Speciation study in the sulfamethoxazole-copper-pH-soil system: implications for retention prediction

Area of Science:

• Environmental Chemistry
• Soil Science
• Environmental Science

Background:

• Sulfamethoxazole (SMX) is a persistent sulfonamide antibiotic widely detected in natural waters.
• Understanding antibiotic transport in soil is crucial due to widespread environmental contamination.

Purpose of the Study:

• To investigate the speciation of the SMX-Cu(II)-H(+) system in solution.
• To determine the combined sorption of SMX and Cu(II) in a natural vineyard soil.

Main Methods:

• Acid-base titrimetry was used to study solution speciation.
• Infrared spectroscopy was employed to analyze combined sorption.
• PhreeqC modeling was utilized to interpret the data.

Main Results:

• SMX is a weak copper chelating agent and soil sorbent at pH 6.
• SMX sorption in soil increased sixfold in the presence of copper.
• Evidence supports the formation of ternary SMX-Cu-soil complexes.

Conclusions:

• Surface-adsorbed cations, like copper, significantly enhance SMX sorption in soil.
• This mechanism is relevant for other strongly complexing cations potentially affecting SMX partitioning.
• Findings provide insights into the environmental fate and transport of sulfonamide antibiotics.