Table 7.

Improved classification criteria of the potential ecological risk index.

${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$	Single Ecological Damage	$\mathit{R}\mathit{I}$	Total Ecological Risk
<10	No damage	<50	No risk
10–40	Mild damage	50–150	Mild risk
40–80	Moderate damage	150–300	Moderate risk
80–160	High damage	300–600	High risk
160–320	Serious damage	600–1200 >1200	Serious risk Extreme risk
>320	Extreme damage

$E_r^i$: potential ecological risk coefficient; RI: total potential ecological risk index.