School of Environment and Natural Resources, Zhejiang University of Science and Technology, Hangzhou, Zhejiang, 310023, China; School of Environmental and Resource Sciences, Zhejiang A&F University, Lin'an, Zhejiang, 311300, China; Global Centre for Environmental Remediation (GCER), Faculty of Science, The University of Newcastle, Callaghan, NSW, 2308, Australia.
School of Environmental and Resource Sciences, Zhejiang A&F University, Lin'an, Zhejiang, 311300, China.
Environ Pollut. 2021 Mar 1;272:116039. doi: 10.1016/j.envpol.2020.116039. Epub 2020 Nov 21.
Phytoremediation of metal(loid)s contaminated sites is widely used, while there is scarce of investigation on the metal-enriched biomass waste safely disposal which resulted in risks of causing secondary pollution to the soil and water bodies and even to human health. Thus, this study compared the effects of ashing and pyrolysis treatments on cadmium (Cd) and zinc (Zn) hyperaccumulation plant Sedum plumbizincicola. Chemical speciation, the Toxicity Characteristic Leaching Procedure (TCLP), and diethylenetriamine pentaacetic acid (DTPA) extraction were employed to characterize the bioavailability and leachability of Cd and Zn in the solid residues after pyrolysis and ashing. The risk assessment code (RAC) and potential ecological risk index (RI) were subsequently used to evaluate the risk of the solid residues to the environment. The results showed that both ashing and pyrolysis treatments could transform the bioavailable Cd and Zn in S. plumbizincicola into a more stable form, and the higher the temperature the greater the stablility. Pyrolysis converted a maximum of 80.0% of Cd and 70.3% of Zn in S. plumbizincicola to the oxidisable and residual fractions, compared with ashing which achieved only a ∼42% reduction. The pyrolysis process minimised the risk level of Cd and Zn to the environment based on the RAC and RI assessments. The results of the TCLP test, and DTPA extraction confirmed that the leaching rate and the bioavailable portion of Cd and Zn in the biochars produced by pyrolysis were invariably significantly (p < 0.05) lower than the solid residues produced by ashing, and reached the lowest at 650 °C. In other words, pyrolysis was better than ashing for thermal treatment of the metal-enriched hyperaccumulator plant, in view of minimising the bioavailability and leachability of Cd and Zn from the solid residues to the environment. This study provides fundamental data on the choice of treatments for the disposal of metal-enriched plant biomass.
植物修复技术被广泛应用于受金属（类）污染场地的修复，但对于富含金属的生物量废物的安全处置研究甚少，这导致了对土壤和水体造成二次污染的风险，甚至对人类健康造成威胁。因此，本研究比较了灰化和热解处理对超积累植物景天酸代谢途径 Cd 和 Zn 的影响。采用化学形态分析、毒性特征浸出程序（TCLP）和二乙三胺五乙酸（DTPA）提取法来描述热解和灰化后固体残余物中 Cd 和 Zn 的生物可利用性和浸出性。随后，采用风险评估码（RAC）和潜在生态风险指数（RI）来评估固体残余物对环境的风险。结果表明，灰化和热解处理均可将超积累植物景天体内的生物可利用 Cd 和 Zn 转化为更稳定的形态，且温度越高，稳定性越强。与灰化相比，热解将最大 80.0%的 Cd 和 70.3%的 Zn 转化为可氧化态和残渣态，而灰化仅能减少约 42%。根据 RAC 和 RI 评估，热解过程可使 Cd 和 Zn 对环境的风险水平最小化。TCLP 测试和 DTPA 提取的结果表明，热解生物炭中 Cd 和 Zn 的浸出率和生物可利用部分始终显著低于（p<0.05）灰化残余物，在 650°C 时达到最低。换句话说，从减少固体残余物中 Cd 和 Zn 向环境的生物可利用性和浸出性来看，热解比灰化更适合富含金属的超积累植物的热处理。本研究为富含金属的植物生物质处理方法的选择提供了基础数据。
