THE REVERSIBILITY OF VIRUS ATTACHMENT TO MINERAL SURFACES

Virus transport through groundwater is limited by attachment to minera l surfaces and inactivation. Current virus transport models do not con sider the implications of the reversibility of virus attachment to min erals. To explore the reversibility of virus attachment to mineral sur faces, we attached PRD1, a bacteriophage considered to be a good model of enteric viruses, to quartz and ferric oxyhydroxide-coated quartz s urfaces over a range of pH values in equilibrium ''static columns.'' F ollowing attachment, we detached the viruses by replacing the pore sol ution with solutions of equal and higher pH. The extent of virus attac hment followed an attachment ''edge'' that occurred at a pH value abou t 2.5-3.5 pH units above the pH(IEP) of the mineral surfaces. Viruses attached below this edge were irreversibly attached until the pH of th e detachment solution exceeded the pH value of the attachment edge. Vi ruses attached above this edge were reversibly attached. Derjaguin-Lan dau-Verwey-Overbeek (DLVO) potential energy calculations showed that t he attachment edge occurred at the pH at which the potential energy of the primary minimum was near zero, implying that the position of the primary minimum (attractive or repulsive) controlled the equilibrium d istribution of the viruses. The results suggest that the reversibility of virus attachment must be considered in virus transport models for accurate predictions of virus travel time.