Sorption and mobility of metformin and guanylurea in soils as affected by biosolid amendment: Batch and column tests

• Published in: Environmental pollution (1987) 2019-01, Vol.244, p.19-27
• Main Authors: Briones, Rowena M., Sarmah, Ajit K.
• Format: Article
• Language: English
• Subjects: Adsorption; Biosolids amendment; Guanylurea; Metformin; Metformin - chemistry; Models, Chemical; Non-equilibrium transport; Soil - chemistry; Soil Pollutants - chemistry
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2018.10.025

Recent classification of metformin as an emerging contaminant warrants assessment of its fate and behaviour in the natural environment especially with land-based application of potentially contaminated wastewaters and biosolids. The present study provided further insight into the sorption mechanisms of metformin and its transformation product guanylurea in soil and upon biosolid fortification. Decreased metformin sorption (12.4%) as measured by the effective distribution coefficient (Kdeff) was observed with biosolids amendment while significant increase (2500%) in guanylurea sorption was calculated. Analysis of co-solute effects confirmed their contrasting sorption mechanisms with the absence of competitive effects in unamended soil. Results of the column tests were in good agreement with the batch sorption studies as the fitted values of retardation factors decreased and increased for metformin and guanylurea, respectively, upon addition of biosolids. The shapes of the breakthrough curves suggest slower desorption rates for both compounds in unamended soil resulting to non-equilibrium conditions and back-end tailings. However, in biosolid-amended soil columns, these tailings were less pronounced resembling equilibrium transport. Results also demonstrated enhanced mobility of both compounds upon biosolids fortification. The non-equilibrium chemical transport model fitted the measured data well (0.975 > r2 > 0.988) especially for unamended soils which suggests the existence of non-equilibrium conditions and rate-limited sorption sites. [Display omitted] •Co-solute effects on metformin (MET) and guanylurea (GUA) sorption in soil.•Biosolid amendment of soil on MET and GUA showed contrasting effects on sorption.•Chemical non-equilibrium transport model fits MET and GUA breakthrough curves well.•Biosolids-amended soil column exhibited higher desorption rates than unamended soil.•Batch and column studies show similar trends in sorption upon biosolid amendment. This study demonstrated the effects of biosolid amendment of soils to the sorption and mobility of metformin and guanylurea in a binary-solute system using a column set-up which is more representative of actual field conditions.