Total nitrogen and pH-controlled chemical speciation, bioavailability and ecological risk from Cd, Cr, Cu, Pb and Zn in the water level-fluctuating zone sediments of the Three Gorges Reservoir

Figures & data

Figure 1. Geographical distribution of the study sampling sites.

Table 1. Physicochemical characteristics of the WLFZ sediments.

Study areas	pH	OM (g·kg^−1)	CEC (cmol·kg^−1)	TN (g·kg^−1)	TP(g·kg^−1)	Clay (%)	Silt (%)	Sand (%)
MS	8.31 ± 0.21a	64.24 ± 6.01a	48.41 ± 9.71a	0.28 ± 0.06a	743.82 ± 330.81a	10.96 ± 5.25	22.3 ± 7.87	66.74 ± 15.23
ZX	8.20 ± 0.42a	65.04 ± 4.08a	37.13 ± 8.32b	0.41 ± 0.09b	696.23 ± 69.22a	9.41 ± 3.36	11.8 ± 4.21	78.79 ± 14.08
MX	7.43 ± 0.91a	68.11 ± 6.25a	19.65 ± 4.43c	0.40 ± 0.05b	840.03 ± 180.25a	5.46 ± 2.52	13.3 ± 5.28	81.72 ± 20.47

Note: Different letters within columns represent significant differences between the mainstream and its tributaries (p < 0.05).

Table 2. Total contents of metals in the WLFZ sediments (mg·kg⁻¹).

Region	Cd	Cr	Cu	Pb	Zn
MS	4.58 ± 0.19b	91.23 ± 4.64b	18.50 ± 1.23a	125.96 ± 2.90b	85.68 ± 2.93a
ZX	6.21 ± 0.07a	93.60 ± 1.83b	18.43 ± 1.61a	134.39 ± 4.00a	88.45 ± 4.92a
MX	6.47 ± 0.12a	137.93 ± 4.83a	18.38 ± 1.59a	137.36 ± 2.97a	91.93 ± 7.64a
Entire study area	5.85	114.76	18.43	133.34	89.66
Background values [19]	0.08	79.00	31.10	30.90	86.50

Note: Different letters within columns represent significant differences between MS and its tributaries (p < 0.05).

Figure 2. Heavy metal fractions in the WLFZ sediment.

Table 3. Relationship between the heavy metal fractions and physicochemical characteristics.

Element	pH	OM	TN	TP	CEC
Pb-F1	0.40	−0.16	0.08	−0.27	0.57**
Pb-F2	0.50*	−0.35	−0.52*	−0.13	0.29
Pb-F3	−0.46*	0.48*	0.55*	0.04	−0.27
Pb-F4	−0.48*	0.21	0.30	0.20	−0.35
Pb-total	−0.38	0.31	0.52*	0.01	−0.10
Cd-F1	−0.49*	0.40	0.56*	0.23	−0.33
Cd-F2	0.48*	−0.47*	−0.50*	−0.31	0.41
Cd-F3	−0.59**	0.33	0.68**	0.31	−0.19
Cd-F4	0.26	−0.12	0.29	0.03	0.45*
Cd-total	−0.45*	0.35	0.63**	0.24	−0.21
Cr-F1	−0.52*	0.37	0.42	0.23	−0.46*
Cr-F2	0.23*	−0.21	−0.65**	0.00	−0.12
Cr-F3	−0.48*	0.32	0.66**	0.25	−0.26
Cr-F4	−0.22	0.16	0.46*	−0.08	0.03
Cr-total	−0.51*	0.35	0.41	0.22	−0.46*
Cu-F1	−0.61^**	0.45	0.52^*	0.22	−0.36
Cu-F2	0.41	−0.38	−0.68^**	−0.17	0.19
Cu-F3	−0.67^**	0.29	0.60^**	0.32	−0.06
Cu-F4	0.29	0.14	−0.22	−0.35	0.27
Cu-total	0.05	−0.24	0.08	−0.49^*	0.49^*
Zn-F1	0.57**	−0.29	−0.48*	−0.22	0.36
Zn-F2	0.41	−0.35	−0.56*	−0.16	0.32
Zn-F3	−0.48*	0.47*	0.46*	−0.07	−0.34
Zn-F4	−0.21	0.44	0.39	0.03	−0.41
Zn-total	0.09	0.37	0.08	−0.16	−0.29

^* p < 0.05

^** p < 0.01.

Table 4. Hakanson’s potential ecological risk index of heavy metals.

Region	Ei					RI	Pollution degree
	Cu	Zn	Cr	Cd	Pb
MS	2.97	1.03	2.31	1740.44	20.38	1767.13	Serious
ZX	2.96	0.99	2.33	2356.85	21.75	2384.88	Serious
MX	2.95	1.06	3.49	2457.42	22.23	2487.15	Serious
Mean	2.96	1.03	2.71	2184.90	20.37

Figure 3. Risk assessment code classification (RAC).

Figure 4. Biological assessment (RSP) of heavy metals.

Tang Q, Bao Y, He X. Sedimentation and associated trace metal enrichment in the riparian zone of the Three Gorges Reservoir, China. Sci Total Environ. 2014;479:258–266.10.1016/j.scitotenv.2014.01.122

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