The differing chemical properties of arsenic (As) and cadmium (Cd) make co-remediation in soil systems a major challenge. This study aimed to gain a mechanistic understanding of how two contrasting biochars (poultry litter and sugar-gum wood) impacted the potential bioavailability of As and Cd in soil matrix varying in initial pH (4.6, 5.7, 6.4, 7.1 and 7.4). The application of poultry-litter biochar significantly increased potential bioavailability of As from 11 to 58 mg kg⁻¹ across all soil pH while the potential bioavailability of Cd was decreased from 15 to 1.5 mg kg⁻¹ at pH $\le$ 6.4. Biochar derived from sugar-gum wood decreased bioavailable As from 11 to 8 mg kg⁻¹ and 14 to 12 mg kg⁻¹ in soils with pH 4.6 and 5.7, respectively, while increased it from 14 to 31 mg kg⁻¹ at pH $\ge$ 6.4. Biochars transformed the residual fraction of As into the exchangeable fraction but the reverse was true for Cd. Biochar application changed the microbial respiration with contrasting dynamic patterns throughout the 30-d incubation. Soil respiration and microbial biomass C responded more quickly in low-pH than high-pH soils due to low As bioavailability at low pH. These new findings provide strong evidence regarding how contrasting biochars control the mobility of As and Cd over a wide range of soil pH within the same soil matrix.

砷 (As) 和镉 (Cd) 的不同化学性质使土壤系统中的协同修复成为一项重大挑战。本研究旨在从机制上了解两种不同的生物炭（家禽垃圾和糖胶木）如何影响初始 pH 值（4.6、5.7、6.4、7.1 和 7.4）不同的土壤基质中砷和镉的潜在生物利用度。家禽垃圾生物炭的应用显著增加作为潜在的生物利用度为11至58毫克千克^-1在所有土壤pH而镉的潜在的生物利用度从15减少到1.5毫克千克^-1在pH$\le$6.4. 源自糖胶木的生物炭在 pH 值为 4.6 和 5.7 的土壤中分别将生物可利用性 As 从 11 至 8 mg kg ^-1和 14 至 12 mg kg ^{-1 降低}，而在 pH 值下从 14 增加至 31 mg kg ^-1$\ge$6.4. Biochars 将 As 的残余部分转化为可交换部分，但 Cd 的情况正好相反。在整个 30 天的孵化过程中，生物炭应用通过对比动态模式改变了微生物呼吸。由于低 pH 下砷的生物有效性低，土壤呼吸和微生物生物量 C 在低 pH 下的反应比高 pH 土壤更快。这些新发现提供了强有力的证据，证明对比生物炭如何在同一土壤基质内在广泛的土壤 pH 值范围内控制 As 和 Cd 的迁移率。