Risk Assessment and Prediction of Heavy Metal Pollution in Groundwater and River Sediment: A Case Study of a Typical Agricultural Irrigation Area in Northeast China

Table 1

Classification of NI.

Class	Pollution degree	NI
0	No pollution	≤0.5
1	Clean	0.5–0.7
2	Warm	0.7–1.0
3	Polluted	1.0–2.0
4	Medium pollution	2.0–3.0
5	Severe pollution	>3.0