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Cd and Zn pollution was observed to often occur simultaneously in soils. However, previous studies focused on single heavy metal instead of Cd and Zn combined pollution. Castor (Ricinus communis) is considered to have great potential for contaminated soil remediation. The resistance of castor seedlings to heavy metals and the mechanism behind it remain unknown. In this study, the tolerance and accumulation ability of castor seedlings to Cd and Zn were investigated, and the accumulation mechanism involving the subcellular distribution in different tissues was further explored. The results on biomass and chlorophyll revealed that castor seedlings have good tolerance to the pollution with 0–5 mg/kg Cd and 380 mg/kg Zn, while not to the heavy pollution with 25 mg/kg Cd and 380 mg/kg Zn. The maximum accumulation concentrations of Cd and Zn, 175.3 mg Cd/kg and 386.8 mg/kg Zn, appeared in castor seedling root instead of stem and leaf, indicating that root played a significant part in accumulating Zn and Cd. The relative low dosage of Cd (0–5 mg/kg) promoted the accumulation of Zn in the subcellular component, while high dosage (25 mg/kg) inhibited the accumulation of Zn. In subcellular accumulation and distribution of castor seedlings, Cd (27.1%–69.4%) and Zn (39.6%–66.6%) in the cell wall was the highest. With the increase of Cd addition, the accumulation of Cd increased in cell wall while decreased in organelle and soluble fraction. Hydroxyl, amino, amides and carboxyl functional groups on cell wall might provided the main binding sites for Cd and Zn.

MSWI fly ashes sampled from 15 large-scale commercial municipal solid waste incineration plants in China were analyzed for seventeen polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDFs) as well as twelve dioxin-like polychlorinated biphenyls (dl-PCBs). The concentration of PCDD/PCDFs and dl-PCBs in fly ash samples ranged from 2.8 to 190 ng g−1, and 59.6 ng g−1 on average. The toxic equivalent (TEQ) ranged from 34 to 2500 ng WHO(2005)-PCDD/PCDF-PCB-TEQ kg−1, and 790 ng WHO(2005)-PCDD/PCDF-PCB-TEQ kg−1 on average. For PCDDs, hexa-chlorinated homolog was the dominant compound except two fly ash samples. Tetra-chlorinated homolog was dominant for PCDFs except one sample. The ratio of PCDDs/PCDFs ranged from 0.32 to 2.44 (average 0.97). The contribution of dl-PCBs to total concentration and TEQ was relatively minimal. Correlation between the concentration of three congeners and total TEQ values of fly ashes was also established. The findings obtained in this work provided overview information on the PCDD/PCDF-PCB content characterization of MSWI fly ash in China, which can be available for MSWI fly ash management in the environment.

With Carassius auratus, one of the main economic fish species in Eastern China as test material, this paper studied the hydroxyl radical generation and oxidative stress in its liver under the effect of 2,4,6-trichlorophenol (2,4,6-TCP). Different doses of 2,4,6-TCP were injected intraperitoneally into the fishes, and the Electron paramagnetic resonance (EPR) spectra of hepatic free radicals, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-s-transferase (GST), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG), and malondialdehyde (MDA) contents were determined 24 h after injection. The results showed that under the effects of 2,4,6-TCP, the generation of free radical that was considered to be hydroxyl radical increased significantly, the activities of antioxidant enzymes decreased, with CAT most strongly affected and followed by SOD and GST, the GSH level decreased significantly while GSSG level had little difference, resulting in a decreased GSH/GSSG ratio, and the MDA content increased significantly. All the test parameters showed that C. auratus was subjected to oxidative stress and damage when exposed to 2,4,6-TCP.