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To our knowledge, this is the first report on exploring the interactive effects of various biochars (BCs) and nanomaterials (NMs) on plant growth and bioavailability of trace elements in soil. This study evaluated the bioavailability and toxicity of arsenic (As), lead (Pb), and NMs to cabbage plants. The BCs were produced from rice husk (RB), sewage sludge, and bamboo wood (WB). The BCs at 2.5 and 5% (w w -1 ), NMs for removing As (NMs-As) and heavy metals (NMs-HM) at 3000 mg kg -1 , and multi-walled carbon nanotubes (CNT) at 1000 mg kg -1 were applied in bioassay and incubation experiments (40 days), along with the unamended soil as the control. Results showed that the NMs-As and NMs-HM decreased seed germination at 3 days after sowing; however, their toxicity was eliminated by BCs. Growth parameters of cabbage revealed that the CNT was the most toxic NMs, as it was translocated in root and leaf cells, which was confirmed by transmission electron microscopic images. Bioavailable Pb was reduced by 1.2-3.8-folds in all amended rhizosphere and bulk soils. Amendments of 2.5% WB + NMs-As and 2.5% RB + NMs-As significantly decreased both bioavailable As and Pb.

This study was carried out to evaluate longevity of available organic materials used for sulfate-reducing bacteria (SRB) activity in vertical flow ponds (VFPs) to treat mine drainage in South Korea. Spent mushroom compost samples (SMC) were tested as substrates in VFPs and analyzed for total organic carbon in VFPs, and were collected to analyze total organic carbon (TOC), T-N, T-P, K, metals and residual cellulose to check the longevity assessment. Chemical analysis revealed that the average contents of Fe, Al and Mn in SMC of VFPs were 19,907, 32,137 and 434 mg/kg, respectively. The contents of Fe and Al in SMC of VFPs were much higher than those of the unused SMC (control), but to the contrary, those of Mn showed a reversed tendency. Average TOC content of the controls was 64.19% but in one of the VFP substrates was as low as 15.92%. This might be resulted from SRB consumed the available organic carbon in SMC as VFPs system aged. Contents of T-N in VFPs tended to decrease as VFPs aged. The residual cellulose ranged from 3.88 to 6.72% (g/g). There existed a negative relationship between residual cellulose contents and ages of VFPs. Assuming that SMC in all VFPs had similar compositions when the VFPs were initially established, trend analysis predicted that the amount of carbon source for SRB might be available for 12-15 years further, depending on VFPs.

The cadmium (Cd) content of rice grain grown in metal-contaminated paddy soils near abandoned metal mines in South Korea was found to exceed safety guidelines (0.2 mg Cd kg⁻¹) set by the Korea Food and Drug Administration (KFDA). However, current remediation technologies for heavy metal-contaminated soils have limited application with respect to rice paddy soils. Laboratory and greenhouse experiments were conducted to assess the effects of amending contaminated rice paddy soils with zerovalent iron (ZVI), lime, humus, compost, and combinations of these compounds to immobilize Cd and inhibit Cd translocation to rice grain. Sequential extraction analysis revealed that treatment with the ameliorants induced a 50-90% decrease in the bioavailable Cd fractions when compared to the untreated control soil. When compared to the control, Cd uptake by rice was decreased in response to treatment with ZVI + humus (69%), lime (65%), ZVI + compost (61%), compost (46%), ZVI (42%), and humus (14%). In addition, ameliorants did not influence rice yield when compared to that of the control. Overall, the results of this study indicated that remediation technologies using ameliorants effectively reduce Cd bioavailability and uptake in contaminated rice paddy soils.