Table 7.

Potential ecological risk indexes of trace elements in river sediments.

Stations		Ecological Risk for Single Metal $\mathrm{E}\begin{array}{c}i\\ r\end{array}$								RI	RI Standard Classes [104]		$\mathrm{E}\begin{array}{c}i\\ r\end{array}$ Standard Classes [7]
		As	Hg	Pb	Cd	Cr	Cu	Zn	Ni		Value	Pollution status	Value	Ecological risk status
South-West	A1	4.36	66.2	4.24	69	3.53	19.56	5.15	7.94	179.98	RI < 150	Low pollution	Er < 40	Low ecological risk
	A2	5.91	68.1	5.18	91	3.67	33.22	4.39	8.16	219.63	150 < RI < 300	Considerable pollution	Er ≤ 80	Moderate ecological risk
	A3	5.95	73.9	4.54	77	3.87	28.78	4.53	8.75	207.32	300 < RI < 600	High pollution	80 < Er ≤ 160	Appreciable ecological risk
North-West	B1	2.49	19.2	0.92	5	1.47	17.11	2.91	3.16	52.26	RI ≥ 600	Very high pollution	160 < Er ≤ 320	High ecological risk
	B2	2.55	20.3	1.05	6	1.47	19.45	3.03	3.46	57.3			Er > 320	Serious ecological risk
	B3	3.33	20.9	2.71	3	1.62	15.11	3.24	3.90	53.81
South-East	C1	4.39	39.7	8.55	7	2.82	23.78	4.12	5.59	95.95
	C2	4.70	46.3	4.37	5	2.89	26.11	3.92	5.96	99.24
	C3	5.04	49.2	4.45	8	2.96	18.56	4.24	6.40	98.84
North-East	D1	3.89	13.3	2.35	9	1.71	20.22	3.44	4.19	58.1
	D2	4.24	15.8	5.54	5	1.98	15.44	3.72	4.56	56.28
	D3	5.07	16.7	2.99	8	2.09	19.56	3.66	4.85	62.91