酸化生物炭对土壤-蔬菜系统中抗生素抗性基因的影响机制

The problem of antibiotic resistance gene (ARGs) residue in soil and vegetables has become one of the important factors affecting human health in 21st Century. The antibiotics and heavy metals in manure of livestock and poultry while applied to soils would induce and promote the formation of ARGs. Acidified biochar, as an important soil amendment, can strongly adsorb antibiotics and heavy metals in alkaline soil. In theory, application of acidified biochar could regulate the abundance and diffusion of ARGs in soils. However, the regulating mechanism has not been studied systematically. This project will investigate the adsorption properties of acidified biochar from different raw materials for Sulfadimidine (SM2) and Cu, and identify the effects of the strongest adsorption performance of acidified biochar on ARGs abundance in soil、lettuce and radish. From the perspective of SM2 and Cu fraction, soil nutrients, mobile genetic elements and microbial communities, the main controlling factors and mechanism of acidified biochar affecting ARGs will be revealed. Moreover, a quantitative relationship between acidified biochar application amount and ARGs will be established. And application measures for acidified biochar will be proposed for enhancing ARGs abundance, promoting vegetable growth and improving soil quality. The successful completion of the project will provide theoretical guidance for protecting food safety and lessening the threat of ARGs to human beings.

土壤和蔬菜中抗生素抗性基因（ARGs）残留问题已成为21世纪影响人类健康的重要因素之一。畜禽粪便以粪肥施入土壤，其中含有的抗生素和重金属会诱导并促进ARGs的形成。酸化生物炭作为重要的土壤改良剂，对碱性土壤中抗生素和重金属有强吸附作用，施用后理论上对ARGs丰度与扩散具有调控作用，但其作用机制还缺乏系统研究。本项目针对畜禽粪便中磺胺二甲嘧啶（SM2）和铜（Cu）污染引起的土壤ARGs残留问题，研究不同原料酸化生物炭对SM2和Cu的吸附能力；明确吸附性能最强的酸化生物炭对土壤、生菜和水萝卜中ARGs的影响；从SM2和Cu形态、土壤养分、可移动基因元件和微生物角度来揭示酸化生物炭影响ARGs的主控因素和作用机理；建立酸化生物炭施加量和ARGs间的定量关系，提出适用于削减ARGs丰度、提高蔬菜生长和改善土壤质量的酸化生物炭施用对策。为保护食品安全及降低ARGs对人类的威胁提供理论依据。

随着粪肥施用和污水灌溉等人类活动的加剧，过量的Cu、抗生素和抗生素抗性基因（Antibiotic resistance genes，ARGs）等污染物在农田土壤中不断汇集。改性（酸化和纳米粒径）生物炭是重要的土壤改良剂，对土壤中抗生素和重金属有强吸附作用，施用对ARGs丰度与扩散以及土壤质量和作物生长的调控作用还缺乏系统研究。本项目针对有机肥施用造成土壤重金属铜（Cu）污染引起的ARGs残留问题，结合吸附试验、盆栽试验研究不同改性生物炭对Cu的吸附迁移能力，以及对土壤中ARGs、土壤理化性质、生菜生长和细菌群落结构的影响，揭示了改性生物炭影响ARGs丰度的主控因素和作用机理。研究结果表明添加酸化纳米生物炭吸附土壤中Cu2+的性能最好，对土壤Cu2+的吸附容量比对照CK高46.2%，生物炭经纳米分级及酸改性后增加其多孔结构、比表面积和官能团种类，显著降低了土壤中有效态铜占总铜的比例（P < 0.05）。添加生物炭和蜡样芽孢杆菌重金属阻控剂能够降低土壤和生菜中ARGs的丰度，0.5%的纳米酸化生物炭和10%的蜡样芽孢杆菌联合施用使得根际土中ARGs和MGEs的绝对和相对丰度降低最多，生菜中抗铜基因的丰度降低97%，ARGs降低98%。这与二者联合施用促进作物生物量的增加，降低土壤中可交换Cu含量和生菜中Cu累积有关。RDA和Network分析结果表明影响土壤和生菜组织中ARGs、MGEs分布的主要贡献因子不同。土壤中的ARGs和MGEs主要由细菌Proteobacteria、Actinobacteriota以及土壤各形态Cu含量所主导。生菜中的蓝藻细菌门、Overground.Cu、Root.Cu显著降低了内生菌中MGEs和sul1、tetG、tetX、ermX的丰度（P<0.05），但驱动着copA、ermF的增加。总之，为了削减土壤ARGs丰度、促进蔬菜生长和改善土壤质量，施用0.5%的纳米酸化生物炭和10%的蜡样芽孢杆菌可有效达到土壤改良目的，为保护食品安全及降低ARGs对人类的威胁提供理论依据。