Indirect effects of COVID-19 on the environment: How plastic contamination from disposable surgical masks affect early development of plants

Abstract

Personal protective equipment, used extensively during the COVID-19 pandemic, heavily burdened the environment due to improper waste management. Owing to their fibrous structure, layered non-woven polypropylene (PP) disposable masks release secondary fragments at a much higher rate than other plastic waste types, thus, posing a barely understood new form of ecological hazard. Here we show that PP mask fragments of different sizes induce morphogenic responses in plants during their early development. Using in vitro systems and soil-filled rhizotrons, we found that several PP mask treatments modified the root growth of Brassica napus (L.) regardless of the experimental system. The environment around the root and mask fragments seemed to influence the effect of PP fabric fragment contamination on early root growth. In soil, primary root length was clearly inhibited by larger PP mask fragments at 1 % concentration, while the two smallest sizes of applied mask fragments caused distinct, concentration-dependent changes in the lateral root numbers. Our results indicate that PP can act as a stressor: contamination by PP surgical masks affects plant growth and hence, warrants attention. Further investigations regarding the effects of plastic pollution on plant-soil interactions involving various soil types are urgently needed.

Keywords: Brassica napus; Non-woven fabric; Polypropylene; Root system architecture.

Graphical abstract

Fig. 1

Root growth parameters of 5-days-old B. napus seedlings grown in two experimental setups supplemented with PP surgical mask fragments of different sizes at 0.5 % and 1 % concentrations: (A) primary root lengths in the in vitro and (B) in the rhizotron systems; (C) lateral root numbers in the in vitro and (D) in the rhizotron systems. Different letters indicate significant differences according to Duncan-test (p ≤ 0.05), n.s.: no significant difference.

Fig. 2

Primary root lengths of B. napus seedlings grown in soil-filled rhizotron systems supplemented with PP surgical mask fragments of different sizes at 0.5 % and 1 % concentrations. Significant differences compared to the control are marked according to Student’s t-test (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001).

Fig. 3

Lateral root numbers of B. napus seedlings grown in soil-filled rhizotron systems supplemented with PP surgical mask fragments of different sizes at 0.5 % and 1 % concentrations. Significant differences compared to the control are marked according to Student’s t-test (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001).

Fig. 4

Lateral root density of B. napus throughout the 14 days of growing period in the soil-filled rhizotron system, supplemented with PP surgical mask fragments of different sizes at 0.5 % and 1 % concentrations.

Fig. 5

Shoot growth parameters of the 14-days-old B. napus seedlings grown in the rhizotron system supplemented with PP surgical mask fragments of different sizes at 0.5 or 1 % concentrations: (A) number of leaves per plant; (B) average leaf size; (C) average leaf area per plant; (D) shoot length; and (E) shoot/root ratio. Different letters indicate significant differences according to Duncan-test (p ≤ 0.05), n.s.: no significant difference.

Fig. 6

The activity of (A) catalase (CAT) and (B) dehydrogenase (DH) enzymes, and (C) the number of aerobic heterotrophic bacteria number measured in the rhizotron soils on the14th day. Different letters indicate significant differences according to Duncan-test (p ≤ 0.05), n.s.: no significant difference.