Predicting springtime herbicide exposure across multiple scales in pacific coastal drainages (Oregon, USA)

Identification of non-point sources watershed pollution such as pesticide runoff is challenging due to spatial and temporal variation in landscape patterns land use environmental conditions. Regional case study monitoring investigations can document region-specific conditions processes inform managers about movement through watersheds. Additionally, modeling field-collected data within these contexts be used predict presence un-sampled areas. During a 45 day period the spring 2019, we sampled sixteen coastal watersheds Oregon, USA for current-use water-borne herbicides commonly forestland vegetation management. At 80 % sampling locations, at least one four was detected integrative passive water samplers, with hexazinone atrazine most detected. In this study, total accumulation compounds compare relative detections upstream management variables using multiple linear regression. An additive effects model developed slope, herbicide activity notified during window, recent clearcut harvest notifications (R2 = 0.8914). The then applied concentrations throughout Oregon’s region three scales Hydrologic Unit Codes (HUCs) 8, 10, 12. differences predicted values were visualized choropleth maps. Subwatersheds (HUC12) grouped by subbasin (HUC8) base mean compared further quantify regional differences. Models that south coast sites have higher than average concentrations, which aligned findings.