Table 7.

Single heavy metal potential environment risk index ($E_r^i$) classification of P. notoginseng cultivation soil (n = 37).

Index	Min	Max	Mean	Sample Frequency Distribution
				${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$ ≤ 40	40 < ${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$ ≤ 80	80 < ${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$ ≤ 160	160 < ${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$ ≤ 320	${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$ > 320
				Slight	Middle	Strong	Very Strong	Extremely Strong
Pb	2.6	17.8	7.3	37	0	0	0	0
Cd	7.4	113.3	44.3	24	9	4	0	0
Cr	0.12	4.8	2.7	37	0	0	0	0
As	2.6	130.0	35.6	22	14	1	0	0
Hg	37.2	785.3	225.2	2	8	13	4	10
Cu	1.1	6.9	3.7	37	0	0	0	0