RESUMEN

The present paper deals with an analysis of total arsenic concentration using ICP-MS/MS and an analysis of concentration of several arsenic species, arsenite (AsIII), arsenate (AsV), monomethylarsonate (MMA), dimethylarsenite (DMA), and trimethylarsine oxide (TMAO), using HPLC-ICP-MS/MS in the PM10 fraction of airborne urban aerosol. The samples were collected during two campaigns, in the autumn of 2022 and in the winter of 2023, at three locations within the central European city of Brno, with the aim to evaluate the seasonal and spatial variations in the PM10 composition. The results confirmed only the seasonal variability in the content of the methylated arsenic species in PM10 influenced by biomethylation processes. To gain better understanding of the possible arsenic origin, a supplementary analysis of the total arsenic concentrations was performed in samples of different size fractions of particulate matter collected using ELPI + . Local emissions, including industrial activities and heating during the winter season, were suggested as the most likely predominant source contributing to the total As content in PM10.

RESUMEN

Groundwater recharge is a viable solution to groundwater overexploitation. However, the injection of recharge water may break the dissolution balance and induce the release of trace elements especially arsenic (As), which has been identified in river deltas. Only a few studies have been conducted in inland basins with high As concentration, high pH, and low Eh. Aiming to analyze As release with groundwater recharge in inland high-As regions and determine the effects of coexisting ions in recharge water, this study established PHase Equilibria Calculation (PHREEQC) models using rainwater and groundwater data from three inland sedimentary basins with slow groundwater flow in semi-arid regions. The simulations fitted with the batch experiments, achieving an R-squared (R2) of 0.98. The coexisting ions in the recharge water significantly affected As release during recharge. Ca2+ inhibited the release of total arsenic (Total-As) by increasing the surface charge of iron oxides. NO3- inhibited Total-As release by promoting the conversion of trivalent As into pentavalent As. Conversely, HCO3- facilitated As release by competing with arsenate for adsorption sites. On the basis of the modeling and batch experiment results, Total-As release with groundwater recharge was predicted. The results indicated that the high Ca2+ concentration in the recharge water inhibited the As release by 83.5 %, which can be used as a strategy to control As release during groundwater recharge in high-As inland basins.

RESUMEN

We explain here that the authors of the article cited in the title have misrepresented the species of As(III) and As(V) in solutions and, in particular, have neglected their speciation as a function of pH. Their discussion of (ad)sorption mechanisms is therefore unsatisfactory, especially since organic matter (flower waste) and the presence of iron oxyhydroxides should be taken into account. Furthermore, the modeling of (ad)sorption kinetics and isotherms was based on linearized equations, whereas the corresponding nonlinear equations should have been used. Therefore, we believe that the authors of the original article should make corrections and additions to it. This Letter to the Editor is motivated by a concern to avoid the dissemination of approximate or even incorrect concepts in the scientific literature, which could mislead novice researchers.

RESUMEN

Arsenic is a ubiquitous toxic metalloid causing serious health problems. Speciation analysis of arsenic in human urine provides valuable insights for large-scale epidemiological studies and informs on sources of exposure as well as human metabolism. The Multi-Ethnic Study of Atherosclerosis (MESA) is a valuable cohort for assessing chronic low-moderate arsenic exposure and health effects in an ethnically diverse US population. We present a state-of-the-art arsenic speciation analysis methodology and its application to 7677 MESA spot urine samples based on high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry. This method is fast, robust and detects a total of 11 individual As species at method detection limits of 0.02-0.03 µg arsenic/L urine for each individual species. Our analytical approach features excellent mean method accuracy (98%) and precision (5%) for the main arsenic species in urine (arsenobetaine, methylarsonic acid, dimethylarsinic acid, and total inorganic As); intra- (3-6%) and inter-day coefficients of variability (5-6%); column recovery (96 ± 7%); and spike recovery (97 ± 6%). The main arsenic species were detectable in ≥95% of urine samples due to the implementation of an oxidation step. Each individual minor arsenic species was detectable in ≤25% of all urines, although at least one of them was detected in almost half the participants. We identified two minor urinary arsenic species as dimethylarsinoylacetic acid and dimethylarsinoylpropionic acid, potential metabolites of seafood-related arsenicals. We observed differences in individual As species excretion by race/ethnicity, with Asian-American participants featuring 3-4 times higher concentrations compared to other participants. We also found differences by site, body mass index, smoking status, rice intake, and water arsenic levels, potentially indicating different exposures or related to individual bio-metabolism. The proposed approach is suitable for epidemiological studies and the collected data will constitute the base for future research on potential health effects of chronic low-level arsenic exposure.

