Species distribution characteristics of arsenic in shellfish seafood collected from Fujian Province of China

Effect of inorganic arsenic in paddy soil on the migration and transformation of selenium species in rice plants

Selenium (Se) in paddy rice is one of the significant sources of human Se nutrition. However, the effect of arsenic (As) pollution in soil on the translocation of Se species in rice plants is unclear. In this research, a pot experiment was designed to examine the effect of the addition of 50 mg As/kg soil as arsenite or arsenate on the migration of Se species from soil to indica Minghui 63 and Luyoumingzhan. The results showed that the antagonism between inorganic As and Se was closely related to the rice cultivar and Se oxidation state in soil. Relative to the standalone selenate treatment, arsenite significantly (p < 0.05) decreased the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, sheaths, leaves, brans and kernels of both cultivars by 21.4%-100.0%, 40.0%-100.0%, 41.0%-100%, 5.4%-96.3%, 11.3%-100.0% and 26.2%-39.7% respectively, except for selenocystine in the kernels of indica Minghui 63 and selenomethionine in the leaves of indica Minghui 63 and the stems of indica Luyoumingzhan. Arsenate also decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, brans and kernels of both cultivars by 34.9%-100.0%, 30.2%-100.0%, 11.3%-100.0% and 5.6%-39.6% respectively, except for selenate in the stems of indica Minghui 63. However, relative to the standalone selenite treatment, arsenite and arsenate decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenite only in the roots of indica Minghui 63 by 45.5%-100.0%. Our results suggested that arsenite and arsenate had better antagonism toward Se species in selenate-added soil than that in selenite-added soil; moreover, arsenite had a higher inhibiting effect on the accumulation of Se species than arsenate.

Characteristics of arsenic speciation in mainly cultured shellfish from Sanmen Bay, Zhejiang Province, China

Sanmen Bay plays a crucial role in economic shellfish aquaculture in China, yet few studies exist on the arsenic speciation of shellfish from this area. In this study, arsenic speciation of 11 cultured shellfish species from Sanmen Bay were analyzed by HPLC/ICP-MS. The results showed that organic arsenic particularly AsB, was the dominant arsenic species, constituting 21 %-71 % of the total arsenic. Conversely, the levels of inorganic arsenic were relatively low, ranging from 0.007 to 0.093 mg/kg, only accounted for 0.2 %-5.7 % of the total arsenic. There was no significant level correlation between inorganic arsenic and total arsenic in Sanmen Bay shellfish, so the concentration of inorganic arsenic did not increase with the total arsenic. Overall, the present study firstly revealed the arsenic speciation of shellfish from Sanmen Bay and also suggested that the proportion of inorganic arsenic should be considered in the revision of arsenic limit values.

Toxic arsenic in marketed aquatic products from coastal cities in China: Occurrence, human dietary exposure risk, and coexposure risk with mercury and selenium

To improve the accuracy of dietary risk assessment of arsenic (As) from aquatic products, toxic As species (As(III), As(V), monomethylarsonic acid [MMA], and dimethylarsinic acid [DMA]) and total As were analyzed in 124 marketed aquatic products from eight coastal cities in China. Distribution characteristics of Toxic As (the sum of the four toxic As species) in the samples and associated risk of human dietary exposure were emphatically investigated. The impact of cooccurrence of As and other chemical elements in the aquatic products was assessed based on our former results of mercury (Hg) and selenium (Se). Toxic As contents (maximum value 0.358 mg kg^-1 wet weight) in the samples accounted for at most 14.1% of total As. DMA was the major component (mean proportion 50.8% for shellfish, 100% for fish) of Toxic As in aquatic products. Shellfish contained more Toxic As than fish did. Mean estimated daily intakes of Toxic As for the residents with aquatic product consumption rates of 46.1-235 g day^-1 ranged from 0.034 to 0.290 μg kg^-1 day^-1. Potential health risk was indicated among those who greatly consumed aquatic products, as their target hazard quotient (THQ) and target cancer risk (TR) values exceeded safety thresholds (1 for THQ, 10^-4 for TR). DMA and MMA exposure contributed to 3.42-7.72% of the THQ_{Toxic As}. Positive correlations between concentrations of As and Hg (Fish: r = 0.47, p < 0.01; Shellfish: r = 0.60, p < 0.01), as well as between that of As and Se (Fish: r = 0.69, p < 0.01; Shellfish: r = 0.37, p < 0.01) were found in the samples. It requires attentions urgently that As and Hg coexposure through aquatic product consumption rose the sum THQ of Toxic As and methylmercury (MeHg) to approximately two to eight times as high as the THQ_{Toxic As}.

