In China, total Hg (HgT) and methylmercury (MeHg) were quantified in rice grain grown in three sites using water-saving rice cultivation methods, and in one Hg-contaminated site, where rice was grown under flooded conditions. Polished white rice concentrations of HgT (water-saving: 3.3±1.6ng/g; flooded: 110±9.2ng/g) and MeHg (water-saving 1.3±0.56ng/g; flooded: 12±2.4ng/g) were positively correlated with root-soil HgT and MeHg contents (HgT: r²=0.97, MeHg: r²=0.87, p<0.05 for both), which suggested a portion of Hg species in rice grain was derived from the soil, and translocation of Hg species from soil to rice grain was independent of irrigation practices and Hg levels, although other factors may be important. Concentrations of HgT and other trace elements were significantly higher in unmilled brown rice (p<0.05), while MeHg content was similar (p>0.20), indicating MeHg infiltrated the endosperm (i.e., white rice) more efficiently than inorganic Hg(II).

Understanding how essential and toxic elements are distributed in cereal grains is a key to improving the nutritional quality of cereal-based products. The main objective of this work was to characterize the distribution of Cd and of nutrients (notably Cu, Fe, Mn, P, S and Zn) in the durum wheat grain. Laser ablation inductively coupled mass spectrometry and synchrotron micro X-ray fluorescence were used for micro-scale mapping of Cd and nutrients. A dissection approach was used to quantitatively assess the distribution of Cd and nutrients among grain tissues. Micro X-ray absorption near-edge spectroscopy was used to identify the Cd chemical environment in the crease. Cadmium distribution was characterized by strong accumulation in the crease and by non-negligible dissemination in the endosperm. Inside the crease, Cd accumulated most in the pigment strand where it was mainly associated with sulfur ligands. High-resolution maps highlighted very specific accumulation areas of some nutrients in the germ, for instance Mo in the root cortex primordia and Cu in the scutellum. Cadmium loading into the grain appears to be highly restricted. In the grain, Cd co-localized with several nutrients, notably Mn and Zn, which challenges the idea of selectively removing Cd-enriched fractions by dedicated milling process.

The increase of annual organic wastes generated worldwide has become a major problem for many countries since the mismanagement could bring about negative effects on the environment besides, being costly for an innocuous disposal. Recently, insect larvae have been investigated to valorize organic wastes. This entomoremediation approach is rising from the ability of the insect larvae to convert organic wastes into its biomass via assimilation process as catapulted by the natural demand to complete its lifecycle. Among the insect species, black soldier fly or Hermetia illucens is widely researched since the larvae can grow in various environments while being saprophagous in nature. Even though black soldier fly larvae (BSFL) can ingest various decay materials, some organic wastes such as sewage sludge or lignocellulosic wastes such as waste coconut endosperm are destitute of decent nutrients that could retard the BSFL growth. Hence, blending with nutrient-rich low-cost substrates such as palm kernel expeller, soybean curd residue, etc. is employed to fortify the nutritional contents of larval feeding substrates prior to administering to the BSFL. Alternatively, microbial fermentation can be adopted to breakdown the lignocellulosic wastes, exuding essential nutrients for growing BSFL. Upon reaching maturity, the BSFL can be harvested to serve as the protein and lipid feedstock. The larval protein can be made into insect meal for farmed animals, whilst the lipid source could be extracted and transesterified into larval biodiesel to cushion the global energy demands. Henceforth, this review presents the influence of various organic wastes introduced to feed BSFL, targeting to reduce wastes and producing biochemicals from mature larvae through entomoremediation. Modification of recalcitrant organic wastes via fermentation processes is also unveiled to ameliorate the BSFL growth. Lastly, the sustainable applications of harvested BSFL biomass are as well covered together with the immediate shortcomings that entail further researches.

