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Aims: Atmospheric trace metal deposition is an important source in agricultural soils and crops, but a large knowledge gap exists between foliar and root uptake of wet/dry deposition. We aim to distinguish the contribution of dry and wet-deposited trace metals to rice plant via foliar and root uptake and to investigate their accumulations during the full growth season. Methods: We performed an atmospheric exposure experiment using customized open top chambers (OTCs) to distinguish the impacts of wet and dry deposition contribution to foliar and root uptake and their mobility in soils. The foliar uptake and then translocation was hypothesized the major pathway of trace metal accumulation in rice grains. Results: Foliar uptake of wet- and dry-deposited Cu, Zn, and Pb played an important role in their accumulations in rice plant, contributing to 44–47%, 23–25%, and 35–37% in rice grains, respectively. The leaf Cu, Zn, and Pb accumulated from atmospheric deposition can be transported upward to rice grains but nodes seem to restrict them downward translocation. Rice leaves cannot directly take up atmospheric As and the deposited As can only accumulate in rice through the root uptake. The trace metals showed high mobility in atmospheric deposition, which significantly increase the bioavailable trace metal fractions in surface soils and soil solutions. Conclusions: This study provides a new insight of similar or even higher contributions of foliar uptake than root uptake of trace metals from atmospheric deposition and that reducing the accumulation of atmospheric trace metals due to deposition on leaves can effectively decrease the accumulation of trace metals in crops. [ABSTRACT FROM AUTHOR]

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 ·O2−, H2O2, 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. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) is widely used as an antibacterial agent, but the specific antibacterial mechanism is still conflicting. This study aimed to investigate the size dependent inhibition of AgNPs and the relationship between inhibition and reactive oxygen species (ROS). Azotobactervinelandii and Nitrosomonaseuropaea were exposed to AgNPs with different particles size (10 nm and 50 nm). The ROS production was measured and the results showed that the generation of ROS related to the particle size and concentrations of AgNPs. At 10 mg/L of 10 nm Ag particles, the apoptosis rate of A. vinelandii and N. europaea were 20.23% and 1.87% respectively. Additionally, the necrosis rate of A. vinelandii and N. europaea reached to 15.20% and 42.20% respectively. Furthermore, transmission electron microscopy images also indicated that AgNPs caused severely bacterial cell membrane damage. Together these data suggested that the toxicity of AgNPs depends on its particle size and overproduction of ROS. [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]