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Contaminated fomites are a cause of concern for the spread of health care-associated infections (HAI's). Previous research has placed emphasis on fomites in patient rooms and patient bathrooms with limited focus on the spread of microorganisms on fomites in non-patient care areas. The present study monitored surrogate virus tracer (MS2 coliphage) spread from public restrooms (used by staff and visitors) to waiting areas in a surgical ward in a Level I Trauma Center. The coliphage (virus) MS2 was added onto the entrance door handle of male and female public restrooms. Four hours later, various surfaces in the restroom and waiting area were sampled. Sampling periods were conducted in duplicate consisting of before cleaning, cleaning with the current cleaning product and procedure and cleaning with an intervention (inclusion of a bleach based disinfectant wipe) in addition to the current cleaning product and procedures. Before cleaning took place, the virus tracer was detected on all 21 of the sites sampled in the restrooms and 5/9 sites within the hallway ranging from 15-50 feet from the restroom. These results indicated that a virus could spread from public restrooms to other sites in the restroom and to locations in the surgical ward. The addition of a bleach based disinfectant wipe reduced the virus by another 90% compared to current disinfecting and cleaning procedures. Coliphage MS2 has been used as a model virus for norovirus and rhinovirus since they exhibit similar survival on fomites and resistance to disinfectants. The data generated can be used in quantitative microbial risk assessment models to assess the risk of pathogens spreading from restrooms to patient waiting areas and patient care areas in healthcare settings. Based on this study, facilities should consider broadening their cleaning and disinfection protocols to include both patient care and non-patient care areas.

The Lower Colorado River Giant Salvinia Task Force has tried a series of physical and chemical activities in an effort to control and eradicate giant salvinia (Salvinia molesta) since 1999. Because these efforts have not produced satisfactory results, biological control using the weevil Cyrtobagous salviniae (Coleoptera: Curculionidae) was applied on the Lower Colorado River by the Animal and Plant Health Inspection Service, United States Department of Agriculture offices in California and Arizona. They released the weevil at four sites in the summer of 2003, four sites in 2004, and eight sites in 2005.We monitored physico-chemical and biological parameters at release and 10 m and 1 km down stream from release sites. Weevils established their colony in the field, but control has not been determined. Integrated pest management (physical, chemical, and biological methods) will be essential for successful management of salvinia in the Lower Colorado River.The low temperature resistance and survival rates of the weevils were tested under three different diurnal temperature regimes (5 to 15 oC , 10 to 20 oC , and 15 to 25 oC ) and two different salvinia densities. At the low temperature range, the survival rate of the weevil was sharply decreased. The relationship between low temperature resistance of weevils and giant salvinia population was tested at the 5 to 15 oC range. The experiment was conducted at three different giant salvinia populations (0, 1, and 3 salvinia per container). The salvinia density had no significant effect on the survival of the weevil.To examine a more efficient method of biological control, we conducted a nitrogen fertilizer experiment on the river. Our goal was to demonstrate that plants fertilized with nitrogen would support a faster growing population of C. salviniae. In the Lower Colorado River, the weevil successfully survived winter and dispersed down the river.

Increasing atmospheric levels of carbon dioxide (CO2) and the potential impact on climate change has caused an increased effort to more accurately quantify terrestrial sources and sinks. Semiarid grasslands cover a significant portion of the Earth's land surface and may be an important sink for atmospheric CO2. This study was conducted to examine the role semiarid grasslands play in the carbon cycle. The relation between surface reflectance and temperature obtained from satellite imagery was used to determine a Water Deficit Index (WDI) to estimate distributed plant transpiration rates for a point in time. Due to the relationship between transpiration and plant CO2 uptake, WDI was directly related to CO2 flux. Satellite images were acquired for a five-year period (1996-2000) during which transpiration and net CO2 flux were measured for a semiarid grassland site in southeastern Arizona. Manual and automatic chamber data were also collected in 2005 and 2006 and used to assess the spatial variability of nighttime soil respiration. Spatial analysis showed the most influential factor affecting nighttime respiration was aspect, where flux from North-facing slopes was significantly (P < 0.05) higher than on South-facing slopes. A strong linear relationship (R2 = 0.97) existed between WDI-derived instantaneous net CO2 flux and daytime net CO2 flux estimates, and was used to generate maps of distributed daytime net CO2 flux. A linear relationship (R2 = 0.88) was also found between daytime and nighttime net CO2 flux, and used in combination with maps of daytime net CO2 flux to create maps of daily net CO2 flux. This study indicated that remote sensing offers an operational, physically-based means of obtaining daily net CO2 flux in semiarid grasslands.