Arsenic (As) and antimony (Sb) are considered as priority environmental pollutants and their accumulation in crop plants particularly in rice has posed a great health risk. This study endeavored to investigate As and Sb contents in paired soil-rice samples obtained from Xikuangshan, the world largest active Sb mining region, situated in China, and to investigate As speciation and location in rice grains. The soil and rice samples were analyzed by coupling the wet chemistry, laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), synchrotron-based micro X-ray fluorescence mapping (μ-XRF) and micro X-ray absorption near-edge structure (μ-XANES) spectroscopy. The results of field survey indicated that the paddy soil in the region was co-polluted by Sb (5.91–322.35 mg kg−1) and As (0.01–57.21 mg kg−1). Despite the higher Sb concentration in the soil, rice accumulated more As than Sb indicating the higher phytoavailability of As. Dimethylarsinic acid (DMA) was the predominant species (>60% on average) in the rice grains while the percentage of inorganic As species was 19%–63%. The μ-XRF mapping of the grain section revealed that the most of As was distributed and concentrated in rice husk, bran and embryo. Sb was distributed similarly to As but was not in the endosperm of rice grain based on LA-ICP-MS. The present results deepened our understanding of the As/Sb co-pollution and their association with the agricultural-product safety in the vicinity of Sb mining area.

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.

Rice is a staple food and major source of nutrients, but it also bioaccumulates toxic elements. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine tissue-level trace metal spatial distribution in rice (Oryza sativa) seeds from the active Xikuangshan Sb mine area in China. Whole grain quantified elemental bioimages showed the highest concentration of Zn (1755 mg/kg) in the embryo andmicro zones of elevated Sb, As, Pb, Cd as high as 280, 57, 31 and 830 mg/kg, respectively on the husk/bran/endosperm tissues. Bioimages suggest that both Sb and Cd may be competing with Zn for binding sites. Both Sb(III) and Sb(V) species were detected in seeds from upstream and downstream fields indicating the presence of toxic Sb(III). Brown rice is a good source of Zn, but white rice is a safer option if rice is grown in a polluted area.

The anaerobic decomposition of coconut endosperm waste (CEW), residue derived from cooking, has been insidiously spewing greenhouse gasses. Thus, the bioconversion of CEW via in situ fermentation by exo-microbes from commercial Rid-X and subsequent valorization by black soldier fly larvae (BSFL) was the primary objective of the current study to gain sustainable larval lipid and protein. Accordingly, various concentrations of exo-microbes were separately homogenized with CEW to perform fermentation amidst feeding to BSFL. It was found that 2.50% of exo-microbes was the threshold amount entailed to assuage competition between exo-microbes and BSFL for common nutrients. The presence of remnant nutrients exuded from the fermentation using 2.50% of exo-microbes was confirmed to promote BSFL growth measured as maximum larval weight gained and growth rate. Although the BSFL could accumulate the highest protein (16 mg/larva) upon feeding with CEW containing 2.50% of exo-microbes, more lipid (13 mg/larva) was stored in employing 0.10% of exo-microbes because of minimum loss to metabolic processes while prolonging the BSFL in its 5th instar stage.

Toxicity of engineered nanoparticles on organisms is of concern worldwide due to their extensive use and unique properties. The impacts of ZnO nanoparticles (ZnO NPs) on seed germination and root elongation of corn (Zea mays L.) and cucumber (Cucumis sativus L.) were investigated in this study. The role of seed coats of corn in the mitigation toxicity of nanoparticles was also evaluated. ZnO NPs (1,000 mg L⁻¹) reduced root length of corn and cucumber by 17 % (p < 0.05) and 51 % (p < 0.05), respectively, but exhibited no effects on germination. In comparison with Zn²⁺, toxicity of ZnO NPs on the root elongation of corn could be attributed to the nanoparticulate ZnO, while released Zn ion from ZnO could solely contribute to the inhibition of root elongation of cucumber. Zn uptake in corn exposed to ZnO NPs during germination was much higher than that in corn exposed to Zn²⁺, whereas Zn uptake in cucumber was significantly correlated with soluble Zn in suspension. It could be inferred that Zn was taken up by corn and cucumber mainly in the form of ZnO NPs and soluble Zn, respectively. Transmission electron microscope confirmed the uptake of ZnO NPs into root of corn. Although isolation of the seed coats might not be the principal factor that achieved avoidance from toxicity on germination, seed coats of corn were found to mitigate the toxicity of ZnO NPs on root elongation and prevent approximately half of the Zn from entering into root and endosperm.

