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Transport of manure-borne Cryptosporidium parvum oocysts through saturated and unsaturated soil columns.

机译:粪便传播的隐孢子虫卵囊通过饱和和不饱和土壤柱的运输。

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Release of manure-borne Cryptosporidium parvum oocysts is the most probable cause of ground and surface water contamination with this pathogen. Our objective was to assess the effect of water saturation on transport of manure-borne oocyst through soil cores. Manure seeded with oocysts was applied on the surface of 10 cm columns filled with either sandy loam or clay loam soils. An eight-hour rainfall simulation provided saturated flow in one set of columns whereas the other set had suction ca. 5 kPa applied at the bottom. The convective-dispersion model with exponential release boundary condition, instantaneous adsorption and first-order kinetic removal of oocysts was used to simulate the transport. Transport parameters were found by fitting the van Genuchten analytical solution to the oocyst profile distributions. Oocysts stayed mostly within the top 8 cm of soil columns. Cumulative oocyst contents in leachates from unsaturated columns were less than 0.1% whereas the saturated columns allowed breakthrough of 0.4 and 1.3% in sandy loam and clay loam soil cores, respectively. The model mimicked the profile distributions of oocysts very well, but failed to simulate breakthrough of small amounts of oocysts. Values of retardation coefficient were less than unity in saturated columns and greater than unity in unsaturated columns. Values of the soil partition coefficient Kd derived from the retardation coefficient values were much less than values reported earlier from batch experiments with the same soils. The removal rates were much higher in saturated than in unsaturated columns. Soil water saturation substantially affected the manure-borne oocyst transport..
机译:粪便传播的隐孢子虫卵囊的释放是该病原体污染地下水和地表水的最可能原因。我们的目标是评估含水饱和度对粪便传播的卵囊通过土壤核心的运输的影响。将接种有卵囊的肥料施于10厘米长的充满沙壤土或粘土壤土的柱子表面。八小时的降雨模拟在一组色谱柱中提供了饱和水流,而另一组色谱柱的吸力约为。底部施加5 kPa。利用具有指数释放边界条件,卵囊的瞬时吸附和一级动力学去除的对流扩散模型来模拟运输。通过将van Genuchten分析解决方案拟合到卵囊轮廓分布中找到运输参数。卵囊大部分留在土壤柱的顶部8厘米之内。来自不饱和柱的渗滤液中的卵囊累积含量小于0.1%,而饱和柱允许沙壤土和粘土壤土的土壤芯分别突破0.4和1.3%。该模型很好地模拟了卵囊的轮廓分布,但未能模拟少量卵囊的穿透。延迟系数的值在饱和柱中小于1,在非饱和柱中大于1。由延迟系数值得出的土壤分配系数Kd的值远小于先前在相同土壤条件下进行分批实验所报告的值。饱和状态下的去除率比不饱和状态下的去除率高得多。土壤水分饱和度极大地影响了粪便传播的卵囊的运输。

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