To isolate microplastics from marine sediment samples for environmental analysis, researchers must follow a strict, multi-step density separation and filtration protocol. First, the sediment sample is dried in an oven at to remove all moisture without melting the synthetic polymers. Once dried, the sample is mixed with a high-density salt solution, typically sodium iodide (), which has a density of . This density is crucial because it allows the lighter plastic particles to float while the heavier mineral sands sink to the bottom. After thorough stirring, the mixture is left to settle for at least . Subsequently, the supernatant—the top liquid layer containing the floating microplastics—is carefully decanted into a vacuum filtration apparatus fitted with a glass fiber filter. It is essential to perform this decanting step prior to adding any organic digestants; introducing hydrogen peroxide to the mixture before separation would cause violent foaming due to the high mineral and organic content of the raw sediment, potentially ejecting the microplastics from the beaker. Finally, the filter containing the collected microplastics is treated with a hydrogen peroxide solution to digest any remaining natural organic matter, leaving the clean microplastics ready for microscopic characterization.
According to the passage, which of the following is the primary risk of introducing hydrogen peroxide to the mixture before performing the decanting step?
- AThe synthetic polymers would melt from the chemical reaction's heat, preventing accurate microscopic characterization.
- BThe high-density sodium iodide solution would fail to separate, causing the microplastics to sink to the bottom with the mineral sands.
- Violent foaming caused by the high mineral and organic content of the raw sediment could eject the microplastics from the beaker.Cevap
- DThe microplastics would be digested by the chemical before they can be collected on the glass fiber filter.