Virus transport through saturated sand columns as affected by different buffer solutions

To accurately examine the mechanisms that control virus retention and trans port in porous media, it is essential to perform experiments under environm entally relevant conditions. Laboratory studies of virus transport are gene rally conducted using buffered solutions. However, there are no standards f or the concentration and composition of the solution, making comparisons be tween different studies difficult. Our objective was to systematically inve stigate the effects of the ionic strength and composition of buffer solutio ns on adsorption of viruses during transport through saturated sand columns . Two phosphate buffered saline solutions (PBS and PBS2) and one artificial ground water (AGW) were used and experiments were conducted under saturate d, steady state flow conditions. Bromide tracer and bacteriophages phi X174 and MS-2 were introduced into saturated sand columns as step inputs and th eir concentrations in the outflow samples were determined. Change in ionic strength did not affect the behavior of phi X174, whereas MS-2 was largely removed in the high ionic strength PBS buffer (0.16 M) but moved through th e columns in the low ionic strength PBS2 and AGW buffers (0.002 M), An addi tional experiment conducted under an ionic strength gradient (from 0.002 to 0.2 M) using PBS indicated that the outflow concentration of MS-2 decrease d slowly from an ionic strength of similar to 0.03 M, reached a minimum at an apparent critical value of similar to 0.1 M, and then increased graduall y. This study also suggests that metals or metal oxides on sand surfaces ca n cause significant virus removal under high ionic strength conditions.