Table 2.

Classification standards of soil heavy metal pollution evaluation.

Degree	${\mathit{P}}_{\mathit{i}}$	Degree of Pollution	Pollution Level
1	$P_i$ ≤ 0.7	Safe	Clean
2	0.7 < $P_i$ ≤ 1	Warning level	Good
3	1 < $P_i$ ≤ 2	Slightly polluted	Soil and plant were polluted
4	2 < $P_i$ ≤ 3	Medium polluted	Soil and plant were moderate polluted
5	$P_i$ > 3	Heavy polluted	Soil and plant were heavy polluted