RESUMEN

It is known that selenium (Se) enhances plant growth and arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated mechanisms are unclear. In this study, P. vittata was exposed to 50 µM arsenate (AsV) under hydroponics plus 25 or 50 µM foliar selenate. After 3-weeks of growth, the plant biomass, As and Se contents, As speciation, malondialdehyde (MDA) and glutathione (GSH and GSSG) levels, and important genes related to As-metabolism in P. vittata were determined. Foliar-Se increased plant biomass by 17 - 30 %, possibly due to 9.1 - 19 % reduction in MDA content compared to the As control. Further, foliar-Se enhanced the As contents by 1.9-3.5 folds and increased arsenite (AsIII) contents by 64 - 136 % in the fronds. The increased AsV reduction to AsIII was attributed to 60 - 131 % increase in glutathione peroxidase activity, which mediates GSH oxidation to GSSG (8.8 -29 % increase) in the fronds. Further, foliar-Se increased the expression of AsIII antiporters PvACR3;1-3;3 by 1.6 - 2.1 folds but had no impact on phosphate transporters PvPht1 or arsenate reductases PvHAC1/2. Our results indicate that foliar-Se effectively enhances plant growth and arsenic accumulation by promoting the GSH-GSSG cycle and upregulating gene expression of AsIII antiporters, which are responsible for AsIII translocation from the roots to fronds and AsIII sequestration into the fronds. The data indicate that foliar-Se can effectively improve phytoremediation efficiency of P. vittata in As-contaminated soils.

Asunto(s)

RESUMEN

Microbially-mediated arsenic biotransformation plays a pivotal role in the biogeochemical cycling of arsenic; however, the presence of arsenic biotransformation genes (ABGs) in urban dust remains unclear. To investigate the occurrence and spatiotemporal distributions of ABGs, a total of one hundred and eighteen urban dust samples were collected from different districts of Xiamen city, China in summer and winter. Although inorganic arsenic species, including arsenate [As(V)] and arsenite [As(III)], were found to be predominant, the methylated arsenicals, particularly trimethylarsine oxide [TMAs(V)O] and dimethylarsenate [DMAs(V)], were detected in urban dust. Abundant ABGs were identified in urban dust via AsChip analysis (a high-throughput qPCR chip for ABGs), of which As(III) S-adenosylmethionine methyltransferase genes (arsM), As(V) reductase genes (arsC), As(III) oxidase genes (aioA), As(III) transporter genes (arsB), and arsenic-sensing regulator genes (arsR) were the most prevalent, collectively constituting more than 90 % of ABGs in urban dust. Microbes involved in arsenic methylation were assigned to bacteria (e.g., Actinomycetes and Alphaproteobacteria), archaea (e.g., Halobacteria), and eukaryotes (e.g., Chlamydomonadaceae) in urban dust via the arsM amplicon sequencing. Temperature, a season-dependent environmental factor, profoundly affected the abundance of ABGs and the composition of microbes involved in arsenic methylation. This study provides new insights into the presence of ARGs within the urban dust.

Asunto(s)

RESUMEN

Green leafy vegetables are essential for a balanced diet, providing vital nutrients for overall well-being. However, concerns arise due to contamination with toxic substances, such as arsenic, posing risks to food safety and human health. This study analyzes inorganic (iAs), monomethyl (MMA), and dimethyl arsenic (DMA) in specific leafy vegetables (Amaranthus tricolor L., Corchorus olitorius L., Cordia myxa L., Hibiscus sabdariffa L., Ipomoea batatas (L.) Lam., Moringa oleifera Lam., and Spinacia oleracea L.) grown in the heavily polluted Ambagarh Chouki region, Chhattisgarh, India. Concentrations of DMA, MMA, and iAs ranged from 0 to 155, 0 to 7, and 131 to 3579 mg·kg-1, respectively. The health quotient (HQ) for iAs ranged between 0.37 and 3.78, with an average value of 2.58 ± 1.08.

