Metribuzin

Herbicide stock solutions were prepared with PESTANAL analytical grade products (HPLC ≥ 98%) and purchased from Sigma-Aldrich (NSW, Australia), including: diuron (CAS 330-54-1), bromacil (CAS 314-40-9), haloxyfop-p-methyl (CAS 72619-32-0), hexazinone (CAS 51235-04-2), imazapic (CAS 104098-48-8), metribuzin (CAS 21087-64-9), propazine (CAS 139-40-2), simazine (CAS 122-34-9), and tebuthiuron (CAS 34014-18-1). Stock solutions (5–600 mg L⁻¹) were prepared in Milli-Q water or filtered seawater (FSW) in 500 mL or 1 L autoclaved Schott bottles. diuron and metribuzin were dissolved using the carrier solvent ethanol (EtOH; ≤ 0.002% v/v in all exposure treatments). Haloxyfop and simazine were dissolved in the carrier solvent dimethyl sulfoxide (DMSO; ≤ 0.006% v/v in all exposure treatments). No solvent carrier was used in the preparation of the remaining herbicide stock solutions.

The fermentation of the toxin-producing fungus Stagonospora cirsii S-47, as well as extraction and purification of stagonolide A (1, Figure 1) and herbarumin I (2, Figure 1), were performed as described [16 (link)]. Tenuazonic acid (13, Figure 12) was isolated from culture filtrate of Alternaria tenuissima according to [93 (link)]. Commercial herbicides with different modes of action used as positive controls in physiological tests were metribuzin, diuron, and paraquat (Sigma-Aldrich, St. Louis, MO, USA) (Figure 12).

The compounds OP, BPA and metribuzin have, respectively, a molecular weight of 206.32, 228.29 and 214.29 g mol⁻¹, a water solubility of 3.1, 300 and 1200 mg L⁻¹ and a Log Kow of 5.50, 3.32 and 1.70 [26 ]. The chemical structures of the compounds are shown in Figure 1. OP at 99.5% purity, BPA at 99.0% purity and metribuzin at a purity ≥98.0% were obtained from Sigma-Aldrich S.r.l., Milan, Italy. All other chemicals used were of extra pure grade and obtained from commercial companies. Methanol solutions of OP, BPA and metribuzin were prepared at a concentration of 2000 mg L⁻¹. Then, appropriate volumes of each solution were combined and diluted with double distilled water to obtain the aqueous mixtures of the compounds used in the experiments. The most concentrated mixture of the compounds used in this work (2 mg L⁻¹) had a methanol content of 0.3%.
The biochar sample was produced through a high-temperature (850 °C) gasification process and the SyngaSmart^® technology of the RESET s.p.a. company, Rome, Italy. Chipped and dried wood from the poplar clone Monviso was used as feedstock.