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Phytohormones, including auxin, abscisic acid, gibberellic acid, ethylene, cytokinin, brassinosteroids, salicylic acid, and jasmonic acid, provide beneficial effects for plants against metal(loid) toxicity. However, their mechanisms in alleviating metal(loid) toxicity in plants have not been fully understood. Here, we summarize phytohormone-mediated detoxification mechanisms of metal(loid)s in plants, including As, Cd, Cr, Hg, and Pb. First, we discussed the functions of phytohormones on plant growth and nutrient uptake, and the effects of metal(loid)s on plant growth and hormone contents. We then discussed the underlying mechanisms of selected phytohormones in alleviating metal(loid) toxicity in plants. Those phytohormones protect plants against metal(loid) toxicity mainly by enhancing plant growth, increasing antioxidant capacity, promoting cell wall synthesis and nutrient uptake, and decreasing metal(loid) accumulation. This review highlights the beneficial roles of phytohormones in reducing plant metal(loid) uptake and in enhancing crop yields, which helps to improve crop production and food safety. [ABSTRACT FROM AUTHOR]

BACKGROUND: Elevating dietary calcium (Ca) intake can reduce metal(loid)oral bioavailability. However, the ability of a range of Ca minerals to reduce oral bioavailability of lead (Pb), cadmium (Cd), and arsenic (As) from indoor dust remains unclear. OBJECTIVES: This study evaluated the ability of Ca minerals to reduce Pb, Cd, and As oral bioavailability from indoor dust and associated mechanisms. METHODS: A mouse bioassay was conducted to assess Pb, Cd, and As relative bioavailability (RBA) in three indoor dust samples, which were amended into mouse chow without and with addition of CaHPO4, CaCO3, Ca gluconate, Ca lactate, Ca aspartate, and Ca citrate at 200–5,000 μg/g Ca. The mRNA expression of Ca and phosphate (P) transporters involved in transcellular Pb, Cd and As transport in the duodenum of mice was quantified using real-time polymerase chain reaction. Serum 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], parathyroid hormone (PTH), and renal CYP27B1 activity controlling 1,25(OH)2D3 synthesis were measured using ELISA kits. Metal(loid) speciation in the feces of mice was characterized using X-ray absorption near-edge structure (XANES) spectroscopy. RESULTS: In general, mice exposed to each of the Ca minerals exhibited lower Pb-, Cd-, and As-RBA for three dusts. However, RBAs with the different Ca minerals varied. Among minerals, mice fed dietary CaHPO4 did not exhibit lower duodenal mRNA expression of Ca transporters but did have the lowest Pb and Cd oral bioavailability at the highest Ca concentration (5,000 μg/g Ca; 51%-95% and 52 -74% lower in comparison with the control). Lead phosphate precipitates (e.g., chloropyromorphite) were observed in feces of mice fed dietary CaHPO4. In comparison, mice fed organic Ca minerals (Ca gluconate, Ca lactate, Ca aspartate, and Ca citrate) had lower duodenal mRNA expression of Ca transporters, but Pb and Cd oral bioavailability was higher than in mice fed CaHPO4. In terms of As, mice fed Ca aspartate exhibited the lowest As oral bioavailability at the highest Ca concentration (5,000 μg/g Ca; 41%-72% lower) and the lowest duodenal expression of P transporter (88% lower). The presence of aspartate was not associated with higher As solubility in the intestine. DISCUSSION: Our study used a mouse model of exposure to household dust with various concentrations and species of Ca to determine whether different Ca minerals can reduce bioavailability of Pb, Cd, and As in mice and elucidate the mechanism(s) involved. This study can contribute to the practical application of optimal Ca minerals to protect humans from Pb, Cd, and As coexposure in the environment. [ABSTRACT FROM AUTHOR]

The biogeochemical transformations and biological effects of metalloids arsenic (As) and selenium (Se) in the environment has been extensively explored during the last decade, mainly owing to their ubiquitous distribution in the environment and their toxicity to biota. Here, we summarized recent research progress regarding As and Se in plant-soil-human ecosystem based on 17 publications in Critical Reviews in Environmental Science and Technology (CREST) during 2018-2021. The topics include: 1) organic As transformation in the environment and inorganic As uptake by plants (4 publications), 2) Se uptake by plants and its interactions with toxic metals in plants (6 publications), 3) As bioaccessibility and remediation of As-contaminated soils (4 publications), and 4) As research across spatial and temporal scale (3 publications). Specifically, the uptake, transformation, toxicity, bioaccessibility of As/Se in the plant-soil-human ecosystem together with pollution control measures are summarized. Future studies should focus on better understanding the cycling and biogeochemistry of As/Se in the environment, further decoding their environmental effects from the One Health perspective. [ABSTRACT FROM AUTHOR]

Soil plays an important role in controlling the biogeochemical cycling of nutrients and contaminants in the environment. Reliable analytical techniques are critical to better understand their transformation in soils. Diffusive Gradients in Thin-films technique (DGT) is one of such techniques, which has become increasingly popular in soil research since 1998. Undeniably, DGT attracts increasing attentions from multidisciplinary researchers worldwide. This is mainly due to its inherent merits, including ease of use, in situ measurement, and biomimetic applications. Further, four important aspects of DGT applications in soil research were summarized. They include: 1) chemical speciation, 2) bioavailability measurement, 3) desorption kinetic modeling, and 4) interfacial process mapping of nutrients and contaminants, with main focus on the progresses achieved during the past five years. In short, DGT is effective in studying the biochemical behaviors of nutrients (e.g., phosphate and nitrate), trace elements (e.g., Cd, Ni, Zn, Cu, Pb, and As), and polar organic compounds (e.g., antibiotics, pesticides, and bisphenols) in soils. Toward the end, we proposed several aspects of applying DGT as a versatile tool in soil research. [ABSTRACT FROM AUTHOR]

Laboratory experiments and mathematical modeling were used to explore the dynamics of kaolinite and Pb in water-saturated porous media. Batch adsorption experiments were used to obtain the adsorption isotherms of Pb onto kaolinite and quartz sand. Both kaolinite and sand adsorbed Pb from water, but the adsorption capacity of kaolinite was about 30 times higher than that of sand. Saturated sand columns were used to examine the transport behaviors of Pb and kaolinite. The presence of kaolinite in the saturated porous media enhanced the mobility of Pb. The presence of Pb on kaolinite and grain surfaces, however, reduced the transport of kaolinite. Additionally, an experiment in which clean kaolinite was passed through sand contaminated with Pb indicated that mobile kaolinite could scavenge the absorbed Pb from the sand surface to facilitate Pb transport. Simulations from the Langmuir model and an advective-dispersive transport model matched well with the experimental data collected from the batch adsorption and column breakthrough studies. DOI: 10.1061/(ASCE)EE.1943-7870.0000250 CE Database subject headings: Porous media; Mathematical models; Water treatment; Water pollution; Experimentation. Author keywords: Colloid; Colloid-facilitated transport; Kaolinite; Pb; Porous media; Modeling.