Department of Environmental Science, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China.
School of Civil Engineering, Wuhan University, Wuhan 430072, China.
J Environ Sci (China). 2016 Sep;47:39-48. doi: 10.1016/j.jes.2016.01.017. Epub 2016 Mar 5.
p-Arsanilic acid (p-ASA) is widely used in China as livestock and poultry feed additive for promoting animal growth. The use of organoarsenics poses a potential threat to the environment because it is mostly excreted by animals in its original form and can be transformed by UV-Vis light excitation. This work examined the initial rate and efficiency of p-ASA phototransformation under UV-C disinfection lamp. Several factors influencing p-ASA phototransformation, namely, pH, initial concentration, temperature, as well as the presence of NaCl, NH4(+), and humic acid, were investigated. Quenching experiments and LC-MS were performed to investigate the mechanism of p-ASA phototransformation. Results show that p-ASA was decomposed to inorganic arsenic (including As(III) and As(V)) and aromatic products by UV-C light through direct photolysis and indirect oxidation. The oxidation efficency of p-ASA by direct photosis was about 32%, and those by HO and (1)O2 were 19% and 49%, respectively. Cleavage of the arsenic-benzene bond through direct photolysis, HO oxidation or (1)O2 oxidation results in simultaneous formation of inorganic As(III), As(IV), and As(V). Inorganic As(III) is oxidized to As(IV) and then to As(V) by (1)O2 or HO. As(IV) can undergo dismutation or simply react with oxygen to produce As(V) as well. Reactions of the organic moieties of p-ASA produce aniline, aminophenol and azobenzene derivatives as main products. The photoconvertible property of p-ASA implies that UV disinfection of wastewaters from poultry and swine farms containing p-ASA poses a potential threat to the ecosystem, especially agricultural environments.
对氨基苯胂酸（p-ASA）在中国被广泛用作促进动物生长的饲料添加剂。有机胂的使用对环境构成了潜在威胁，因为它主要以原形由动物排泄，并且可以通过 UV-Vis 光激发进行转化。本工作考察了在 UV-C 消毒灯照射下 p-ASA 光转化的初始速率和效率。研究了影响 p-ASA 光转化的几个因素，即 pH 值、初始浓度、温度以及 NaCl、NH4(+)和腐殖酸的存在。通过淬灭实验和 LC-MS 研究了 p-ASA 光转化的机制。结果表明，p-ASA 通过 UV-C 光直接光解和间接氧化分解为无机砷（包括 As(III)和 As(V))和芳香族产物。直接光解的 p-ASA 氧化效率约为 32%，HO 和 (1)O2 的氧化效率分别为 19%和 49%。直接光解、HO 氧化或 (1)O2 氧化导致砷-苯键断裂，同时形成无机 As(III)、As(IV)和 As(V)。(1)O2 或 HO 将无机 As(III)氧化为 As(IV)，然后氧化为 As(V)。As(IV)可以通过歧化或简单地与氧气反应产生 As(V)。p-ASA 的有机部分的反应产生苯胺、氨基酚和偶氮苯衍生物等主要产物。p-ASA 的光转化性质意味着含有 p-ASA 的家禽和猪养殖场废水的 UV 消毒对生态系统，特别是农业环境构成了潜在威胁。
