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The aggregation, transport and deposition kinetics (i.e. attachment and release) of TiO(2) nanoparticles (nano-TiO(2)) were investigated as a function of ionic strength and the presence of anionic (sodium dodecylbenzene sulfonate, SDBS) and non-ionic (Triton X-100) surfactants in 100% critical micelle concentration (CMC). The electrolyte concentration of the suspensions dictated the kinetic stability of nano-TiO(2) thus influencing the transport and retention of the nanoaggregates in the saturated porous medium. With increasing ionic strength, the interaction between approaching nano-TiO(2) and nano-TiO(2) already deposited onto collectors surfaces seemed to be more favorable than the interaction between approaching nano-TiO(2) and bare collectors surfaces. The abrupt and gradual reduction in electrolyte concentration during the flushing cycles of the column experiments induced the release of previously deposited nano-TiO(2) suggesting attachment of nano-TiO(2) through secondary energy minimum., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Traditional microscopy methods for the detection and quantification of Cryptosporidium parvum in soil matrices are time-consuming, labor-intensive, and lack sensitivity and specificity. This research focused on developing a qPCR protocol for the sensitive and specific detection and quantification of C. parvum in natural soil matrices and soil-water extracts. The physico-chemical parameters - lysis media, number of thermal shocks and thawing temperatures - controlling DNA extraction efficiency were investigated. Experimental results identified oocyst age as a critical parameter affecting oocyst disruption and quantification. The most efficient oocyst disruption method for C. parvum oocysts regardless of their age was established as 5 thermal shocks with thawing at 65°C in Tris-EDTA (TE) buffer. In addition to the purification columns used to remove PCR inhibitors present in environmental matrices, a combination of 3mM MgCl(2) and 600ng/μl BSA yielded the highest amplicon yield for both young and aged oocysts. Sucrose flotation was determined to be a better oocyst isolation method than two-phase flotation. The optimized parameters for DNA extraction and the qPCR assay resulted in very specific and sensitive detection of C. parvum. Minimum detection limits were 0.667 for young C. parvum oocysts and 6.67 for aged C. parvum oocysts per PCR reaction. The accuracy of the detections and quantifications was 0.999. Protocol performance was tested in contrasting soil samples and soil-water extract samples on the basis of percentage of recovery (PR) values. Depending on the number of oocysts used to inoculate the samples, the average PR values ranged from 7.2 to 43.5%, 29.3-52.5%, and 11.5-60.8% for Trenton, Greenson, and Sparta soil-water extracts, respectively, and 12.1-77% for DI water. PR values ranged from 4.3% to 107.8% for Trenton, Greenson and Sparta soil samples., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Transport of manufactured nano-TiO(2) in saturated porous media was investigated as a function of morphology characteristics, pH of solutions, flow velocity, and the presence of anionic and non-ionic surfactants in different concentrations. Surfactants enhanced the transport of nano-TiO(2) in saturated porous media while a pH approaching the point of zero charge of nano-TiO(2) limited their transport. The deposition process, a retention mechanism of nano-TiO(2) in saturated porous media was impacted by surfactant and pH. In Dispersion 1 systems (pH 7), the size of the nano-TiO(2) aggregates was directly related to the presence of surfactants. The presence of non-ionic surfactant (Triton X-100) induced a size reduction of nano-TiO(2) aggregates that was dependent on the critical micelle concentration. In Dispersion 2 systems (pH 9), the stability provided by the pH had a significant effect on the size of nano-TiO(2) aggregates; the addition of surfactants did impact the size of the nano-TiO(2) aggregates but in less significance as compared to Dispersion 1 systems. The electrostatic and steric repulsion forces in connection with the size of nano-TiO(2) aggregates and flow velocity impacted the single-collector efficiency and attachment efficiency which dictated the maximum transport distance of nano-TiO(2) for the Dispersion 1 and Dispersion 2 systems. By doubling the flow velocity at pH 9, the No Surfactant, 50% CMC Triton X-100, 100% CMC Triton X-100 and 100% CMC SDBS dispersion systems allowed nano-TiO(2) to attain maximum transport distances of 0.898, 2.17, 2.29 and 1.12 m, respectively. Secondary energy minima played a critical role in the deposition mechanisms of nano-TiO(2). Nano-TiO(2) deposited in the secondary energy wells may be released because of changes in solution chemistry. The deposition of nano-TiO(2) in primary and secondary energy minima, the reversibility of their deposition should be characterized to analyze the transport of nanoparticles in porous media. This is necessary to assess the risk of nanoparticles to the environment and public health., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

