Spremembe lastnosti konvencionalne in biorazgradljive plastike zaradi okoljskega staranja

Filipič, Ula (author), Kalčikova, Gabriela (mentor)

Plastika je izjemno priljubljena zaradi svoje vzdržljivosti, nizke cene in široke uporabnosti v številnih industrijskih panogah. Večina uporabljene plastike je izdelana iz polimerov, ki niso biorazgradljivi. Zaradi nepravilnega ravnanja z odpadki velik delež te plastike konča v okolju, kjer zaradi svoje obstojnosti ostaja še vrsto let in tako prispeva k onesnaževanju tal in vodnih virov ter predstavlja nevarnost za ekosisteme. Med najbolj razširjenimi vrstami plastičnega onesnaženja je mikroplastika (MP). MP je izredno heterogeno onesnaževalo, saj se razlikuje po velikosti, barvi, specifični gostoti in kemijski sestavi. V okolju je MP izpostavljena različnim fizikalno-kemijskim dejavnikom kot so UV sevanje, fizična abrazija in kemična oksidacija. Druga možnost pa je tudi biološko staranje, kjer se na MP vežejo mikroorganizmi, ki tvorijo na površini biofilm. Ne glede na način pa staranje povzroči različne spremembe v fizikalno-kemijskih lastnostih MP, posledično pa tudi njene interakcije z okoljem. Namen diplomske naloge je bil raziskati, kako biološko staranje v površinskih vodah vpliva na lastnosti konvencionalne in biorazgradljive MP. MP smo starali 9 tednov v površinski vodi, ki je vsebovala mikroorganizme. V tem času se je na MP razvil biofilm, ki smo ga ovrednotili z določanjem količine biofilma, količine ekstracelularnih polimernih snovi in klorofila a. Ovrednotili pa smo tudi spremembe v lastnostih MP zaradi staranja, kjer smo ugotovili, da pri obeh tipih MP pride do kemijskih sprememb na površini MP. Z vrstično elektronsko mikroskopijo smo pri biorazgradljivi MP opazili spremembe na površini ter posamezne celice, medtem ko pri konvencionalni MP ni bilo vidnih morfoloških sprememb, videl pa se je sloj ekstracelularnih polimernih snovi. Preučevali smo tudi adsorpcijo in kroženje hranil ter ugotovili, da se na starano MP adsorbira in se porablja precej več fosforja, ki je ključno hranilo za mikroorganizme. Na podlagi rezultatov smo ugotovili, da se biofilm razvija na konvencionalni in biorazgradljivi MP različno ter da tudi različno vpliva na lastnosti MP.

• Language: Slovenian
• Keywords: adsorbcija, biofilm, hranila, karakterizacija, mikroplastika
• Work type: Bachelor thesis/paper
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-160787-c53c9f43-7483-876d-60ec-d6d7e6c3e2b8
• Publication date in RUL: 04.09.2024

Secondary language

• Language: English
• Title: Changes in the properties of conventional and biodegradable plastics due to environmental aging

Abstract

Plastic is an extremely popular material in many industries due to its durability, low cost, and wide range of applications. Most of the plastic used is made from polymers that are not biodegradable. Due to improper waste management, a significant amount of this plastic ends up in the environment, where it remains for many years due to its persistency. This contributes to soil and water pollution and poses a threat to ecosystems. One of the most widespread types of plastic pollution are microplastics (MP). MP are an extremely heterogeneous pollutant that varies in size, colour, specific density, and chemical composition. In the environment, MP are exposed to various physical and chemical factors, such as UV radiation, physical abrasion, and chemical oxidation. Another possibility is biological aging, in which microorganisms attach to MP and form a biofilm on the surface. Regardless of the method, aging causes changes in the physical and chemical properties of MP, subsequently affecting its interaction with the environment. The aim of the thesis was to investigate how biological aging in surface waters affects the properties of conventional and biodegradable MP. We aged MP for 9 weeks in freshwater containing microorganisms. During this period, a considerable amount of biofilm developed on MP, which was evaluated by determining the amount of biofilm, extracellular polymeric substances, and chlorophyll a. We also evaluated the changes in MP properties due to aging and both MP showed changes in the chemical structure. In addition, changes in surface morphology and individual cells were observed on biodegradable MP, while no changes in morphology but a layer of extracellular polymeric substances was visible on conventional MP. We also studied the adsorption and cycling of nutrients and found that aged MP adsorbed and utilize significantly more phosphorus, which is an important nutrient for microorganisms. From the results, we concluded that the biofilm develops differently on conventional and biodegradable MP and that it also affects the properties of MP differently.

• Keywords: adsorption, biofilm, characterization, microplastics, nutrients