Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Sci Technol. 2022 May 17;56(10):6639-6646. doi: 10.1021/acs.est.2c00632. Epub 2022 May 3.
Phosphorus (P) and sulfur (S) are usually involved simultaneously in the immobilization of heavy metals in sewage sludge during pyrolysis, and thus their speciation in sewage sludge-derived biochar (SSB) profoundly affects the recycling of the nutrients and the environmental risks of sewage sludge. Here, we investigated the speciation evolution of P and S in SSB induced by ageing processes in soil using X-ray absorption near edge structure spectroscopy. Results showed that Ca-bound compounds like hydroxyapatite dominated the P forms, while over 60% of S existed as reduced inorganic sulfides in the SSB. The stable Ca-associated P species in SSB tended to be transformed gradually into relatively soluble species during ageing in soil. The speciation composition of S in SSB remained almost unaffected when aged in pot soils, whereas about 33.6% of reduced sulfides were transformed into oxidized species after 1-year ageing in field soils. SSB significantly increased the proportion of sulfides and the contents of available P and S in the amended soil but showed relatively weak effects on the speciation distribution of P in the soil because of their similar compositions. These findings provide insights into biogeochemistry of nutrients and behaviors of heavy metals in SSB after its application to the soil environments.
磷（P）和硫（S）通常在热解过程中同时参与重金属在污水污泥中的固定，因此它们在污水污泥衍生生物炭（SSB）中的形态强烈影响营养物质的回收和污水污泥的环境风险。在这里，我们使用 X 射线吸收近边结构光谱研究了土壤老化过程中 SSB 中 P 和 S 的形态演变。结果表明，羟磷灰石等钙结合化合物主导了 P 形态，而超过 60%的 S 以还原无机硫化物的形式存在于 SSB 中。在土壤老化过程中，SSB 中稳定的与 Ca 相关的 P 物种趋于逐渐转化为相对可溶性的物种。在盆栽土壤中老化时，SSB 中 S 的形态组成几乎没有变化，而在田间土壤中老化 1 年后，约 33.6%的还原硫化物转化为氧化物种。SSB 显著增加了添加土壤中硫化物的比例以及有效 P 和 S 的含量，但由于其相似的组成，对土壤中 P 的形态分布的影响相对较弱。这些发现为 SSB 施用于土壤环境后营养物质的生物地球化学和重金属的行为提供了深入了解。