This study quantified Cd, Pb, and Cu content, and the soil–plant transfer factors of these elements in rice paddies within Cam Pha, Quang Ninh province, northeastern Vietnam. The rice paddies are located at a distance of 2 km from the large Coc Sau open-pit coal mine. Electron microprobe analysis combined with backscattered electron imaging and energy-dispersive spectroscopy revealed a relatively high proportion of carbon particles rimmed by an iron sulfide mineral (probably pyrite) in the quartz–clay matrix of rice paddy soils at 20–30 cm depth. Bulk chemical analysis of these soils revealed the presence of Cd, Cu, and Pb at concentrations of 0.146 ± 0.004, 23.3 ± 0.1, and 23.5 ± 0.1 mg/kg which exceeded calculated background concentrations of 0.006 ± 0.004, 1.9 ± 0.5, and 2.4 ± 1.5 mg/kg respectively at one of the sites. Metals and metalloids in Cam Pha rice paddy soils, including As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn, were found in concentrations ranging from 0.2 ± 0.1 to 140 ± 3 mg/kg, which were in close agreement with toxic metal contents in mine tailings and Coc Sau coal samples, suggesting mining operations as a major cause of paddy soil contamination. Native and model Oryza sativa L. rice plants were grown in the laboratory in a growth medium to which up to 1.5 mg/kg of paddy soil from Cam Pha was added to investigate the effects on plant growth. A decrease in growth by up to 60 % with respect to a control sample was found for model plants, whereas a decrease of only 10 % was observed for native (Nep cai hoa vang variety) rice plants. This result suggests an adaptation of native Cam Pha rice plants to toxic metals in the agricultural lands. The Cd, Cu, and Pb contents of the native rice plants from Cam Pha paddies exceeded permitted levels in foods. Cadmium and Pb were highest in the rice plant roots with concentrations of 0.84 ± 0.02 and 7.7 ± 0.3 mg/kg, suggesting an intake of these metals into the rice plant as shown, for example, by Cd and Pb concentrations of 0.09 ± 0.01 and 0.10 ± 0.04 mg/kg respectively in the rice grain endosperm. The adaptation of native rice plants, combined with bioaccumulation ratios of 1 ± 0.6 to 1.4 ± 0.7 calculated for Cd transfer to the rice grain endosperm, and maximum Cd transfer factors of 4.3 ± 2.1 to the plant roots, strongly suggest a continuous input of some toxic metals from coal-mining operations to agricultural lands in the region of Cam Pha. In addition, our results imply a sustained absorption of metals by native rice plant varieties, which may lead to metal accumulation (e.g., Cd) in human organs and in turn to severe disease.

The removal of Cr³⁺ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated. Adsorption tests were performed in batch systems for evaluating the influence of the solution’s pH, adsorbent mass, contact time, initial Cr³⁺ concentrations, and solution temperature during the adsorption process. Kinetic, adsorption isotherm, and thermodynamic studies were performed to investigate the mechanisms that control adsorption. Ideal conditions for the adsorption process included pH of the solution of 5.5 and 8 g L⁻¹ adsorbent mass, within 60 min time contact between adsorbent and adsorbate. Maximum adsorption capacities by Langmuir model for rind, endosperm, and endosperm + episperm of the J. curcas were, respectively, 22.11, 18.20, and 22.88 mg g⁻¹, with the occurrence of chemosorption in mono and multilayers. Results show that the biosorbents obtained from J. curcas have a high potential to recuperate Cr³⁺ from contaminated water sources.