Asunto(s)

RESUMEN

Current human health risk assessments of soil arsenic (As) contamination rarely consider bioaccessibility (IVBA), which may overestimate the health risks of soil As. The IVBA of As (As-IVBA) may differ among various soil types. This investigation of As-IVBA focused As from geological origin in a typical subtropical soil, lateritic red soil, and its risk control values. The study used the SBRC gastric phase in vitro digestion method and As speciation sequential extraction based upon phosphorus speciation extraction method. Two construction land sites (CH and HD sites) in the Pearl River Delta region were surveyed. The results revealed a high content of residual As (including scorodite, mansfieldite, orpiment, realgar, and aluminum arsenite) in the lateritic red soils at both sites (CH: 84.9%, HD: 91.7%). The content of adsorbed aluminum arsenate (CH: 3.24%, HD: 0.228%), adsorbed ferrum arsenate (CH: 8.55%, HD: 5.01%), and calcium arsenate (CH: 7.33%, HD: 3.01%) were found to be low. The bioaccessible As content was significantly positively correlated with the As content in adsorbed aluminum arsenate, adsorbed ferrum arsenate, and calcium arsenate. A small portion of these sequential extractable As speciation could be absorbed by the human body (CH: 14.9%, HD: 3.16%), posing a certain health risk. Adsorbed aluminum arsenate had the highest IVBA, followed by calcium arsenate, and adsorbed ferrum arsenate had the lowest IVBA. The aforementioned speciation characteristics of As from geological origin in lateritic red soil contributed to its lower IVBA compared to other soils. The oxidation state of As did not significantly affect As-IVBA. Based on As-IVBA, the carcinogenic and non-carcinogenic risks of soil As in the CH and HD sites decreased greatly in human health risk assessment. The results suggest that As-IVBA in lateritic red soil should be considered when assessing human health risks on construction land.

Asunto(s)

RESUMEN

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3 mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30 days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3 mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0-31.9 µg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield.

Asunto(s)

RESUMEN

In the present study, an efficacious, safe, inexpensive and eco-friendly microextraction was provided by deep eutectic solvents based on dispersive liquid-liquid microextraction (DLLME - DES) followed by GFAAS. A series of DESs were synthesised using l-menthol as hydrogen bond acceptor (HBA) and carboxylic acids with 4, 6, 8 and 10 carbon atoms as hydrogen bond donors (HBD). The synthesised DESs were used as extractants of arsenic ions. Under optimised conditions, good linearity with coefficient of determination (r2) 0.992 and an acceptable linear range of 0.3-100 µg kg-1 was obtained. The limit of detection was 0.1 µg kg-1 (S/N = 3) for arsenite (As(III)) ions, and a high enrichment factor (EF = 200) was obtained. The enhancement factor and extraction recovery (ER%) of the method were 340 and 60%, respectively. RSDs including inter- and intra-day ranged from 3.2% to 5.8% in three examined concentrations. After a specific digestion, the capability of the synthesised DES in the extraction of As(III) from rice was tested. Total inorganic arsenic was separated similarly after reduction of arsenate (As(V)) to As(III), and As(V) concentration was calculated by difference. Using a second digestion method, total arsenic concentration (sum of organic and inorganic arsenic) in the samples was determined.

Asunto(s)

RESUMEN

Despite the widespread use of biochar for soil and sediment remediation, little is known about the impact of pyrolysis temperature on the biogeochemistry of arsenic (As) and lead (Pb) and microorganisms in sediment under reducing conditions. In this study, we investigated the effects of pyrolysis temperature and the addition of glucose on the release and transformation of As and Pb, as well as their potential effects on the bacterial community in contaminated sediments. The addition of biochar altered the geochemical cycle of As, as it favors specific bacterial groups capable of changing species from As(V) to As(III) through fermentation, sulfate respiration and nitrate reduction. The carbon quality and content of N and S in solution shaped the pH and redox potential in a way that changed the microbial community, favoring Firmicutes and reducing Proteobacteria. This change played a fundamental role in the reductive dissolution of As and Pb minerals. The addition of biochar was the only efficient way to remove Pb, possibly as a function of its sorption and precipitation mechanisms. Such insights could contribute to the production or choice of high-efficiency biochar for the remediation of sediments subjected to redox conditions.

