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As an important class of flavonoids, anthocyanin has been used to enhance plant-defensive mechanisms against heavy metal stress. However, there are few available reports regarding surface spraying of anthocyanin for reduction of Cd poisoning in rice and its practical applications in paddy fields. After rice growing, measurements were taken of rice growth, pigments, the antioxidant system, thiol compounds, and distribution of Cd in rice tissues. The results showed that surface spraying anthocyanin could promote rice growth, and relative to the control, total chlorophyll significantly increased by 22.62% after surface spraying of 7.5 g L -1 anthocyanin. Simultaneously, Cd accumulation in rice grains was 0.17 ± 0.02 mg kg -1 , which was significantly decreased by 46.88% relative to the control. In the pot experiment (40-day-old rice), treatment with 7.5 g L -1 anthocyanin resulted in decreases of ·O 2 - , H 2 O 2 , and malondialdehyde contents in rice leaves, while the activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase were increased by 59.10, 23.81, 41.75, and 9.39%, respectively. Meanwhile, contents of glutathione, ascorbic acid, non-protein thiols, and phytochelatins showed respective increases of 7.24, 14.49, 42.81, and 41.13% compared with the control value. Subcellular analysis revealed that surface spraying of anthocyanin increased organelle and soluble fractions of Cd in leaf cells. In conclusion, surface spraying of 7.5 g L -1 anthocyanin was mainly attributed to increased antioxidant activities and subcellular sequestration of Cd in organelles and soluble fractions in rice leaves to reduce Cd accumulation in rice grains in the field.

Identification the sources of heavy metals can effectively control and prevent agricultural soil pollution. Here we performed a three-year mass balance study along a gradient of soil pollution near a smelter to quantify the potential contribution and net cadmium (Cd) fluxes and predict Cd concentration in rice grains by multiple regression (MR) and back propagation (BP) neural network. The Cd inputs were mainly from the irrigation water (54.6–60.8%) in the moderately polluted and background sites but from atmospheric deposition (90.9%) in the highly polluted site. The Cd outputs were mainly from the surface runoff (55.8–59.5%) in the moderately polluted and background sites, but from Sedum plumbizincicola phytoextraction (83.6%) in the highly polluted site. The soil Cd concentrations, the annual fluxes of atmospheric deposition, pesticides and fertilizers, irrigation water, surface runoff, and leaching water were selected as the dependent factors to predict Cd concentrations in rice grains. The genetic algorithms (GA)-BP neural network model gives the best prediction accuracy compared to the BP neural network model and multivariate regression analysis. The major implication is that the health risks through the consumption of rice can be rapidly assessed based on the Cd concentrations in rice grains predicted by the model. [Display omitted] • A 3-year study of Cd mass balances were performed by an accurate plot experiment near a smelter. • Irrigation-water Cd input contributed 55–61% to background and moderately polluted cultivated soils. • Surface-runoff and leaching-water outputs were the main output pathways of Cd in agroecosystem. • Rice grain Cd were accuracy predicted by GA-BP neural network based on mass balance factors. [ABSTRACT FROM AUTHOR]

Anthocyanin extract has been applied in agricultural production and enhanced tolerance of plants to adverse effects of Cd stress. Rice was subjected to different concentration of Cd and blueberry anthocyanin, and the effects on rice growth, antioxidative defense, Cd distribution in rice tissues, FTIR and TEM characterization of rice leaves were examined to explain the Cd reductions in rice grains and the protective mechanisms by blueberry anthocyanin. Foliar spray of blueberry anthocyanin at tillering and booting stages was effective for reducing Cd concentration in rice grains and increasing the rice yield, anthocyanin and Cd concentration of rice leaves under 1.0 and 10.0 mg/kg Cd stress. The Cd concentration in rice grains was less than the China national standard of Cd for rice grains (0.2 mg/kg) after surface spraying by 5.0–12.5 g/L blueberry anthocyanin under 1.0 mg/kg Cd stress, while 7.5 g/L spray concentration was the best choice. Blueberry anthocyanin spraying prevents Cd from being transferred from leaves to rice grains mainly by fixation of Cd in soluble and organelle fractions at the tillering and booting stages, and reduces H 2 O 2 and MDA accumulation in rice leaves to decrease Cd toxicity. Combined with FTIR and TEM characterization of rice leaves, the results indicated that surface spraying of 7.5 g/L blueberry anthocyanin under 1.0 mg/kg Cd stress could effectively relieve Cd oxidative damage, and form chelates with Cd ions to immobilize Cd in rice leaves. Hence, blueberry anthocyanin could be used as a foliar resistance control agent to reduce Cd accumulation in rice grains through chelate compound synthesis and decrease Cd toxicity by preventing membrane lipid peroxidation and H 2 O 2 accumulation. [Display omitted] • Foliar application of blueberry anthocyanin effectively reduced Cd accumulation in rice grains under 1.0 mg/kg Cd stress. • Foliar application of blueberry anthocyanin relieved Cd oxidative damage in rice leaves. • Foliar application of blueberry anthocyanin mainly isolated and immobilized Cd in soluble and organelle fractions. [ABSTRACT FROM AUTHOR]

Background: Cd and Pb were the main pollution elements in Pb-Zn mining areas. Several studies have focused on heavy metal pollution and risk assessment in the Huize Pb-Zn mining area. In the present study, the soil aggregate composition, chemical properties, contents and chemical fractions of Cd and Pb were analysed in soils at depths of 0-60 cm in the Huize Pb-Zn mining area. Agricultural soils were sampled at depths of 0-20, 20-40 and 40-60 cm surrounding the Pb-Zn mine. The particle size fractions were determined by the aggregate composition of macro-aggregates (0.25-2 mm), micro-aggregates (0.053-0.25 mm), silt (0.002-0.053 mm) and colloid (< 0.002 mm).Results: There was a large proportion of the macro-aggregate (52.4%) and less of the colloid (1.8%). With a decrease in particle size, the pH, organic matter contents, cation exchange capacity, and free iron oxide increased in the soil aggregates. Although the total and available Cd and Pb contents were highest in the colloid, the macro-aggregate maximally contributed to the total Cd (48.18%), total Pb (53.48%) and available Pb (47.42%) content, and the colloid maximally contributed to the available Cd (47.21%) in soils. The Cd and Pb existed primarily as residual fractions, followed by Fe-Mn oxide fraction and the exchangeable fraction in soil aggregates. There were higher distribution factors for the residual and exchangeable fractions of both Cd and Pb in the colloid (DF > 33). Furthermore, there were close correlations between the Cd and Pb fractions and the pH and the phosphorus content and between the exchangeable Pb content and the content of organic matter, cation exchange capacity, and free iron oxide in soil aggregates.Conclusion: Cd and Pb existed mainly in the micro-aggregate and colloid and that their chemical fractions were closely related to the chemical properties in soil aggregates of the polluted farmland. [ABSTRACT FROM AUTHOR]