Heavy metal pollution is a major concern of the public due to their threats to the safety of food chains. A 60-day pot experiment was conducted using Macleaya cordata as plant material to investigate the phytoremediation potential and anti-oxidative responses of M. cordata under different Cd stress. Significant growth inhibition phenomenon and toxic symptoms were not detected in the experiment. The high biomass of the plant provided high accumulation capacity for Cd with an average dry weight of 3.6 g. The maximum extraction amount of Cd was 393 μg·plant(-1), suggesting that this species had potential for phytoremediation of Cd-contaminated soil. A slight increase of chlorophyll (CHL) content was observed in Cd10 treatment. The plant was confirmed to have relatively high tolerance to the Cd stress on the basis of tolerance indexes (TI), relative water content, and CHLa/CHLb ratio. M. cordata could maintain high level of superoxide dismutase (SOD) activity under Cd stress, indicating strong tolerance capacity for reactive oxygen species (ROS) in plant cells. Catalase (CAT) activity show a certain range of decline in the experiment compare to the control. And peroxidase (POD) activity in leaves changed irregularly when compared to the control. The malondialdehyde (MDA) content increased as Cd concentration elevated compared to the control. In addition, as an inedible crop with relatively high economic value, M. cordata have shown the advantage of high biomass and high tolerance under Cd stress, which can provide a new plant resource for sustainable phytoremediation.
A B S T R A C TThe mediation effect of reduced graphene oxide (rGO) on the oxidative transformation of 1,4-hydroquinone (H 2 Q) to 1,4-benzoquinone (BQ) in aqueous solution was investigated using a batch method and electron paramagnetic resonance. The results showed that the autoxidation of H 2 Q was spin-restricted and extremely slow in acidic and neutral pH range, but this process can be dramatically accelerated when rGO was added. In the presence of 33.3 mg L À1 rGO, more than 76.0% of H 2 Q was oxidized to BQ within 36 h. The enhancement effects of rGO were attributed to the combined contribution of the high chemical reactivity of graphenic edges and defects on rGO and the high electron conductivity of graphene basal surface of rGO. It is proposed that dissolved oxygen reacted with graphenic edges and defects of rGO to produce surface-bound oxygen intermediates, which capture H atoms from the phenolic hydroxyl groups of H 2 Q and facilitate the generation of semiqui- Ó 2015 Elsevier Ltd. All rights reserved.
IntroductionGraphene is a two-dimensional structure consisting of sp 2 hybridized carbons that is only one atom thick, and can be regarded as the basic building block of other sp 2 hybridized carbon materials, such as graphite, fullerene, carbon nanotubes, etc [1]. Since its discovery, graphene-based nanomaterials (GBNs) have been demonstrated to have promising applications in diverse disciplines [2]. In environment science and technology, GBNs are mainly considered as superior adsorbents to remove contaminants from waters and gases due to its large theoretical specific surface area and high ability of modification [3][4][5][6][7][8][9]. For example, it was found that sulfonated graphene was one of the best adsorbents for 1-naphthol due to the occurrence of p-p interaction between 1-naphthol and graphene surface [4]. Sun et al. [7] showed that the maximum adsorption capacity of acridine orange on graphene oxide (GO) reached striking 3.3 g g
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