近三十年农田土壤磷分子形态的研究进展

农田土壤磷的赋存形态决定迁移、转化及归趋过程,单单通过全磷或有效磷含量并不能全面、准确、长效地评估土壤磷的养分供应能力和生态环境风险,探索可持续的农田磷素管理措施迫切需要能够科学表征、准确认识土壤磷形态。随着分析测试技术发展,农田土壤磷形态领域经历了以传统连续提取法为主的分级组分研究,到目前基于先进光谱技术的分子形态研究的发展历程。液相磷-31核磁共振技术(P-NMR)、基于同步辐射的X射线吸收近边结构谱技术(P-XANES)是当今土壤磷分子形态表征的主流技术,分别促进土壤多种有机磷和无机磷(铁磷/钙磷/铝磷)分子形态的有效识别。借助Histcite软件进行引文网络分析,梳理了近三十年(1990—2019年)土壤磷分子形态研究发展历程中具有重大借鉴意义的关键性成果,基于此综述了该领域的发展脉络,归纳发现农田土壤磷分子形态研究最初主要借助P-NMR技术侧重有机磷分子形态表征,而后过渡至与同步辐射XANES以及X射线微探针技术相结合,实现了土壤磷分子形态的全面认识。最后,对多谱学技术联用推动土壤磷分子形态研究的发展趋势进行了展望。

Molecular Speciation of Phosphorus in Agricultural Soils: Advances over the Last 30 Years

Phosphorus (P) speciation in agricultural soils determines its transformation, transport as well as fate. A comprehensive and accurate assessment of phyto-availability and environmental risk of soil P, particularly in the long term, cannot be achieved based only on routine soil tests for total P or available P. Therefore, it is essential to fully characterize and accurately understand the speciation of soil P for sustainable P management. Past research on characterization of soil P using the technique of traditional sequential fractionation could reveal information of operationally-defined P pools only, while researchers are currently able to identify soil P species at the molecular level with the aid of advanced spectroscopic tools, among which, solution P-31 nuclear magnetic resonance (P-NMR) and synchrotron-based X-ray absorption near-edge fine structure (XANES) spectroscopies are nowadays state-of-the-art techniques. These advanced techniques substantially facilitate our understanding of the various forms of organic, and inorganic P including P associated with Fe oxides, Al oxides and Ca minerals. Based on citation network analysis using Histcite software, this paper summarized key achievements of great significance during the development of the research on soil P characterization, reviewed development context of the research in this field over the last 30 years (from 1990 to 2019). It was found that the initial understanding of molecular P speciation, particular for organic P, in soils was mainly based on the technique of P-NMR, then more comprehensive understanding of soil P speciation at the molecular level was achieved once the technique was used in combination of synchrotron-based XANES and X-ray microprobe. Finally, this review presented a perspective on future trends of the application of multiple spectroscopic techniques in the research on soil P molecular speciation.