Table 1. Recovery of seeded microplastics from sediment samples by direct counting of NR-stained fragments after NR staining with or without inclusion of the density separation step.
| Protocol | No extraction step | With extraction | ||
|---|---|---|---|---|
| Matrix amount | 0.5 g | 1.0 g | 5.0 g | 5.0 g |
| Microplastic type | Mixed polymers | Mixed polymers | nylon | PE |
| Number seeded | 30 | 30 | 20 | 20 |
| Sample | CAP1 coarse sand | LIT 7C coarse sand | ||
| Replicate 1 | 32 | 27 | 20 | 17 |
| Replicate 2 | 29 | 27 | 20 | 21 |
| Replicate 3 | 31 | 30 | 19 | 20 |
| Mean | 31 | 28 | 20 | 19 |
| S.D. | 1.5 | 1.7 | 0.5 | 1.7 |
| Recovery % | 102 | 93 | 98 | 97 |
| Sample | SPI 6 fine silt | LIT 81C fine silt | ||
| Replicate 1 | 28 | 28 | 17 | 16 |
| Replicate 2 | 29 | 32 | 20 | 20 |
| Replicate 3 | 30 | 28 | 14 | 17 |
| Mean | 29 | 29 | 17 | 18 |
| S.D. | 10 | 2.3 | 2.4 | 1.7 |
| Recovery % | 97 | 98 | 85 | 88 |
The mixed polymer sample contained a total of 30 microplastics, 5 each of: nylon, PS, PVC, PET, PE and PP.