A Comprehensive Method for Water Environment Assessment considering Trends of Water Quality

Table 1

Classification of water area functions in GB3838-2002.

Classification standard value items	Class I	Class II	Class III	Class IV	Class V
pH	6–9
DO	7.5	6	5	3	2
CODMn	2	4	6	10	15
CODCr	15	15	20	30	40
BOD5	3	3	4	6	10
NH3-N	0.15	0.5	1	1.5	2
TN	0.2	0.5	1	1.5	2
TP	0.02	0.1	0.2	0.3	0.4