Removal of MCPA and 2,4D from water and mitigation of phytotoxicity using Vacuum UV treatment
Author
Romanelli, Paula Maria
Term
4. Term
Publication year
2022
Submitted on
2022-07-29
Abstract
Denne afhandling undersøger, om en avanceret oxidationsproces med vakuum‑UV (VUV) kan fjerne de udbredte chlorphenoxy‑herbicider MCPA og 2,4D fra vand og samtidig mindske deres økotoksiske og fytotoksiske effekter på ikke‑målorganismer. Spiket postevand (10 mg/L) blev behandlet med VUV og prøvetaget over 0–32 minutter; restkoncentrationer blev bestemt med HPLC (C18‑kolonne, acetonitril/buffer pH 4, detektion ved 230 nm). Akut toksicitet blev kvantificeret som EC50 baseret på vækst for Lactuca sativa (salat), Lepidium sativum (karse), Raphidocelis subcapitata (grøn mikroalge) og Bacillus subtilis (jordbakterie) efter 18–120 timers eksponering. Udgangs‑EC50’erne var lave for planter (L. sativa: 0,017 mg/L for MCPA og 0,068 mg/L for 2,4D; L. sativum: 0,029 mg/L for MCPA og 0,041 mg/L for 2,4D) og høje for alge og bakterie (R. subcapitata: 50 mg/L for MCPA og 100 mg/L for 2,4D; B. subtilis: >100 mg/L for begge). VUV‑behandling fjernede fuldstændigt 10 mg/L MCPA efter 8 minutter og 2,4D efter 32 minutter med nedbrydningshastighedskoefficienter på henholdsvis 0,87 min⁻1 og 0,16 min⁻1. Degraderingen af MCPA og 2,4D blev afspejlet i stigende tilsyneladende EC50‑værdier og dermed reduceret toksicitet; for salat og karse faldt toksiciteten efter VUV med MCPA med faktor 4–1,5 og 7–8 ved 2 og 4 minutter, og for 2,4D med faktor 2–0,57 og 4–1,16 ved 2 og 4 minutter. Resultaterne peger på, at VUV‑AOP effektivt kan fjerne MCPA og 2,4D fra vand og samtidig afbøde fytotoksicitet, især for følsomme afgrøder.
This thesis examines whether a vacuum‑UV (VUV) advanced oxidation process can remove the widely used chlorophenoxy herbicides MCPA and 2,4D from water and mitigate their eco‑ and phytotoxic effects on non‑target organisms. Tap water spiked at 10 mg/L was treated by VUV and sampled over 0–32 minutes; residual concentrations were quantified by HPLC (C18 column, acetonitrile/buffer pH 4, UV detection at 230 nm). Acute toxicity was determined as EC50 based on growth for Lactuca sativa (lettuce), Lepidium sativum (cress), Raphidocelis subcapitata (green microalga), and Bacillus subtilis (soil bacterium) after 18–120 hours of exposure. Initial EC50s were low for plants (L. sativa: 0.017 mg/L for MCPA and 0.068 mg/L for 2,4D; L. sativum: 0.029 mg/L for MCPA and 0.041 mg/L for 2,4D) and high for alga and bacterium (R. subcapitata: 50 mg/L for MCPA and 100 mg/L for 2,4D; B. subtilis: >100 mg/L for both). VUV treatment completely removed 10 mg/L MCPA after 8 minutes and 2,4D after 32 minutes, with decay rate coefficients of 0.87 min⁻1 and 0.16 min⁻1, respectively. Degradation was reflected in increased apparent EC50 values and thus reduced toxicity; for lettuce and cress, toxicity decreased after VUV with MCPA by 4–1.5‑fold and 7–8‑fold at 2 and 4 minutes, and for 2,4D by 2–0.57‑fold and 4–1.16‑fold at 2 and 4 minutes. Overall, the results indicate that VUV‑AOP can effectively remove MCPA and 2,4D from water while mitigating phytotoxicity, particularly for sensitive crops.
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