharge points, and the presence of sandy Quartzarenic Neosol in these areas increases the vulnerability of the groundwater to contamination from herbicides This paper reports the water quality monitored in some wells located in the recharge area and the removal of Diuron and Hexazinone by means of adsorption in granular activated carbon (GAC), preceded or not by preoxidation with chlorine and chlorine dioxide in a pilot plant. The results indicated that Diuron was more strongly adsorbed than Hexazinone and that the saturation time of the GAC in the test with preoxidation was shorter than in the test without preoxidation, which may have occurred mainly due to the formation of by-products that competed with the adsorption of the herbicides.