2.2.1. Preparation of Hg Stock Solution

A serial dilution of Hg standard solution was made to the intended concentrations using analyzed reagent-grade Hg standard (1000 μg/mL dilute in nitric acid; Ultra Scientific), and adjust the pH value of the solution to 7.0 for various dosage and Hg concentration experiments. In contrast, the pH value of artificial waters was measured to be 7.6, 8.2, 8.3 for freshwater, estuary water, and seawater conditions, respectively, determined by the ions present (Table S1) to evaluate the effect of salinity and DOM on Hg adsorption. 0.1 M HNO3 or 0.1 M NaOH were used to adjust the pH of solutions.
