Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris
July 28th, 2018
Most microplastic research to date has occurred in marine systems where suspended solid levels are relatively low. Focus is now shifting to freshwater systems, which may feature high sediment loads and floating debris. This protocol addresses collecting and analyzing microplastic samples from aquatic environments that contain high suspended solid loads.
This method will help researchers quantify microplastic loads in rivers, which often contain high sediment loads, as they are a major source of plastic debris to the ocean. The main advantage of this technique is that it enables filtering and sorting of microplastics and water samples with high sediment loads at sizes not typically included in previous studies. To begin rinse the filtration device and nylon mesh sieves three times with deionized water.
Then place the mesh sieves into each union joint, with the pour sizes decreasing from top to bottom. To prevent leaks seal each joint tightly. Next wet a mixed cellulose ester membrane filter with deionized water.
While the filter is still damp fold it into a cone. Then place a stainless steel mesh basket into the last union joint. Carefully place the folded membrane filter into the basket.
Fold the lip of the filter over the edge of the joint. Next place a mesh sieve on top of the membrane filter in the last union joint. Ensure that all of the union joints are sealed tightly.
Then attach the hose form the top of the filtering flask to the base of the filtration device. Turn on the vacuum pump, ensuring that the pressure does not exceed 127 milliliters of mercury. Using a 500 milliliter graduated cylinder measure the total volume of the sample.
Next record the volume of the sample and transfer it to the filtration device. To empty the filtering flask turn off the pump and detach the two hoses from the flask. Then empty the flask into a waste container.
To continue the filtration cycle reattach the hoses and turn on the pump. Once the entire sample has been filtered use deionized water to rinse the sample container and graduated cylinder three times. After each rinse filter the deionized water used to rinse the container and graduated cylinder.
Using deionized water rinse the walls of the filtration device three times. Then turn off the vacuum pump, and use a deionized water wash bottle to rinse the edges of the union joint. Turn the pump off and use forceps to remove the mesh sieve from the union joint.
Place the sieve in a covered Petri Dish and dry it at 60 degrees celsius for 24 hours. Repeat this process for each union joint. Then turn the vacuum pump on and rinse the edges of a membrane filter using a deionized water wash bottle.
Wash the particulates at the edges of the filter into the center, and ensure that all of the water passes through the filter. Next use forceps to remove and unfold the membrane filter. Place the filter in a foil envelope and dry at 60 degrees celsius for 24 hours.
First examine the membrane filter under a stereo microscope. Suspected plastics will not have cellular structure. The fibers will have equal thickness throughout, and the particles will not appear shiny.
Remove suspected plastics from the filter and place them into a collection vial containing 70%ethanol. Record the color and shape of each suspected plastic. For nylon mesh sieves stored in Petri Dishes after all suspected plastics have been removed from the filter examine the lid and bottom of the Petri Dish for additional suspected plastics.
To validate this protocol three samples from Oso Bay were spiked with 10 blue polyethylene particles and 50 green nylon fibers. On average, 100%of the polyethylene particles and 92%of the nylon fibers were recovered from the samples. The loss of fibers may be due to a small amount of sample loss during filtration or incorrect identification.
Once mastered multiple filtration apparatus can be run simultaneously with samples taking less than two hours each to filter. Sample sorting times under the microscope however are sample specific. While attempting this procedure it's important to remember to account for potential contamination using lab equipment and field blanks for each step in the process.
Following this procedure other methods like Fourier Transform Infrared Spectroscopy can be used to verify material properties. With its development this technique enables researchers studying environmental contaminates to explore microplastic pollution and waterways with high suspended sediment loads, as well as floating and submerged debris.
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Overview
This protocol addresses the collection and analysis of microplastic samples from freshwater systems, which often contain high sediment loads. It enables researchers to quantify microplastic loads in rivers, a significant source of plastic debris to the ocean.
Key Study Components
Area of Science
- Environmental Science
- Freshwater Ecology
- Pollution Research
Background
- Microplastic research has primarily focused on marine systems.
