Combined effects of sulfamethazine and sulfamethoxazole on a freshwater microalga, Scenedesmus obliquus: toxicity, biodegradation, and metabolic fate

Jiu Qiang Xiong, Sun Joon Kim, Mayur B. Kurade, Sanjay Govindwar, Reda A.I. Abou-Shanab, Jung Rae Kim, Hyun Seog Roh, Moonis Ali Khan, Byong Hun Jeon

Research output: Contribution to journalArticlepeer-review

179 Scopus citations

Abstract

This study investigated the environmental effects of two common emerging contaminants, sulfamethazine (SMZ) and sulfamethoxazole (SMX), and their mixture using a green microalga, Scenedesmus obliquus. The calculated EC50 values of SMZ, SMX, and their mixture (11:1 wt/wt) after 96 h were 1.23, 0.12, and 0.89 mg L-1, respectively. The toxicity of the mixture could be better predicted using a concentration addition model than an independent action model. The risk quotients of SMZ, SMX, and their mixture were >1 during the experiment, indicating their high potential risks on aquatic microorganisms. Despite their toxicity, S. obliquus exhibited 17.3% and 29.3% removal of 0.1 mg L-1 and 0.2 mg L-1 after 11 days of cultivation. The changes of SMZ and SMX removal were observed when combined, which showed a significantly improved removal of SMZ (up to 3.4 folds) with addition of SMX (0.2 mg L-1). The metabolic pathways of SMZ and SMX were proposed according to mass spectroscopic analysis, which showed six metabolites of SMX and seven intermediates of SMZ, formed as a result of ring cleavage, hydroxylation, methylation, nitrosation, and deamination.

Original languageEnglish (US)
Pages (from-to)138-146
Number of pages9
JournalJournal of Hazardous Materials
DOIs
StatePublished - May 15 2019

Bibliographical note

Publisher Copyright:
© 2018 Elsevier B.V.

Keywords

  • Pharmaceutical contaminants
  • biodegradation
  • metabolic products
  • microalgae
  • sulfamethazine and sulfamethoxazole
  • toxicity modeling.

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