生物炭影响土壤-韭菜系统中噻虫嗪归趋代谢的作用机制

Chinese chive is a favored medicinal and edible vegetable in China. However, the improper application of high toxic pesticides causes serious pesticide residue problem. The neonicotinoid pesticides are frequently used as the soil treat agent in the agricultural production. The high detected rate of neonicotinoid pesticides residue thus poses potential risk to the soil environment and the food safety. Biochar, as a novel environmental-friendly material shows great potential to control the contaminates in soil. However, the effect and mechanism of biochar on the accumulation of neonicotinoid pesticides in plant is not clear. Based on the results of previous study, the biochar samples were produced from different biomass feedstocks in this study. The characteristics and mechanism of different biochar to adsorption and degradation of the typical neonicotinoid pesticide thiamethoxam and the metabolite clothianidin will be explored. In this study, the effect of biochar on the distribution, degradation and metabolism of the typical neonicotinoid pesticide thiamethoxam in the “soil-Chinese Chive root-Chinese plant” system will be explored. The environmental behaviors of thiamethoxam, including adsorption, desorption, and degradation, in the biochar-root-soil interface will be studied. We focus on the action characteristic and type of biochar on the degradation and metabolism of biochar for thiamethoxam in soil, especial in rhizosphere soil, and reveal the mechanism of biochar effect to the accumulation of thiamethoxam and its metabolites in Chinese Chives. The results of this study could provide basic data for the feasibility of using biochar to control the risk of neonicotinoid pesticides to soil environment.

韭菜是深受百姓喜爱的药食同源蔬菜，但农药不规范使用导致残留问题突出。新烟碱类农药在生产中使用量大、残留时间长且易被植物吸收，对土壤环境及食品安全产生潜在危害。新型环保材料生物炭在土壤污染物控制方面表现出巨大潜力，但生物炭对新烟碱类农药向植物中累积的影响及作用机制并不清楚。本项目拟在前期研究基础上，通过不同生物质为原料制备生物炭，研究不同类型的生物炭对典型新烟碱类农药噻虫嗪的吸附特性和化学降解的影响；考察生物炭对噻虫嗪在“土壤-韭菜根-韭菜植株”中分布及降解代谢的影响规律；开展噻虫嗪及其主要代谢物在生物炭-土壤-根界面的吸附、解吸、降解等环境行为研究,深入探讨生物炭对噻虫嗪在土壤，特别是根际土壤中降解代谢的作用方式，最终阐明生物炭影响噻虫嗪及其代谢物向韭菜中累积的机制。相关结果将为建立土壤中新烟碱类农药污染防治措施提供重要理论依据。

生物炭在土壤污染物控制方面表现出巨大潜力，但缺乏生物炭影响农药噻虫嗪在土壤-蔬菜生态系统中归趋的相关信息。通过盆栽实验，研究了450℃裂解条件下木材生物炭对韭菜吸收噻虫嗪及其在土壤中降解的影响。结果表明：.韭菜生长42天后，生物炭BC450添加土壤中韭菜的生长显著提高。生物炭的添加使韭菜对噻虫嗪和代谢物噻虫胺的吸收分别降低22.8%和37.6%。然而，噻虫嗪在土壤中的半衰期从89.4天上升到120天，表明生物炭添加增加了噻虫嗪在土壤中的持久性。在42 d的培养过程中，施用1.5%的生物炭BC450可使噻虫胺产量减少23.1%。生物炭BC450的添加可以显著降低整个栽培期土壤中噻虫嗪和噻虫胺的生物有效度。生物炭对噻虫嗪和噻虫胺的吸附增强了生物炭添加土壤对噻虫嗪和噻虫胺的吸附能力，从而导致了噻虫嗪生物有效性的降低和持久性的增加，降低了韭菜对噻虫嗪的吸收。.为了探明生物降解与非生物降解过程中生物炭对农药的影响，研究了生物炭BC450在灭菌和非灭菌土壤中对噻虫嗪的降解过程。灭菌后土壤中噻虫嗪的半衰期显著增加，说明生物降解在噻虫嗪消解中发挥了相对重要的作用。在无菌土壤中，CK和生物炭BC450处理土壤中噻虫嗪的半衰期分别为191天和131天，说明生物炭BC450加快了噻虫嗪的非生物消解速度。添加生物炭BC450后，生物降解的贡献从68.1%下降到36.9%。虽然生物炭BC450的添加增加了非生物降解，但由于对微生物有效性的降低，生物降解仍在生物炭BC450添加土壤中占主导地位，导致噻虫嗪在处理土壤中相对于未处理土壤的持续时间更长。.同时，生物炭添加增加了土壤微生物多样性，改变了微生物群落结构。土壤微生物群落组成的变化，可能是由于噻虫嗪有效性的降低和土壤性质的改善。尽管放线菌的丰度与噻虫嗪的生物降解有关，但韭菜对噻虫嗪吸收减少的主要原因是生物炭添加的土壤增加了噻虫嗪的持久性，从而导致了噻虫嗪生物有效性的降低。.相关研究结果为生物炭在农业土壤中噻虫嗪及其代谢产物噻虫胺的吸收提供了有价值的信息，并将有助于指导生物炭在修复新烟碱类农药污染土壤中的实际应用。