Multivariate correlation between concentrations of selected herbicides andderivatives in outflows from selected US midwestern reservoirs

Multivariate correlations between the concentrations of selected herbicides and herbicide derivatives in outflows from selected reservoirs in the Midw estern United Stares for April 1992 through September 1993 were investigate d using principal component analysis (PCA) and multivariate curve resolutio n (MCR). Two independent sources for alachlor ethanesulfonic acid, one majo r source related to spring flush and seasonal runoff and another minor sour ce related to groundwater, were identified using PCA. Results of MCR provid ed a semiquantitative interpretation of the environmental sources of the ob served herbicide concentrations in reservoir outflows and allowed the exami nation of their temporal and geographical distributions. Samples with highe r herbicide concentrations were collected from reservoirs in Indiana and Oh io, especially during the late spring and summer.