Investigation of tissue level distribution of functional groups and associated trace metals in rice seeds (Oryza sativa L.) using FTIR and LA-ICP-MS

Development of matrix-specific standards for LA-ICP-MS zinc analysis in sand flathead (Platycephalus bassensis)

The use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyse soft tissues is limited because of the lack of suitable certified reference materials resulting in difficulties with calibration. In this study, several laboratory-prepared thin agarose sections were tested as matrix-specific standards. Our results showed 1 mm thin agarose sections were suitable as calibration standards for LA-ICP-MS Zn analyses in fish muscle, especially when the signal intensity of 66Zn was normalised to 13C. The thin agarose standard sections were used for LA-ICP-MS Zn analyses in the muscle of melanised and non-melanised sand flathead collected from a polluted estuary and assigned with different melanisation scores. Zn levels in melanised regions of fish muscle were determined to be significantly higher than non-melanised regions across all melanisation scores, though Zn levels in the melanised regions of muscle were not significantly different between sand flathead with different melanisation scores. In non-melanised regions of muscle from fish with melanisation and fish unaffected by melanisation, Zn levels were around baseline levels. Overall, this study has successfully developed matrix-specific standards for LA-ICP-MS analysis of soft tissues, thus allowing broader application of this analytical technique in future environmental pollution studies.

Effects of soil amendments on Cd and As mobility in the soil-rice system and their distribution in the grain

The accumulation, mobilization, and distribution of toxic metal(loid)s in rice are key factors that affect food security and determine bio-utilization patterns. In this study, five soil amendments with different components were used in paddy fields to study the key factors: organic amendments: (1) polyaspartic acid (OA1) and (2) organic fertilizer (OA2); inorganic amendments: (3) kaolinite (IA1) and (4) magnesium slag (IA2); and organic-inorganic composite amendments: (5) modified biochar/quicklime (OIA). Although the Cd and As exhibited opposite chemical dissolution behaviors, IA1/OIA, can simultaneously reduce their accumulation and transfer coefficients in rice tissues, while other amendments only work for one of them. The in situ distribution in grains showed that IA1/OIA changed the original Cd distribution in the lemma and palea, whereas all amendments reduced Cd accumulation in the germ. In contrast, OA1/IA2 amendments led to more As accumulation in the rice husks and bran than in the endosperm center, and the germ had higher As signals. Because of their similar transport pathways and interactions, the concentrations of Cd and As in the grains were correlated with a variety of mineral elements (Fe, Mo, Zn, etc.). Changes in the Cd/As concentration and distribution in rice were achieved through the improvement of soil properties and plant growth behavior through amendments. The application of OIA resulted in the highest immobilization indices, at 82.17 % and 35.34 % for Cd and As, respectively. The Cd/As concentrations in the rice grains were highly positively correlated with extractable-Cd/As in the soil (Cd: R2 = 0.95, As: R2 = 0.93). These findings reveal the migration and distribution mechanisms of Cd and As in the soil-rice system, and thus provide fundamental information for minimizing food safety risk.

Towards a Standardized Approach for the Geographical Traceability of Plant Foods Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Principal Component Analysis (PCA)

This paper presents a systematic literature review focused on the use of inductively coupled plasma mass spectrometry (ICP-MS) combined with PCA, a multivariate technique, for determining the geographical origin of plant foods. Recent studies selected and applied the ICP-MS analytical method and PCA in plant food geographical traceability. The collected results from many previous studies indicate that ICP-MS with PCA is a useful tool and is widely used for authenticating and certifying the geographic origin of plant food. The review encourages scientists and managers to discuss the possibility of introducing an international standard for plant food traceability using ICP-MS combined with PCA. The use of a standard method will reduce the time and cost of analysis and improve the efficiency of trade and circulation of goods. Furthermore, the main steps needed to establish the standard for this traceability method are reported, including the development of guidelines and quality control measures, which play a pivotal role in providing authentic product information through each stage of production, processing, and distribution for consumers and authority agencies. This might be the basis for establishing the standards for examination and controlling the quality of foods in the markets, ensuring safety for consumers.

