Table 1 Seasonal changes in water physicochemical parameters and permissible limits for drinking, irrigation practices and aquatic life.

SN	Parameters	Lekki Lagoon						Lagos Lagoon						Permissible limits
		Dry season			Wet season			Dry season			Wet season			Permissible limits
		Min	Max	Mean ± S.D	Min	Max	Mean ± S.D	Min	Max	Mean ± S.D	Min	Max	Mean ± S.D	Si (Drinking water quality)	Sz (Irrigation)	Sx (Aquatic live survival)
1	pH (at 25 °C)	6.99	8.01	7.37 ± 0.37^a	6.15	7.05	6.58 ± 0.40^b	7.20	7.80	7.51 ± 0.22^a	5.63	6.74	6.22 ± 0.38^b	5.5–9.0	8.5	6.5–8.5
2	Temperature (°C)	30.15	30.94	30.46 ± 0.27^a	27.54	29.71	28.44 ± 0.75^b	28.45	30.98	29.66 ± 0.86^a	26.25	27.75	27.15 ± 0.59^c	–	–	8–28
3	DO (mg/L)	3.77	4.65	4.05 ± 0.32^d	4.55	5.12	4.74 ± 0.21^bc	4.95	5.55	5.21 ± 0.21^b	6.25	7.10	6.61 ± 0.31^a	> 4	–	> 5
4	TSS (mg/L)	6.78	16.44	11.58 ± 3.17^d	28.95	35.57	31.90 ± 2.98^a	15.25	18.64	17.44 ± 1.17^c	22.87	26.05	24.20 ± 1.45^b	10–50	100	100
5	BOD (mg/L)	21.08	30.45	26.43 ± 3.23^b	154.28	197.81	176.88 ± 6.72^a	7.25	8.99	8.27 ± 0.56^d	10.25	12.75	11.52 ± 1.05^c	50	–	50
6	COD (mg/L)	104.85	120.45	106.41 ± 3.87^d	284.85	371.45	339.25 ± 11.73^c	1015.03	1089.98	1058.52 ± 29.16^b	2753.90	2887.60	2815.48 ± 52.48^a	250	–	–
7	EC (uS/cm)	203.84	238.63	217.29 ± 12.36^a	103.98	133.45	117.72 ± 16.94^b	40.73	51.75	47.02 ± 3.94^c	4.33	6.35	5.16 ± 0.74^d	250	3000	–
8	TDS (mg/L)	403.56	574.56	492.03 ± 50.28^b	1278.58	1660.76	1417.28 ± 106.45^a	14.65	27.43	21.95 ± 4.30^d	55.27	65.85	61.84 ± 4.17^c	< 1000	2000	500
9	Salinity (ppt)	4.98	5.98	5.55 ± 0.37^a	3.60	4.58	4.01 ± 0.39^b	3.78	6.45	5.12 ± 1.00^a	0.89	2.59	1.65 ± 0.68^c	–	–	–
10	Alkalinity (mg/L)	70.36	85.66	78.63 ± 6.03^c	9.78	14.71	12.18 ± 1.01^d	105.19	167.65	129.51 ± 21.69^a	71.25	96.95	86.40 ± 8.58^b	200	600	250

All the values are expressed in duplicate.
Within the same row, values marked with identical superscripts do not differ significantly.
*Si^45,46; Sz⁴⁷; Sx^48,54,56,58.

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