可溶性有机质对纳米颗粒土壤生物效应的调控作用与机制

Increased use of engineered nanoparticles raises concerns about their environmental impacts. Nanoparticulate titanium dioxide (nano-TiO2) and zinc oxide (nano-ZnO), two widely-used nanoparticles, are prone to accumulate in soils. It has been reported that nano-TiO2 and nano-ZnO can reduce soil microbial biomass and diversity, suppress some functionally significant microbial groups, and translocate from soil to plant tissues through root. However, little is known about how the nanoparticle effects will be modulated by dissolved organic matter (DOM) in soils. We plan to extract DOM from three agricultural soils located across the Northern and Southern China. The mechanisms of DOM in modulating nano-TiO2 and nano-ZnO effects on soil organisms will be elucidated by examining the adsorption of DOM onto nanoparticle surface, the role of DOM in altering aggregation, sedimentation and mobility of nanoparticles, and the role of DOM in modifying nanoparticle effects on soil bacterial, fungal and protozoal communities as well as some key biological processes. We attempt to test the hypothesis that the adsorption of DOM onto nanoparticle surface will change aggregation, sedimentation and mobility of nanoparticles, and thus modulate nanoparticle effects on soil organisms. This project aims to provide insights into the environmental behaviors and biological effects of nanoparticles, and thus provide theoretical basis for the intentional modulation of nanoparticle effects on soil organisms.

纳米材料的环境安全性日益受到关注。纳米TiO2和ZnO应用广泛，易在土壤中累积。研究表明纳米TiO2和ZnO可降低土壤微生物量和多样性，抑制特定微生物功能类群，并通过根系向植物地上部分传输。然而，对土壤可溶性有机质（DOM）如何调控纳米TiO2和ZnO的土壤生物效应知之甚少。本研究拟从东北黑土、华北潮土、南方红壤三种典型农业土壤中提取DOM，通过研究纳米颗粒对DOM的吸附作用，DOM对纳米颗粒的凝聚性、沉降性、可移动性的调控作用，及DOM如何改变纳米颗粒对土壤细菌、真菌、原生动物群落和关键土壤生物过程的影响，揭示DOM调控纳米TiO2和ZnO土壤生物效应的机制。拟验证以下科学假设：DOM可吸附于纳米颗粒表面，进而改变纳米颗粒的凝聚性、沉降性和可移动性，最终改变纳米颗粒的土壤生物效应。这项研究有望加深我们对纳米颗粒环境行为和生物效应的认识，为人工调控土壤中纳米颗粒的生物效应提供理论依据。

本项目旨在建立纳米颗粒模拟土壤暴露实验系统，进而揭示纳米颗粒的新型土壤环境风险和生物效应，解析环境因子特别是可溶性有机质对纳米颗粒不利影响的调控作用，以其为评估和调控纳米颗粒的土壤生物效应提供数据支撑和理论依据。在项目期内，圆满完成预定研究任务，实现了研究目标，在以下几方面取得重要进展。（1）在对多种纳米颗粒理化特性系统表征的基础上，将纳米颗粒土壤生物效应与其理化特性和暴露时间相关联，揭示了不同理化特性纳米颗粒在不同暴露情景下对土壤氨氧化微生物的影响差异。（2）首次在真实土壤介质中发现稀土氧化物纳米颗粒可通过共选择和基因水平转移机制，诱导土壤中抗生素抗性基因丰度和多样性的显著增加，进而诱导土壤微生物群落水平抗生素抗性的增强，从新的角度揭示了人工纳米材料的土壤环境风险。（3）将植物纳入到纳米颗粒暴露系统中，发现由于植物不同生长阶段根系分泌的可溶性有机质的差异，影响纳米颗粒的生物有效性，进而调节人工纳米材料的土壤生物效应，该研究为如何调控纳米材料在土壤生态系统中的不利影响提供了新的思路和数据支撑。发表12篇SCI论文，培养3名博士后和1名硕士研究生。