Table 1.

Relationship between the potential ecological risk index of an individual element $E_r^i$ and pollution levels.

${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$	Ecological Risk Level of Single-Factor Pollution	RI	General Level of Potential Ecological Risk
$E_r^i<40$	low	RI < 150	low
$40\le E_r^i<80$	moderate	150 ≤ RI < 300	moderate
$80\le E_r^i<160$	considerable	300 ≤ RI <600	considerable
$160\le E_r^i<320$	high	RI ≥ 600	very high
$E_r^i\ge$320	very high