Co-pyrolysis of sewage sludge and straws has been used to improve the pore structure and reduce the ecological risks of heavy metals in sewage sludge-derived biochars. However, to date, no study has focused on the effects of biochar derived from sewage sludge/straws on the immobilization and phytoavailability of heavy metals in soil. Here, we studied the effects of biochar derived from sewage sludge/cotton stalks (SCB) and that derived from sewage sludge alone (SSB) on the remediation of sandy loam soil contaminated by Pb, Cu, and Zn. SCB amendment decreased the bioavailable forms of Pb, Cu, and Zn in the soil by 19.0%, 34.9%, and 18.2%, respectively, and reduced their accumulation in ryegrass by 28.6%, 50.1%, and 30.0%, respectively, compared with those by SSB amendment. Furthermore, SCB amendment transformed more metals from the acid-soluble fraction to the oxidizable fraction than SSB amendment, indicating that complexation played a more critical role in SCB amendment than in SSB amendment. Both biochar amendments effectively improved soil water holding capacity, increased the supply of available P, N, and K, and promoted ryegrass growth. The findings of this study show the benefits of SCB over SSB for the remediation of heavy metal-contaminated soil.

污水污泥和秸秆的共热解已被用于改善孔隙结构并降低污水污泥衍生生物炭中重金属的生态风险。然而，迄今为止，还没有研究关注源自污水污泥/秸秆的生物炭对土壤中重金属的固定化和植物有效性的影响。在这里，我们研究了源自污水污泥/棉杆 (SCB) 的生物炭和源自污水污泥 (SSB) 的生物炭对修复受 Pb、Cu 和 Zn 污染的砂壤土的影响。与 SCB 相比，SCB 改良剂使土壤中 Pb、Cu 和 Zn 的生物可利用形式分别降低了 19.0%、34.9% 和 18.2%，并将它们在黑麦草中的积累量分别降低了 28.6%、50.1% 和 30.0%那些通过 SSB 修正案。此外，与 SSB 修正相比，SCB 修正将更多的金属从酸溶部分转化为可氧化部分，表明络合在 SCB 修正中比在 SSB 修正中起更关键的作用。两种生物炭改良剂都有效地提高了土壤持水能力，增加了可用 P、N​​ 和 K 的供应，并促进了黑麦草的生长。本研究的结果表明，SCB 在修复重金属污染土壤方面优于 SSB。