The effect of flow impedance on deposition of Cryptosporidium parvum oocysts with or without a vetiver buffer strip

Content Provider	Semantic Scholar
Author	Hussein, Jenan Mohammed Ghadiri, Hossein Lutton, Mavourneen Smolders, Andrew Schneider, Peter H.
Copyright Year	2008
Abstract	Cryptosporidium parvum oocysts can be transported in overland flow from faecal deposits of grazing animals causing potential water contamination problems. Deposition of oocysts can occur when overland flow encounters vegetative buffers and its transport capacity is decreased in the upslope backwater region. Deposition of oocysts was investigated using a large rainfall simulator, with and without a vetiver buffer strip. Oocysts-spiked slurries were applied to two contrasting soils and the resultant oocyst/ sediment depositions from the flow were compared. The buffers substantially reduced suspended sediment loads from the two soils and increased the oocyst concentration in the soil with >99% of the deposited oocysts measured upslope of the buffer. 2008 Elsevier Ltd. All rights reserved. Transport of oocysts of the protozoan parasite, Cryptosporidium parvum, from faecal deposits of grazing animals into adjacent water storage reservoirs poses potential public health risks in Australia and elsewhere (SEQWater, 2002–2003; Wohlsen et al., 2004). The oocysts are primarily transported by overland flow (Atwill et al., 2002; Trask et al., 2004) which can be intercepted by vegetative buffers (Tate et al., 2004; Ferguson et al., 2007). When flow encounters a buffer, a backwater (ponded area) is created upslope of the buffer and flow velocity and concomitant transport capacity are reduced, causing deposition of sediments (and therefore sorbed-oocysts). The backwater may extend for several metres upslope of the buffer depending on slope, flow and type of vegetation (Ghadiri et al., 2001; Hussein et al., 2007a,b) and may remove up to 98% of inflow sediment by deposition (Meyer et al., 1995; Dorioz et al., 2006). The oocyst load reduction is dependent on release from faecal deposits (Tyrrel and Quinton, 2003; Atwill et al., 2006), soil type/density (Atwill et al., 2002; Tate et al., 2004) as well as vegetation, rainfall intensity/duration and slope (Davies et al., 2004; Trask et al., 2004; Ferguson et al., 2007). In most previous studies, oocysts were applied at the upslope edge of, or in the buffers, and so the researchers did not effectively simulate the presence of the backwater and assess its effect on oocyst transport. There are therefore few representative studies on which to base an understanding of the entrapment of oocysts by backwater development. This communication compares the oocyst deposition from flow with and without the presence of a vetiver (Vetiveria zizaniodes L.) buffer strip. The work formed part of a larger project examining the effect of transport of oocysts over different soil types under applied rainfall. Soils from two contrasting grazing sites near Wivenhoe Dam in Queensland Australia (27 802600 S; 152 3901100 E) were used for the experiments: Site A (never inundated) and Site B (frequently inundated). Site B soil was more erodible due to its higher silt (Si1⁄4 41%) and lower total carbon (C1⁄4 1.1%) contents compared to the sandier Site A soil (Si1⁄4 25%, C1⁄4 2.7%). The flow experiments were carried out in the Griffith University Tilting-Flume Simulated Rainfall Facility. Three experiments were firstly conducted for each soil without a buffer. A 6 0.5 m section of the flume was lined with new black plastic for each experiment and filled with 0.06 m depth of homogenised soil (<10 mm). Soils were saturated, equilibrated for 1 h, and then random samples were taken to determine pre-test concentrations of Cryptosporidium oocysts using a sterile 10 ml syringe. All soil samples were chilled immediately (4 C) and transported to the Queensland Health Laboratory and analysed using the method of Lacovski et al. (2004). Ten minutes before rainfall application, the flume was raised to 5% slope and a purified, oocyst-spiked, suspension (100 ml of Reverse Osmosis water with 1 108 of gamma-irradiated oocysts, BTF Precise Microbiology) was applied to the soil surface, 3 m from the flume exit. Simulated rainfall (average drop diameter of 2.2 mm) was applied for 40 min at a rate of 138 5 mm h 1 * Corresponding author. Tel.: þ61 7 37116071. E-mail address: janethussein@bigpond.com (J. Hussein).
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Alternate Webpage(s)	http://www.vetiver.org/AUS_pathogens.pdf
Alternate Webpage(s)	https://research-repository.griffith.edu.au/bitstream/handle/10072/21270/52045_1.pdf;sequence=1
Language	English
Access Restriction	Open
Subject Keyword	Autonomic nervous system Bidirectional texture function Buffers Characteristic impedance Chemical vapor deposition Cryptosporidium parvum Cryptosporidium sp:Prid:Pt:Stool:Nom:Organism specific culture Dam Collapse Diameter (qualifier value) Email Emoticon Entrapment of Medical Device or Device Component Experiment Feces Fill Host-Parasite Interactions Infertility Large Maxima and minima Ninety Nine Oocysts Osmosis Persistent vegetative state Physical vapor deposition Protozoa Quantitative impedance Reservoir Device Component Resultant Sediment Simulation Simulators Soil Suspensions Velocity (software development) Vetiveria zizanioides Water Pollution Word lists by frequency
Content Type	Text
Resource Type	Article