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[en] Polygonum perfoliatum L. is a Mn-tolerant plant as considered having the potential to revegetate in manganese mine wasteland. The glasshouse experiments were carried out to evaluate its tolerance and physiological response in different Mn concentrations (5, 500, 1000, 2000, 5000, and 10,000 μmol L−1). Absorption bands of P. perfoliatum differed greatly in lipids, proteins, and carbohydrates. With elevated levels of Mn (5–2000 μmol L−1), absorbance changed little, which demonstrated that lower Mn concentrations had negligible influence on transport functions. As Mn concentrations in excess of 2000 μmol L−1, absorbance increased slightly but eventually decreased. Furthermore, a hydroponic culture was carried out in order to study its changes of ultrastructure with the increasing Mn concentrations (5, 1000, and 10,000 μmol L−1). Lower Mn levels with 5 and 1000 μmol L−1 had no breakage function to the ultrastructure of P. perfoliatum. However, as Mn concentration was up to 10,000 μmol L−1, visible damages began to appear, the quantity of mitochondria in root cells increased, and the granum lamellae of leaf cell chloroplasts presented a disordered state. In comparison with the controls, black agglomerations were found in the cells of P. perfoliatum under the controlling concentration of Mn with 1000 and 10,000 μmol L−1 for 30 days, which became obvious at higher Mn concentrations. As Mn concentration was 10,000 μmol L−1, a kind of new acicular substance was developed in leaf cells and intercellular spaces, possibly indicating a resistance mechanism in P. perfoliatum. These results confirm that P. perfoliatum shows potential for the revegetation of abandoned manganese tailings.
[en] A mining district in south China shows significant metal(loid) contamination in paddy fields. In the soils, average Pb, Cd and As concentrations were 460.1, 11.7 and 35.1 mg kg−1 respectively, which were higher than the environmental quality standard for agricultural soils in China (GB15618-1995) and UK Clea Soil Guideline Value. The average contents of Pb, Cd and As in rice were 5.24, 1.1 and 0.7 mg kg−1 respectively, which were about 25, 4.5 or 2.5 times greater than the limit values of the maximum safe contaminant concentration standard in food of China (GB 2762-2012), and about 25, 10 or 1 times greater than the limit values of FAO/WHO standard. The elevated contents of Pb, Cd and As detected in soils around the factories, indicated that their spatial distribution was influenced by anthropogenic activity, while greater concentrations of Cd in rice appeared in the northwest region of the factories, indicating that the spatial distribution of heavy metals was also affected by natural factors. As human exposure around mining districts is mainly through oral intake of food and dermal contact, the effects of these metals on the viability and MT protein of HepG2 and KERTr cells were investigated. The cell viability decreased with increasing metal concentrations. Co-exposure to heavy metals (Pb+Cd) increased the metals (Pb or Cd)-mediated MT protein induction in both human HepG2 and KERTr cells. Increased levels of MT protein will lead to greater risk of carcinogenic manifestations, and it is likely that chronic exposure to metals may increase the risk to human health. Nevertheless, when co-exposure to two or more metals occur (such as As+Pb), they may have an antagonistic effect thus reducing the toxic effects of each other. Capsule: Metal contaminations in paddy soils and rice were influenced by anthropogenic activity; metal co-exposure induced MT protein in human cells. - Highlights: • Pb, Cd and As in paddy soils and rice were higher than national and FAO standards. • Pb, Cd and As spatial distribution was mainly influenced by anthropogenic activity. • The HepG2 and KERTr cell viability decreased with increasing metal concentrations. • Co-exposure to heavy metals increased MT protein induction in HepG2 and KERTr cells. • Co-exposure to some metals (As+Pb) may have an antagonistic effect.