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This project is aimed to provide a comprehensive study on the fate and transport of viruses that are found in manures and biosolids and their potential to contaminate groundwater and food crops as a result of land application of manures and biosolids. The proposed project will be carried out in a systematic manner that integrates experiments at different scales and covers both applied and basic research components. <P>The specific objectives that will be addressed are: <ol> <LI> determine the survival potential of selected viruses in representative manures and biosolids, and on plants grown in soils amended with these materials; <LI> measure sorption and desorption of viruses by manures, biosolids, and soils; <LI> examine the soil factors and manure/biosolids application methods controlling the leaching potential of viruses using large undisturbed soil columns containing benchmark soil series of the Mid-Atlantic U.S.; <LI>elucidate the mechanisms of virus retention and transport during leaching under saturated and unsaturated flow conditions in controlled laboratory column studies.
Non-Technical Summary: Land application of manures and biosolids for the production of agronomic crops and fresh produce is a cost-effective and beneficial means to use these by-products of animal production and municipalities. However, studies have shown that manures and biosolids can contain pathogenic viruses known to cause human diseases. As a result, contamination of ground waters and food supplies by viruses found in manures and biosolids is an emerging and serious public health issue in the U.S. This project is designed to provide a comprehensive study on the effects of waste properties, types, treatment and application practices on the survival and migration of viruses in soil and groundwater, as well as on plants. The information obtained from this project will be used to develop guidelines on watershed-scale management practices that protect food safety and water quality. This project will also provide fundamental information on how viruses of different properties interact with the most reactive components of soil materials. <P> Approach: Our primary interest is in the fate and transport of pathogenic viruses that are introduced to soils through land application of manures/biosolids. The mobility of viruses will first depend on how long they can survive in their host media (e.g., manure and biosolids) and on how strongly they interact with the constituents present in these materials. Therefore, microcosm experiments will be conducted to determine the survival characteristics of selected viruses in manures and biosolids representative of those applied to crop land in the Mid-Atlantic region. Because wastes applied to land have the potential to contaminate harvestable plant tissues, the survival of those viruses on plant tissues will also be assessed. Batch-scale experiments will be conducted to measure the amount and reversibility of virus sorption by manures, biosolids, as well as the benchmark soils selected. Transport experiments will be conducted at two different scales. Large columns (20 cm i.d. by 0.5 m or 1 m in length) containing undisturbed soil cores will be used for leaching experiments under simulated rainfall conditions. These experiments will generate information on the effect of manure/biosolids physico-chemical properties and application methods on the fate and transport of viruses in soil and allow evaluation of the effects of soil type and key soil management practices on virus leaching and inactivation. Small columns (10-cm long and 3.7-cm i.d.) packed with model soil materials and homogenized soils will be used to systematically test the effect of individual key variables related to manure and biosolids application on the retention and transport of the selected viruses. These experiments will be conducted under well-characterized systems that allow careful control of individual variables, and can provide insight and direct quantitative information on virus transport under both saturated and unsaturated flow conditions. The column experiments at the two scales are complementary to each other. The large undisturbed columns, while more heterogeneous, are more representative of the natural environment. They will allow us to obtain a better understanding of the effect of soils and management practices on the extent and range in pathogen leaching that can be expected in the Mid-Atlantic U.S. The small columns are better suited for obtaining mechanistic information of the individual processes involved. The larger column experiments will help identify the key soil properties and processes and critical management factors related to virus leaching. They can also be used to guide the design of the small column experiments which, in turn, can be used to help explain the macroscopic observations made at the larger scale of the undisturbed columns. Four pathogenic viruses (hepatitis A, adenovirus, rotavirus, and norovirus) and two model bacteriophages (MS2 and phiX174), representing a wide range of survival and surface characteristics, will be used in the proposed studies. Plaque-forming-unit, cell culture, and PCR assays will be used to quantify the viruses.