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Photochemical Processes in Sunlit Surface and Atmospheric Waters

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Photochemistry".

Deadline for manuscript submissions: closed (15 December 2019) | Viewed by 23912

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Special Issue Editor

Prof. Dr. Davide Vione

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Guest Editor

Department of Chemistry, Universita degli Studi di Torino, Torino, Italy
Interests: pollutants’ photo-fate; modeling of environmental photo-reactions; surface-water photochemistry; photo-fenton reaction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It is my pleasure to invite you to contribute to this Special Issue of the MDPI journal Molecules on the topic of the photochemistry of surface (which may be broadly interpreted as both freshwater and saltwater) and atmospheric waters. This is an excellent opportunity to present original data or literature reviews on a growing research topic that encompasses both the photochemical functioning of natural ecosystems/aquatic compartments, and the photochemical degradation of pollutants or of molecules of environmental relevance (including the photoinactivation of pathogens). If you intend to contribute with a review, it is my suggestion to choose a topic where it is possible to outline the development of research in the last five years (which of course does not mean that pre-2014 citations are not allowed, but that the main body of the review should possibly cover the post-2014 research). I would also draw your attention to a couple of issues that can be of some importance:

1) The topic of photochemical processes for water and wastewater treatment is outside the scope of this issue, while the problems concerning the underwater light field in natural aquatic ecosystems are included within the scope;

2) Molecules is an open access journal, thus please have a look at the journal policy concerning the article processing charges.

I hope that you may consider the opportunity to give a contribution to this special issue, which will hopefully provide a collection of papers that will make up a reference for the scientists who work in the field, or who would like to start undertaking research in environmental photochemistry.

Sincerely,

Prof. Dr. Davide Vione
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Photochemical reactions: direct photolysis and indirect photochemistry
Photochemical functioning of natural ecosystems
Naturally-occurring photosensitisers
Photodegradation of pollutants and of important natural molecules
Photochemical generation of compounds/species of environmental importance
Photoinduced metal cycling
Combined photochemical and microbial processes
Solar disinfection and pathogen photoinactivation
Novel techniques to assess phototransformation reactions in the environment
Photochemical processes in the atmospheric aqueous phase

Published Papers (5 papers)

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Research

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14 pages, 1932 KiB

Open AccessArticle

Mapping the Photochemistry of European Mid-Latitudes Rivers: An Assessment of Their Ability to Photodegrade Contaminants

by Luca Carena and Davide Vione

Molecules 2020, 25(2), 424; https://doi.org/10.3390/molecules25020424 - 20 Jan 2020

Cited by 7 | Viewed by 3215

Abstract

The abiotic photochemical reactions that take place naturally in sunlit surface waters can degrade many contaminants that pose concern to water bodies for their potentially toxic and long-term effects. This works aims at assessing the ability of European rivers to photoproduce reactive transient intermediates, such as HO^• radicals and the excited triplet states of chromophoric dissolved organic matter (³CDOM*), involved in pollutant degradation. A photochemical mapping of the steady-state concentrations of these transients was carried out by means of a suitable modeling tool, in the latitude belt between 40 and 50°N. Such a map allowed for the prediction of the photochemical lifetimes of the phenylurea herbicide isoproturon (mostly undergoing photodegradation upon reaction with HO^• and especially ³CDOM*) across different European countries. For some rivers, a more extensive dataset was available spanning the years 1990–2002, which allowed for the computation of the steady-state concentration of the carbonate radicals (CO₃^•⁻). With these data, it was possible to assess the time trends of the photochemical half-lives of further contaminants (atrazine, ibuprofen, carbamazepine, and clofibric acid). The calculated lifetimes were in the range of days to weeks, which might or might not allow for efficient depollution depending on the river-water flow velocity. Full article

(This article belongs to the Special Issue Photochemical Processes in Sunlit Surface and Atmospheric Waters)

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34 pages, 4381 KiB

Open AccessArticle

A Critical View of the Application of the APEX Software (Aqueous Photochemistry of Environmentally-Occurring Xenobiotics) to Predict Photoreaction Kinetics in Surface Freshwaters

by Davide Vione

Molecules 2020, 25(1), 9; https://doi.org/10.3390/molecules25010009 - 18 Dec 2019