Appraisal of a novel extraction technique for estimation of cadmium content in pea seedlings based on human health risk assessment

In this study, a novel extraction and safety evaluation method for heavy metals based on different functions of plants was proposed, and an edible plant (pea) was used as the research material to explore the feasibility of the novel method. Pea sprouts were cultured in cadmium (Cd) concentrations of 0, 1.0, 3.0, and 5.0 mg L-1, respectively. The Cd in pea sprouts was continuously extracted with 100 °C distilled water, 60% ethanol, 6% acetic acid, and simulated gastric juice. It was observed that highest amount of Cd (48.65-58.87%) was found in the extraction of roots with 6% acetic acid, followed by 100 °C distilled water (28.68-37.61%). While in stems, most of the Cd (70.73-85.39%) was extracted by 6% acetic acid. The recovery rate of the sequential chemical extraction technique employed in this experiment was between 93 and 106%. Compared with traditional methods, this study has its development potential in two aspects. First, it can determine which steps of sequential extractions of heavy metals in plants are the most harmful to humans. Secondly, corresponding measures can be taken to reduce heavy metals in vegetables used daily, such as soaking edible vegetables in vinegar for a short time. Novelty statement: In this study, a novel extraction and safety evaluation method for heavy metals based on different functions of plants was proposed, and an edible plant (pea) was used as the research material to explore the feasibility of the novel method. Compared with the commonly used extraction methods, the novel method is more reasonable and has greater development potential.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry Imaging in Biology

Elemental imaging gives insight into the fundamental chemical makeup of living organisms. Every cell on Earth is comprised of a complex and dynamic mixture of the chemical elements that define structure and function. Many disease states feature a disturbance in elemental homeostasis, and understanding how, and most importantly where, has driven the development of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as the principal elemental imaging technique for biologists. This review provides an outline of ICP-MS technology, laser ablation cell designs, imaging workflows, and methods of quantification. Detailed examples of imaging applications including analyses of cancers, elemental uptake and accumulation, plant bioimaging, nanomaterials in the environment, and exposure science and neuroscience are presented and discussed. Recent incorporation of immunohistochemical workflows for imaging biomolecules, complementary and multimodal imaging techniques, and image processing methods is also reviewed.

Exposure to heavy metal contamination and probabilistic health risk assessment using Monte Carlo simulation: a study in the Southeast Iran

The rice contamination to heavy metals and its associated health risks have been less addressed in the southeast of Iran. In the present study, in the mentioned region, we assessed the concentration of nine elements in rice, and the health risk related to the measured elements was determined using the data which were gathered by a questionnaire. For this purpose, 36 samples of the 12 most widely consumed rice brands were collected. Using ICP-MS, the concentrations of Ni, Cr, Hg, Sr, Mn, Fe, Se, Ba, and Zn were measured in the studied samples as 0.599 ± 0.124, 0.483 ± 0.28, 0.0157 ± 0.005, 0.85 ± 1.307, 11.5 ± 1.97, 178.46 ± 67.27, 0.212 ± 0.083, 0.845 ± 0.62, and 8.416 ± 1.611 mg/kg, respectively. We found that, regarding the other studies, the levels of Ni, Cr, Hg, Fe, and Ba were higher. Besides, using 258 distributed questionnaires among citizens, the daily rice consumption was determined to be 295.66 ± 171.005 g/person/ day. Based on this consumption rate and Monto Carlo uncertainty simulation, Fe (0.741 ± 0.54 mg/kg/day) and Se (8.95E-04 ± 6.33E-04 mg/kg/day) showed the highest and lowest daily intake, respectively. Also, using Hazard Quotient (HQ), the non-carcinogenic risk effects of the surveyed elements were estimated. The obtained results of HQ revealed that Fe (2.48) and Mn (1.06) could pose non-carcinogenic health risks to consumers. Moreover, the calculated hazard Index showed that the overall health risk of the surveyed elements is in an unsafe range.

