Effects of foliar spraying different sizes of zinc fertilizer on the growth and cadmium accumulation in rice.

BACKGROUND: Nanotechnology has been widely applied in agricultural science. During the process of reducing metal toxicity and accumulation in rice, nanomaterials exhibit size effects. However, there is limited knowledge regarding these size effects. We aim to explore the impact of fertilizer with various sizes of ZnO nanoparticles (ZnO-NPs) on rice growth and cadmium (Cd) accumulation and to elucidate the potential mechanism of Cd reduction in rice. Foliar applications of different concentrations (0.5 and 2 mmol L-1) and different sizes (30 and 300 nm ZnO-NPs) of zinc (Zn) fertilizer (Zn(NO3)2) were performed to investigate the effects on rice growth, Cd accumulation and subcellular distribution, and the expression of Zn-Cd transport genes. RESULTS: The results suggested that all the foliar sprayings can significantly reduce the Cd concentrations in rice grains by 41-61% with the highest reduction in the application of ZnO-NPs with large size and low concentration. This is related to the enhancement of Cd fixation in leaf cell walls and downregulation of Cd transport genes (OsZIP7, OsHMA2, OsHMA3) in stem nodes. Foliar ZnO-NPs applications can increase the Zn concentration in grains by 9-21%. Foliar applications of Zn(NO3)2 and small-sized ZnO-NPs promoted plant growth and rice yield, while the application of large-sized ZnO-NPs significantly reduced rice growth and yield. CONCLUSION: The study suggests that the rice yield and Cd reduction are dependent on the size and concentration of foliar spraying and the use of large-sized ZnO-NPs is the most effective strategy when considering both yield and Cd reduction comprehensively. © 2024 Society of Chemical Industry.

Health risks to local residents from the exposure of heavy metals around the largest copper smelter in China.

Non-ferrous smelting releases lots of heavy metals to the environment. Although numerous studies have focused on pollution in the environment, fewer have studied the adverse health effects. In the current study, samples of food, hair and urine were collected and analyzed for zinc (Zn), iron (Fe), chromium (Cr), nickel (Ni), lead (Pb) and copper (Cu) from residents of 3 villages near the largest copper smelter in China. The estimated daily intake (EDI), target hazard quotient (THQ), and Hazard Index (HI) were used to estimate and analyze the health risks to local residents (children, adults, and seniors). The Zn, Cr, Ni, Fe, Pb and Cu concentrations in food ranged from 16.02 to 61.48 mg kg-1, 0.23-13.64 mg kg-1, 0.10-5.90 mg kg-1, 19.16-170.05 mg kg-1, 0.15-3.62 mg kg-1, and 0.53-2.74 mg kg-1, respectively. Zn, Cr, Ni and Pb concentrations in all vegetables were above the national tolerance limits. Children had higher EDIs of heavy metals than that of adults and seniors. The THQ of single elements and the HI of combined elements indicated that the EDI of Pb and Cu showed the highest potential health risks, followed by the EDI of Zn and Fe, and Ni, Cr. High EDI of heavy metals resulted in much higher concentrations of heavy metals in hair and urine samples than those of normal Chinese residents, showing that residents around the smelter have potential health risks through daily food intake. The main sources of these heavy metals were from the consumption of rice and vegetables and it is imperative that measures should be taken to control this urgent problem.

Exposure risk of local residents to copper near the largest flash copper smelter in China.

Copper (Cu) smelting released large amounts of Cu and contaminated the environment. However, few studies have investigated the Cu exposure risks for people located near Cu smelters. In this study, atmospheric bulk deposition, food from local families, drinking water and biological samples (hair and urine) were collected in three villages near the largest flash Cu smelter in China. The objective of the current study was to investigate how non-ferrous metals smelting affect the human health. Total atmospheric Cu depositions (56-767µgm-2yr-1) were one or two orders of magnitude greater than that of unpolluted rural areas. The Cu concentrations in locally grown vegetables and dietary chronic daily intake (CDI) of local residents showed a consistently decreasing trend with atmospheric Cu depositions. Dietary intake of vegetables and rice were the two major pathways of total CDI, which accounted for >93% totally. The Cu exposure showed higher potential non-carcinogenic risk to human health of local residents, especially children living around the Cu smelter through food consumptions. Health impact monitoring data revealed that mean Cu concentrations in hair and urine samples were ranged from 5.13 to 28.85mgkg-1 and 19.90 to 54.61µgL-1 in the three villages, respectively. Significant correlation between hair Cu concentrations and the CDI of Cu indicated food ingestion had adverse effects on the health of the local residents. The result suggested that nonferrous metal smelter should be away from residential area and locally produced crops became unsuitable for consumption. Therefore, effective measures on Cu pollution management and control in the surrounding area should be formulated and implemented.