Author
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Hunter, William |
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Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/23/2012 Publication Date: 1/1/2013 Citation: Hunter, W.J. 2013. Pilot-scale vadose zone microbial biobarriers removed nitrate leaching from a cattle corral. Current Microbiology. 68:52-59. Interpretive Summary: Microbial based biobarriers are an established technique for removing contaminants from aquifers and nearly saturated soils but their ability to function in drier soils has not been evaluated under field conditions. This study evaluated the use of biobarriers in the vadose zone of a semiarid soil. This field study was conducted in cattle pen soil in northeastern Colorado and evaluated the ability of the microbial biobarriers to remove nitrate from soil water as it percolated through the soils native to the location. An important feature of the study was that the biobarriers were installed well above the water table near the soil surface. Biobarriers evaluated included a control that contained only sand and treatment biobarriers that contained sand blended with sawdust, soybean oil, or sawdust and soybean oil. Results show that the treatment biobarriers removed from 62 to 96% of the nitrate from percolating soil water and projected biobarrier life was such that barriers of this type should last for many years before substrates need to be replaced. The studies showed that simple biobarriers containing carbon substrates such as sawdust or soybean oil can be used to stimulate microbial denitrification in dry shallow soils and that biobarriers of this type might be used to prevent the movement of nitrate into groundwater. Technical Abstract: activities that involve animal wastes can result in the contamination of subsurface soils by nitrates. In saturated or nearly saturated soils microbial biobarriers are a common method used to remove contaminants from water. This field study was conducted beneath a cattle pen in northeast Colorado and evaluated the ability of vadose-zone microbial biobarriers to remove nitrate from soil water as it percolated through the semiarid soils native to the location. A distinctive feature of the study was that the biobarriers were installed well above the water table in semiarid soils near the soil surface. Biobarriers evaluated included a control that contained only sand and treatment biobarriers that contained sand blended with sawdust, soybean oil, or sawdust and soybean oil. Results show that all of the treatment biobarriers removed nitrate from percolating soil water. Water collected from beneath the control barriers contained 99 mg L-1 nitrate-N while nitrate-N levels in water that moved through the sawdust, soybean oil, and sawdust plus soybean oil based barriers averaged 4, 17, and 28 mg L-1 nitrate-N for removal efficiencies of 96, 62, and 72%, respectively. Nitrite-N, 6.8 mg L-1, was detected in waters from the sawdust plus soybean oil based barriers. With all three substrate combinations biobarrier life was such that barriers of this type should last for many years before substrates need to be replaced. The studies showed that carbon substrate addition can be used to stimulate microbial denitrification in semiarid vadose-zone soils and that shallow vadose-zone-biobarriers might be used to prevent the movement of nitrate into deeper soils. |
