DataSheet1_Field verification of low-level biochar applications as effective ameliorants to mitigate cadmium accumulation into Brassica campestris L from polluted soils.docx

Introduction: Cadmium (Cd) has been recognized as a significant contributor to the pollution of farmland soils in China, and biochars have been reported to be effective in mitigating soil Cd pollution. However, most studies have been conducted in laboratory or greenhouse settings, not at a field scale, and the biochars used have been applied at unrealistically high amounts (>10 t/ha).
Methods: In this research, three biochars: rice straw biochar (RSB), pig manure biochar (PMB) and rice husk biochar (RHB) were produced from readily available farm residues. Then the effects at low-level application (1.8 and 3.6 t/ha) on Cd were investigated in a field experiment cropped with rape (Brassica campestris L.).
Results: Batch adsorption experiments indicated Cd adsorption capacity of three biochars followed the order of RSB (43.5 mg/g) > PMB (33.3 mg/g) > RHB (24.4 mg/g). Field experiment indicated biochar amendments could slightly change soil pH and cation exchange capacity (CEC); yet led to considerable and significant decreases in extractable Cd concentrations [reductions of: 43%–51% (PMB), 29%–35% (RSB) and 17%–19% (RHB)]. Reduced extractable Cd correlated with lower Cd concentrations in rape plants. PMB and RSB were more effective in decreasing Cd phytoaccumulation into edible parts of rape (>68% reduction) than RHB.
Discussion: Low-level application of PMB or RSB could efficiently decrease the phytoaccumulation of Cd from soils into crops. These results demonstrate the reality of biochar-based remediation solutions to contribute to the mitigation of diffuse Cd contamination in farmland. The results also highlight the need to trail biochars in the presence of the soil to be targeted for remediation.

引言：镉（Cadmium, Cd）已被证实是造成我国农田土壤污染的关键污染物之一，而生物炭（biochar）已被证明可有效缓解土壤镉污染问题。然而，现有相关研究多在实验室或温室环境中开展，尚未实现田间尺度的应用，且所使用的生物炭施用量远超合理水平（>10 t/ha）。
方法：本研究以易得的农业废弃物为原料，制备了3种生物炭：稻草生物炭（Rice Straw Biochar, RSB）、猪粪生物炭（Pig Manure Biochar, PMB）与稻壳生物炭（Rice Husk Biochar, RHB）。随后设置1.8 t/ha与3.6 t/ha两个低施用量梯度，在种植油菜（Brassica campestris L.）的大田试验中，探究上述生物炭对土壤镉的调控效果。
结果：批量吸附实验结果显示，3种生物炭对镉的吸附容量依次为：稻草生物炭（43.5 mg/g）>猪粪生物炭（33.3 mg/g）>稻壳生物炭（24.4 mg/g）。大田试验结果表明，施加生物炭可小幅改变土壤pH值与阳离子交换量（Cation Exchange Capacity, CEC），但可显著降低土壤可提取态镉含量：猪粪生物炭处理降幅为43%~51%，稻草生物炭处理为29%~35%，稻壳生物炭处理为17%~19%。土壤可提取态镉含量的降低与油菜植株内镉浓度的降低呈显著相关。相较于稻壳生物炭，猪粪生物炭与稻草生物炭在抑制镉向油菜可食用部分的植物累积方面效果更优（降幅>68%）。
讨论：低施用量的猪粪生物炭或稻草生物炭可有效降低土壤镉向农作物的植物累积量。上述结果证实了基于生物炭的修复技术可切实缓解农田镉面源污染。同时，本研究也凸显了针对目标修复土壤开展原位生物炭试验的必要性。