Exploring the Root Cause for Chronic Kidney Disease of Unknown Etiology (CKDu) via Analysis of Metal Ion and Counterion Contaminants in Drinking Water: A Study in Sri Lanka

Table 2

Descriptive statistics of the chemical composition of well water samples in all the sampling locations: Ambagaswewa GND in Polonnaruwa district, Wewalketiya GND in Anuradhapura district, and reference site (Buddangala GND in Ampara district).

Concentration of variables	Ambagaswewa GND				Wewalketiya GND				Reference site (Buddhangala GND)				SLS standards SLS 614 : 2013
	Mean	SD	Minimum	Maximum	Mean	SD	Minimum	Maximum	Mean	SD	Minimum	Maximum
Cd (µg/L)	0.178	0.162	ND	0.660	3.440	2.072	1.120	9.350	0.124	0.008	0.030	0.340	3
Pb (μg/L)	1.229	1.537	ND	6.080	5.422	3.687	1.000	17.350	1.368	0.196	0.000	7.420	10
Cr (μg/L)	0.203	0.423	ND	1.880	11.510	36.860	1.000	48.000	ND	ND	ND	ND	50
As (μg/L)	0.336	0.414	ND	1.650	ND	ND	ND	ND	0.161	0.065	ND	2.850	10
Zn (μg/L)	3.138	5.451	ND	22.59	50.93	20.97	20.00	87.60	4.793	0.790	ND	33.44	3000
Cu (μg/L)	6.470	19.04	ND	175.0	10.61	25.82	3.210	250.0	3.990	1.230	0.210	106.0	1000
Ca (mg/L)	74.10	15.50	ND	135.0	90.7	72.1	11.0	288.0	23.90	14.64	ND	39.83	100
Mg (mg/L)	18.51	25.15	ND	89.57	41.46	31.68	10.00	112.6	16.14	11.90	90.00	156.5	30
Na (mg/L)	1266	1682	205.0	8905	1518	2099	126.0	8845	3684	5175	114.0	8382	200
K (mg/L)	505.4	379.6	0.000	1403	119.2	36.50	14.20	555.3	640.0	582.0	0.000	1832	N/A
Fe (mg/L)	6.814	3.957	2.250	17.46	20.27	13.26	6.680	64.38	28.10	95.00	1.000	526.5	0.3
Mn (mg/L)	21.36	44.56	0.130	166.3	11.09	8.540	1.080	41.59	29.80	79.40	0.200	340.2	0.3
Co (mg/L)	0.019	0.072	0.000	0.383	ND	ND	ND	ND	ND	ND	ND	ND	N/A
Ni (mg/L)	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	0.02
Fluoride (mg/L)	1.260	0.654	0.320	3.160	1.370	0.658	0.220	3.020	0.505	0.081	0.100	3.200	1
Phosphate (mg/L)	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	2.0
Nitrate (mg/L)	2.520	1.475	0.220	5.890	0.669	0.348	0.150	1.290	1.127	ND	0.110	3.330	50

ND: not detected; N/A: not available.