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Title:Staranje nitrogvajakola pod vplivom sončne svetlobe
Authors:Delić, Ajda (Author)
Kroflič, Ana (Mentor) More about this mentor... New window
Šala, Martin (Mentor) More about this mentor... New window
Files:.pdf Ajda_Delic.pdf (1,62 MB)
 
Language:Slovenian
Work type:Master's thesis (m2)
Tipology:2.09 - Master's Thesis
Organization:FZO - Faculty of Environmental Sciences
Abstract:Nitrogvajakoli so rumeno obarvane spojine, ki prispevajo k absorpciji rjavega ogljika v ozračju. Na podnebje vplivajo z absorbiranjem svetlobe v bližnjem UV in vidnem delu spektra, saj po absorpciji sproščajo toploto, kar vodi v ogrevanje ozračja. Poleg tega imajo škodljiv vpliv tudi na ekosistem. Prisotnost v ozračju in njihovi mehanizmi nastanka so že raziskani, mehanizmi razpadanja v vodni fazi ozračja pa so malo znani. V tem delu smo raziskali, kako sončna svetloba vpliva na staranje nitrogvajakolov v ozračju. Z uporabo fotospektroskopije smo najprej proučili spektroskopske lastnosti vodnih raztopin gvajakola, 4-nitrogvajakola, 5-nitrogvajakola in dinitrogvajakola ter kako nanje vpliva pH. Preiskovani nitrogvajakoli v vidnem delu spektra močno absorbirajo le pri visokih pH, dinitrogvajakol pa zaradi nekoliko nižjega pKa absorbira tudi že pri rahlo kislih pH vrednostih. pH raztopin 4-nitrogvajakola in 5-nitrogvajakola različnih koncentracij smo pred fotolizo prilagodili na vrednost atmosferskih vod (pH okoli 5), nato pa smo jih izpostavili sončnemu simulatorju z močjo enega sonca. Produkte fotorazgradnje smo ločili in identificirali s tekočinsko kromatografijo sklopljeno s pretočnim spektrometrom in tandemskim masnim spektrometrom (LC-UV/Vis-MS/MS). Fotorazgradnja nitrogvajakolov poteka zelo počasi. Najdeni produkti imajo ohranjen aromatski obroč in eno ali več nitro skupin (dinitrogvajakol, 4-nitrokatehol). Zaključimo lahko, da so nitrogvajakoli v vodni fazi ozračja obstojni, absorbirajo v širokem območju pH vrednosti in s svojimi absorpcijskimi lastnostmi skupaj s produkti fotorazgradnje prispevajo k vplivu rjavega ogljika na podnebje.
Keywords:Rjavi ogljik, nitrogvajakol, fotorazpad, spektroskopske lastnosti, vpliv pH, identifikacija produktov, LC-UV/Vis-MS/MS
Year of publishing:2020
Source:Nova Gorica
COBISS_ID:17958147 Link is opened in a new window
URN:URN:SI:UNG:REP:H3B77FOJ
Views:400
Downloads:21
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Secondary language

Language:Undetermined
Title:Nitroguaiacol aging under sunlight conditions
Abstract:Nitroguaiacols are yellow-colored compounds that contribute to the absorption of brown carbon in the atmosphere. Thus, they influence the climate by absorbing sunlight in the near UV and visible regions, followed by the release of heat, which leads to climate change. They are also known for their effects on the ecosystem. Their presence in the atmosphere and formation mechanisms have already been studied, while little is known about their degradation mechanisms in the atmospheric aqueous-phase. In this work, we investigated how sunlight affects the aging of nitroguaiacols. Using photospectroscopy, we studied the spectroscopic properties of aqueous solutions of guaiacol, 4-nitroguaiacol, 5-nitroguaiacol and dinitroguaiacol, including the effect of pH. Nitroguaiacols strongly absorb in the Vis range only at high pH values, while dinitroguaiacol (lower pKa determined) absorbs also at slightly acidic pH. Before photolysis, the pH of the aqueous solutions of 4-nitroguaiacol and 5-nitroguaiacol was adjusted to that of the atmospheric waters (pH around 5) and the solutions were then exposed to a solar simulator (sunlight equivalent to one sun). Photodissociation products were separated and identified with use of liquid chromatography coupled to a flow spectrometer and tandem mass spectrometer (LC-UV/Vis-MS/MS). The photodegradation of nitroguaiacol is very slow. The detected products retained the aromatic ring, and one or more nitro groups (dinitroguaiacol, 4-nitrocatechol). The results imply that nitroguaiacols are long-lasting in the atmospheric aqueous phase and absorb in a broad pH range. With their absorption characteristics, together with the photodegradation products, they can increase the effect of brown carbon on climate change.
Keywords:Brown carbon, nitroguaiacol, photodegradation, spectroscopic characteristics, pH effect, product identification, LC-UV/Vis-MS/MS


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