The inactivation of polioviruses in soil was examined and reported upon in two chapters. The results presented in Chapter II entitled “Enterovirus Inactivation in Soil” showed that the inactivation of radioactively labeled poliovirus type-1 and coxsackievirus B-1 in soils saturated with surface water, groundwater and septic tank liquor was directly proportional to temperature. Virus persistence was also related to soil type and the liquid amendment in which viruses were suspended. At 37^oC, no infectivity was recovered from saturated soil after 12 days, and at 4^oC viruses persisted for at least 155 days. No infectivity was recovered from dried soil regardless of temperature, soil type, or liquid amendment. Additional experiments showed that evaporation was largely responsible for the decreased recovery of infectivity from drying soil, however, increased rates of inactivation at low soil moisture levels may have amplified the virucidal effects of soil evaporation.

The experimental results in Chapter III entitled “Structural Changes Associated with Poliovirus Inactivation in Soil” indicated that the loss of infectivity of poliovirus in moist and dried soils was a result of irreversible damage to the virus particles. The damage included dissociation of viral genomes and capsids, and degredation of viral RNA in the soil environment. Under drying conditions, capsid components could not be recovered from the soils. Further studies in sterile soils indicated that, under most conditions, the viral RNA was probably damaged prior to dissociation from the capsid. However, in sterile dried soil RNA genomes were recovered largely intact from the soil. These results suggest that poliviruses are inactivated by different mchanisms in moist and drying soils.

Taken together, the finds in Chapters II and III suggest that any virus hazard associated with the application of wastewater or sewage sludge to agricultural land can be greatly reduced or eliminated by allowing the soil to dry after waste application

Project No. A-052 NMEX