Environmental Sciences Europe

Table 2 Grade standards for potential ecological risks

From: Evaluating ecological risks and tracking potential factors influencing heavy metals in sediments in an urban river

Risk level	Low risk	Moderate risk	High risk	Very high risk	Disastrous risk
Grade	I	II	III	IV	V
\(E_{r}^{i}\)	< 30	30–60	60–120	120–240	> 240
PERI	< 100	100–200	200–400	> 400

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