Biosolids phosphorus forms, transformation and bioavailability in soil

磷(P)的回收利用是极其重要的，因为磷酸盐工业预测在未来100到250年内可用的磷储量将耗尽。在农业用地上施用生物固体有助于封闭城乡营养循环。然而，为了有效地管理农业生态系统中的生物固体磷，需要更好地了解生物固体磷的形态、转化和生物利用度。施用量不当，既可能造成作物减产，也可能造成土壤磷积累，环境风险增大。生物固体中磷的总浓度一般在1 - 5%的干重基础上下降，其中70 - 90%以无机形式存在。要了解生物固体磷加入土壤后的生物利用度，不仅需要了解这些材料中磷的形态和数量，还需要了解可以改变磷行为、磷转化动力学及其与土壤和植物根系相互作用的元素或材料的形态和数量。传统的物种形成方法对生物固体P化合物的鉴定提供了有限的见解。作为化学提取的替代方法，先进的光谱技术最近被用于表征土壤中P的种类和改良剂。x射线吸收近边结构技术是研究磷固相形态的最新光谱工具之一，该技术可以区分磷的沉淀相和吸附相。利用P-31核磁共振波谱技术，生物固体中不同的磷化合物也被鉴定出来，这种技术可以直接提供有机磷的分子和结构表征。生物固体P形态将使用先进的分析技术进行表征。在研究期间，将评估土壤性质、湿度和温度对生物固体磷转化的影响。此外，还将研究生物固体磷在土壤和根际的转化、其在土壤中的生物有效性和流动性。最后，定量分析施用生物固体磷在土壤中的残留效应。

Recycling of phosphous (P) is exteremly important as the phosphate industry predicts exhaustion of available P reserves in next 100 to 250 years. Land application of biosolids on agricultural lands helps closing the rural-urban nutrient cycle. However, to effectively manage biosoilds P in agro-ecosystems, a better understanding of biosolids P forms, transformation and bioavailability is required. Improper application rates can result in either losses of crop yield or P accumulation in soil with increased environmental risks. Total concentrations of P in biosolids generally fall in range of 1 to 5% dry weight basis, 70 to 90% of which is in inorganic forms. Understanding the bioavailability of biosolids P after addition to soil requires an understanding of not only the forms and amounts of P in these materials, but also the forms and amounts of elements or materials that can modify P behaviour, kinetics of P transformation and its interactions with soil and plant roots. Traditional speciation methods provide limited insight into identification of biosolids P compounds. As an alternative to chemical extraction, advanced spectroscopic techniques have been recently offered for characterization of P species in soil and amendments. The X-ray Absorption Near-Edge Structure technique is one of the latest spectroscopic tools for solid phase speciation of P. This technique can distinguish between precipitated and adsorbed phases of P. Different P compounds in biosolids have also been identified using P-31 Nuclear Magnetic Resonance spectroscopy, a technique that provides direct molecular and structural characterization of organic P. Through greenhouse and field study, biosolids P forms will be characterized using advanced analytical techniques. Effects of soil properties, moisture and temperature on biosolid P transformation over the study period will be evaluated. As well, biosolids P transformation in soil and rhizosphere, its bioavailability and mobility in the soil will be investigated. Finally, the residual effect of applied biosolid P in the soil will be quantified.