Fig. 3. Ratio of napropamide mass measured (M) in a particular soil layer divided by the total mass (M_t) of napropamide applied to the surface layer of the column after passing 440 mL of water (approximately 1.3 pore volumes if started at saturation) through columns containing soil with sewage sludge applied (SS) and soil without sewage sludge applied (NoSS). Data points of the curve are located at the bottom of each soil sample section and are the average of the three replications. Error bars are ±1 standard error of the mean.