10.1021/es070295h.s001
Tamar Kohn
Tamar
Kohn
Matthew Grandbois
Matthew
Grandbois
Kristopher McNeill
Kristopher
McNeill
Kara L. Nelson
Kara L.
Nelson
Association with Natural Organic
Matter Enhances the
Sunlight-Mediated Inactivation of
MS2 Coliphage by Singlet Oxygen
American Chemical Society
2007
inactivation rate constants
Suwannee river humic acid
Aldrich humic acid
SRHA
AHA
Pony lake fulvic acid
bulk solution
PLFA
Natural Organic Matter Enhances
MS 2
Singlet OxygenMS 2 coliphage
NOM
MS 2. FHA
MS 2 Coliphage
kob
mg
Fluka humic acid
1 O 2 concentration
MS 2 inactivation rate
adsorption equilibrium constants
2007-07-01 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Association_with_Natural_Organic_Matter_Enhances_the_Sunlight_Mediated_Inactivation_of_MS2_Coliphage_by_Singlet_Oxygen/2999377
MS2 coliphage, a surrogate for human enteric viruses, is
inactivated by singlet oxygen (<sup>1</sup>O<sub>2</sub>) produced via sunlight-mediated excitation of natural organic matter (NOM) in
surface waters. The <sup>1</sup>O<sub>2</sub> concentration within a NOM
macromolecule or supramolecular assembly ([<sup>1</sup>O<sub>2</sub>]<sub>internal</sub>) is
orders of magnitude higher than in the bulk solution
([<sup>1</sup>O<sub>2</sub>]<sub>bulk</sub>). In close proximity of NOM, MS2 is thus exposed
to an elevated <sup>1</sup>O<sub>2</sub> concentration ([<sup>1</sup>O<sub>2</sub>]<sub>NOM</sub>), and inactivation
is likely to be enhanced as compared to the bulk solution.
In experiments using a solar simulator, we determined [<sup>1</sup>O<sub>2</sub>]<sub>bulk</sub>,
[<sup>1</sup>O<sub>2</sub>]<sub>internal</sub>, as well as the association of MS2 with four
NOMs (Fluka humic acid, FHA; Suwannee river humic acid,
SRHA; Aldrich humic acid, AHA; Pony lake fulvic acid,
PLFA), and studied their effect on the MS2 inactivation rate
constant, <i>k</i><sub>obs,</sub> over a range of 1−25 mg NOM/L. The <i>k</i><sub>obs</sub>
values were modeled as the sum of the inactivation rate
constants in close proximity to the NOM and in the bulk
solution, assuming Langmuir-type adsorption of NOM onto
MS2. FHA and SRHA exhibited 13−22 fold greater
adsorption equilibrium constants than AHA and PLFA.
Inactivation in the bulk solution contributed between 2%
(20 mg/L FHA) and 39% (5 mg/L AHA) toward the overall <i>k</i><sub>obs</sub>.
Thus, even for the less adsorbing NOM, inactivation was
dominated by [<sup>1</sup>O<sub>2</sub>]<sub>NOM</sub> rather than [<sup>1</sup>O<sub>2</sub>]<sub>bulk</sub>. Changes in solution
chemistry to promote closer interactions between MS2
and NOM also enhanced <i>k</i><sub>obs</sub>. Addition of Mg<sup>2+</sup> to neutralize
the negative surface charge of MS2 and NOM increased
<i>k</i><sub>obs</sub> up to 4.1-fold. Similarly, lowering the solution pH closer
to the isoelectric point of MS2 (pI = 3.9) enhanced <i>k</i><sub>obs</sub> 51-fold in 5 mg/L AHA.