Academy of Agricultural Planning and Engineering, Key Laboratory of Technologies and Models for Cyclic Utilization from Agricultural Resources, Ministry of Agriculture, Beijing, 100125, China.
Academy of Agricultural Planning and Engineering, Key Laboratory of Technologies and Models for Cyclic Utilization from Agricultural Resources, Ministry of Agriculture, Beijing, 100125, China.
Chemosphere. 2022 Jan;287(Pt 2):132116. doi: 10.1016/j.chemosphere.2021.132116. Epub 2021 Aug 31.
Biochar application as a soil amendment has attracted worldwide attention. Nevertheless, polycyclic aromatic hydrocarbons (PAHs) formed during biochar production might enter into ecosystems and threaten human health after application to soil. Continuous pyrolysis systems tend to cause an accumulation of PAHs in biochar owing to short residence time and rapid cooling. This study conducted a comprehensive assessment regarding potential risk of PAHs in biochars produced by a continuous pyrolysis system based on bioavailability, leaching behavior, toxic equivalent quantity, health risk and phytotoxicity of PAHs. Results showed that the concentrations of total PAHs in biochars were in the range of 93.40-172.40 mg/kg, exceeding the European Biochar Certificate standard. 3-rings PAHs were the predominant groups. The percentages of total freely dissolved and leachable PAHs were lower than 1%. RH contained the least bioavailable and leachable PAHs concentration and phytotoxicity compared with CS and PS, which might attribute to the characteristic of three biochars. CS and PS were acidic and exhibited high levels of DOC and VFAs, while RH was strongly alkaline and presented greater aromaticity and higher surface area, which might have resulted in high adsorptive capacity and decreased bioavailability of PAHs. When the biochar application rate was higher than 0.6 t/ha, the incremental lifetime cancer risk value for human exposure to biochar-borne PAHs through the biochar-amended soil was over 10, suggesting carcinogenic risks. Germination index values of biochars ranged from 25.66 to 88.95%. Phytotoxicity mainly was caused by bioavailable PAHs and dissolved organic compounds. Overall, these findings highlighted that although the percentage of bioavailable PAHs was low, the potential health risk and phytotoxicity of PAHs in biochars produced by a continuous pyrolysis system was of a great concern. High biochar application rates should be avoided without processing both for soil safety and human health.
生物炭作为土壤改良剂的应用已引起全球关注。然而，生物炭生产过程中形成的多环芳烃（PAHs）在施用于土壤后可能会进入生态系统并威胁人类健康。由于停留时间短和快速冷却，连续热解系统往往会导致生物炭中 PAHs 的积累。本研究基于生物炭的生物有效性、浸出行为、毒性当量、健康风险和多环芳烃的植物毒性，对连续热解系统生产的生物炭中 PAHs 的潜在风险进行了综合评估。结果表明，生物炭中总多环芳烃的浓度范围为 93.40-172.40 mg/kg，超过了欧洲生物炭证书标准。三环 PAHs 是主要的组。总自由溶解和可浸出 PAHs 的百分比低于 1%。与 CS 和 PS 相比，RH 含有最少的生物可利用和可浸出的 PAHs 浓度和植物毒性，这可能归因于三种生物炭的特性。CS 和 PS 呈酸性，具有较高的 DOC 和 VFAs 水平，而 RH 呈强碱性，具有较高的芳香度和较高的表面积，这可能导致对 PAHs 的高吸附能力和降低生物可利用性。当生物炭施用量高于 0.6 t/ha 时，通过添加生物炭的土壤中人类接触生物炭携带的 PAHs 的增量终生癌症风险值超过 10，表明存在致癌风险。生物炭的发芽指数值范围为 25.66-88.95%。生物毒性主要是由生物可利用的 PAHs 和溶解有机化合物引起的。总的来说，这些发现强调了尽管生物可利用的 PAHs 比例较低，但连续热解系统生产的生物炭中 PAHs 的潜在健康风险和植物毒性仍令人担忧。为了土壤安全和人类健康，在不进行处理的情况下，应避免高生物炭施用量。
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