Effects of soaking, acidity and temperature on cadmium and lead removal from rice

In this research, effect of soaking time, acidity and temperature on the removal of lead and cadmium from rice was investigated. Different rice treatments were involved i.e. three soaking times (0, 15, and 30 min), three temperatures (20, 25, and 30 °C) and four concentrations of glacial acetic acid (0.5%, 1%, 2%, and 3%). Results showed that few samples have shown lead concentrations above the maximum limit set by the World Health Organization (WHO) and the UN Food and Agriculture Organization (FAO) of 0.2 mg/kg, whereas, all cadmium concentrations were below the limit of 0.4 mg/kg. A decrease in lead and cadmium concentrations were observed with increasing time of soaking. Lead had the lowest concentration at 20 °C, while cadmium had the lowest concentration at 30 °C. Cadmium concentration decreased with increasing water acidity, while the lead concentration reached the lowest concentration with 1% acidity.

Protective Effect of foliar application of sulfur on photosynthesis and antioxidative defense system of rice under the stress of Cd

This paper investigates the effect of foliar application of sulfur on photosynthesis and antioxidative defense system of rice under the stress of Cd. The initial field studies showed that foliar spray of S was effective for reducing Cd concentration in rice and increasing the grain yield. However, the physiological mechanisms remain less clear on how the foliar application of S alleviates Cd toxicity in rice. Chlorophyll fluorescence, as a measure of photosynthesis, was taken to estimate the efficiency of photosystem II (PSII) photochemistry after the foliar application of S. The increase of photosynthetic parameters, i.e. the maximum photochemical efficiency of PSII reaction center (Fv/Fm), the actual PSII photochemical efficiency (ΦPSII), the photochemical quenching coefficient (qP), indicated that the foliar treatment alleviated the toxicity of Cd to PSII. The decrease of non-photochemical quenching coefficient (NPQ) indicated the increase of photochemical reaction efficiency with more absorbed light energy for photochemical reactions. Fourier Transform Infrared (FTIR) spectra showed that the foliar treatment stimulated the syntheses of lignin, lipids, aliphatic acid, polysaccharides, carboxylate and proteins. Micrographs of transmission electron microscope (TEM) also revealed the reduced mobility of Cd in cells. Foliar application of S effectively reduced the damage of Cd stress by maintaining the integrity of cell structure and participating in metabolic activities such as protein synthesis.

Tissue level distribution of toxic and essential elements during the germination stage of corn seeds (Zea mays, L.) using LA-ICP-MS

Both essential and toxic metal contaminants impact agricultural crops by bioaccumulation in plants. The goal of this study was to evaluate the tissue-level spatial distribution of metal(loids) in corn seeds (Zea mays, L.) from contaminated corn fields near the Xikuangshan (XKS) antimony mine in Hunan, China, and compared them with corn (Zea mays everta L., popcorn) grown in a farm in Amherst, MA that practices sustainable farming as a control. How toxic and essential metals translocate through the roots and shoots during early stages of germination was also investigated. The cleaned corn seed samples were mounted in resin blocks and longitudinally dissected into thin sections. The laser ablation parameters were optimized, and the instrument was calibrated using tomato leaf standard reference material (NIST SRM 1573a) in a pellet form. Tissue level distributions of metal(loid)s As, Cd, Hg, Sb and Zn in corn seeds collected were determined using (LA-ICP-MS). Seeds from the control farm were germinated and their roots and shoots were analyzed to determine tissue level concentrations and their spatial distributions. It was found that seeds from the XKS mine region in China had higher overall concentration of all elements analyzed due to metal(loids) absorbed from contaminated mine soils. Metal(loids) concentrations were highest in the embryo (∼360 mg/kg) and pericarp (∼0.48 mg/kg) compared with the endosperm of corn seeds. Essential element Zn was found in the embryo and emerging coleoptile and radicle. Finally, in both roots and shoots, element concentrations were highest proximally to the tip cap compared to distal concentrations and later translocated to distal tissue regions. This study offers unique insights of metal(loid) bioaccumulation and translocation in corn and thus is better able to track metal(loids) contaminants trafficking in our food systems.

