【正文】 olution systems are shown in Table 2. Coef?cients of determination (R2) for the multiplesite adsorption Q/I ?ttings of the pesticides ranged from to in the adsorption sites of Region 1 and from to in Region 2. Distribution coef?cient (Kd), de?ned as the ratio of concentrations in the adsorbed and solution phases, of the pesticides in the soilsolution systems varied with different amounts of ZVI applied. The Kd values of alachlor ranged from a low of 215 L g1 to a high of 3,608 L g1, while the Kd values of metalaxy ranged from 110 to 2,680 L g1. TheKd values are closely related to the values of buffering capacity (BC) that is described using Q and I factors. The calculated values of BC for alachlor ranged from 338 to 3,608 and those for metalaxyl varied from 173 to 4,208 in the soilsolution systems. The values of Kd and BC of the pesticides were signi?cantly higher in the adsorption sites of Region 1 than in Region 2 sites. Also, the pesticide BC values were signi?cantly higher in the clayey soil (CCL)solution system than in the sandysoil (CLS)solution system without ZVI application. Schwab et al. (2022) also reported similar results that adsorption coef?cients of alachlor were 4– 20 times higher for loam and silt loam soils than for aquifer sandy soils. However, the BC values 22 signi ?cantly increased after applying ZVI in the both adsorption sites, Regions 1 and 2, in the soilsolution systems. The BC values were higher in the sandy soil (CLS)when pared with the clayey soil (CCL) system, especially in the adsorption sites of Region 1. That is, the pesticide BC values in sandy soil system were dramatically escalated with increasing ZVI application rates. Therefore, these results indicated that the ZVI application critically affects the pesticide sorption Q/I relationships in soilsolution system. Conclusions In this study, impacts of ZVI application on the behavior of alachlor and metalaxyl in water and two different soilsolution systems were evaluated using the pesticide adsorption Q/I relationships. Concentrations of both pesticides declined in the aqueous and soil systems due to natural degradation and/or adsorption mechanism. When applying ZVI in the systems, the solution concentration of alachlor rapidly declined and was almost not detected at 5 days after ZVI treatment. However, metalaxyl concentration gradually decreased during the ?rst 7 days and then negligibly declined until the end of the experimental period. In addition, the concentrations of 23 alachlor and metalaxyl in the soilsolution system were initially reduced by 45 and 25%, respectively, within the ?rst day of reaction due to soil surface adsorption. Thus, the decreases in alachlor concentration in water and soil solution associated with applying ZVI in the both systems were caused by both dechlorination and iron/soil surface sorption. The changes of metalaxyl concentration occurred mostly due to only iron/soil surface sorption. On the other hand, the pesticide adsorption quantity– intensity (Q/I) ?ttings appeared as multiplesite sorption curves. Distribution coef?cient (Kd) and buffering capacity (BC) of the pesticides in the soilsolution systems were signi ? cantly higher in the adsorption sites of Region 1 than in those of Region 2 and varied with amounts of ZVI application and different properties of soils. Both pesticide BC values were signi?cantly higher in the clayey soil system than in the sandy soil system without ZVI application. However, the BC values distinctly increased after applying ZVI in the both adsorption sites. 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