Fig. 4

Equilibrium distribution map for a freshwater system with natural particles (organic carbon) and microplastic particles under two different concentration scenarios. Experimental conditions (plastic LSR = 10³ L kg⁻¹, Scenario I) are shown in the top panel and environmental conditions (plastic LSR = 10¹⁰ L kg⁻¹, Scenario II) in the bottom panel. Crosses, circles, and pluses show the aqueous equilibrium concentrations at pH 4, pH 7, and pH 10, respectively, in µg L⁻¹ calculated with the experimentally determined D_P for PE (black symbols) and for PS (red symbols) and the investigated substances. For both cases, a constant concentration of 10⁻⁵ kg L⁻¹ OC was assumed. K_OC values were estimated using EPISuite 4.1