The Effect of Fishing Nets Aging on Metal Uptake

Fishing nets are mainly constituted of Polyethylene (PE), Polyamide, Polyethylene terephthalate (PET), Polypropylene (PP), and Nylon. While new, these plastics exhibit pristine mechanical performance but lose it as they age. But what about their metal adsorptive performance? Literature finds that plastics like PET and PVC accumulate Al, Cr, Mg, Fe, Co, Ni, Zn, Cd, and Pb, even when exposed to very low concentrations. This is mainly true for aged PVC (Kedzierski et al. Adsorption/desorption of Micropollutants. Mar Pollut Bull. 127:684–694, 2018). In this study, we look at the effect of age on the properties of fishing nets, including their capacity to adsorb metals. Because fishnets are in great part constituted by PE, we used standardized PE pellets as our reference. In calorimeter signaling, we observed that end-of-life fishing nets display a very different differential scanning calorimetry (DSC) pattern; both new and old fishing nets are very different from standardized PE polymer. Preliminary results show that Cr, Cu, Pb, and Se adsorption onto fishing nets occurs in the first 10 min to 6 h of exposure (24 h for Se). The maximum uptake was registered at 11 mg Cr kg‒1, 38 mg Cu kg‒1, 27 mg Pb kg‒1, and 15 mg Se kg‒1. All these concentrations refer to old end-of-life PE fishing nets, where new, unused PE fishing nets adsorb 2–20 times less (Old in this chapter refers to used fishing nets. The term is not attempting to attribute a particular life span/age to the nets). A comparison to different EU directives that regulate metal content in plastics for different end-uses shows that the old end-of-life PE fishing nets, after exposure to heavy metals, do not meet the regulations for hazardous waste. We believe that Greenlandic old waste fishing nets can be used to clean the wastewater, or metal-contaminated water, in Greenland and eventually, the rest of the world.