LC/ICP-MS AND COMPLEMENTARY TECHNIQUES IN BESPOKE AND NONTARGETED SPECIATION ANALYSIS OF ELEMENTS IN FOOD SAMPLES

Chemical elements speciation analysis of food samples has been among the most important scientific topics over the last decades. Food samples are comprised of high variety of chemical compounds, from which many can interact with metals and metalloids, forming complex elemental species with various influence on the human body. It is particularly important not only to determine the amount of certain chemical element in food sample but also to identify the form in which given element occurs in given sample. Employment of bespoke and nontargeted speciation methods, with the use of liquid chromatography inductively coupled plasma mass spectrometry (LC/ICP-MS) and complementary techniques, provides more complete picture on the metals and metalloids speciation in food. This review discusses issues concerning speciation analysis of metals and metalloids in food samples with the use of LC/ICP-MS as a leading technique in elemental speciation nowadays and a complimentary technique intended for their identification. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Metabolic and residual characteristic of different arsenic species contained in laver during mouse digestion

Laver is one of the major arsenic contributors to human diets. The study on metabolic and residual characteristic of each arsenic species contained in laver is important to scientifically assess the intake risk of arsenic in the laver. The metabolic and residual characteristic of main arsenic species in laver, namely arsenate [As(V)], dimethylarsinic acid [DMA(V)] and two arsenosugars, was investigated by mouse experiments in this study. The results showed that the intake of higher-dose laver did not lead to a notable increase of As(V) concentration in mouse muscle/organs and feces. In contrast, DMA(V) excretion in feces and DMA(V) residue in muscle/organs showed a close correlation with laver-dose intake. Most DMAsSugarMethoxy was translated into other arsenic species and then was together excreted out via mouse feces; two dominant arsenic species, arsenosugar DMAsSugarMethoxy and DMAsSugarPhosphate, were not detected in mouse muscle/organs after 20-Day or 30-Day feeding whether in lower-dose laver groups containing 1/36 (mass ratio) of the laver in mouse feed or higher-dose laver groups containing 1/6 (mass ratio) of the laver in mouse feed. About 65-77% of total arsenic digested by mouse was excreted out via feces; only 0.12-0.78% of it was accumulated in mouse organs/muscle. The results of this study provided valuable knowledge for comprehending the stability and metabolic characteristics of different arsenic species from Fujian laver in vivo, also for more scientifically assessing the intake risk of arsenic in laver.

In vitro bio-accessibility and distribution characteristic of each arsenic species in different fishes and shellfishes/shrimps collected from Fujian of China

It is very important to consider the bio-accessibilities and concentrations of each arsenic species, not total arsenic, in seafood in order to accurately assess internal exposure level and health risk of arsenic from seafood. Herein, the concentrations and in vitro bio-accessibilities of each arsenic species in various fishes and shellfishes/shrimps were extensively investigated. Experimental results showed that arsenic species and contents in shellfishes/fishes remarkably varied with the difference of fish/shellfish species or individuals and sampling area, and arsenobetaine (AsB) is dominant arsenic species for fishes and shellfishes/shrimps. Different arsenic species in the same fish/shellfish have quite different bio-accessibilities, and the bio-accessibilities of each arsenic species also varied with fish/shellfish species or individuals. As³⁺ in fishes/shellfishes was partly oxidized to form As⁵⁺ during gastrointestinal digestion, and thus it is more reasonable and practicable to evaluate the bio-accessibilities of inorganic arsenic (iAs, total As³⁺ and As⁵⁺), not individual As³⁺ and As⁵⁺. Fishes and shellfishes/shrimps have similar bio-accessibilities of iAs, AsB and total arsenic, whereas have different bio-accessibilities of MMA (monomethylarsonic acid), DMA (dimethylarsinic acid), and two un-identified arsenic (Ui-As1 and Ui-As2). The results of this study provided a valuable knowledge for accurately assessing the health risk of arsenic in seafood.