- Freshwater systems may have high sediment loads and floating debris.
- Understanding microplastic distribution in rivers is crucial for environmental health.
- This study aims to fill the gap in knowledge regarding freshwater microplastics.
Purpose of Study
- To develop a method for collecting microplastic samples from rivers.
- To analyze the impact of high sediment loads on microplastic quantification.
- To provide a standardized protocol for future research in freshwater environments.
Methods Used
- Rinse filtration devices and nylon mesh sieves with deionized water.
- Use decreasing mesh sizes in union joints to filter samples.
- Seal joints tightly to prevent leaks during filtration.
- Wet a mixed cellulose ester membrane filter with deionized water.
Main Results
- The method allows for effective filtering of microplastics in high sediment environments.
- Researchers can quantify microplastic loads at sizes not typically included in previous studies.
- Results contribute to understanding the transport of plastics from rivers to oceans.
- This technique enhances the accuracy of microplastic research in freshwater systems.
Conclusions
- The developed protocol is effective for analyzing microplastics in freshwater systems.
- It addresses the challenges posed by high sediment loads.
- Future studies can utilize this method to further investigate freshwater microplastic pollution.
Frequently Asked Questions
Executive Industry Relevance
This protocol enables biopharma R&D teams to assess microplastic contamination in aquatic environments relevant to water sourcing for manufacturing and formulation processes. By capturing particles <300 µm in high-sediment conditions, it supports risk evaluation of particulate impurities in water used for drug production, cleaning, or cooling systems. The method enhances predictive confidence in environmental monitoring programs tied to GMP-adjacent operations and supply chain resilience.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of particulate-induced cellular stress pathways in vitro using environmentally relevant microplastic mixtures.
- Operational Value: Provides standardized isolation of sub-300 µm particles for toxicological screening in discovery assays.
Screening & Assay Development
- Scientific Value: Generates quantifiable microplastic fractions for dose-response profiling in phenotypic screening assays.
- Operational Value: Ensures reproducible sample preparation across variable water sources, reducing assay noise from sediment interference.
Translational & Preclinical Research
- Scientific Value: Supports mechanistic de-risking by linking environmental exposure models to organ-specific accumulation and inflammatory endpoints.
- Operational Value: Enables cross-study comparability of microplastic burden in preclinical disease models via consistent sizing and polymer characterization.
Pipeline & Workflow Integration
The method fits within environmental risk assessment workflows, informing early-stage formulation decisions and facility siting strategies by characterizing particulate loads in process water intakes.
- Discovery Biology: Delivers characterized microplastic particulates and fibers for hypothesis testing on membrane integrity and oxidative stress mechanisms.
- Screening: Provides size-fractionated samples enabling reliable high-throughput screening of particle-cell interactions.
- Analytics: Delivers polymer-specific identification via micro ATR-FTIR, allowing correlation of plastic type with biological response.
- Translational Research: Connects environmental exposure data to preclinical models through standardized particle dosing and recovery metrics.
- Enterprise Reuse: Adaptable filtration volumes and mesh sizes allow deployment across multiple sites and water sources with standardized SOPs.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in environmental toxin studies by providing chemically and physically defined microplastic preparations.
- Operational Value: Achieves 100% recovery for polyethylene particulates and 92% for nylon fibers, ensuring reliable quantification for longitudinal monitoring.
- Strategic Value: Informs capital allocation for water purification upgrades by identifying persistent particulate challenges in source water.
- Portfolio Impact: Supports risk-adjusted advancement decisions by quantifying microplastic burden in water used for cell culture or buffer preparation.
Implementation Considerations
- Requires expertise in filtration techniques, microscopy, and ATR-FTIR polymer identification.
- Depends on vacuum pumps, graduated cylinders, and custom filtration devices with union joints and mesh sieves.
- Necessitates standardized rinsing and drying protocols to prevent cross-contamination between samples.
- Must account for fiber loss during handling and validate recovery using spiked controls per sample batch.
- Adaptation to extreme flow rates or biofouling conditions may require pretreatment steps not detailed in the source.
