Staranje mikroplastike v površinskih vodah in spremembe njenih lastnosti

magistrsko delo

Marjeta Spasović (Author), Gabriela Kalčíková (Mentor), Marjan Marinšek (Thesis defence commission member), Aleš Podgornik (Thesis defence commission member)

Abstract

Plastiko se vsesplošno uporablja zaradi obstojnosti, nizke cene ter možnosti aplikacije v številnih panogah. Plastika, ki se najpogosteje uporablja, je sestavljena iz polimerov, ki niso biorazgradljivi in je zato izjemno obstojna v okolju, velik delež pa se je izgubi v naravi zaradi nepravilnega odlaganja odpadkov. Predvideva se, da je v okolju 4900 milijonov ton plastičnih odpadkov. Med najbolj razširjeno vrsto plastičnega onesnaženja sodi mikroplastika (MP). Definira se jo kot delce plastike, za katere so značilne dimenzije manjše od 1 mm. Je izredno heterogeno onesnaževalo, saj se razlikuje po velikosti, barvi, specifični gostoti in kemijski sestavi. Delci so izpostavljeni različnim fizikalno kemijskim dejavnikom, ki povzročajo t.i. staranje MP, zaradi česar se ji lastnosti še dodatno spreminjajo. Poleg tega je MP v stiku z naravnimi suspendiranimi delci in organizmi, ki vplivajo na nastanek biofilma na površini MP. Biofilm, ki se tvori na MP je sestavljen iz raznovrstne mikrobne skupnosti heterotrofov, avtotrofov, plenilcev in simbiontov, ki ji rečemo »plastisfera«. Ta združba je distinktivna za MP in se razlikuje od tiste na naravnih substratih. Nastanek biofilma na površini MP vpliva na njeno vertikalno gibanje in dolgoročno distribucijo v vodnem okolju. Poleg tega postane MP, zaradi biofilma in matrice zunajceličnih polimernih snovi lepljiva, kar promovira tvorbo heteroagregatov iz MP in mikrobnih združb. Tvorba agregatov dodatno učinkuje na maso delca in posledično sedimentacijo. Namen magistrske naloge je bil ovrednotiti spremembe lastnosti MP tekom njenega staranja v površinski vodi. MP smo izpostavili simuliranim naravnim razmeram z 12 tedensko inkubacijo v površinski vodi, ki je vsebovala naravno prisotne mikroorganizme. Vsak 2. teden smo preverili količino biofilma, ki se je razvil na MP, količino zunajceličnih polimernih snovi (EPS), aktivnosti ureaz ter koncentracijo klorofilov a in b. Vodo smo vsak teden zamenjali s svežo in jo analizirali (pH, TOC, amonijevi ioni, nitritni ioni, nitratni ioni, fosfatni ioni, kloridni ioni, število mikroorganizmov). Na koncu smo primerjali lastnosti surove MP in starane MP. Določili smo gostoto, število delcev na maso ter adsorpcijo kovin in delce opazovali pod optičnim in vrstičnim elektronskim mikroskopom. Tekom poskusa se je na MP razvil biofilm, ki je MP spremenil lastnosti; gostota starane MP je bila večja od surove MP, število delcev starane MP je bilo manjše od števila delcev surove MP ter starana MP je adsorbirala večje količine kovine. MP se torej, ob tvorbi biofilma, spremenijo lastnosti in posledično se spremeni tudi njeno obnašanje in razporeditev v okolju.

Keywords

mikroplastika;onesnaževala;adsorpcija;biofilm;staranje;karakterizacija;magistrska dela;

Data

Language:	Slovenian
Year of publishing:	2022
Typology:	2.09 - Master's Thesis
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher:	[M. Spasović]
UDC:	504.5(043.2)
COBISS:	131041283
Views:	50
Downloads:	23
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Aging of microplastics in surface water and changes of their properties
Secondary abstract:	Plastic is widely used due to its durability, low cost and the possibility of application in many industries. The most frequently used plastic is composed of polymers that are not biodegradable and is therefore extremely persistent in the environment, and a large proportion of it is lost in nature due to improper waste disposal. It is estimated that there are 4900 million tons of plastic waste in the environment. Probably the most widespread type of plastic pollution are microplastics (MP). They are defined as plastic particles with typical dimensions of less than 1 mm. They are an extremely heterogeneous pollutant as they differ in size, colour, specific density and chemical composition. The particles are exposed to various physico chemical factors that cause the so-called aging of MP, causing their properties to change further. In addition, MP are in contact with natural suspended particles and organisms that affect the formation of biofilm on the surface of MP. The biofilm that forms on MP consists of a diverse microbial community of heterotrophs, autotrophs, predators and symbionts, called the “plastisphere”. This community is distinctive for MP and differs from that on natural substrates. The formation of biofilm on the surface of MP affects their vertical movement and long-term distribution in the aquatic environment. In addition, MP become sticky due to the biofilm and the matrix of extracellular polymeric substances, which promotes the formation of heteroaggregates from MP and microbial communities. The formation of aggregates additionally affects the mass of the particle and the resulting sedimentation. The aim of the master’s thesis was to evaluate the changes in MP properties during their aging in surface water. Pristine MP were exposed to simulated natural conditions with a 12 week incubation in surface water containing naturally occurring microorganisms. Every 2 weeks, we checked the amount of biofilm that developed on MP, the amount of extracellular polymeric substances (EPS), the urease activity and the concentration of chlorophylls a and b. The water was replaced with fresh water every week and analysed (pH, TOC, ammonium ions, nitrite ions, nitrate ions, phosphate ions, chloride ions, number of microorganisms). Finally, we compared the properties of pristine MP and aged MP. We determined the density, the number of particles per mass and the adsorption of metals and observed the particles under an optical and scanning electron microscope. During the experiment, a biofilm developed on the MP which changed the properties of MP; the density of aged MP was higher than that of pristine MP, the number of particles of aged MP was smaller than the number of particles of pristine MP, and the aged MP adsorbed larger amounts of the metal. Therefore, when a biofilm is formed, MP’s properties change and, consequently, their behaviour and distribution in the environment are altered.
Secondary keywords:	aging;biofilm;characterization;microplastics;Univerzitetna in visokošolska dela;
Type (COBISS):	Master's thesis/paper
Study programme:	1000376
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, smer Kemijsko inženirstvo
Pages:	64 str.
ID:	16487851