Concentrations, Spatial Distributions, and Sources of Heavy Metals in Surface Soils of the Coal Mining City Wuhai, China

Table 1

The statistical characteristics of concentrations of soil heavy metals in Wuhai (mg/Kg).

Element	Mean	Max	Min	SD	CV (%)	Background^a	Grade I^b	Grade II^c
As	9.31	16.8	6.37	2.30	24.7	6.30	15	30
Hg	0.12	4.95	0.01	641	539	0.028	0.15	0.5
Cr	61.7	104	44.7	9.81	15.9	36.50	90	200
Ni	24.7	58.3	16.2	5.58	22.6	17.30	40	50
Cu	19.6	122	12.1	14.0	71.5	12.90	35	100
Zn	55.2	371	29.4	44.8	81.2	48.60	100	250
Cd	0.16	0.50	0.06	0.08	48.3	0.037	0.2	0.3
Pb	28.0	316	15.2	38.8	139	15.00	35	300

^aSoil background values in Inner Mongolia Autonomous Region. ^bGrade I of the Chinese Soil Environmental Quality Standard (GB15618-1995). ^cGrade II of the Chinese Soil Environmental Quality Standard, 6.5 < pH < 7.5 (GB15618-1995).