Research Article
Water Quality in Marginal Seas off China in the Last Two Decades
Table 1
Seawater Quality Standard of China (GB3097-1997, excerpt; unit: mg L−1).
| Item | Clean water (Category I) | Relatively clean water (Category II) | Slightly polluted water (Category III) | Medium polluted water (Category IV) | Heavily polluted water (inferior to Category IV) |
| Dissolved oxygen | >6 | >5 | >4 | >3 | <3 | Chemical oxygen demand (COD) | ≤2 | ≤3 | ≤4 | ≤5 | ≥5 | Biochemical oxygen demand (BOD5) | ≤1 | ≤3 | ≤4 | ≤5 | ≥5 | Inorganic nitrogen (as N) | ≤0.20 | ≤0.30 | ≤0.40 | ≤0.50 | ≥0.50 | Phosphate (as P) | ≤0.015 | ≤0.030 | ≤0.045 | ≥0.045 | Mercury | ≤0.00005 | ≤0.0002 | ≤0.0005 | ≥0.0005 | Cadmium | ≤0.001 | ≤0.005 | ≤0.010 | ≥0.010 | Lead | ≤0.001 | ≤0.005 | ≤0.010 | ≤0.050 | ≥0.050 | Chromium (VI) | ≤0.005 | ≤0.010 | ≤0.020 | ≤0.050 | ≥0.050 | Total chromium | ≤0.05 | ≤0.10 | ≤0.20 | ≤0.50 | ≥0.50 | Arsenic | ≤0.020 | ≤0.030 | ≤0.050 | ≥0.050 | Copper | ≤0.005 | ≤0.010 | ≤0.050 | ≥0.050 | Zinc | ≤0.020 | ≤0.050 | ≤0.10 | ≤0.50 | ≥0.50 | Oil | ≤0.05 | ≤0.30 | ≤0.50 | ≥0.50 |
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