title: Ecological risk assessment of herbicides in Japan: Integrating spatiotemporal variation in exposure and effects using a multimedia model and algal density dynamics models.
abstract: Application of herbicides to paddy fields in Japan has strong seasonality, and their environmental concentrations exhibit clear spatiotemporal variation. The authors developed an approach that combines a multimedia environmental exposure model (Grid-Catchment Integrated Modeling System) and density dynamics models for algae. This approach enabled assessment of ecological risk when the exposure concentration shows spatiotemporal variation. First, risk maps of 5 herbicides (pretilachlor, butachlor, simetryn, mefenacet, and esprocarb) were created from the spatial predictions of environmental concentrations and 50% inhibitory concentrations of the herbicides. Simulations of algal density dynamics at high-risk sites were then conducted by incorporating the predicted temporal dynamics of the environmental concentration of each herbicide at the sites. The results suggested that the risk of pretilachlor was clearly the highest of the 5 herbicides, in terms of both the spatial distributions and the temporal durations. The present study highlights the importance of integrating exposure models and effect models to clarify spatial and temporal risk and to develop management plans for chemical exposure that shows high spatiotemporal variation.
authors.affiliation: Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Takehiko I
authors.initials: TI
authors.lastname: Hayashi
authors.affiliation: Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Imaizumi
authors.affiliation: Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yokomizo
authors.affiliation: Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Norihisa
authors.initials: N
authors.lastname: Tatarazako
authors.affiliation: Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Suzuki
mesh_terms: D000083:Acetanilides / Q000633:toxicity; D000465:Algorithms; D003470:Culture Media; D004784:Environmental Monitoring / Q000379:methods*; D006540:Herbicides / Q000633:toxicity*; D007564:Japan; D008954:Models, Biological; D018570:Risk Assessment; D045483:Rivers; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D000083:Acetanilides; D003470:Culture Media; D006540:Herbicides; D014874:Water Pollutants, Chemical; C118050:pretilachlor
keywords: Algae; Dynamic energy budget; Fate model; Generalized threshold model; Population-level ecological risk assessment