Iron and Zinc in the Embryo and Endosperm of Rice (Oryza sativa L.) Seeds in Contrasting 2'-Deoxymugineic Acid/Nicotianamine Scenarios

Iron and Zn deficiencies are worldwide nutritional disorders that can be alleviated by increasing the metal concentration of rice (Oryza sativa L.) grains via bio-fortification approaches. The overproduction of the metal chelator nicotianamine (NA) is among the most effective ones, but it is still unclear whether this is due to the enrichment in NA itself and/or the concomitant enrichment in the NA derivative 2'-deoxymugineic acid (DMA). The endosperm is the most commonly consumed portion of the rice grain and mediates the transfer of nutrients from vegetative tissues to the metal rich embryo. The impact of contrasting levels of DMA and NA on the metal distribution in the embryo and endosperm of rice seeds has been assessed using wild-type rice and six different transgenic lines overexpressing nicotianamine synthase (OsNAS1) and/or barley nicotianamine amino transferase (HvNAATb). These transgenic lines outlined three different DMA/NA scenarios: (i) in a first scenario, an enhanced NA level (via overexpression of OsNAS1) would not be fully depleted because of a limited capacity to use NA for DMA synthesis (lack of -or low- expression of HvNAATb), and results in consistent enrichments in NA, DMA, Fe and Zn in the endosperm and NA, DMA and Fe in the embryo; (ii) in a second scenario, an enhanced NA level (via overexpression of OsNAS1) would be depleted by an enhanced capacity to use NA for DMA synthesis (via expression of HvNAATb), and results in enrichments only for DMA and Fe, both in the endosperm and embryo, and (iii) in a third scenario, the lack of sufficient NA replenishment would limit DMA synthesis, in spite of the enhanced capacity to use NA for this purpose (via expression of HvNAATb), and results in decreases in NA, variable changes in DMA and moderate decreases in Fe in the embryo and endosperm. Also, quantitative LA-ICP-MS metal map images of the embryo structures show that the first and second scenarios altered local distributions of Fe, and to a lesser extent of Zn. The roles of DMA/NA levels in the transport of Fe and Zn within the embryo are thoroughly discussed.

Effect of competitive adsorption on zinc removal from aqueous solution and zinc smelting effluent by eucalyptus leaf-based magnetic biosorbent

The objectives of this study were to investigate the competitive sorption behaviors and mechanisms of heavy metals onto ELMB, a novel eucalyptus-leaf-based magnetic biosorbent, and to study the potential application of ELMB in the treatment of actual zinc smelting effluent after a necessary pretreatment process. ELMB and ELMB-metals systems were characterized using several techniques. Competitive sorption of Zn²⁺ with Pb²⁺, Cu²⁺ and Cd²⁺ onto ELMB was studied by batch experiments and the used sorbent was separated under a magnetic field. The results show that the ELMB can be considered as paramagnetic material with various functional groups on its surface. The presence of Pb²⁺, Cu²⁺ and Cd²⁺ significantly decreases the sorption of Zn²⁺ in either the binary system or multimetal systems. The order of adsorption preference is Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ in multimetal systems and the sequence of competitive ability to zinc is: Pb²⁺ > Cu²⁺ > Cd²⁺. Non-competitive Langmuir multicomponent isotherm model fits to the adsorption data of Pb²⁺ and Cu²⁺ well in aqueous solution. The co-existent Ca²⁺ and SO₄^2- decrease the removal efficiencies of heavy metals while the presence of Na⁺ and Cl^- shows little effect in the multimetal solution. In the case of actual zinc smelting effluent, "pretreatment + ELMB sorption" is successfully applied to remove heavy metals and the contents of Zn²⁺ and its associated metals are well below discharge limits.