Fig. 4. The probability distribution of the 9-yr runoff concentrations (µg L^–1) predicted with Monte Carlo simulation (MCS) virtual parameters (3600 runs). 1REAT, chemical concentration in first paddy water runoff; CUM, cumulative chemical concentration in paddy runoff over a 21-day treatment period; TW21, time-weighted chemical concentration in water runoff over a 21-day treatment period.