Effects of solution chemistry on the sunlight inactivation of particles-associated viruses MS2

Abstract

The inactivation efficacy of bacteriophage MS2 by simulated sunlight irradiation was investigated to understand the effects of MS2 aggregation and adsorption to particles in solutions with different components. Kaolinite and Microcystis aeruginosa were used as model inorganic and organic particles, respectively. Lower pH and di-valent ions (Ca2+) were main factors on the aggregation and inactivation of MS2. In the presence of both particles, there was no significant impact on the MS2 inactivation efficacy by kaolinite (10–200mM) or Microcystis aeruginosa (102–105Cells/mL) in 1mM NaCl at pH 7. However at lower pH 3, MS2 aggregates formed in the particle-free and kaolinite-containing solutions, caused lower inactivation since the outer viruses of aggregation protect the inner viruses. In addition, more MS2 adsorbed on Microcystis aeruginosa at lower pH (3 and 4). Microcystis aeruginosa would act as a potential photosensitizer for ROS production to inactivate the adsorbed MS2, since extracellular organic matter (EOM) of Microcystis aeruginosa was detected in this study, which has been reported to produce ROS under solar irradiation. At pH 7, Na+ had no effect on the inactivation of MS2, because MS2 was stable and dispersed even at 200mM Na+. MS2 aggregated and adsorbed on particles even at 10mM Ca2+ and led to lower inactivation. Kaolinite cannot offer enough protection to adsorbed MS2 as aggregation and Microcystis aeruginosa acts as potential photosensitizer to produce ROS and inactivate the adsorbed MS2 at high concentration of Ca2+. In particle-free solution, SRNOM inhibited MS2 inactivation by shielding the sunlight and coating MS2 to increase its survival.