Asunto(s)

RESUMEN

Dietary patterns provide a comprehensive assessment of food consumption, including essential nutrients and potential exposure to environmental contaminants. While pro-vegetarian (PVG) dietary patterns have shown health benefits in adults, their effects on children are less well studied. This study aims to explore the association between children's adherence to the most common PVG dietary patterns and their exposure to metals, assessed through urine concentration. In our study, we included a population of 723 children aged 4-5-years from the INfancia y Medio Ambiente (INMA) cohort in Spain. We calculated three predefined PVG dietary patterns, namely general (gPVG), healthful (hPVG), and unhealthful (uPVG), using dietary information collected through a validated Food Frequency Questionnaire. Urinary concentrations of various essential and heavy metals (Co, Cu, Zn, Se, Mo, Pb, and Cd) were measured using mass spectrometry. Additionally, urinary arsenic speciation, including arsenobetaine (AsB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic arsenic (iAs), was measured. The sum of urinary MMA and iAs was used to assess iAs exposure. We estimated primary (PMI) and secondary iAs methylation (SMI) indices. To explore the association between PVG dietary patterns in quintiles and metal exposure, we utilized multiple-adjusted linear regression models and the quantile g-computation approach. Compared with the lowest quintile, participants in the highest quintile of gPVG showed a 22.7% lower urinary Co (95% confidence interval (CI): -38.7; -1.98) and a 12.6% lower Se (95%CI: -22.9; -1.00) concentrations. Second quintile of adherence to hPVG was associated with a 51.7% lower urinary iAs + MMA concentrations (95%CI: -74.3; -8.61). Second quintile of adherence to an uPVG was associated with a 13.6% lower Se levels (95%CI: -22.9; -2.95) while the third quintile to this pattern was associated with 17.5% lower Mo concentrations (95%CI: -29.5; -2.95). The fourth quintile of adherence to gPVG was associated with a 68.5% higher PMI and a 53.7% lower SMI. Our study showed that adherence to a gPVG dietary pattern in childhood may modestly reduce the intakes of some essential metals such as Co and Se. Further investigations are warranted to explore any potential health implications.

Asunto(s)

RESUMEN

For centuries, Hawaiians have gathered seaweed for food, medicine, and ceremonial purposes. Seaweed contains nutrients, but some varieties can accumulate toxic elements. We measured target macrominerals (Na, Mg, P, K, Ca), microminerals (B, V, Mn, Co, Cu, Zn, Mo), and nonessential/toxic elements (As, Sr, Cd, Sn, Hg, Pb, and U) in a sample of wild-collected and cultivated seaweeds from Hawai'i. The samples consisted of brown (Sargassum aquifolium, Sargassum echinocarpum), red (Gracilaria parvispora, Halymenia formosa, Halymenia hawaiiana), and green (Ulva ohnoi) seaweed. Elemental composition was determined by inductively coupled plasma (ICP)-atomic emission spectroscopy and ICP-mass spectrometry (MS). Speciation of As was conducted by using liquid chromatography-ICP-MS. S. echinocarpum per 80 g serving was high in Ca (~37% daily value [DV]), U. ohnoi was high in Mg (~40%DV), H. formosa was high in Fe (~40%DV), and G. parvispora was high in Mn (~128%DV). In this study, the highest amounts of toxic elements were observed in S. aquifolium and S. echinocarpum (27.6 mg inorganic As/kg fdw), G. parvispora (43.3 mg Pb/kg fdw) and H. formosa (46.6 mg Pb/kg fdw). These results indicate that although seaweeds from Hawai'i contain a variety of nutrients, some species can accumulate high amounts of toxic elements.

