Identification of recharge waters, groundwater flowpaths, and solute sources is needed to best manage the increasing salinity of the Hueco Bolson aquifer, the primary water resource for El Paso, Texas and Juárez, Mexico. To address these issues, we have analyzed for a suite of geochemical tracers on water samples collected from 33 discrete vertical zone test holes. On the basis of δD and δ¹⁸O data, two regional recharge sources were recognized, one originating from western mountain-fronts and one from through-flow of the adjacent Tularosa aquifer. Chloride concentrations were strongly correlated with lithologic formations and both Cl/Br and ³⁶Cl ratios suggested halite dissolution within the Ft. Hancock formation as the primary chloride source. In contrast, sulfur isotopes indicated that most sulfate originates from Tularosa Permian gypsum sources. These sources suggested that chloride salinization of wells is the result of direct upconing of waters from the Ft. Hancock formation.

The Middle San Pedro Basin in southeastern Arizona is a typical alluvial basin in the semi-arid southwestern United States with a rapidly growing population that is dependent upon groundwater resources for water supply. This study investigated recharge areas, compartmentalization and potential mixing of water sources, and travel times of groundwater throughout the basin using variations in major ion chemistry (water type, Ca/Sr ratios, SO4/Cl ratios) and isotope ratios (18O, 2H, 3H, 34S, 13C, 14C) of groundwaters, surface waters and precipitation in conjunction with hydrogeologic data (e.g. hydraulic head and hydrostratigraphy). Recent recharge (<50 years) has occurred within mountain systems along the basin margins, and in shallow floodplain aquifers adjacent to the San Pedro River. Groundwaters in confined aquifers in the central basin were recharged at high elevation in the fractured bedrock and have been extensively modified by water-rock reactions over long timescales (up to 34,600 years). These results can be used to constrain physical assumptions of future groundwater flow models designed to help make improved water management decisions.

Degradation of streams in urban-rural fringe regions occurs through complex interactions between hydrological, physical, chemical and biological mechanisms of the stream environment and surrounding landscape. Biological monitoring using macroinvertebrates may capture the complex and cumulative influences of land activity on the stream environment. The Salmon River catchment in the township of Langley, British Columbia, Canada straddles urban and rural environments in the Lower Fraser Valley. To date the Salmon River catchment has been subject to several environmental surveys. Following these earlier investigations, this study quantified relationships between the stream environment and changing land activity, across multiple scales, from 1975 to 2005, using macroinvertebrates as environmental integrators. Current and historical water, sediment, and macroinvertebrate information along with land use and land-cover evaluations were used to quantify relationships between the macroinvertebrate community and land activity in the catchment. Spatial and seasonal results for specific conductivity (a total dissolved ion indicator) and NO₃⁻-N and PO₄³ (nutrient indicators) traced groundwater and overland inputs to the stream environment. Nitrate guideline exceedances occurred at groundwater-influenced sites. Elevated sediment trace metal concentrations and Zn guideline exceedances occurred mid-reach in the catchment. Peak total macroinvertebrate and sensitive taxa abundance occurred mid-reach in the catchment in 2005, while richness and proportional sensitive abundance peaks were seen at groundwater-influenced sites. The dominance of tolerant to moderately pollution tolerant taxa occurred throughout. Despite historical water quality concerns at groundwater-influenced sites, greater shifts in community composition occurred in headwaters regions. Patterns of land use and land cover changed in sensitive areas (i.e. above aquifer and in the headwaters). A greater number of correlations between land activity and macroinvertebrate measures occurred at streams sites with 100 m buffers. The abundance of sensitive taxa positively correlated with the amount of agricultural land use, while rarefaction declined. Several Macroinvertebrate functional feeding groups correlated positively to forest cover, while sensitive taxa abundance and Zn concentrations declined. Results suggest continued water quality and sediment trace metal concerns, while macroinvertebrate results point to nutrient enrichment and greater historical variability in headwaters regions. Agricultural activity appears to have a stronger influence on aspects of the stream environment despite the presence of urban-rural land activity.

Nitrate, arsenic and vanadium are all potential groundwater contaminants. Traditional physical/chemical methodologies are often too technical or expensive for rural environments. Biofiltration has been shown to remove a wide range of contaminants depending on the operating parameters. This research examined the possibility of using the denitrifying bacteria, Paracoccus denitrificans, to remove nitrate, arsenic and vanadium simultaneously from groundwater with varying iron concentrations. During bench-scale testing nitrate concentrations were reduced by up to 73%, even with the metals present. Without iron, arsenic and vanadium removal was insignificant. Removal increased when iron was added as it was found that arsenic and vanadium could be removed adsorptively by iron hydroxides. With 1 mg/L of iron present, removal rates of 67% and 91% were achieved for arsenic and vanadium, respectively. When the iron was increased to 2 mg/L, the removal rates increased to 85% and 96%, respectively.

No description available.