Speciation analysis of organoarsenic species in marine samples: method optimization using fractional factorial design and method validation

Organoarsenic species in marine matrices have been studied for many years but knowledge gaps still exist. Most literature focuses on monitoring of arsenic (As) species using previously published methods based on anion- and cation-exchange high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). These studies are often limited to few As species and/or only specific method performance characteristics are described. Most marine certified reference materials (CRMs) are only certified for arsenobetaine (AB) and dimethylarsinate (DMA), making it difficult to evaluate the accuracy of analytical methods for other organoarsenic species. To address these gaps, the main objective of this work was to develop and validate a method for speciation analysis of a broad range of organoarsenic species in marine matrices. Optimum extraction conditions were identified through a 2^7–3 fractional factorial design using blue mussel as test sample. The effects of sample weight, type and volume of extraction solution, addition of H₂O₂ to the extraction solution, extraction time and temperature, and use of ultrasonication were investigated. The highest As recoveries were obtained by using 0.2 g as sample weight, 5 mL of aqueous methanol (MeOH:H₂O, 50% v/v) as extractant, extraction carried out at 90 °C for 30 min, and without ultrasonication. Anion- and cation-exchange HPLC-ICP-MS settings were subsequently optimized. The method detected a total of 33 known and unknown As species within a run time of 23 and 20 min for cation-exchange and anion-exchange, respectively. A single-laboratory validation was conducted using several marine CRMs: BCR 627 (tuna fish tissue), ERM-CE278k (mussel tissue), DORM-4 (fish protein), DOLT-5 (dogfish liver), SQID-1 (cuttlefish), TORT-3 (lobster hepatopancreas), and CRM 7405-b (hijiki seaweed). Method performance characteristics were evaluated based on selectivity, limits of detection and quantification, linearity, trueness, precision, and measurement uncertainty. This work proposes an extraction procedure which allowed satisfactory quantification of As species with low solvent and energy consumption, supporting “Green Chemistry” principles. The study also presents a new set of As speciation data, including methylated arsenic species and arsenosugars, in recently issued marine CRMs, which will be valuable for future speciation studies on As. This work is the first to report a total of 33 different As species in marine CRMs.

Underlying mechanisms responsible for restriction of uptake and translocation of heavy metals (metalloids) by selenium via root application in plants

Since selenium (Se) was shown to be an essential element for humans in 1957, the biofortification of Se to crops via foliar spraying or soil fertilization has been performed for several decades to satisfy the daily nutritional need of humans. Appropriate doses of Se were found to counteract a number of abiotic and biotic stresses, such as exposure to heavy metals (metalloids) (HMs), via influencing the regulation of antioxidant systems, by stimulation of photosynthesis, by repair of damaged cell structures and functions, by regulating the metabolism of some substances and the rebalancing of essential elements in plant tissues. However, few concerns were paid on why and how Se could reduce the uptake of a variety of HMs. This review will mainly address the migration and transformation of HMs regulated by Se in the soil-plant system in order to present a hypothesis of why and how Se can reduce the uptake of HMs in plants. The following aspects will be examined in greater detail, including 1) how the soil characteristics influences the ability of Se to reduce the bioavailability of HMs in soils and their subsequent uptake by plants, which include soil Se speciation, pH, water regime, competing ions and microbes; 2) how the plant root system influenced by Se affects the uptake or the sequestration of HMs, such as root morphology, root iron plaques and root cell wall; 3) how Se combines with HMs and then sequesters them in plant cells; 4) how Se competes with arsenic (As) and thereby reduces As uptake in plants; 5) how Se regulates the expression of genes encoding functions involved in uptake, translocation and sequestration of HMs by Se in plants.

