Case Study of the Relationship between Aqua Regia and Real Total Contents of Harmful Trace Elements in Some European Soils
Figure 2
Scatterplots of aqua regia versus real total contents of less reliably characterised harmful chemical elements. Explanation. Symbol of each trace element is followed by measurement units. Hollow rhombs show samples with less than 8 laboratory measurements of aqua regia and real total contents of trace element. High leverage points eliminated from data set after preliminary stage S0 of stepwise polynomial regression are indicated in red; possibly influential points eliminated from the data set in the next stage S1 are indicated in magenta. Outliers for Se and Ag are indicated in blue, since implementation of stepwise polynomial regression for these elements was impossible.