Nanoparticles are an emerging contaminant of concern. They are used in many products and industries and, due to a lack of regulation, are entering the natural environment through our waste streams. Studies examining the transport of nanoparticles in porous media have observed divergences between data and theory. Transport data also varies greatly across studies, adding complexity to the determination of the important factors in nanoparticle transport. These main factors and key areas of deviation from theory were determined by comparing and contrasting various studies of nanoparticle transport. To further examine behavior and retention mechanisms of nanoparticles in porous media, nano-sized titanium dioxide (nano-TiO₂) was used in miscible-displacement transport experiments, followed by force measurements by Atomic Force Microscopy (AFM) between the same nanoparticles and porous media. Ionic strength ranged from 0.0015 - 30 mM, and solution chemistries were varied from pH 4.5 (favorable attachment) to 8 (unfavorable attachment). To determine the possible presence of secondary minima attachment, detachment transport experiments were performed for the unfavorable attachment conditions. Calculations were performed using DLVO theory, which is often used to describe colloid and nanoparticle retention, and compared to measured force profiles. Mass recoveries for the transport experiments ranged from 28-80%. Retention under favorable conditions was much greater than under unfavorable conditions, as was anticipated. Detachment was observed, indicating the potential presence of secondary minima. Large adhesive forces were measured by AFM and were affected by solution chemistry. Force profiles were highly variable, especially under unfavorable attachment conditions. Secondary minima were observed, even at a 0.0015 mM ionic strength. DLVO theory, while qualitatively accurate, largely under-predicted attractive and repulsive forces and their range of influence. Variability in the force profile and potential conformational changes of nanoparticle aggregates were postulated to be influential in nanoparticle transport. Retention of the nanoparticles under unfavorable conditions was postulated to involve secondary minima and the effects of surface roughness. These mechanisms, which are not represented in DLVO theory, are likely causes of the observed divergence of experimental results from theory. Improved understanding of retention mechanisms will hopefully enhance our understanding of the potential impacts of nanoparticles on the natural environment.

Due to the history of hardrock mining in the southwestern United States, environmental contamination at legacy mine sites is an ongoing problem. Mine wastes, the primary source of contamination, particularly tailings are the uneconomical byproducts of hardrock mining that are generally deposited near a mine. Due to the geochemistry of sulfide orebodies (the source of many valuable metals including Zn, Pb, and Cu), the residues of sulfide ore extraction often have high concentrations of toxic contaminants such as As, Pb and Cd, which are released into the environment due to chemical and mineralogical changes following exposure of the tailings to oxygen and water. The secondary precipitates formed by tailings oxidation are primarily fine particles and due to the dry climate of desert southwestern US, the lack of soil moisture and structure, and the lack of vegetative cover on the tailings surface, contaminated dusts consisting of these secondary precipitates can be generated and spread to nearby communities by wind erosion of the tailings surface. Ingestion or inhalation of these wind-borne dusts can cause health problems resulting from contaminant exposure that depend on the lability of the contaminants in the biofluids that the dust particles come into contact with, a parameter that can be determined using in vitro bioaccessibility assays. This research project concentrated on a tailings pile at the Iron King Mine and Humboldt Smelter Superfund site (IKMHSSS), a disused mine site located in the town of Dewey-Humboldt, AZ. Previous studies at IKHMSSS have revealed that the top meter of the tailings pile encompasses the entirety of a general pyrite (FeS₂) weathering sequence, with the lower levels dominated by pyrite and other minor sulfide minerals (e.g. ZnS, FeAsS, PbS), an intermediate layer dominated by sulfate salts, ferrihydrite and other amorphous Fe(III) oxyhydroxides, and a surface layer dominated by crystalline tertiary precipitates such as jarosite (KFe₃(SO₄)₂(OH)₆). Samples were taken from seven distinct layers differentiated by color, texture and morphological characteristics, and the PM₁₀ fraction of each sample was isolated using a cyclone dust generator. The PM₁₀ samples were then treated with synthetic biofluids designed to mimic physiological conditions present in the human respiratory system and gastrointestinal tract, and the aqueous concentations of As, Fe, Pb and SO₄ were measured at successive time points to determine the chemical kinetics of contaminant release into the synthetic interstitial fluids. The solution data was complemented by x-ray diffraction and x-ray absorption spectroscopy experiments performed at the Stanford Synchrotron Radiation Laboratory. These studies found that the in vitro bioaccessibility of both Pb and As was highest for the unweathered deep tailings samples and lowest for the partially-oxidized transition zone samples. The primary factors found to control bioaccessibility were the presence of labile Fe³⁺ and SO₄²⁻ in the samples, both of which are required to drive the precipitation of secondary minerals capable of incorporating trace elements such as As and Pb into their structure.

