N | As | Pb | Cd | Cr | Cu | Zn | Hg |
Lower | +0.5 | −0.736 | −0.866 | −0.5 | +0.866 | −0.075 | +0.5 |
Lower middle | +0.970 | +0.956 | −0.681 | −0.831 | −0.681 | +0.955 | +0.681 |
Middle | +0.101 | +0.164 | +0.619 | +0.084 | +1* | +0.187 | −0.5 |
High | +0.404 | +0.414 | +0.784 | −1* | +0.757 | −0.027 | +0.328 |