Research study
Objectives
Isolate microplastics from atmospheric samples from the Ria Formosa Natural Park
Identify and quantify the microplastics present in the monthly samples for a time-series study
Test the methodology for the sediment samples analysis
Sampling
Atmospheric particles
The atmospheric samples consist in the atmospheric particles deposited on passive collectors, that are a funnel in a bottle. They are placed in the exterior of the Centro de Ciência Viva do Algarve, a small museum of science education for children, in Faro, Portugal. Approximatively after a month of atmospheric deposition, we use distilled water to collect the particles and we take them to the lab.
Sediments
We sampled sediments from the Ria Formosa Natural Park to test the methodology for microplastic isolation from this type of sample. We withdrew approximatively 100g of sediments from three different locations of the Ria Formosa, in Praia de Faro.
Experimental procedures
In the laboratory, the goal was to isolate the microplastics from the organic and inorganic matter through different filtrations and digestion steps. An overview of the experimental procedure for atmospheric samples is shown in the video below.
The first filtration consists in recovering the highest number of particles from our sample in a filter. The goal is to reduce the volume of the sample to save chemical reagents. To this filter, we add hydrgen peroxide to remove the organic components. We leave it a certain time in the stove at 50°C to provoke the reaction. This is what we call the digestion step. Following this reaction, we proceed to a second filtration of the sample with a smaller silicon filter with 5µm pores. This smaller filter is the one that we will be using for further analysis.
There is not a standardized methodology that allows a fast and accurate identification and quantification of microplastics yet. Different methodologies exist. We have tried some of them and we have tried some modified ones. We are trying to find the optimal procedure to isolate the microplastics, taking into account other practical factors.
Chemical analysis and treatment of the results
Following the laboratory work, our optimal method up to now requires the micro-FTIR (Fourier Transformed Infrared) spectroscope to analyse the particles filtered with the 5µm pore size silicon filters. This instrument has a great potential. It identifies and quantifies the components of the sample.
Next step was to distinguish the plastic particles from the other particles and classify them by polymer type. To do so, we used an R program and Microsoft Excel.
The goal is to do a time series with an identification and quantification of the microplastics present in each type of sample, and thus compare the data for the three different environments.