To investigate the coupled effects of solution chemistry and hydrodynamics on the mobility of quantum dot (QD) nanoparticles in the vadose zone, laboratory scale transport experiments involving single and/or sequential infiltrations of QDs in unsaturated and saturated porous media, and computations of total interaction and capillary potential energies were performed. As ionic strength increased, QD retention in the unsaturated porous media increased; however, this retention was significantly suppressed in the presence of a non-ionic surfactant in the infiltration suspensions as indicated by surfactant enhanced transport of QDs. In the vadose zone, the non-ionic surfactant limited the formation of QD aggregates, enhanced QD mobility and transport, and lowered the solution surface tension, which resulted in a decrease in capillary forces that not only led to a reduction in the removal of QDs, but also impacted the vadose zone flow processes. When chemical transport conditions were favorable (ionic strength of 5 × 10(-4)M and 5 × 10(-3)M, or ionic strengths of 5 × 10(-2)M and 0.5M with surfactant), the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were meso-scale processes, where infiltration by preferential flow results in the rapid transport of QDs. When chemical transport conditions were unfavorable (ionic strength of 5 × 10(-2)M and 0.5M) the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were pore-scale processes governed by gas-water interfaces (GWI) that impact the mobility of QDs. The addition of surfactant enhanced the transport of QDs both in favorable and unfavorable chemical transport conditions. The mobility and retention of QDs was controlled by interaction and capillary forces, with the latter being the most influential. GWI were found to be the dominant mechanism and site for QD removal compared with solid-water interfaces (SWI) and pore straining. Additionally, ripening phenomena were demonstrated to enhance QDs removal or retention in porous media and to be attenuated by the presence of surfactant., (Copyright © 2010 Elsevier B.V. All rights reserved.)

When oocysts of the protozoan Cryptosporidium parvum contaminate drinking water supplies, they can cause outbreaks of Cryptosporidiosis, a common waterborne disease. Of the different pathways by which oocysts can wind up in drinking water, one has received little attention to date; that is, because soils are often considered to be perfect filters, the transport of oocysts through the subsoil to groundwater is generally ignored. To evaluate the significance of this pathway, a series of laboratory experiments investigated subsurface transport of oocysts. Experiment 1 was carried out in a vertical 18-cm-long column filled either with glass beads or silica sand, under conditions known to foster fingered flow. Experiment 2 involved undisturbed, macroporous soil columns subjected to macropore flow. Experiment 3 aimed to study the lateral flow on an undisturbed soil block. The columns and soil samples were subjected to artificial rainfall and were allowed to reach steady state. At that point, feces of contaminated calves were applied at the surface along with a known amount of potassium chloride to serve as a tracer, and rainfall was continued at the same rate. The breakthrough of oocysts and chloride, monitored in the effluent, demonstrate the importance of preferential flow on the transport of oocysts. Compared with chloride, peak oocyst concentrations were not appreciably delayed and, in some cases, occurred even before the chloride peak. Recovery rates for oocysts were low, ranging from 0.1 to 10.4% of the oocysts originally applied on the columns. However, the numbers of oocysts present in the effluents were still orders of magnitude higher than 10 oocysts, the infectious dose considered by the U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, to be sufficient to cause Cryptosporidiosis in healthy adults. These results suggest that the transport of oocysts in the subsurface via preferential flow may create a significant risk of groundwater contamination in some situations.

Non-aqueous phase liquids enter the vadose zone as a result of spills or leaking underground storage facilities, thus contaminating groundwater resources. Measuring the contaminant concentrations is important in assessing the risk to human health and the environment and to develop effective remediation. This research presents the development and application of the light transmission method (LTM) for three-phase flow systems, aimed at investigating unstable fingered flow in a soil-air-oil-water system. The LTM uses the hue and intensity of light transmitted through a slab chamber to measure fluid content, since total liquid content is a function of both hue and light intensity. Evaluation of the LTM is obtained by comparing experiments with LTM and synchrotron X-rays. The LTM captures the spatial resolution of the fluid contents and can provide new insights into rapidly changing, two-phase and three-phase flow systems. Application of the LTM as a visualization technique for environmental and physical phenomena is noted. Visualization by LTM of groundwater remediation by surfactants as well as visualization of model cluster growth and fractal dimensions was also explored.