. 2011 Apr 8;8(4):1084–1109. doi: 10.3390/ijerph8041084

Table 1.

Summary statistics for hydrochemical data in Taiwan (unit: EC as μS/cm, others as mg/L).

Groups		Temp.	pH	E.C.	TH	TDS	Cl ⁻	NH₄-N	NO₃-N	SO₄²⁻	TOC	Fe²⁺	Mn²⁺

North	Min	18.2	3.6	70.0	5.5	44.5	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.2	N.D. ^a	N.D. ^a
(n = 1,796)	Median	25.2	6.4	498.0	176.0	318.0	19.4	0.1	0.8	55.8	2.1	0.8	0.8
	Max	30.5	9.9	27,200.0	4,890.0	24,800.0	11,300.0	55.2	24.8	1,330.0	91.8	140.0	12.9
	Mean	25.2	6.4	695.7	209.0	463.1	84.6	0.9	2.0	73.9	2.7	2.1	0.5
	S.D.	1.6	0.7	1,682.2	229.9	1,223.0	602.9	3.5	2.9	91.2	3.2	7.6	1.1

South	Min	22.0	5.5	168.0	32.4	120.0	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.1	N.D. ^a	N.D. ^a
(n = 2,013)	Median	27.2	7.0	899.0	378.0	591.0	34.4	0.1	0.1	100.0	1.5	0.18	0.4
	Max	32.4	10.5	82,300.0	14,400.0	64,200.0	31,900.0	37.4	65.4	5,420.0	9.7	16.6	8.0
	Mean	27.3	7.0	3,857.0	717.5	2,726.3	1,138.8	1.1	2.6	250.9	1.8	0.9	0.6
	S.D.	1.2	0.4	10,507.6	1,338.1	7,787.2	3,983.6	2.56	5.1	560.5	1.4	1.8	0.8

Total	Min	18.2	3.6	70.0	5.5	44.5	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.1	N.D. ^a	N.D. ^a
(n = 3,809)	Median	26.5	6.8	668.0	273.0	442.0	23.9	0.1	0.4	72.9	1.8	0.8	0.2
	Max	32.4	10.5	82,300.0	14,400.0	64,200.0	31,900.0	55.2	65.4	5,420.0	91.8	140.0	12.9
	Mean	26.3	6.7	2,366.4	477.7	1,659.2	641.7	1.0	2.3	167.5	2.3	1.4	0.5
	S.D.	1.7	0.6	7,884.2	1,017.6	5,832.9	2972.0	3.0	4.2	421.6	2.4	5.4	0.9

	MDL	–	–	–	5	–	1.6	0.02	0.01	1.0	0.05	0.005	0.005

	< N.D.(n) ^a	0	0	0	0	0	17	853	444	32	1	310	589

Groups		Na⁺	K⁺	Ca²⁺	Mg²⁺	Alk	As ^b	Cd ^b	Cr ^b	Cu ^b	Pb ^b	Zn ^b

North	Min	2.6	0.1	0.57	N.D.	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a

(n = 1,796)	Median	23.6	2.8	45.70	13.3	141.5	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.020

	Max	7,380.0	257.0	308.00	742.0	744.0	0.185	0.018	0.022	0.211	0.082	7.980

	Mean	65.6	5.1	52.77	18.9	157.3	0.003	0.001	0.002	0.003	0.003	0.050

	S.D.	359.3	13.3	38.53	39.0	104.6	0.010	0.001	0.001	0.007	0.004	0.207

South	Min	1.9	0.1	4.29	0.4	11.1	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a

(n = 2,013)	Median	39.1	4.5	106.00	24.6	299.0	0.002	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.003

	Max	15,200.0	1,040.0	630.00	3,070.0	1,030.0	0.191	0.009	0.032	0.484	0.104	0.334

	Mean	618.5	30.0	125.80	93.0	308.4	0.009	0.001	0.002	0.002	0.003	0.007

	S.D.	2,054.4	91.1	84.00	268.6	137.1	0.019	0.001	0.002	0.011	0.005	0.015

Total	Min	1.9	0.1	0.57	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a

(n = 3,809)	Median	28.2	3.4	78.40	17.6	219.0	0.001	N.D. ^a	N.D. ^a	N.D. ^a	N.D. ^a	0.007

	Max	15,200.0	1,040.0	630.00	3,070.0	1,030.0	0.191	0.018	0.032	0.484	0.104	7.980

	Mean	357.8	18.3	91.37	58.0	237.1	0.006	0.001	0.002	0.003	0.003	0.027

	S.D.	1,538.5	68.0	75.87	200.5	144.2	0.016	0.001	0.002	0.010	0.005	0.144

	MDL	0.1	0.1	0.1	0.1	0.1	0.0005	0.001	0.005	0.005	0.005	0.005

	< N.D.(n) ^a	0	0	0	3	5	1,553	3,457	3,539	3,336	3,429	838

N.D. represents values are lower than method detection limit (MDL);

Values for constituents lower than MDL were replaced with MDL/2.