|Malone, Robert - Rob|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2009
Publication Date: 9/11/2009
Citation: Guzman, J., Fox, G., Malone, R.W., Kanwar, R. 2009. Escherichia coli Transport from Surface-Applied Manure to Subsurface Drains through Artificial Biopores. Journal of Environmental Quality. 38:2412-2421. Interpretive Summary: Previous research suggests that bacteria move to subsurface drains primarily through soil cracks and biopores (e.g., worm holes). However, this phenomena is poorly understood. Therefore, we investigated the importance of surface connected and disconnected (buried) biopores on Escherichia coli (E. coli) transport to biopores in close proximity to subsurface drains. In surface connected biopores, E. coli transport to the drain was dependent on the soil type and the layer thickness between the end of the biopore and drain. Buried biopores contributed flow and E. coli to the drain in the less sorptive soil (loamy sand) and the sorptive soil (sandy loam) containing a wide pore space distribution caused by the soil packing technique. Our research confirms that biopores can result in rapid transport of E. coli into subsurface drains and deepens our understanding of the mechanisms involved with this. This research will help scientists more clearly understand the flow of bacteria though soil and design farming practices that reduce this movement to streams and rivers.
Technical Abstract: Transport of pathogenic bacteria in soils primarily occurs through soil mesopores and macropores (e.g., biopores and cracks). Field research has demonstrated that biopores and subsurface drains can be hydraulically connected. This research was conducted to investigate the importance of surface connected and disconnected (buried) biopores on Escherichia coli (E. coli) transport when biopores are located near subsurface drains. A soil column (28 x 50 x 95 cm) was packed with loamy sand and sandy loam soils to bulk densities of 1.6 and 1.4 Mg m-3, respectively, and containing an artificial biopore located directly above a subsurface drain. The sandy loam soil was packed using two different methods: moist soil sieved to 4.0 mm and air dried soil manually crushed and then sieved to 2.8 mm. A 1-cm constant head was induced on the soil surface in three flushes: (1) water, (2) diluted liquid swine manure with E. coli 48 hours later, and (3) water 48 hours after the manure. E. coli transport to the drain was observed with either open surface connected or buried biopores. In surface connected biopores, E. coli transport to the drain was a function of the soil type and the layer thickness between the end of the biopore and drain. Buried biopores contributed flow and E. coli to the drain in the less sorptive soil (loamy sand) and the sorptive soil (sandy loam) containing a wide (i.e., with mesopores) pore space distribution prevalent due to the moist soil packing technique. Biopores provide a mechanism for rapidly transporting E. coli into subsurface drains during flow events.