Sepiolite is recommended for the remediation of Cd-contaminated paddy soil

Figures & data

Figure 1.  X-ray diffraction patterns of sepiolite (A) and lime (B). •: Sepiolite; □: Quartz;▴:Calcium Hydroxide; ○: Calcite.

Figure 2.  Relationships between soil pH and Cd concentrations in soil extracted by 0.1M NaNO₃ (A), 0.01 M CaCl₂ (B) and DTPA (C). (◊) CK: Control (unamended); (▴) L: Lime applied at 150 g m⁻²; (▪) S: Sepiolite applied at 2250 g m⁻²; (•) LS: Lime applied (at 150 g m⁻²) in a mixture with sepiolite (at 2250 g m⁻²). ^***Significant at p <0.001; ^*Significant at p <0.05.

Table I. Mean values of pH, CEC, CaCO₃, DCB-Fe and single-extractable Cd in plough-layer soils treated by different amendments (n=3 for each treatment).

					Soil-extractable Cd (mg kg^−1)
Treatments	Soil pH	CEC cmol kg^−1	CaCO3 g kg^−1	DCB-Fe g kg^−1	NaNO3	CaCl2	DTPA
CK	5.35 c	10.68 b	0.77 d	16.61 a	0.12 a	0.48 a	1.24 a
L	5.89 b	11.59 ab	1.70 c	17.60 a	0.05 b	0.23 b	1.09 b
S	6.28 b	11.88 ab	2.50 b	18.47 a	ND c	0.03 c	1.06 b
LS	6.79 a	12.27 a	4.92 a	18.17 a	ND c	0.01 c	1.07 b
Source of variation
L	**	ns	***	ns	**	**	ns
S	***	*	***	ns	***	***	*
L×S	ns	ns	***	ns	**	*	ns
Means (n=3) followed by the same letter within a row are not significantly different (LSD p <0.05).
ND: not detectable; ns: not significant; ^*significant at p>0.05; ^**significant at p <0.01; ^***significant at p <0.001.

Figure 3.  Distribution of cadmium (%) in soil affected by different amendments (□) EX: Water-soluble plus exchangeable Cd; (

) CB: Carbonate-bound Cd; (□) OX: Fe/Al oxides-bound Cd; (□) OC: Organic-bound Cd; (▪) RES: Residual Cd. The percentages assigned the same letter are not significantly different between treatments (LSD, p>0.05).

Figure 4.  Biomass productions obtained for different treatments (kg ha⁻¹, Dry weight) (□) CK; (□) L;(□) S;(▪) LS. Means and standard errors followed by the same letter are not significantly different (LSD, p>0.05).

Figure 5.  Cadmium contents (mg kg⁻¹, Dry weight) in brown rice, hull and straw (□) CK; (□) L; (□) S; (▪) LS. Means and standard errors followed by the same letter are not significantly different (LSD, p>0.05).