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چکیده
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Agricultural manures are the source of several pathogenic microorganismsin surface and groundwater that could cause diseases and adversely affect human health. Some strains of E. coli, an indicator microorganism, when transported over and/or through the soils reaching the water resources, cause urinary tract infections, diarrheal diseases, and contribute to infant mortality, fatal renal or neurological complications. To the best of the authors' knowledge, there is no information about the bacterial transport through natural/intact calcareous and gypsiferous soils. In this study, we selected four soil types to investigate the influence of lime and gypsumcontent on transport and filtration of E. coli released fromcowmanure during saturated and unsaturated flows. Intact soil columns from Hamadan and Isfahan provinces in Iran were transported to the laboratory. Cow manure was applied to the surface of each column at a rate of 10 Mg ha −1 dry basis. Soil columns were leached up to four pore volumes (PVs) at 20 °C. E. coli influent (C )andeffluent (C) concentrations were measured by the platecount method and C o o /C values were drawn vs. PV as breakthrough curves (BTCs). Filtration coefficient (λ ), relative adsorption index (S R ), and maximumdepth of potential contamination (Z ) were calculated as indices of filtration and transport processes. Our results illustrated that contamination of water is possible where flooding irrigation systems occur in the low-lime soil due to lowionic strength and salinity, and greater structural stability. The BTCs showed that preferential pathways are greater in the low-lime soils than in the other studied soils. The presence of the natural lime and gypsum affected solution chemistry, macro and microporosity of the studied soils, which resulted in more bacterial filtration. The soils high in lime and gypsum also had maximum values for λ f and S R , respectively. MinimumZ max max was observed in the high-lime soil and its mean was significantly lo
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