Swine manures generally contain high levels of copper (Cu) resulting from its use as a growth promoter in feedstuff. Pyrolysis can further concentrate Cu whereas decrease its available fraction in swine manures. Here we investigated the speciation transformation of Cu and associated elements in swine manures induced by pyrolysis using multiple X-ray absorption spectroscopies. Results showed that over 82% of Cu existed as Cu(I)–S and Cu(I)–thiolate complexes in swine manures, which were transformed into stable Cu(I)₂S during pyrolysis at a low temperature of 300 °C and partially oxidized and desulfurized into Cu(II) compounds at a high temperature of 500 °C. The speciation evolution of Cu in swine manures was consistent with the speciation distribution of sulfur in feedstuff and its following changes in swine manures during pyrolysis. About 58% of phosphorus existed as CaHPO₄ and struvite in swine manures, which were gradually transformed into stable Ca-bound species such as hydroxyapatite during pyrolysis. The formation of stable phosphate, together with concentrated carbonates, significantly decreased the available Cu in pyrolyzed manures. These findings suggested that the high levels of S and P in feedstuff profoundly affected the speciation of Cu in the swine manures and derived biochars. This study has important implications to our understanding of the behaviors of heavy metals in manure-derived biochars once entering soil environments.

中文翻译：

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热解诱导猪粪中铜的形态演变。

猪粪通常含有高含量的铜（Cu），这是由于其用作饲料中的生长促进剂。热解可以进一步浓缩铜，而减少其在猪粪中的可用含量。在这里，我们使用多种X射线吸收光谱法研究了热解诱导的猪粪中Cu和相关元素的形态转化。结果表明，猪粪中超过82％的Cu以Cu（I）-S和Cu（I）-硫醇盐络合物的形式存在，并转化为稳定的Cu（I）₂S在300°C的低温下热解过程中，在500°C的高温下部分氧化并脱硫成Cu（II）化合物。猪粪中铜的形态演变与饲料中硫的形态分布及其在热解过程中猪粪的变化一致。CaHPO ₄存在约58％的磷猪粪中的鸟粪石和鸟粪石，在热解过程中逐渐转变成稳定的钙结合物种，例如羟基磷灰石。稳定的磷酸盐以及浓碳酸盐的形成显着降低了热解肥料中的有效铜含量。这些发现表明，饲料中高含量的硫和磷深刻影响了猪粪和衍生生物炭中铜的形态。这项研究对我们了解粪便来源的生物炭进入土壤环境后重金属的行为具有重要意义。