Microbial and chemical tracer movement through Granular, Ultic, and Recent Soils

Abstract

The ability of New Zealand soils to renovate dairy-shed effluent following application to land is being evaluated. We investigated the pattern of transport of faecal coliforms, a host-specific Salmonella bacteriophage and a non-reactive chemical tracer (Br-), when applied to large, intact lysimeter soil cores (460 mm dia. × 520-700 mm high) of three contrasting soils. The soils were imperfectly drained Ultic and Granular Soils and a well-drained Recent Soil. A depth of 25 mm of dairy-shed effluent containing faecal coliforms and spiked with bacteriophage and Br-was applied to the soil at a rate of 5 mm h -1 followed by up to 1 pore volume of simulated rainfall applied at 5 mm h -1 . This application rate is generally much slower than the soil's saturated hydraulic conductivity except in the Ultic Soil where saturated hydraulic conductivity is slower. Resulting leachates, collected continuously, were analysed for the microbial and bromide tracers. The phage tracer moved rapidly through all soils, peaking early in the leachates and then tailing off in a pattern indicative of bypass flow. Faecal coliforms also moved rapidly through the Ultic and Granular Soils but numbers were much lower or not detectable in leachate from the Recent Soil. In contrast, bromide moved uniformly through Granular and Recent Soils but peaked early at about 0.5-0.8 pore volume.The microbial data suggest the soil structure in the Ultic and Granular Soils makes them vulnerable to leaching of microbes into shallow water bodies.

Interaction of Escherichia coli and Soil Particles in Runoff

“…The key findings of these soil column experiments have been that the breakthrough curves for bacteria are very different from those of a conservative chemical tracer, thereby implying that different transport mechanisms are involved (19,20,26). In our studies of the horizontal transport of E. coli, the most striking result is the very similar shapes and timings of the E. coli and bromide breakthrough curves.…”

Prioritisation of farm scale remediation efforts for reducing losses of nutrients and faecal indicator organisms to waterways: A case study of New Zealand dairy farming

“…Nonetheless, some obvious sources have been identified that provide a few clues as to where mitigations might be best targeted in the first instance. Documented sources of faecal bacteria transferred from grazed pastoral soils to waterways include the rapid drainage loss of irrigated FDE applied to soils that exhibit a high degree of preferential flow (McLeod et al, 2003(McLeod et al, , 2004, rain-fed mole-pipe drainage , border dyke wash (Carey et al, 2004) and effluent pond discharges (Craggs et al, 2004;Hickey et al, 1989). Overland flow is also believed to be a major contributor of the total microbial load delivered to streams (Hunter et al, 1992;Vinten et al, 2004).…”

Leaching and ponding of viral contaminants following land application of biosolids on sandy-loam soil

“…Preferential flow was reported in earlier lysimeter work McLeod et al, 2001McLeod et al, , 2003McLeod et al, , 2004Pang et al, 2008;Jiang et al, 2008). The transport rate measured in laboratory scale experiments may be considerably lower than the transport rate in the natural environment because the preferential flow pathways allow contaminants to bypass the soil matrix.…”

“…Several researchers have evaluated lysimeters containing undisturbed soil to investigate manure contaminant and microbial tracer transport in soil systems Carlander et al, 2000;McLeod et al, 2001McLeod et al, , 2003McLeod et al, , 2004Pang et al, 2008;Jiang et al, 2008). Soil depth in these lysimeters ranged from 40 to 100 cm with diameters ranging from 30 to 60 cm (volume ranged from 0.028 to 0.28 m 3 ).…”