生物炭释放的水分散性胶体对土壤磷迁移的影响及生态效应

Biochar can alter phosphorus cycle in agricultural field, but studies mainly focus on the agricultural merits of biochar application and lack of understanding of the environmental risk. The water dispersible colloids are the most important and active part of biochar. In the present study, we hypothesis that(1)biochar colloids affect particle size distribution of soil phosphorus, change the loss of potential of soil phosphorus; (2)the combination of biochar colloids and phosphorus produce colloidal phosphorus which has different mobility and bioavailability compared dissolved phosphorus. Preliminary results show that the colloidal phosphorus accounted for 23-62% of the total water soluble phosphorus of biochar. These colloids showed high availability. In order to study the migration of phosphorus with these colloids and the subsequent algae response, we plan to: (1) separate the water-dispersible colloidal form biochar with cross flow filtration and use the technique of NMR、IR、X-RAY and TEM to investigate the content, characteristics of water dispersible colloid of biochar and its control factors; (2) use the soil culture experiments and column leaching experiments to reveal the effects of biochar on soil colloids phosphorus transformation and to explore the phosphorous loss potential;(3) use the alga culture experiments to discuss the impact of biochar colloidal phosphorus on the growth of the dominate offshore algae. This research has important implications for revealing the environment and ecological effect of biochar application and providing vital reference for the application of biochar.

生物炭同土壤磷素研究多侧重其农艺价值而对环境效应认识不足。生物炭释放的水分散性胶体(简称生物炭胶体)是生物炭中最重要、最活跃的成分，本研究假设(1)生物炭胶体影响了土壤磷素粒径分配，改变土壤磷素的流失潜能；(2)生物炭胶体与磷结合形成胶体磷，在移动性和有效性方面同溶解磷存在很大差异。预研结果表明胶体磷约占生物炭中总水溶性磷23-62％，并且有效性较高。针对生物炭中水分散性胶体的释放，生物炭胶体对磷素迁移的影响，受纳水体藻类响应等问题，本研究计划采用切向流超滤技术提取生物炭胶体，阐明生物炭中水分散性胶体组成、特性及控制因素；通过不同土壤培养和饱和柱淋溶试验，探讨生物炭胶体对土壤中磷素粒径分配和流失潜能的影响，揭示生物炭胶体对土壤磷素迁移影响和作用机理；通过藻类培养实验，揭示生物炭胶体对黄渤海主要优势藻类的有效性影响。通过该研究揭示生物炭施用的环境影响和生态效应，为生物炭应用提供借鉴和指导。

生物炭对土壤磷素形态转化和生物有效性的影响是当前研究热点。研究表明生物炭添加对土壤磷有效性主要受生物炭材料、炭化条件、土壤类型等因素的影响。生物炭释放的水分散性胶体(简称生物炭胶体) 能够在环境中长期存在，具有较强的移动性，是生物炭中最重要、最活跃的组成成分。本研究首先明确了不同材料（玉米，小麦，花生壳）在不同炭化温度下磷的形态转化，建立了炭化过程中磷转移转化的模式；探讨了利用离心法、沉降法和球磨法用于生物炭胶体的分离技术，最终确定了采用球磨转速500rpm,球磨时间6h,球料重量比为23：1的条件下进行湿法（乙醇）球磨，得到了平均粒径为1.9μm的小麦生物炭胶体；通过对生物炭胶体磷化学形态分析和磷液体核磁共振技术分析，说明生物炭胶体在炭化过程中有机磷含量迅速降低，主要转化为惰性和难溶性磷；磷吸附和解吸实验表明，生物炭胶体可以大大增加土壤中磷素流失潜能；通过室内模拟培养实验，结果表明生物炭胶体对酸性土壤活性磷大多表现为正激发效应，而对碱性土壤活性磷基本为负激发效应，因此生物炭胶体在酸性土壤应用可能会蕴涵更大的环境风险。最后，通过室内模拟实验表明较低温度（300℃和400℃）的生物炭更有利于增加土壤有效磷含量，提高作物对磷素的吸收利用。该研究揭示了生物炭施用的环境影响和生态效应，可为生物炭应用提供借鉴和指导。