RESUMEN

The organoarsenical feed additive roxarsone (ROX) is a ubiquitous threat due to the unpredictable levels of arsenic (As) released by soil bacteria. The earthworms representing soil fauna communities provide hotspots for As biotransformation genes (ABGs). Nonetheless, the role of gut bacteria in this regard is unclear. In this study, the changes in As speciation, bacterial ABGs, and communities were analyzed in a ROX-contaminated soil (50 mg/kg As in ROX form) containing the earthworm Eisenia feotida. (RE vs. R treatment). After 56 d, earthworms reduced the levels of both ROX and total As by 59 % and 17 %, respectively. The available As content was 10 % lower in the RE than in R treatment. Under ROX stress, the total ABG abundance was upregulated in both earthworm gut and soil, with synergistic effects observed following RE treatment. Besides, the enrichment of arsM and arsB genes in earthworm gut suggested that gut bacteria may facilitate As removal by enhancing As methylation and transport function in soil. However, the bacteria carrying ABGs were not associated with the ABG abundance in earthworm gut indicating the unique strategies of earthworm gut bacteria compared with soil bacteria due to different microenvironments. Based on a well-fit structural equation model (P = 0.120), we concluded that gut bacteria indirectly contribute to ROX transformation and As detoxification by modifying soil ABGs. The positive findings of earthworm-induced ROX transformation shed light on the role of As biomonitoring and bioremediation in organoarsenical-contaminated environments.

Asunto(s)

RESUMEN

A new ionic liquid modified polymer gel containing methylimidazolium groups (poly(MIA)) is proposed as a sorbent for the separation and enrichment of trace inorganic and organic arsenic species in surface waters. The poly(MIA) was synthesized by chemical modification of polymeric precursor using post-polymerization modification of poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate). The composition, structure, morphology, and surface properties of the prepared particles were characterized using elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption measurements. Optimization experiments showed that at pH 8, monomethylarsonic acid (MMAs), dimethylarsinic acid (DMAs), and As(V) were completely retained on the poly(MIA), while the sorption of As(III) was insignificant. The desorption experiments revealed that due to the weaker binding of organic arsenic species, selective elution with 1 mol/L acetic acid for MMAs + DMAs, followed by elution with 2 mol/L hydrochloric acid for As(V), ensured their quantitative separation. The adsorption kinetic and mechanism were defined. The analytical procedure for As(III), As(V), MMAs, and DMAs determination in surface waters was developed and validated through the analysis of certified reference material.

RESUMEN

The total arsenic mass fraction as well as the arsenic speciation were studied in four different mushroom species with inductively coupled plasma mass spectrometry and high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry, respectively. Arsenic mass fractions detected in the mushrooms were covering a range from 0.3 to 22 mg As kg-1 dry mass. For the arsenic speciation, species like arsenobetaine, inorganic arsenic, or dimethylarsinic acid were found, which are commonly detected in mushrooms, but it was also proven that the recently discovered novel compound homoarsenocholine is present in Amanita muscaria and Ramaria sanguinea. Moreover, a previously unidentified arsenic species was isolated from Ramaria sanguinea and identified as trimethylarsonioacetamide, or in short: arsenobetaine amide. This new arsenical was synthesized and verified by spiking experiments to be present in all investigated mushroom samples. Arsenobetaine amide could be an important intermediate to further elucidate the biotransformation pathways of arsenic in the environment.

Asunto(s)

RESUMEN

Arsenic is ranked as the first compound in the Substance Priority List 2023 by the Agency for Toxic Substances and Disease Registry (ATSDR). The most prominent entrance to the human body is through drinking water wherein the predominant species are arsenite and arsenate. The more toxic As(III) has rigorously threatened human health worldwide; hence, speciation and separation are the need of the hour. In this article, we have reported a simple method of arsenic speciation by wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer. Valence to core (VtC) electronic transitions, i.e., AsKß2,5 fluorescence lines were used for arsenic speciation. This speciation study by WD-XRF entails direct measurement of activated alumina pellets containing arsenate and arsenite species adsorbed from water sample without separation of the trivalent and pentavalent species. This is the first report wherein the X-ray technique has been explored for speciation analysis of arsenic and the biggest advantage of the method lies in its applicability to direct analysis of synthesized nanotubes or other solid-phase extraction sorbents entrapping both the arsenic species. For determination of total arsenic using activated alumina as adsorbent, the most intense AsKα1,2 analytical lines were used and the instrumental limit of detection and the lower limit of quantification were 0.23 µg/L and 0.89 µg/L, respectively. For speciation, these limits were calculated to be 50 µg/L and 200 µg/L, respectively.

