Risk Assessment of Heavy Metal Pollution by Three Plants at Zihu River in Nanjing, China

Health Risk Assessment of Heavy Metals in Soils before Rice Sowing and at Harvesting in Southern Jiangsu Province, China

Rice, one of the most important staple crops in China, is easily contaminated by heavy metal pollution from industrial development. In this work, we systematically investigated the heavy metal (Cr, Cd, Pb, Zn, and Cu) and metalloid (Hg and As) concentrations in paddy soils and different rice tissues in southern Jiangsu Province, China. The potential ecological hazard index method and in vitro simulation test were used to evaluate the influence of heavy metals on local resident health. The results showed that, before rice sowing and at the harvesting period, the order of Eri values was EriCd>EriHg>EriAs>EriPb>EriCu>EriCr>EriZn. The low-risk index values (91.63 and 30.29) for the heavy metals indicated the low risk at the two stages in the study area based on the potential ecological hazard index. As determined with Tessier’s five-stage sequential extraction procedure, the proportions of the chemical speciation of the heavy metals were as follows: residual > organic matter-bound > iron-manganese oxide-bound > carbonate-bound > exchangeable. The order of the values of the accumulation and transfer factors was Cd (3.16) > Cu (0.42) > Zn (0.28) > Pb (0.25) > As (0.07) > Cr (0.04) > Cr (0.03) and root > stem > leaves, respectively. In vitro simulation tests showed that, in both adults and children, the daily amount of Pb and Cd intake through the soil-oral cavity route in the study area did not exceed the daily tolerance for Pb and Cd proposed by the WHO. In summary, although there is no obvious danger to local adults and children, it is necessary to be aware of the possibility of rice contamination from Cd in the soil.

Carotenoid and superoxide dismutase are the most effective antioxidants participating in ROS scavenging in phenanthrene accumulated wheat leaf

Polycyclic aromatic hydrocarbons (PAHs) are a kind of pollutants which could stimulate stress reaction in plant cells. In this study, we systematically verify that PAHs could induce an oxidative stress in plants, and describe their damages on wheat leaf subcellular structure and organelle, together with the contributions of antioxidants working against reactive oxygen species. The observation of transmission electron microscope exhibits that cell structures become plasmolyzed and distorted, and organelles disappear under phenanthrene (a model PAH) treatments. Osmiophilic granules arise with increasing phenanthrene concentrations, displaying the evidence for oxidative stress. As more H₂O₂ produce, and the accumulation of H₂O₂ is a fatal reason for cell death under PAH treatments. Through cluster analysis, Pearson correlation coefficient, principal component analysis and redundancy analysis, carotenoid and superoxide dismutase are the two most effective antioxidants to scavenge superoxide radicals among nine major antioxidants (ascorbate, glutathione, polyamines, α-tocopherol, carotenoid, catalases, ascorbate peroxidase, superoxide dismutase and glutathione-S-transferase), glutathione-S-transferase is a potential antioxidant, and Asa-GSH cycle would turn active under higher phenanthrene treatments. Ascorbate peroxidase and α-tocopherol would cause leaf moisture increase. Thus, this work provides better comprehension on the antioxidant performances and their potential application to improving plants' resistance under PAH pollution in the environment.