Insights into pH-dependent transformation of gibberellic acid in aqueous solution:Transformation pathway,mechanism and toxicity estimation

• 作者: Li Zhang Yajun Sun Zhimin Xu Wenjing Zhang Guoxin Huang Fei Liu Liang Chen
• 来源期刊: 环境科学学报（英文版）
• 年，卷（期）: 2021,（6）
• 页码范围: 1-10
• 页数: 10页
• 语种: 英文

摘要

Gibberellic acid(GA3)is widely used in agriculture and maybe transfer with groundwater flow,which is an endocrine disruptor,but few studies have focused on the transformation pathway and toxicity assessment of GA3 and its products.Here,GA3 and its transformation products in aqueous solution were identified and quantified by liquid chromatography mass spectrometry hybrid ion trap time-of-flight(LCMS-IT-TOF)and high-performance liquid chromatography(HPLC),respectively.The results showed that the half-life of GA3 trans-formation in ultrapure water was 16.1-24.6 days at pH=2.0-8.0,with the lowest half-life occurring at pH=8.0 and highest half-life occurring at pH=3.3.Isomerized gibberellic acid(Iso-GA3)and gibberellenic acid(GEA)were the main transformation products with a lit-tle hydroxy gibberellic acid(OH-GA3).In North China groundwater,the mass balance of GA3 and its products was 76.2％,including Iso-GA3(58％),GEA(7.9％),GA3(7.3％)and OH-GA3(3％)after reaching transformation equilibrium.Using Gaussian 09 for chemical computation,it was found that the transformation mechanism of GA3 was dependent upon the bond en-ergy and the stereochemical feature of its molecular structure.GA3 always isomerized from the γ-lactone ring due to the lowest bond energy between the oxygen terminus of the y-lactone ring and A ring.While GA3 and its transformation products all had developmental toxicity,the predicated LC50(96 hr)and LD50 of the main products of GA3 were much lower than those of GA3,indicating GA3 would be transformed into higher toxicity derivatives in water environments,posing a significant health risk to humans and the environment.