Relationship between Cadmium Fractions Obtained by Sequential Extraction of Soil and the Soil Properties in Contaminated and Uncontaminated Paddy Soils

Table 2

Soil Cd content and fractions of total Cd.

Soil	Total	0.1 M HCl^a	Cd content by sequential extraction					Fraction of total Cd
			Exchangeable	Inorganically bound	Organically bound	Oxide occluded	Residue	0.1 M HCl	Exchangeable	Inorganically bound	Organically bound	Oxide occluded	Residue
	(mg kg^−1)	(mg kg^−1)	(mg kg^−1)					(%)
Uncontaminated-1	0.22	0.11	0.069	0.037	0.046	0.045	0.022	50.3	31.5	16.7	21.1	20.6	10.2
Uncontaminated-2	0.36	0.21	0.043	0.131	0.105	0.036	0.042	58.7	12.0	36.8	29.5	10.0	11.7
Uncontaminated-3	0.33	0.18	0.051	0.119	0.108	0.024	0.024	56.4	15.7	36.5	33.0	7.4	7.4
Uncontaminated-4	0.27	0.18	0.105	0.053	0.073	0.021	0.017	65.2	39.0	19.5	27.2	7.9	6.3
Uncontaminated-5	0.29	0.23	0.079	0.085	0.091	0.017	0.022	78.0	27.0	28.8	30.9	5.8	7.5
Uncontaminated-6	0.23	0.16	0.092	0.058	0.059	0.012	0.013	68.0	39.3	24.9	25.0	5.1	5.7
Uncontaminated-7	0.21	0.17	0.047	0.052	0.079	0.012	0.019	79.6	22.5	24.7	38.0	5.9	8.9
Uncontaminated-8	0.21	0.15	0.064	0.050	0.063	0.015	0.018	73.4	30.4	23.9	30.0	7.3	8.5
Uncontaminated-9	0.22	0.10	0.035	0.048	0.061	0.039	0.036	44.1	15.9	21.7	28.0	17.8	16.6
Uncontaminated-10	0.28	0.18	0.073	0.057	0.070	0.052	0.027	65.3	26.2	20.3	25.0	18.6	9.8
Contaminated-1	0.43	0.33	0.096	0.113	0.140	0.063	0.020	76.1	22.2	26.2	32.4	14.5	4.6
Contaminated-2	0.55	0.31	0.166	0.118	0.163	0.083	0.019	56.9	30.2	21.5	29.6	15.1	3.5
Contaminated-3	0.58	0.43	0.113	0.167	0.200	0.079	0.025	73.3	19.4	28.6	34.2	13.4	4.3
Contaminated-4	0.61	0.39	0.224	0.126	0.164	0.070	0.023	63.7	36.8	20.8	27.1	11.5	3.7
Contaminated-5	0.62	0.43	0.107	0.187	0.184	0.104	0.038	69.2	17.2	30.2	29.7	16.7	6.1
Contaminated-6	0.67	0.50	0.048	0.192	0.258	0.141	0.031	73.8	7.2	28.6	38.4	21.0	4.7
Contaminated-7	0.67	0.60	0.137	0.193	0.218	0.077	0.049	89.2	20.3	28.6	32.3	11.5	7.3
Contaminated-8	0.74	0.45	0.288	0.129	0.132	0.155	0.032	60.4	39.1	17.5	18.0	21.1	4.3
Contaminated-9	0.79	0.62	0.272	0.202	0.168	0.117	0.031	78.9	34.4	25.6	21.3	14.8	3.9
Contaminated-10	0.88	0.75	0.142	0.280	0.231	0.166	0.061	85.5	16.1	31.8	26.2	18.9	7.0
Uncontaminated-AV	0.26	0.17	0.07	0.07	0.08	0.03	0.02	63.9	25.9	25.4	28.8	10.6	9.2
Contaminated-AV	0.65	0.48	0.16	0.17	0.19	0.11	0.03	72.7	24.3	26.0	28.9	15.9	4.9
-test

Cd content extracted with 0.1 mol L⁻¹ HCl (1 : 5 w/v).