Heavy Metal Residues in Soil and Accumulation in Maize at Long-Term Wastewater Irrigation Area in Tongliao, China

Table 2

Metal concentrations (mg/kg) in the soil samples collected from wastewater-irrigated and groundwater-irrigated areas ( = 20).

	Wastewater-irrigated area	Groundwater-irrigated area
Cr	29.86 ± 4.46^a	28.77 ± 3.67^a
Pb	7.39 ± 4.21^b	7.15 ± 4.84^b
Ni	13.30 ± 3.76^ab	12.84 ± 3.34^b
Zn	86.00 ± 66.90^c	62.54 ± 26.74^c

Note: means followed by different letters within a column are significantly different from each other at P < 0.05 according to DMRT.