Mean concentrations of heavy metals (mg kg⁻¹) in soils from Yunnan compared to the data compiled from the literature.

Region	As	Cd	Pb	Cr	Reference
Yunnan, China	19.2	0.22	57.6	106	35
Agricultural soils, China	10.7	0.24	32.1	62.2	39
Background value of China	11.2	0.10	26.0	61.0	34
São Paulo, Brazil	1.38	0.1	10.1	36.6	38
USA	5.20	1.60	37.0	16.0
England and Wales	15.0	0.33	49.0	68.0	36
Australia	3.00	0.04	13.0	48.0	37
Chinese soil guidelines (Grade I)	15	0.2	35	90	35