Both onsite septic disposal systems and private drinking water wells are commonly utilized in rural areas of Canada. The coexistence of septic systems and drinking water wells has the potential to greatly impact the quality of water obtained in these settings. Human enteric viruses have been recognized as a potential source of groundwater borne disease, although the level of risk they pose and the processes responsible for their transport are poorly understood. As a result of thin overburden, low storage capacity, and high groundwater velocities, fractured rock aquifers are potentially at highest risk to viral contamination. However, only limited research has been conducted to explore this concern. The current study was conducted to investigate both the rate of occurrence of human viruses in fractured rock aquifers and the transport mechanisms acting in these settings. A survey was conducted to identify the prevalence of human enteric viruses in three fractured rock aquifers located across Canada. A total of 61 samples were collected from 28 wells drilled in aquifers in Ontario, Newfoundland, and British Columbia. Molecular PCR techniques were utilized to determine virus presence. Results showed that 37.7% of samples and 58.1% of wells were at some time positive for viruses. Virus presence was found to increase with housing density and viruses were found to travel distances of at least 40 meters. Poor correlation was found between the presence of viruses and traditional bacterial indicators. A field-scale viral infiltration experiment was conducted to investigate viral transport behavior. The bacteriophage ф-X174 and the fluorescent dye Lissamine FF were utilized as viral and solute tracers, respectively. Tracers were applied to an exposed rock outcrop exhibiting fractures with known connection to two nearby wells. Breakthrough was extremely rapid and the colloidal processes of decreased dispersion and slow-release kinetic sorption were identified. This study has provided concrete evidence that viral contamination poses a significant threat to fractured groundwater aquifers in rural areas where onsite septic disposal practices are utilized. The results observed in this study suggest that current set back distances and monitoring techniques may be inadequate to prevent exposure to human viruses. / Thesis (Master, Civil Engineering) -- Queen's University, 2010-11-09 23:07:31.595

No description available.

An assessment of the groundwater quality at the Olusosun landfill in Lagos, Nigeria was conducted to determine interactions between the landfill wastes and the groundwater and the potential migration of pollutants into the neighbouring communities. Groundwater samples were collected from four locations within the landfill bi-weekly for three months (March 19, 2013 to May 28, 2013), and analysed for water quality parameters and metals. The results indicated that the concentrations of some metals (Cr, Fe, Cd, Mn, and Co) and other water quality parameters in some sampling locations were slightly above the World Health Organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ) standard limits. Lead was also detected in the groundwater samples, though at concentrations within the standard limits. Conclusively, the Olusosun landfill has impaired groundwater quality, thereby, posing environmental and human health concerns to the neighbouring communities of Oregun, Ketu and Ojota.

Multiple parameters were monitored during an 18-month period in two karst groundwater basins in Woodford County, Kentucky, in order to assess the effects of land use on water quality. Blue Hole Spring drains a primarily urban area, whereas spring SP-2 drains an agricultural area. Water-quality parameters were monitored manually weekly or biweekly, as well as more frequently during storms. Discharge (Q), temperature (T), specific conductance (SC), and turbidity were continuously monitored and logged at 15-minute intervals. It is hypothesized that pathogen and sediment concentrations would be lower at SP-2 than at Blue Hole Spring due to differences in land use between basins. Average Q was greater at Blue Hole than at SP-2, and SC values were greater at Blue Hole than at SP-2 for 70 of 71 sample sets. During two monitored storms, as Q increased, SC decreased and turbidity increased. Biweekly Blue Hole fecal coliform (FC), total coliform (TC), and atypical colonies (AC) values averaged 160, 3,600, and 40,000 cfu/100 mL, respectively, and fluctuated more than at SP-2. Biweekly SP-2 FC, TC, and AC values averaged 130, 2,000, and 8,300 cfu/100 mL, respectively. Biweekly values for AC/TC averaged 14.29 at Blue Hole and 6.27 at SP-2. AC/TC ratios were greater at Blue Hole than at SP-2 for 29 of 31 biweekly sample sets. There is a statistically significant difference between the biweekly data sets from the two sites, as well as between data collected under WET and NORMAL flow conditions at each site. Male-specific coliphage (MSP) was detected in most samples collected from Blue Hole, but was never detected at SP-2. Given the proximity of the basins, differences in water quality appear to reflect differences in land use, as hypothesized. Results were similar to other studies in the Inner Bluegrass region. For both Blue Hole and SP-2, wet weather was associated with changes in certain parameters. This study has also shown that the AC/TC ratio appears to be a valid tool for determining the source of contamination within karst ground-water systems as well as in surface water.

The design of pump and treat systems for groundwater remediation is often aided by numerical groundwater modelling. Model predictions are uncertain, with this uncertainty resulting from unknown parameter values, model structure and future system forcings. Researchers have begun to suggest that uncertainty in groundwater model predictions is largely dominated by structural/conceptual model uncertainty and that multiple conceptual models be developed in order to characterize this uncertainty. As regulatory bodies begin to endorse the more expensive multiple conceptual model approach, it is useful to assess whether a multiple model approach provides a signi cant improvement over a conventional single model approach for pump and treat system design, supplemented with a factor of safety. To investigate this question, a case study located in Tacoma, Washington which was provided by Conestoga-Rovers & Associates (CRA) was used. Twelve conceptual models were developed to represent conceptual model uncertainty at the Tacoma, Washington site and a pump and treat system was optimally designed for each conceptual model. Each design was tested across all 12 conceptual models with no factor of safety applied, and a factor of safety of 1.5 and 2 applied. Adding a factor of safety of 1.5 decreased the risk of containment failure to 15 percent, compared to 21 percent with no factor of safety. Increasing the factor of safety from 1.5 to 2 further reduced the risk of containment failure to 9 percent, indicating that the application of a factor of safety reduces the risk of design failure at a cost directly proportional to the value of the factor of safety. To provide a relatively independent estimate of a factor of safety approach a single "best" model developed by CRA was compared against the multiple model approach. With a factor of safety of 1.5 or greater, adequate capture was demonstrated across all 12 conceptual models. This demonstrated that in this case using the single \best" model developed by CRA with a factor of safety would have been a reasonable surrogate for a multiple model approach. This is of practical importance to engineers as it demonstrates that the a conventional single model approach may be su cient. However, it is essential that the model used is a good model. Furthermore, a multiple model approach will likely be an excessive burden in cases such as pump and treat system design, where the cost of failure is low as the system can be adjusted during operation to respond to new data. This may not be the case for remedial systems with high capital costs such as permeable reactive barriers, which cannot be easily adjusted.