Table 1.

Concentration (mg·L⁻¹; Mean ± SD) of heavy metals (HM) in water and values of National Environmental Quality Standards (NEQS) in water samples collected from three sites (Indus Delta, Sandspit and, Miani Hor) in three different seasons (monsoon, post-monsoon and pre-monsoon).

HM	NEQS, 1997	Sandspit					Miani Hor					Indus Delta
		Monsoon	Post-monsoon	Pre-monsoon	Average	%Δ#	Monsoon	Post-monsoon	Pre-monsoon	Average	%Δ#	Monsoon	Post-monsoon	Pre-monsoon	Average	%Δ#
Hg	< 0.01	16.5 ± 0.12a	14.7 ± 0.14b	11.47 ± 0.20c	14.22 ± 2.55	142,100	13.5 ± 0.18a	12 ± 0.16b	9.58 ± 0.16c	11.69 ± 1.98	116,800	15.9 ± 0.13a	13.9 ± 0.36b	13.1 ± 0.17c	14.33 ± 1.46	143,200
Cd	< 0.1	2.4 ± 0.19a	2.01 ± 0.14a	1.31 ± 0.08b	1.92 ± 0.57	1820	1.14 ± 0.08a	0.88 ± 0.06b	0.56 ± 0.03c	0.86 ± 0.29	760	0.64 ± 0.02a	0.47 ± 0.02b	0.40 ± 0.01c	0.50 ± 0.12	400
As	< 1.0	29.5 ± 0.25a	21.4 ± 0.22b	17.1 ± 0.18c	22.66 ± 6.27	2166	18.6 ± 0.27a	17.2 ± 0.24b	15.2 ± 0.26c	17.00 ± 1.66	1600	19.4 ± 0.16a	18.7 ± 0.13b	16.5 ± 0.11c	18.20 ± 1.53	1720
Pb	< 0.5	15.9 ± 0.22a	10.7 ± 0.12b	10.12 ± 0.18c	12.24 ± 3.18	2348	1.68 ± 0.16a	1.39 ± 0.18b	1.04 ± 0.09c	1.37 ± 0.32	174	0.87 ± 0.03a	0.79 ± 0.02b	0.73 ± 0.03c	0.80 ± 0.07	60
Cu	< 1.0	3.9 ± 0.13a	2.9 ± 0.10b	1.84 ± 0.05c	2.89 ± 1.04	189	1.7 ± 0.13a	1.03 ± 0.06b	0.77 ± 0.03c	1.17 ± 0.49	17	1.53 ± 0.1a	1.11 ± 0.12b	0.93 ± 0.03c	1.19 ± 0.31	19
Cr	< 1.0	49.3 ± 0.37a	43.6 ± 0.32b	41.9 ± 0.20c	44.91 ± 3.87	4391	4.28 ± 0.08a	3.71 ± 0.15b	1.33 ± 0.09c	3.11 ± 1.56	211	1.38 ± 0.12a	0.99 ± 0.07b	0.84 ± 0.03c	1.07 ± 0.28	7
Zn	< 5.0	4.7 ± 0.17a	3.61 ± 0.09b	3.00 ± 0.11bc	3.77 ± 0.89	− 25	1.33 ± 0.1a	1.26 ± 0.13b	0.78 ± 0.03c	1.12 ± 0.30	− 78	0.86 ± 0.02a	0.71 ± 0.02b	0.55 ± 0.02c	0.71 ± 0.16	− 86
Fe	< 8.0	49.2 ± 0.24a	45.6 ± 0.34b	40.97 ± 0.11c	45.27 ± 4.15	466	0.97 ± 0.06a	0.84 ± 0.04b	0.51 ± 0.02c	0.77 ± 0.24	− 90	1.41 ± 0.14a	1.16 ± 0.14b	1.01 ± 0.05c	1.19 ± 0.20	− 85
Al	< 0.5*	20.3 ± 0.35a	17.4 ± 0.27b	16.7 ± 0.10c	18.14 ± 1.92	3528	12.7 ± 0.14a	12.2 ± 0.24a	10.6 ± 0.22b	11.84 ± 1.12	2268	10.0 ± 0.12a	6.63 ± 0.14b	4.24 ± 0.16c	6.97 ± 2.90	1294
Se	< 0.5	0.086 ± 0.005a	0.068 ± 0.008b	0.068 ± 0.0ab08b	0.074 ± 0.01	− 85	0.028 ± 0.007a	0.023 ± 0.005a	0.014 ± 0.005b	0.02 ± 0.01	− 96	0.08 ± 0.005a	0.07 ± 0.008a	0.04 ± 0.008b	0.06 ± 0.02	− 88
∑		192	162	144	166		56	51	40	49		52	45	38	45

*taken from ASQG, 2010, not available in NEQS, 1997. ^#%Δ is calculated by comparing average observed values with the limits described in NEQS, 1997. ^ap < 0.001, ^bp < 0.01, ^cp < 0.05.