Photodegradation Mechanism Of Terbutaline In Water

Terbutaline as a kind of PPCP (Pharmaceuticals and Personal Care Products) can treat asthma and bronchitis for human used purpose. For another hand, it belongs to β2-adrenoceptor agonists (known as "lean meat powder") and can produce lean meat and promote growth. It is widely used in the livestock and considered as one of major feed additive medicines to increase the proportion of lean meat. As a veterinary medicine the amount of terbutaline is5-10times of that for human. The presence of two hydroxyl groups on the phenyl ring make terbutaline hydrophilic (with log Kow=-1.07) can easily solute in water and not easily biodegradable. It has potential harm for the environment.Terbutaline is selected as the subject of this study because of its widely used in the livestock. We study the pseudo first order rate constants for the photodegradation of terbutaline increase in different DOM, to know the reaction rate constant of1△O2, the reaction rate constant of·OH, the contribution of singlet oxygen to the indirect photolysis of terbutaline and the contribution of the hydroxyl radical. Then use one kind of DOM (1R101N) to study the effects of pH, initial concentration and D2O, N2and O2.In chapter2, varied nature organic matters were employed to investigate the indirect photo transformation of terbutaline, which is a major feed additive medicine to increase the proportion of lean meat. In the indirect photolysis of terbutaline,1△O2plays an important role among the·OH and3DOM*. The reaction rate constant of1△O2was determined as4.9×106M-1s-1at pH7.0, while the reaction rate constant of·OH was6.87×109M-1s-1. The contribution of singlet oxygen to the indirect photolysis of terbutaline (19%-44%) was higher than that of the hydroxyl radical (1%-7%).In chapter3and4, the pseudo first order rate constants for the photodegradation of terbutaline increase with increasing pH, which indicates that pH mainly affects the reaction rate of the singlet oxygen with the phenol part of the terbutaline. Quinones were identified as the main photosensitized products through LC-MS/MS analysis. It is also proposed that the degradation pathway of terbutaline involves reaction between the phenol part of terbutaline and singlet oxygen. This finding strongly suggests that singlet oxygen was important factor for the photodegradation of terbutaline in natural waters.