球囊霉素相关土壤蛋白（GRSP）对土壤中PAHs植物可利用性的影响及机制

Understanding the phytoavailability of polycyclic aromatic hydrocarbons (PAHs) in soils is essential to assessing their environmental fate and risks. Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts living in association with the roots of the majority of land plants. The extensive network of AMF hyphae spreads from mycorrhizal roots into the surrounding soil, and glomalin-related soil protein (GRSP) is produced and enters into the soil as AMF hyphae decompose. GRSP can accumulate in the soil to several g/kg, and the carbon concentration of GRSP can be 2-25 times that of humic acid and even as much as 25% of the total soil carbon content. Unfortunately, it is unclear how GRSP influences the PAH phytoavailability in the soil environment. Therefore, this project aims to examine the impact of GRSP-influenced phytoavailability of PAHs in soils using field and greenhouse experiments together with microcosm and batch equilibrium techniques. Parameters including plant concentration, accumulation mass, concentration factor, and translocation factor will be adopted to evaluate the phytoavailability of PAHs in soils. The mechanisms of GRSP-influenced phytoavailability of soil PAHs will be elucidated, basing on the observations of the GRSP-induced changes of PAH forms in soil, PAH release from soil solids into solution, PAH sorption from solution onto root surface, and PAH transfer from root surface into inner root layers. The findings of this project will provide valuable insight into the role of GRSP in soil PAH phytoavailability and will be beneficial for the alleviation of plant PAH risk at contaminated sites.

土壤中多环芳烃（PAHs）的植物可利用性是影响其植物污染风险的一个最关键因素。丛枝菌根真菌（AMF）菌丝会分泌大量球囊霉素相关土壤蛋白（GRSP）、并将其释放到土壤中；然而，GRSP对土壤中PAHs植物可利用性有何影响？国内外仍不清楚，这限制了人们对AMF调控土壤PAHs污染作用机制的深入了解。本项目利用田间试验结合温室盆栽、微宇宙、批平衡等试验方法，以植物PAHs含量、积累量、富集系数、传输系数为参数，研究GRSP影响土壤中PAHs植物可利用性的基本规律；探讨GRSP作用下土壤中PAHs形态变化，剖析GRSP对PAHs土→水→根传质过程的影响，系统地探明GRSP影响土壤中PAHs植物可利用性的作用机制。通过开展本研究，试图揭示AMF及其菌丝影响植物吸收PAHs的内在本质，丰富人们对土壤中GRSP环境功能的认识，为利用AMF及GRSP来减低污染区植物PAHs污染风险提供重要思路和依据。

土壤中多环芳烃（PAHs）的植物可利用性直接制约着其植物吸收和污染风险，丛枝菌根真菌（AMF）常被用于作物生产，然而接种AMF土壤中数量庞大的球囊霉素相关土壤蛋白（GRSP）对PAHs植物可利用性有何影响？人们对此仍缺乏了解。本项目研究了GRSP对PAHs植物可利用性的影响规律，从GRSP作用下土壤中PAHs形态变化、土-水-根传质过程方面，揭示了影响机制。主要结果：①以根中PAHs含量和根系富集系数（RCF）为指标，阐明了GRSP对PAHs植物可利用性的影响规律。发现施用总GRSP（T-GRSP）或易提取GRSP（EE-GRSP）可促进黑麦草根系吸收积累PAHs，促进效应随GRSP施用量提高呈先升后降的趋势。明确了GRSP作用下根部PAHs的微观分布特征，发现根中吸附态PAHs占比最高（>88%）。②剖析了GRSP作用下土壤PAHs形态变化。外源GRSP有利于土壤中PAHs可提取态和结合态残留的形成，添加GRSP增大了土壤中溶解性有机碳（DOC）、胡敏素（HM）等组分含量，其DOC含量与PAHs可提取态残留显著正相关，HM含量与HM结合态残留显著正相关；施入土壤后GRSP逐渐演化为有机质组成部分，进而影响PAHs形态变化。③探明了GRSP作用下PAHs的土/水界面过程。菲在黄棕壤上的吸附等温线为线型，发现GRSP抑制了黄棕壤吸附菲，随T-GRSP和EE-GRSP浓度提高，土壤吸附菲的分配系数Kd值下降，GRSP抑制吸附效应增强。残留GRSP主导着吸附平衡溶液DOC的组成特征，溶液中GRSP与菲结合抑制了黄棕壤吸附菲。④揭示了GRSP作用下PAHs的水/根传质过程。分配作用主导了黑麦草根对PAHs的吸附行为，施加GRSP促进了根吸附PAHs，促进效应随GRSP浓度提高呈先升后降的趋势；根吸附态PAHs含量和根积累量与Kd显著正相关，表明GRSP通过影响PAHs根/水间吸附过程进而制约根吸收积累PAHs。共发表学术论文19篇。研究成果丰富了人们对GRSP土壤环境功能的认识和理解，为后续利用AMF及GRSP来调控植物PAHs污染风险提供了基础依据。