不同含水率条件下土壤中赤霉酸自然衰减规律研究

作为一种施用范围广、用量大的微毒农药，赤霉酸（GA3）的高溶解度会造成其在土壤中的弱吸附和强迁移并伴随强烈的自然衰减，且受到间歇性灌溉过程中变化土壤含水率的影响，因此有必要系统研究不同含水率条件下土壤中GA3的自然衰减规律。通过设置10%、20%、30%的3种土壤含水率，研究了不同土壤含水率条件下GA3的自然衰减规律，分析了土壤微生物对GA3自然衰减过程的影响，定性识别了GA3自然衰减产物。结果表明：（1）实验结束（34 d）时初始含水率为10%、20%和30%的灭菌组和未灭菌组土壤中GA3的自然衰减率分别为87.77%、89.70%、90.70%和87.70%、94.47%、95.87%，其自然衰减半衰期分别为12.38，12.16，12.60 d和8.56，6.80，7.07 d；（2）含水率对灭菌组土壤GA3的自然衰减速率无显著影响，未灭菌组在不同土壤含水率条件下GA3自然衰减速率有差异（20%土壤含水率最大）；（3）在水解作用的基础上，土壤微生物降解进一步促进了GA3的自然衰减，且生物降解贡献率为39.62%±7.58%；（4）GA3主要自然衰减产物为异构赤霉酸与赤霉烯酸（其中异构赤霉酸占比更大），未来需要进一步关注GA3自然衰减产物在环境中的生物毒性与环境风险。上述研究结果有助于进一步深入理解农业生产过程土壤中GA3的环境行为，并为其环境毒性及潜在风险评估与管控提供数据支撑。

Study on the natural attenuation mechanism of gibberellic acid in soil under different water content conditions

As a micro-toxic pesticide with a wide application range and large dosage, the high solubility of gibberellic acid (GA3) causes its weak adsorption and strong migration in soil, accompanied by strong natural attenuation, and it is also affected by changing soil water content during intermittent irrigation. Therefore, it is necessary to systematically study the natural attenuation mechanism of GA3 in soil under different water content conditions. In this study, the natural attenuation mechanism of GA3 under different soil water content conditions was investigated by setting three soil water contents of 10%, 20% and 30%, the influence of soil microorganisms on the natural attenuation process of GA3 was analyzed, and the natural attenuation products were qualitatively identified. The results show: (1) at the end of the experiment (34 d), the natural attenuation rates of GA3 in the soil of the sterilized group and the unsterilized group with initial water content of 10%, 20% and 30% were 87.77%, 89.70%, 90.70% and 87.70%, 94.47%, 95.87%, respectively, and the natural attenuation half-lives were 12.38 d, 12.16 d, 12.60 d and 8.56 d, 6.80 d, 7.07 d, respectively. (2) Soil water content had no significant effect on the natural attenuation rate of GA3 in the soil of the sterilized group, while the natural attenuation rate of GA3 in the unsterilized group was different under different soil water content (the largest in the 20% soil water content). (3) On the basis of hydrolysis, biodegradation further promoted the natural degradation of GA3, with a biodegradation contribution rate of 39.62%±7.58%. (4) The main natural attenuation products of GA3 were isomerized gibberellic acid (Iso-GA3) and gibberellenic acid (GEA) (of which Iso-GA3 accounted for a larger proportion). The more attention should be paid to the biotoxicity and environmental risks of the natural attenuation products of GA3 in the environment in the future. This study can help to understand the environmental behavior of GA3 in agricultural soils and provide data support for the assessment and control of its environmental toxicity and potential risk.