Estudis d’adsorció i desorció de metalls en (micro)plàstics

Abstract

(Micro)plastics are solid particles formed by polymers, insoluble in water and with a particle

size of less than 5 mm. Its presence in different aquatic environments has caused a potential

pollution impact on the environment and human health. Some of them also contain metals due

to their own manufacture or obtained from adsorption processes through the medium. So, this

combination of metals and (micro)plastics causes an increase in their toxicity and danger to

the ecosystem.

The main objective of this work is to study, through controlled laboratory experiments, the

adsorption and desorption of metals in different types of samples of commercial (micro)plastics

(polyethylene 53-63μm, 3mm) and environmental ((micro)plastics collected in Mediterranean

Sea and Atlantic Ocean) as well as fragments of fishing nets and samples collected in the

agropiles of the Mediterranean cormorant (Phalacrocorax aristotelis desmarestii).

It should be noted that different analytical techniques (ICP-MS, ICP-OES and TXRF) were

used during the work to determine the concentration of the metals present in the extracts

obtained in the adsorption and desorption studies. The μ-XRF technique has also been used

to determine the presence of metals in the solid samples of (micro)plastics.

The results obtained in the adsorption experiments have shown that the adsorption capacity

depends on the type of metal, chemistry of the aqueous solution and particle size of the (micro)plastic. In the latter case, it should be noted that the adsorption of metals is higher for

samples of (micro)plastics of smaller size.

In order to study the metal content that can be released from the (micro)plastic samples and

evaluate their possible danger in the exposed environment, different leaching tests have been

applied. It was found that some of the samples studied (fishing nets) had a considerable

leaching of metals with values of up to 1000 μg/kg (Pb) and that the metals present could

migrate in simulated gastric conditions of seabirds. Several metals (Pb, Cu, Fe, Cd, Zn, Cr

and Ti) were also identified in the (micro)plastic samples collected in the Mediterranean Sea

and the Atlantic Ocean. However, these metals were not easily desorbed from the samples.

This fact can be related to the aging of this type of samples in sea water