Modelling the removal and reversible immobilization of murine noroviruses in a Phaeozem under various contamination and rinsing conditions

Abstract

Enteric viruses entering the soil with contaminated irrigation water can reach groundwater or be internalized in plants through their roots without being inactivated. Their fate in the soil depends on the virus, the soil and the soil solution. In order to write a mathematical model suitable for a Calcaric Phaeozem, we investigated the removal of murine norovirus and reversible immobilization in aggregate columns according to a saturation procedure, conditions between contamination and rinsing time, temperature and soil solution. Viruses were quantified before and after 0.45‐μm filtration with an RT‐qPCR (real‐time polymerase chain reaction). Experimental results supported a model that combined free and colloidal transport of viruses in mobile water, exchange of free viruses between mobile and immobile water, virus removal and reversible virus adsorptions on suspended colloids, the outer aggregate surface and the inner aggregate particles. For an artificial soil solution at 20°C, the fate of viruses in contaminations lasting 1 to 7 days followed by 7 hours of rinsing was described by combining 0.38 log10 daily removal and weak reversible immobilization using a Freundlich adsorption isotherm (kF = 1120, nF = 1.53), which explained why free viruses prevailed in mobile water. Partial drying without aggregate desaturation did not affect virus recovery. Magnesium cation enrichment induced geochemical changes that faded over time, resulting in up to ten times more viruses adsorbed on suspended colloids than free and enhanced adsorption on outer aggregate surfaces. Likewise, groundwater rich in Mg2+ slowed remobilization. The fate of murine norovirus within a Calcaric Phaeozem can be described by a model that takes into account geochemical fluctuations.Highlights How far does soil reduce the risk of noroviruses from irrigation reaching groundwater or roots? Virus removal over a 5‐day average residence time in Phaeozem is about two log10. Reversible virus immobilization is weak; Mg intake favours it, together with colloidal transport. Virus removal and reversible adsorption can be modelled for better assessment of contamination risk.