Changes in the esterase activities in soil for 4 weeks with or without PBSA. The peripheral soils of the PBSA film: OKA (black circles) and TKB (black triangles); the no treatment soils (without PBSA film) for control: OKA (white circles) and TKB (white triangles). The data represent geometric means with error bar indicating 1 standard error of 6 independent assays. Asterisk and dagger represent a significant increase (α = 0.025) in the esterase activity from the 0-day controls of each soil sample. P values represent significance levels between the esterase activity in the soils with and without PBSA film.