Perfluorinated compounds (PFCs) are a class emerging contaminants that have been implicated in bladder cancer and other human health problems. Due to the widespread exposure to humans, persistence in the environment, and their negative effects on human health, we need to develop a treatment method to degrade these chemicals into harmless species. Perfluorooctanoic acid (PFOA, C₈HF₁₅O₂) is one of the top representatives of PFCs commonly reported to be found in water sources, hence it was chosen as the model compound and focus in this project. We examined an iron-activated persulfate oxidation (IAPO) method to decompose aqueous PFOA, and tested the reaction under various conditions, including: oxic, anoxic, and anoxic/dark conditions. We observed 𝑐𝑎. 64% of PFOA (beginning with solution phase concentration fo 𝑐𝑎. 1.64*10⁻⁶ mol L⁻¹) was transformed after four hours under anoxic conditions. This was about seven times higher than measured under oxic conditions, and about five times higher than anoxic/dark conditions. Therefore, we concluded that IAPO can decompose PFOA at 25 °C, the ambient condition temperature. This method can potentially be used as an inexpensive and environmentally-friendly PFOA remediation method, with potential application to other PFCs in groundwater and soil. In addition, this method may be applicable for surface water sources such as potable water reservoirs, waste water effluent, and extracted groundwater.

Chlorinated solvents, such as tetrachloroethene (PCE), trichloroethene (TCE), and carbon tetrachloride (CT), are primary contaminants of concern for a vast majority of federal and state Superfund sites in the US due to their prior widespread use as solvents for numerous industrial and commercial applications. Source-zones containing large quantities of contaminant are typically present at sites contaminated by chlorinated solvents. Particularly in regions such as the SW US, these source zones reside, at least in part, in the extensive vadose zones typical of these regions. There are two primary concerns associated with sites that contain vadose-zone contaminant sources. First, discharge of contaminant vapor from the vadose-zone source may impact the underlying groundwater. This could contribute to overall risk posed by the site, and delay attainment of groundwater cleanup goals. Second, contaminant vapor from the vadose-zone source may migrate to the land surface and transfer into buildings, thereby causing vapor intrusion. The focus of this research is the development and application of innovative methods for characterizing vadose-zone contamination. Phytoscreening is a new, rapid, and relatively low-cost characterization technology that can be used to screen an area for the presence of select contaminants such as chlorinated VOCs. Phytoscreening is based on the sampling and analysis of plant tissues (branch, trunk, leaf, seed, needle) to detect the presence of contamination in soil and groundwater. Phytoscreening is applied to three sites in Arizona to evaluate its use in semi-arid environments. In addition, all available field data sets have been compiled to examine potential correlations between contaminant concentrations measured for tree tissue and those for groundwater. Contaminant concentrations were detected in tree tissue samples collected from two of the three Arizona sites. A review of the field site data suggests that a correlation exists between PCE and TCE concentrations measured for tree tissue and those measured in groundwater. The correlation can be used to estimate vegetation concentrations when groundwater concentrations are known. The reasonable degree of correlation supports the use of phytoscreening as a robust screening tool to provide a first-order characterization of anticipated concentrations of contaminants in groundwater. This tool can also be used to screen an area for vapor intrusion potential. A sampling method for the determination of chlorinated contaminant vapor concentrations present in the vadose zone, specifically trichloroethene (TCE), has been developed, and was applied at the Tucson International Airport Authority (TIAA) Superfund site. The method was modified from the NIOSH Manual of Analytical Methods (NMAM) # 1022 for TCE, and is targeted to situations requiring cost effective sample collection, particularly for cases when concentrations are at or below maximum contaminant levels (MCLs). In the modified NIOSH method, TCE vapor is sampled using a solid sorbent cartridge containing coconut shell charcoal arranged into primary and secondary sections. Gas Chromatography with Mass Spectrometry is used to confirm and quantify the presence of TCE. The results of laboratory tests demonstrate a maximum TCE vapor load of approximately 22 mg before breakthrough to the secondary section, and a recovery of approximately 97%. The results of a performance comparison test conducted in the field demonstrated that results obtained with the cartridge samplers were similar to those obtained with the use of standard Summa canisters. Landfill waste often serves as a long-term source of volatile organic compounds (VOCs) in the vadose zone. In turn this contamination can have a significant impact on groundwater and on residential or commercial indoor air quality through vapor intrusion. Sulfur hexafluoride (SF₆) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF₆, CH₄, CO₂, and VOCs. The travel times determined for SF₆ from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate only gas phase diffusion. In addition, significant concentrations of CH₄ and CO₂ were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF₆ are caused by advective transport associated with landfill gas generation. A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. A well-defined source zone was created by injection and extraction of a non-reactive gas (SF₆). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local-extraction point, whereas increases were observed for monitoring points located between the local-extraction point and the source zone. The results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.

