Variables: dissolved_organic_carbon concentration electric_conductivity pH Substances: 1-Propanesulfonate (KCXFHTAICRTXLI-UHFFFAOYSA-N) 18-beta-Glycyrrhetinic acid (MPDGHEJMBKOTSU-YKLVYJNSSA-N) 5-Methylpyridine-3-carboxylic-acid (DJDHHXDFKSLEQY-UHFFFAOYSA-N)