Interakcije modelne plavajoče rastline z okoljsko relevantno mikroplastiko ter možnost njenega odstranjevanja s fitoremediacijo

Rozman, Ula (author), Kalčikova, Gabriela (mentor), Jemec Kokalj, Anita (comentor)

Mikroplastika, ki jo definiramo kot delce plastike v velikosti od 1 do 1000 µm, je trenutno eno od najbolj razširjenih onesnaževal. Kljub velikemu številu raziskav na področju mikroplastike o interakcijah med mikroplastiko in vodnimi organizmi, predvsem z rastlinami, do sedaj ni bilo veliko znanega. Zato smo v okviru doktorske disertacije preučevali interakcije med različnimi tipi okoljsko relevantne mikroplastike ter modelno vodno rastlino, malo vodno lečo Lemna minor L., z namenom razvoja fitoremediacijske metode za odstranjevanje mikroplastike iz vodnega okolja. Najprej smo preučevali kratkotrajne (7-dnevne) vplive različnih tipov mikroplastike, med katere smo poleg surove mikroplastike vključili tudi starano mikroplastiko (tj. mikroplastiko, ki je bila predhodno izpostavljena simuliranim okoljskim razmeram) ter mikroplastiko s predhodno adsorbiranimi onesnaževali (kovinskimi nanodelci nTiO2 in nZnO), saj so takšni tipi mikroplastike pogosto najdeni v okolju. Surova mikroplastika je imela minimalni vpliv na malo vodno lečo, saj je na rast korenin vplivala le mikroplastika v obliki fragmentov ter mikroplastika, s katere so se izluževali aditivi. Staranje mikroplastike je sicer bistveno spremenilo fizikalno-kemijske lastnosti mikroplastike, vendar se vpliv na rastlino, v primerjavi s surovo mikroplastiko, ni spremenil. Študij adsorpcije nTiO2 in nZnO na mikroplastiko je pokazal, da sta količina vezanih nanodelcev in moč vezave odvisna od tipa nanodelcev, saj so bile interakcije med mikroplastiko in nTiO2 močnejše kakor med mikroplastiko in nZnO. Kljub razliki v količini in moči vezave pa se vpliv mikroplastike z adsorbiranimi nTiO2 in nZnO na malo vodno lečo ni razlikoval od vpliva surove mikroplastike. V drugem delu smo se osredotočili le na en tip mikroplastike in preučevali dolgotrajne interakcije (12 tednov) z modelno rastlino. Tekom izpostavitve mikroplastika ni imela močnega vpliva na rastlino, saj se je vpliv pokazal le pri rasti korenin, ki pa po 8. tednu ni bil več prisoten, kar kaže na aklimatizacijo rastline. Med poskusom se je tedensko v povprečju na rastlino vezalo 25 % mikroplastike. Sledil je še poskus fitoremediacije in prišli do ugotovitve, da bi se glede na določeno konstanto hitrosti odstranjevanja okoljsko relevantne koncentracije mikroplastike v vodnem okolju pri danih razmerah dalo odstraniti v dveh mesecih. Glede na minimalni vpliv in sposobnost vezave mikroplastike na modelno rastlino lahko sklepamo, da je uporaba fitoremediacije mikroplastike iz vodnega okolja možna, hkrati pa sodi med ekonomsko ugodne, enostavne in okolju prijazne in situ metode.

• Language: Slovenian
• Keywords: adsorpcija, fitoremediacija, mala vodna leča, mikroplastika, vodni makrofiti
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-147052
• COBISS.SI-ID: 158743043
• Publication date in RUL: 22.06.2023

Secondary language

• Language: English
• Title: Interactions of a model floating plant with environmentally relevant microplastics and the possibility of its removal by phytoremediation

Abstract

Microplastics, defined as plastic particles from 1 to 1000 µm in size, are currently one of the most widespread pollutants. Despite numerous studies, not much is known about the interactions between microplastics and aquatic organisms, especially plants. Therefore, the aim of the thesis was to investigate the interactions between different types of environmentally relevant microplastics and the model aquatic plant, duckweed Lemna minor, to develop a phytoremediation method to remove microplastics from the aquatic environment. We investigated the short-term (7-day) effects of different types of microplastics, including pristine microplastics, aged microplastics (i.e., microplastics previously exposed to simulated environmental conditions), and microplastics with previously adsorbed pollutants (metal nanoparticles nTiO2 and nZnO), as such types of microplastics are common in the environment. Pristine microplastics had minimal effects on duckweed, as only microplastics in the form of fragments and microplastics from which additives leached affected root growth. Aging significantly changed the physico-chemical properties of the microplastics, but the effects on the plant did not change compared to the pristine microplastics. The study of the adsorption process of nTiO2 and nZnO on microplastics showed that the amount of nanoparticles bound and the binding strength depended on the type of nanoparticles, as the interactions between microplastics and nTiO2 were stronger than between microplastics and nZnO. Despite the differences in the amount and strength of binding, the effects of microplastics with adsorbed nTiO2 and nZnO on duckweed did not differ from the effects of pristine microplastics. In the second part, we focused only on one type of microplastics and studied long-term interactions (12 weeks) with duckweed. During the exposure, microplastics did not have significant effects on the plant, as the effect was only seen in root growth, which was absent after the eighth week of exposure, indicating acclimation of the plant. Furthermore, an average of 25% of the microplastics adhered to the plant per week. Finally, a phytoremediation experiment was conducted, and we concluded that the environmentally relevant concentrations of microplastics in the aquatic environment can be removed within two months under the given conditions. Based on the minimal impact of microplastics and the ability to bind to the plant, we can conclude that the phytoremediation of microplastics from the aquatic environment is possible and it is also a low-cost, simple, and environmentally friendly in situ method.

• Keywords: adsorption, aquatic macrophytes, duckweed, phytoremediation, microplastics