Arid lands comprise vast regions of terrestrial land, highlighting the importance of understanding their role in the global carbon cycle. The objective of this study was to determine the effect of Prosopis velutina (mesquite), Larrea tridentata (creosote) and a combination of Bouteloua barbata, Bouteloua aristidoides, Aristida adscensionis, and some Cynodon dactylon (mixed grass) vegetation types on soil organic carbon (SOC) dynamics and quality in an arid, hyperthermic ecosystem of southern Arizona. This was accomplished by quantifying vegetation type control over: (i) local scale SOC stocks; (ii) soil aggregate stability; (iii) SOC turnover and microbial community composition; (iv) the distribution of SOC in physically defined fractions; and (v) the thermal nature and composition of SOC. The results from this study demonstrated significant variation in SOC dynamics and quality between vegetation with potential feedbacks to SOC sequestration of atmospheric CO₂.

An invasive variety of the common reed Phragmites australis, the M haplotpye, has been implicated in the spread of this species into North American salt marshes normally dominated by the salt marsh grass Spartina alterniflora (smooth cordgrass). Phragmites australis is spreading into North American coastal marshes that are experiencing reduced salinities, while Spartina spp. are spreading into northern European brackish marshes that are experiencing increased salinities. We compared the salt tolerance and other growth characteristics of the invasive, M haplotype with two native haplotypes (F and AC) in greenhouse experiments. The M haplotype retained 50% of its growth potential up to 0.4 M NaCl, whereas the F and AC haplotypes did not grow above 0.1 M NaCl. The M haplotype produced more shoots per gram of rhizome tissue and had higher relative growth rates than the native haplotypes on both freshwater and saline water treatments. The M haplotype also differed from the native haplotypes in shoot water content and the biometrics of shoots and rhizomes. The results offer an explanation for how the M haplotype is able to spread in coastal salt marshes and support the conclusion of DNA analyses that the M haplotype is a distinct ecotype of P. australis.We then compared the growth, competitive ability, salt tolerance and osmotic adjustment of M haplotype P. australis and S. alterniflora along a salinity gradient in greenhouse experiments. Spartina alterniflora produced new biomass up to 0.60 M NaCl, whereas P. australis did not grow well above 0.2 M NaCl. When the two species were grown in mixed cultures, P. australis was less affected by competition than S. alterniflora at lower salinities but the competitive advantage reversed above 0.2 M NaCl. The greater salt tolerance of S. alterniflora compared to P. australis was due to its ability to use Na+ for osmotic adjustment in the shoots. On the other hand, at low salinities P. australis was more competitive because it produced more shoots per gram of rhizome tissue than S. alterniflora. These studies illustrate how ecophysiological differences shift the competitive advantage from one species to another along a salinity gradient.