Cited by 37 | Viewed by 4045

Abstract

The APEX (aqueous photochemistry of environmentally occurring xenobiotics) software computes the phototransformation kinetics of compounds that occur in sunlit surface waters. It is free software based on Octave, and was originally released in 2014. Since then, APEX has proven to be a remarkably flexible platform, allowing for the addressing of several environmental problems. However, considering APEX as a stand-alone software is not conducive to exploiting its full potentialities. Rather, it is part of a whole ecosystem that encompasses both the software and the laboratory protocols that allow for the measurement of substrate photoreactivity parameters. Coherently with this viewpoint, the present paper shows both how to use APEX, and how to experimentally derive or approximately assess the needed input data. Attention is also given to some issues that might provide obstacles to users, including the extension of APEX beyond the simple systems for which it was initially conceived. In particular, we show how to use APEX to deal with compounds that undergo acid–base equilibria, and with the photochemistry of systems such as stratified lakes, lakes undergoing evaporation, and rivers. Hopefully, this work will provide a reference for the smooth use of one of the most powerful instruments for the modeling of photochemical processes in freshwater environments. All authors have read and agreed to the published version of the manuscript. Full article

(This article belongs to the Special Issue Photochemical Processes in Sunlit Surface and Atmospheric Waters)

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14 pages, 2474 KiB

Open AccessArticle

Microbiological Evaluation of 5 L- and 20 L-Transparent Polypropylene Buckets for Solar Water Disinfection (SODIS)

by M. Inmaculada Polo-López, Azahara Martínez-García, Maria Jesus Abeledo-Lameiro, Hipolito H. Gómez-Couso, Elvira E. Ares-Mazás, Aurora Reboredo-Fernández, Tracy D. Morse, Lyndon Buck, Kingsley Lungu, Kevin G. McGuigan and Pilar Fernández-Ibáñez

Molecules 2019, 24(11), 2193; https://doi.org/10.3390/molecules24112193 - 11 Jun 2019

Cited by 22 | Viewed by 4655

Abstract

Background: Solar water disinfection (SODIS) is an appropriate technology for household treatment of drinking water in low-to-middle-income communities, as it is effective, low cost and easy to use. Nevertheless, uptake is low due partially to the burden of using small volume polyethylene terephthalate bottles (1.5–2 L). A major challenge is to develop a low-cost transparent container for disinfecting larger volumes of water. (2) Methods: This study examines the capability of transparent polypropylene (PP) buckets of 5 L- and 20 L- volume as SODIS containers using three waterborne pathogen indicators: Escherichia coli, MS2-phage and Cryptosporidium parvum. (3) Results: Similar inactivation kinetics were observed under natural sunlight for the inactivation of all three organisms in well water using 5 L- and 20 L-buckets compared to 1.5 L-polyethylene-terephthalate (PET) bottles. The PP materials were exposed to natural and accelerated solar ageing (ISO-16474). UV transmission of the 20 L-buckets remained stable and with physical integrity even after the longest ageing periods (9 months or 900 h of natural or artificial solar UV exposure, respectively). The 5 L-buckets were physically degraded and lost significant UV-transmission, due to the thinner wall compared to the 20 L-bucket. (4) Conclusion: This work demonstrates that the 20 L SODIS bucket technology produces excellent bacterial, viral and protozoan inactivation and is obtained using a simple transparent polypropylene bucket fabricated locally at very low cost ($2.90 USD per unit). The increased bucket volume of 20 L allows for a ten-fold increase in treatment batch volume and can thus more easily provide for the drinking water requirements of most households. The use of buckets in households across low to middle income countries is an already accepted practice. Full article

(This article belongs to the Special Issue Photochemical Processes in Sunlit Surface and Atmospheric Waters)

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Graphical abstract

11 pages, 2414 KiB

Open AccessArticle

The Effects of Reactant Concentration and Air Flow Rate in the Consumption of Dissolved O₂ during the Photochemistry of Aqueous Pyruvic Acid

by Alexis J. Eugene and Marcelo I. Guzman

Molecules 2019, 24(6), 1124; https://doi.org/10.3390/molecules24061124 - 21 Mar 2019

Cited by 10 | Viewed by 5904

Abstract

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O₂(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O₂(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O₂(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min⁻¹. For the range of [PA]₀ covered under air saturated conditions and 30 mL min⁻¹ flow of air in this setup, the estimated half-lives of O₂(aq) consumed by the photolytic radicals fall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O₂(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O₂-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol. Full article

(This article belongs to the Special Issue Photochemical Processes in Sunlit Surface and Atmospheric Waters)

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Review

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23 pages, 1728 KiB

Open AccessReview

Photochemistry of the Cloud Aqueous Phase: A Review

by Angelica Bianco, Monica Passananti, Marcello Brigante and Gilles Mailhot

Molecules 2020, 25(2), 423; https://doi.org/10.3390/molecules25020423 - 20 Jan 2020

Cited by 37 | Viewed by 5432

Abstract

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H₂O₂, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO^• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate. Full article

(This article belongs to the Special Issue Photochemical Processes in Sunlit Surface and Atmospheric Waters)

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