Contrasting aqueous-phase responses of clomazone and imazethapyr after contact with heat-treated microalgal biomass

Description

Heat-treated microalgae may be candidate sorptive materials for contaminated waters, but a decrease in the aqueous analytical signal does not establish a sorption mechanism. We compared chromatographic responses for clomazone (nominally 20 µg L⁻¹) and imazethapyr (100 µg L⁻¹) after contact with heat-treated biomass of Chaetoceros muelleri, Desmodesmus sp., and Scenedesmus obliquus. Each herbicide–biomass combination was evaluated across 12 central-composite-design runs (pH 5.6–8.4; NaCl preparation concentrations 28.02–165.20 mg L⁻¹). The endpoint was the calculated relative change between initial and final aqueous LC–ESI–MS/MS peak areas, rather than a recovery-corrected mass-removal efficiency. Positive calculated values occurred in 30 of 36 clomazone runs and 5 of 36 imazethapyr runs. For clomazone, all 12 responses were positive with S. obliquus (10.55 ± 4.08% across design conditions) and Desmodesmus sp. (16.47 ± 19.06%), although the latter showed greater dispersion. Responses for imazethapyr were predominantly negative or inconsistent. Five of six fitted quadratic models showed significant lack of fit and did not support process optimization. Because herbicide-only controls, biomass blanks, matrix-matched recovery measurements and a solid–liquid mass balance were unavailable, the observed changes must be interpreted as apparent aqueous-phase signals; biosorption was not demonstrated. For treatment-development decisions, the results prioritize confirmatory tests of clomazone with S. obliquus and Desmodesmus sp., without demonstrating remediation performance.

Institutions

• Instituto Federal Sul-rio-grandense

  Rio Grande do Sul, Pelotas
• Universidade Federal de Pelotas

  Rio Grande do Sul, Pelotas

Categories

Funders

• Coordenação de Aperfeicoamento de Pessoal de Nível Superior

  Ministry of Education

  Federal District, Brasília

Licence