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| Serial number | Cr (mg L−1) | Zn (mg L−1) | Cu (mg L−1) | Ni (mg L−1) |
|---|---|---|---|---|
| NBB-1 | 0.014 | 0.064 | 0.014 | 0.041 |
| NBB-2 | 0.016 | 0.054 | 0.012 | 0.048 |
| NBB-3 | 0.020 | 0.070 | 0.013 | 0.039 |
| NBB-4 | 0.023 | 0.062 | 0.013 | 0.032 |
| NBB-5 | N. D. | — | N. D. | 0.054 |
| NBB-6 | N. D. | — | N. D. | 0.032 |
| NBB-7 | N. D. | — | N. D. | 0.052 |
| NBB-8 | N. D. | — | N. D. | 0.067 |
| Limitsb | 15 | 100 | 100 | 5 |
N. D.: not detected.
Limits in GB 5085.3-2007.
