Comparisons: waffle - regional patterns of 4 common drinking water contaminants

Waffle charts are colorized and faceted by contaminant (Pb, Fe, NO3-, and Sr) and region (West, Central, Midwest, East). Each 10 x 10 waffle charts shows the proportion of study area that contains high, moderate, and low concentrations where 1 square = 1 % of region. Figure contains callouts where, for example, NO3- in the Central U.S. show greater proportions of high due to fertilizer use and permeable soils.