title: Conceptual model and experimental framework to determine the contributions of direct and indirect photoreactions to the solar disinfection of MS2, phiX174, and adenovirus.
abstract: Sunlight inactivates waterborne viruses via direct (absorption of sunlight by the virus) and indirect processes (adsorption of sunlight by external chromophores, which subsequently generate reactive species). While the mechanisms underlying these processes are understood, their relative importance remains unclear. This study establishes an experimental framework to determine the kinetic parameters associated with a virus' susceptibility to solar disinfection and proposes a model to estimate disinfection rates and to apportion the contributions of different inactivation processes. Quantum yields of direct inactivation were determined for three viruses (MS2, phiX174, and adenovirus), and second-order rate constants associated with indirect inactivation by four reactive species ((1)O2, OH(•), CO3(•-), and triplet states) were established. PhiX174 exhibited the greatest quantum yield (1.4 × 10(-2)), indicating that it is more susceptible to direct inactivation than MS2 (2.9 × 10(-3)) or adenovirus (2.5 × 10(-4)). Second-order rate constants ranged from 1.7 × 10(7) to 7.0 × 10(9) M(-1) s(-1) and followed the sequence MS2 > adenovirus > phiX174. A predictive model based on these parameters accurately estimated solar disinfection of MS2 and phiX174 in a natural water sample and approximated that of adenovirus within a factor of 6. Inactivation mostly occurred by direct processes, though indirect inactivation by (1)O2 also contributed to the disinfection of MS2 and adenovirus.
authors.affiliation: Laboratory of Environmental Chemistry, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mattle
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
authors.forename: Tamar
authors.initials: T
authors.lastname: Kohn
mesh_terms: D000256:Adenoviridae / Q000528:radiation effects*; D010584:Bacteriophage phi X 174 / Q000528:radiation effects*; D004203:Disinfection / Q000379:methods*; D007700:Kinetics; D017909:Levivirus / Q000528:radiation effects*; D008962:Models, Theoretical; D013472:Sunlight; D038301:Virus Inactivation / Q000528:radiation effects*; D014871:Water Microbiology