Chemical actinometry

Kuhn, H. J.; Braslavsky, Silvia E.; Schmidt, R.

doi:10.1351/pac198961020187

Cited by 208 publications

(149 citation statements)

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“…Samples were transported to the laboratory under refrigeration. Sampling dates and lake features are reported in (Kuhn et al, 2004). Figure 1 shows the emission spectrum of the lamps, taken with an Ocean Optics SD2000 CCD spectrophotometer and normalised to the actinometry data, taking into account the Pyrex TMP is a suitable probe to measure the formation rate of T*, R T* (Halladja et al, 2007;Minella et al, 2011) …”

Section: Methodsmentioning

confidence: 99%

Photochemical production of organic matter triplet states in water samples from mountain lakes, located below or above the tree line

Laurentiis¹,

Minella²,

Maurino³

et al. 2012

Chemosphere

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davide.vione@unito.it (D.V.). AbstractThe production of triplet states (T*) of chromophoric dissolved organic matter (CDOM), reacting with the probe molecule 2,4,6-trimethylphenol (TMP) was measured upon irradiation of water samples, taken from lakes located in a mountain area (NW Italy) between 1450 and 2750 m above sea level. The lakes are located below or above the tree line and surrounded by different vegetation types (trees, alpine meadows or exposed rocks). The most photoactive samples belonged to lakes below the tree line and their fluorescence spectra and CDOM optical features suggested the presence of a relatively elevated amount of humic (allochthonous) material. The lowest (negligible) photoactivity was found for a lake surrounded by exposed rocks. Its CDOM showed an important autochthonous contribution (due to in-lake productivity) and considerably higher spectral slope compared to the other samples, suggesting low CDOM molecular weight and/or aromaticity.Among the samples, CDOM photoactivity (measured as the rate of TMP-reactive T* photoproduction) decreased with changing vegetation type in the order: trees, meadows, rocks. It 3 could be connected with decreasing contribution from catchment runoff and increasing contribution from autochthonous processes and possibly precipitation.

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Section: Methodsmentioning

confidence: 99%

Photochemical production of organic matter triplet states in water samples from mountain lakes, located below or above the tree line

Laurentiis¹,

Minella²,

Maurino³

et al. 2012

Chemosphere

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“…power metre equipped with a UV-sensitive probe. The incident photon flux in the solution volume was (5.32±0.41)⋅10 −5 Einstein L −1 s −1 , actinometrically determined with the ferrioxalate method (Kuhn et al, 2004). The lamp emission spectrum was measured with a calibrated Ocean Optics USB2000 CCD spectrophotometer and normalised to the actinometry data, to obtain the spectral photon flux density reported in Figure 1.…”

Section: Aqueous Solution Experimentsmentioning

confidence: 99%

Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles

Laurentiis

Socorro

Vione

et al. 2013

Atmospheric Environment

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Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone in aqueous solution and at the aerosol interface: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles. Atmos. Environ. 2013, 81, 569-578. DOI: 10.1016/j.atmosenv.2013 You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions:(1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.(2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy. AbstractIn addition to direct photolysis, degradation of organic compounds by solar light can also occur by indirect photolysis or photo-sensitised processes. These reactions are important because they are involved in, among others, direct and indirect climate changes, adverse health effects from inhaled particles, effects on cloud chemistry and ozone production. In this work, the importance of atmospheric photo-sensitisation is evaluated in bulk aqueous solution and on the surface of aerosol deliquescent particles. Irradiation experiments in aqueous solution indicate that 4-carboxybenzophenone (CBP) is able to photosensitise the degradation of 4-phenoxyphenol (4PP). The process takes place via the CBP triplet state ( 3 CBP*), which has an oxidising nature. 4PP is fluorescent, unlike the photosensitizer CBP, with two emission bands at ∼320 and ∼380 nm. However, addition of CBP to a 4PP solution considerably decreases the intensity of 4PP fluorescence bands and causes a very intense new band to appear at ∼420 nm. This behaviour suggests a possible interaction between CBP and 4PP in solution, which could favour further light-induced processes. Moreover, the new band overlaps with the fluorescence spectrum of atmospheric HULIS (HUmic-LIke Substances), suggesting that supramolecular photosensitizer-substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4PP coated on silica particles (gas-solid system) was also investigated under simulated sunlight, and in the presence of variable relative humidity. The water molecules inhibit the degradation of 4PP, induced by 3 CBP* on the surface of aerosol particles, indicating that the process could be even faster on particles than in solution. We demonstrate that phenol substances adsorbed on aerosol surfaces and in bulk solution are substantially altered upon photosensitised processes.

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“…(Milan, Italy) power meter. The incident photon flux in solution was 3.1×10 −6 Einstein L −1 s −1 , measured by ferrioxalate actinometry (Kuhn et al, 2004). Figure 1 reports: (i) the emission spectrum of the lamp, measured with an Ocean Optics SD 2000 CCD spectrophotometer and normalised to the actinometry results, and (ii) the absorption spectrum of MCPA at two different pH values, taken with a Varian Cary 100 Scan UV-Vis spectrophotometer.…”

Section: Irradiation Experimentsmentioning

confidence: 99%

Effect of dissolved organic compounds on the photodegradation of the herbicide MCPA in aqueous solution

Vione

Khanra²,

Das³

et al. 2010

Water Research

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This works shows that the addition of phenol and 2-propanol as model organic compounds significantly decreases the direct photolysis quantum yield of 4-chloro-2-methylphenoxyacetic acid (MCPA) upon UVB irradiation in aqueous solution. Laser flash photolysis data suggest that 2-propanol is able to decrease the formation of the MCPA excited states under irradiation. A decrease from 0.54 to 0.34 of the photolysis quantum yield of the anionic form of MCPA (which prevails over the undissociated one in surface waters) could have a considerable impact on the MCPA lifetime in ecosystems where the direct photolysis is the main phototransformation pathway. In surface water bodies where the direct photolysis has comparable kinetics as the reaction with • OH, a decrease of the quantum yield would enhance the relative importance of the • OH pathway, which yields considerably less toxic intermediates than the direct photolysis.

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Chemical actinometry

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Cited by 208 publications

References 0 publications

Photochemical production of organic matter triplet states in water samples from mountain lakes, located below or above the tree line

Photochemical production of organic matter triplet states in water samples from mountain lakes, located below or above the tree line

Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles

Effect of dissolved organic compounds on the photodegradation of the herbicide MCPA in aqueous solution

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