Heavy metal accumulation during the last 30 years in the Karnaphuli River estuary, Chittagong, Bangladesh

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Table 2 Concentrations of Al and other heavy metal in surface and core sediment

Site	Layer (cm)	Al (%)	Cr (mg/kg)	Cu (mg/kg)	Ni (mg/kg)	Pb (mg/kg)	Zn (mg/kg)
S1	0–5	4.67	77.70	20.34	35.01	24.26	59.69
S2	0–5	4.85	78.39	20.54	34.10	24.35	61.37
S3	0–5	5.86	99.08	32.26	41.27	23.66	74.32
S4	0–5	5.92	91.38	23.38	39.82	23.70	66.36
S5	0–5	5.92	90.54	33.06	41.10	25.05	65.89
C1	0–1	2.80	102.30	25.44	42.15	24.98	70.18
	2–3	4.47	102.70	34.86	48.03	25.44	77.97
	4–5	4.27	100.90	34.24	48.05	25.38	77.28
	6–7	3.93	79.95	17.82	33.67	23.08	50.75
	8–9	4.51	79.69	18.70	32.46	23.15	50.93
	10–11	4.92	92.19	26.24	40.89	25.54	66.52
	12–13	4.95	97.22	32.28	43.96	26.61	73.56
	14–15	4.42	104.60	34.43	47.17	25.63	82.10
	16–17	5.31	83.69	23.92	38.26	23.51	64.23
	18–19	6.26	119.70	58.17	56.20	27.46	116.30
	20–21	5.68	119.30	45.93	55.82	28.38	101.40
	22–23	5.34	111.80	42.04	51.93	27.17	88.73
	24–25	4.75	99.62	31.88	42.84	25.05	70.54
	26–27	4.78	88.27	25.76	38.22	25.47	67.72
	28–29	4.78	91.85	28.83	39.78	24.91	69.27
	30–31	4.14	88.60	26.77	38.78	24.42	64.02
	32–33	4.16	90.48	26.72	38.69	25.22	66.07
	34–35	4.97	87.21	27.04	38.43	24.09	66.32
	36–37	4.76	89.53	27.07	39.41	24.90	71.91
	38–39	4.26	90.27	30.09	39.03	25.96	64.81
	40–41	5.82	101.60	35.97	43.75	26.25	77.97
	42–43	6.45	105.30	36.39	47.08	24.68	87.96
Background value^a			77.20	33.00	56.10	22.80	95.00