Asunto(s)

RESUMEN

The ability of an organism to biomethylate toxic inorganic arsenic (As) determines both, the amount of As available for uptake higher up the food chain and the toxicity of bioavailable As. An exposure study was conducted to determine ability of farmed crickets to metabolize dietary arsenate. Crickets were exposed to 1.3 ± 0.1, 5.1 ± 2.5 and 36.3 ± 5.6 mg kg-1 dietary arsenate and quantitation of total As showed retention of 0.416 ± 0.003, 1.3 ± 0.04 and 2.46 ± 0.09 mg kg-1, respectively. Speciation analysis revealed that crickets have well developed ability to biomethylate dietary arsenate and the most abundant methylated As compound was DMA followed by MMA, TMAO and an unknown compound. Arsenobetaine, although present in all feed, control and As-rich, was measured only in the control crickets. To assess the bio-accessibility of the As species, crickets were subjected to simulated gastrointestinal digestion. The results showed that majority of As was extracted in saliva, followed by gastric and intestinal juice, which mass fraction was equal to residue. Over 78% of total As was shown to be bio-accessible with methylated species reaching 100% and iAs over 79% bio-accessibility. Additionally, arsenite and arsenate have shown different distributions between sequential leachate solutions. Bioaccumulation of As was observed in the studied crickets although it does not seem to occur to the same extent at higher exposure levels.

Asunto(s)

RESUMEN

Alcohol consumption alters gut microflora and damages intestinal tight junction barriers, which may affect arsenic (As) oral bioavailability. In this study, mice were exposed to arsenate in the diet (6 µg/g) over a 3-week period and gavaged daily with Chinese liquor (0.05 or 0.10 mL per mouse per day). Following ingestion, 78.0% and 72.9% of the total As intake was absorbed and excreted via urine when co-exposed with liquor at daily doses of 0.05 or 0.10 mL, significantly greater than when As was supplied alone (44.7%). Alcohol co-exposure significantly altered gut microbiota but did not significantly alter As biotransformation in the intestinal tract or tissue. Significantly lower relative mRNA expression was observed for genes encoding for tight junctions in the ileum of liquor co-exposed mice, contributing to greater As bioavailability attributable to enhanced As absorption via the intestinal paracellular pathway. However, As concentration in the liver, kidney, and intestinal tissue of liquor-treated mice was decreased by 24.4%-42.6%, 27.5%-38.1%, and 28.1%-48.9% compared to control mice. This was likely due to greater renal glomerular filtration rate induced by alcohol, as suggested by significantly lower expression of genes encoding for renal tight junctions. In addition, in mice gavaged daily with 0.05 mL liquor, the serum antidiuretic hormone level was significantly lower than control mice (2.83 ± 0.59 vs. 5.40 ± 1.10 pg/mL), suggesting the diuretic function of alcohol consumption, which may facilitate As elimination via urine. These results highlight that alcohol consumption has a significant impact on the bioavailability and accumulation of As.

RESUMEN

Inorganic and methylated thioarsenates have recently been reported to form in paddy soil pore waters and accumulate in rice grains. Among them, dimethylmonothioarsenate (DMMTA) is particularly relevant because of its high cytotoxicity and potential misidentification as nonregulated dimethylarsenate (DMA). Studying DMMTA uptake and flag leaf, grain, and husk accumulation in rice plants during grain filling, substantial dethiolation to DMA was observed with only 8.0 ± 0.1, 9.1 ± 0.6, and 1.4 ± 0.2% DMMTA remaining, respectively. More surprisingly, similar shares of DMMTA were observed in control experiments with DMA, indicating in planta DMA thiolation. Exposure of different rice seedling varieties to not only DMA but also to arsenite and monomethylarsenate (MMA) revealed in planta thiolation as a common process in rice. Up to 35 ± 7% DMA thiolation was further observed in the shoots and roots of the model plant Arabidopsis thaliana. Parameters determining the ratio and kinetics of thiolation versus dethiolation are unknown, yet, but less DMA thiolation in glutathione-deficient mutants compared to wild-type plants suggested glutathione concentration as one potential parameter. Our results demonstrate that pore water is not the only source for thioarsenates in rice grains and that especially the currently nonregulated DMA needs to be monitored as a potential precursor of DMMTA formation inside rice plants.

Asunto(s)