Mobility of arsenic in the growth media of rice plants (Oryza sativa subsp. japonica. 'Koshihikari') with exposure to copper oxide nanoparticles in a life-cycle greenhouse study.

The increasing arsenic (As) concentration in agriculture media poses increasing risks to both environment and human health. Arsenic mobility determines its bioavailability and entry into the food chain. Nanoparticle application may help to control As mobility in crop cultivation media, and thus decreasing As bioavailability for plants. This research studied the adsorption kinetics of As(V) on copper oxide nanoparticles (nCuO) and nCuO dissolution in a hydroponic solution, and the effects of nCuO on As mobility in a greenhouse system exposed to As(V) addition of 10 mg/kg and nCuO at 0.1-100 mg/L for a life-cycle growth of rice. Arsenic adsorption was dependent on both the total mass and the concentration of nCuO as well as the initial concentration of As(V), while nCuO dissolution was mainly dependent on nCuO concentration regardless of As(V). Arsenic in the simulated paddy was quickly mobilized from soil to aqueous phase during week 1, and further interacted with components in water phase, sediment-water interfacial transition and rice plants. Copper (Cu) and As speciation in the soil were observed by X-Ray Absorption Near Edge Spectrometry. Dissolved Cu was complexed with organic ligands. As(V) was adsorbed to kaolinite, or reduced to As(III) and adsorbed to ferrihydrite. Percent As removal from water phase in the growth container was determined by both nCuO application and As(V) initial concentration. Based on our previous finding that As accumulation in rice grains was significantly decreased by nCuO at 50 mg/L and the results of this study on As adsorption capacity of nCuO and As removal from water due to nCuO application, nCuO at 50 mg/L was proposed to be an appropriate application in rice paddy to immobilize As. Further research is needed in actual agriculture to verify the appropriate nCuO application and get an integrated beneficial effect for rice plants and humans.

Exposure to Copper Oxide Nanoparticles and Arsenic Causes Intergenerational Effects on Rice (Oryza sativa japonica Koshihikari) Seed Germination and Seedling Growth.

Offspring generation (F1) rice (Oryza sativa japonica Koshihikari) seed germination and seedling growth tests were conducted for 18 d to investigate intergenerational effects of arsenic (As) and copper oxide nanoparticles (nCuO), with seeds harvested from a life cycle study exposed to As (0 and 10 mg/kg) and nCuO (0, 0.1, 1.0, 10, 50, and 100 mg/L). Seed germination and seedling growth of F1 plants were influenced by treatments experienced by parent generation (F0) plants (p < 0.05). Seeds produced from plants in F0 treatment with nCuO 50 mg/L had the lowest germination percentage and shortest seedling shoot length and root length in F1 control (F1C) and As at 10 mg/kg (F1As) alone treatments (p < 0.05). The shoot length and root length were decreased, whereas the number of root branches was increased in F1As treatment compared with F1C (p < 0.001). Interaction of As and nCuO also caused differential seed germination and seedling growth at various nCuO concentrations in quasi-F0 treatment (seeds receiving the same exposure as F0 plants; p < 0.05). Copper and As uptake in F1C seedlings were not affected by seeds' F0 exposure; this indicated that the transgenerational effects on rice seedling growth were not dependent on total Cu or As uptake in seedlings. The enhanced effects on seedlings from quasi-F0 treatment were influenced by additional exposure to nCuO and As that also interacted to affect Cu and As uptake in seedlings. Environ Toxicol Chem 2019;38:1978-1987. © 2019 SETAC.

Distribution and Speciation of Copper and Arsenic in Rice Plants ( Oryza sativa japonica 'Koshihikari') Treated with Copper Oxide Nanoparticles and Arsenic during a Life Cycle.

A 6 × 2 factorial study was conducted to investigate the effects of copper oxide nanoparticles (nCuO, 0-100 mg/L), arsenic (As, 0-10 mg/kg), and their interaction on uptake, distribution, and speciation of Cu and As in rice plants ( Oryza sativa japonica 'Koshihikari'). Arsenic (in As-addition treatments) and Cu in seedling roots (SRs) were 1.45 and 1.58 times those in soil, respectively. Arsenic and Cu concentrations further increased in mature plant roots (MRs), which were 2.06 and 2.35 times those in soil, respectively. Arsenic and Cu concentrations in seedling shoots (SSs) were 79% and 54% lower than those in SRs, respectively. The mature stems, however, contained only 3% and 44% of As and Cu in SSs. Copper in flag leaves did not vary much compared to that in stems, whereas As was 14.5 times that in stems. Species transformations of Cu and As were observed in rice including reductions of Cu(II) to Cu(I) and As(V) to As(III). Arsenic in dehusked grains was negatively correlated with Cu and was lowered by nCuO below the WHO (World Health Organization) maximum safe concentration for white rice (200 ng/g). This may alleviate As adverse effects on humans from rice consumption.