Using TOPSIS Model with Modified Entropy Weight for Water Quality Assessment in Guizhou Province, China | Wuhan University Journal of Natural Sciences

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Table 1

Surface Water Environmental Quality Standard limits

Index	Indicator	Level I	Level II	Level III	Level IV	Level V
1	pH	6-9
2	Ammonia Nitrogen (NH₃-N) ≤	0.15	0.5	1	1.5	2
3	Fluoride (F) ≤	1	1	1	1.5	1.5
4	Cadmium (Cd) ≤	0.001	0.005	0.005	0.005	0.01
5	Chromium(VI) (Cr(VI)) ≤	0.01	0.05	0.05	0.05	0.1
6	Mercury (Hg) ≤	0.00005	0.00005	0.0001	0.001	0.001
7	Chemical Oxygen Demand (COD) ≤	15	15	20	30	40
8	Volatile Hydroxybenzene (VH) ≤	0.002	0.002	0.005	0.01	0.1
9	Sulfide (Sul) ≤	0.05	0.1	0.2	0.5	1
10	Lead (Pb) ≤	0.01	0.01	0.05	0.05	0.1
11	Cyanide (Cya) ≤	0.005	0.05	0.2	0.2	0.2
12	Arsenic (As) ≤	0.05	0.05	0.05	0.1	0.1
13	Petroleum (Pet) ≤	0.05	0.05	0.05	0.5	1
14	Copper (Cu) ≤	0.01	1	1	1	1
15	Five-day Biochemical Oxygen Demand (BOD₅) ≤	3	3	4	6	10
16	Zinc (Zn) ≤	0.05	1	1	2	2
17	Anionic Surfactants (AnS) ≤	0.2	0.2	0.2	0.3	0.3
18	Total Phosphorus (TP) ≤	0.02 LoR: 0.01	0.1 LoR: 0.025	0.2 LoR: 0.05	0.3 LoR: 0.1	0.4 LoR: 0.2

Levels of water quality I-V represent excellent, good, mild polluted, moderately polluted, severe polluted, respectively; LoR: Lake or reservoir; The unit of data: pH is dimensionless and the others are mg/L.

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