Distribution characteristics of cadmium and lead in particle size fractions of farmland soils in a lead–zinc mine area in Southwest China

Environmental Systems Research

Table 3 Correlations between the chemical fractions of cadmium and lead and the soil properties

Heavy metals	Chemical fractions	pH	Organic matter (g/kg)	CEC (mol/kg)	Free iron oxide (mg/kg)	Phosphorus (g/kg)
Cd	EXC	− 0.302**	− 0.058	− 0.031	0.066	− 0.236**
	CA	− 0.133	− 0.098	− 0.015	− 0.017	− 0.042
	R₂O₃	0.058	− 0.052	− 0.105	− 0.133	− 0.272**
	OM	− 0.062	− 0.112	0.085	0.052	0.175*
	RES	0.182*	0.096	0.058	0.029	0.218**
Pb	EXC	0.133	0.209*	0.507**	0.609**	0.232**
	CA	0.076	− 0.063	0.067	0.006	− 0.152
	R₂O₃	− 0.039	− 0.032	− 0.178*	− 0.240**	− 0.348**
	OM	− 0.255**	− 0.066	− 0.075	− 0.118	0.018
	RES	− 0.023	− 0.402	− 0.158	− 0.132	0.166*

EXC, exchangeable fraction; CA, carbonate-bound fraction; R₂O₃, Fe–Mn oxide-bound fraction; OM, organic matter-bound fraction; RES, residue fraction
* P < 0.05, correlation
** P < 0.01, significantly correlation; n = 180