Sand is a very abundant element on our planet, being the second most used natural resource. It hides treasures in the form of minerals and chemical elements but also polluting residues in the form of microplastics. This fact is mainly due to the unstoppable increase in the production of plastics that have a very short useful life. Our objectives are to use with our students the resources offered by the ecosystems of the eastern Almeria beaches as a basis for carrying out simple laboratory procedures suitable for determining the microplastic content. The associated methodologies for obtaining and exposing the experimental results consist of sampling, separation, transformation, quantification and statistical data treatment techniques and are directed by the teaching staff of the intermediate level training cycle of laboratory operations.

FIRST CHALLENGE. Selection of beaches for sampling. sampling plan

TEACHER: Jaime Usano Alemany

The milestone consisted of empathizing with the problem posed, debating, investigating and proposing solutions. We do this in the classroom using group dynamics techniques and the promotion of soft skills in students. Specifically, we carried out a “design thinking” and “visual thinking” dynamic where the students had to investigate the problem, discuss its causes and possible solutions, empathize with the causes and prototype the ideas that emerged during the interaction in the groups.

Apart from the specific prototypes that emerged, the results of the dynamics were very positive in that the students had to work as a team, bring out their creativity, work on their capacity for synthesis and their communication skills.

SECOND CHALLENGE. Sampling

TEACHER: Jaime Usano Alemany

Sampling objectives

The fundamental objective of the sampling is to obtain representative samples of the beaches near the IES Jaroso de Cuevas del Almanzora institute in order to quantify the microplastic content. Specifically, it is intended to assess not only the presence of microplastics in the sand but also if there are appreciable differences between the sand collected in the intertidal zone and that collected in the supralittoral zone. To do this, the microplastics will be separated from the sand by the flotation/filtration method using a saturated solution of NaCl (common salt). This methodology has proven to be one of the simplest and most effective methods published to date. In addition, it does not require the use of chemical products or highly specialized equipment, which makes it a very suitable technique to be used by teachers and students of different educational stages.

Specifications of the material to be sampled

The material to be sampled is beach sand. Sand is a set of small loose fragments of rocks, minerals, or exoskeletons of marine animals. In geology, the material composed of particles whose size varies between 0.063 and 2 mm is called sand. The beaches to be sampled are the main beaches that are close to the educational center. Thus, we aim to take samples from the following locations:

1. Beach 1. Luis Siret Beach. Location: Villaricos (Cuevas del Almanzora).
2. Beach 2. Quitapellejos Beach. Location: Vera-Playa.
3. Beach 3. Cala Marqués. Vera-Playa town.
4. Beach 4. El Playazo. Location: Vera-Playa.
5. Beach 5. Puerto Rey. Location: Vera-Playa.
6. Beach 6. Las Marina-Bolaga. Location: Vera Playa.

Sampling methodology

Sampling will be carried out following a stratified methodology within each location and systematic in each of the established areas. Thus, within each beach two sampling zones will be delimited, the intertidal zone and the supratidal zone. This is intended to corroborate whether there are differences in the presence of microplastics in these two areas. In turn, in each of the areas a systematic sampling will be carried out following a line parallel to the sea and taking samples at different equidistant points. We estimate taking 4 sampling points in each of the zones, taking a total of 8 samples per beach.

In addition, at each sampling point a 30*30 cm grid will be delimited and the first 3 centimeters of sand will be collected in a properly labeled and identified polyethylene plastic bag. The label format is shown in the attached figure. Each team leader will be responsible for the collection, selection and correct identification of each sample. In addition, the latter will have to rigorously fill out the sample taking statement. The team leaders are made up of CFGM 1st year laboratory operations students.

Packaging, conservation, storage and transport procedures

The containers used consist of A4 size self-closing propylene bags. On the other hand, the code to use in the identification will be the following:

• P + number: indicates the sampled beach
• Letter: indicates the sampling zone (supratidal or intertidal).
• number: indicates the sample number:

For example: P1A1: beach 1, supratidal zone, sample 1.

Once the samples are collected, they will be taken to the educational center for storage until the corresponding analysis is carried out. This material does not require specific storage conditions or conservation requirements.

Name of the laboratory in charge of analyzing the sample

LABORATORY IES JAROSO Av/ Carlos Herrera, 25, 04610, CUEVAS DEL ALMANZORA (ALMERIA) Tel. 950 45 17 05 / @ 04002052.laboratorio@g.educaand.es

THIRD CHALLENGE. Sample treatment: sieving, flotation-filtration methods

TEACHER: Jaime Usano Alemany

Conditioning.

Once in the laboratory, the samples were subjected to a process of homogenization, reduction of the size of the sample by quartering and drying in an oven at 50ºC until the elimination of the remaining moisture from the sand.

Screening and separation of microplastics by flotation.

Once dry, the sand was subjected to sieving to select, on the one hand, the fraction of sand between 1.0 and 6.0 mm and, on the other hand, the fraction smaller than 1.0 mm. Both fractions were weighed in each case to determine the granulometry of each of the selected beaches. Finally, a mass of approximately 150g made up of both fractions was introduced into a 500mL beaker with a saturated NaCl solution. With this procedure, the microplastics contained in the sand are separated by flotation. The sample is then allowed to settle for one hour and the supernatant (water) is vacuum filtered through a 0.45 µm filter. The filter is kept in a Petri dish for counting.

Microplastic count

For the count of microplastics, each of the filters was visualized through binocular loupes, photographing the most conspicuous microplastics in each sample. All those particles and fibers that appeared to be microplastics were counted using a standardized testimonial.