Improved grain yield and lowered arsenic accumulation in rice plants by inoculation with arsenite-oxidizing Achromobacter xylosoxidans GD03

Arsenite is the predominant arsenic species in flooded paddy soil, and arsenite bioaccumulation in rice grains has been identified as a major problem in many Asian countries. Lowering arsenite level in rice plants and grain via accelerating arsenite oxidation is a potential strategy to help populations, who depended on rice consumption, to reduce the internal exposure level of arsenic. We herein isolated a strain, Achromobacter xylosoxidans GD03, with the high arsenite-oxidizing ability and plant growth-promoting traits. We observed that arsenite exposure could promote A. xylosoxidans GD03 to excrete indole-3-acetic acid and thus promoted rice growth. The pot culture experiments of Indica rice cultivar Guang You Ming 118 (GYM118) demonstrated that A. xylosoxidans GD03 inoculation of paddy soil (4.5-180 × 10⁸ CFU GD03/kg soil) significantly accelerated arsenite oxidation in flooded soil. The daily arsenic oxidation rate with GD03 inoculation was 1.5-3.3 times as that without strain GD03 inoculation within the whole growth period of Indica GYM118 in the presence of the native microflora. It thus led to a 34-69%, 43-74%, 24-76% and 35-57% decrease in arsenite concentration of the stems, leaves, bran and grain of Indica GYM118 respectively and a 59-96% increase in rice grain yield. The paddy soil inoculated with 40.0 mL/kg of A. xylosoxidans GD03 resulted in a lowest As(III) concentrations in all rice organs of Indica GYM118, which equivalent to only 24-50% of the As(III) concentrations in the group without GD03 inoculation. The results highlight that a highly arsenite-oxidizing bacterium could accelerate arsenite oxidation of paddy soil when facing competition with the native microflora, thus decrease arsenic toxicity and bioavailable soil arsenic.

Arsenic in shellfish: A systematic review of its dynamics and potential health risks

Arsenic is the most toxic element for humans. Presenting naturally in aquatic ecosystems and due to anthropogenic action, this semi-metal transfers to shellfish through the food chain. This systematic review aims to explain the dynamic of arsenic in the marine aquatic system, investigating factors that affect its bioaccumulation. A total of 64 articles were considered from three databases. The key abiotic factor influencing the presence of arsenic in shellfish is anthropogenic contamination, followed by geographic location. The crucial biotic factor is the genetics of each species of shellfish, including their diet habits, habitat close to the sediment, metabolic abilities, physiological activities of organisms, and metal levels in their habitats and food. Finally, arsenic presents an affinity for specific tissues in shellfish. Despite containing mostly less toxic organic arsenic, shellfish are a relevant source of arsenic in the human diet.

Effect of selenium in soil on the toxicity and uptake of arsenic in rice plant

Selenium can regulate arsenic toxicity by strengthening antioxidant potential, but the antagonism between selenite or selenate nutrient and the translocation of arsenic species from paddy soil to different rice organs are poorly understood. In this study, a pot experiment was designed to investigate the effect of selenite or selenate on arsenite or arsenate toxicity to two indica rice cultivars (namely Ming Hui 63 and Lu You Ming Zhan), and the uptake and transportation of arsenic species from paddy soil to different rice organs. The results showed that selenite or selenate could significantly decrease the arsenate concentration in pore water of soils, and thus inhibited arsenate uptake by rice roots. However, the existence of selenite or selenate didn't decrease arsenate concentration in rhizosphere pore water of two indica rice cultivars. There existed good antagonistic effect between selenite or selenate and the uptake of arsenite and arsenate in rice plant in the case of low arsenic paddy soil. However, this antagonism depended on rice cultivars, arsenic species and arsenic level in soil. There existed both synergistic and inhibiting effects between the addition of selenite or selenate and the uptake of trimethylarsinoxide and dimethylarsinic acid by two indica rice cultivars, but the mechanism was unclear. Both selenite and selenate are all effective to decrease the translocation of inorganic arsenic from the roots to their above-ground rice organs in arsenite/arsenate-spiked paddy soil, but selenate had stronger inhibiting effect on their transfer factors than selenite.