Table 4 Classification criteria of Er and RI.
\(E{}_{{\text{r}}}\) | RI | Pollution level |
|---|---|---|
≤ 40 | ≤ 150 | Mild ecological hazards |
40–79 | 150–299 | Moderate ecological hazards |
80–159 | 300–600 | Strong ecological hazards |
160–320 | ≥ 600 | Very strong ecological hazard |
≥ 320 | Extremely strong ecological hazards |
