As the demand for water increases across the southwestern United States, the region's utilization of and dependence on water stored in groundwater aquifers has risen in kind. The Coconino Aquifer (C-aquifer) underlies much of the southwestern Colorado Plateau and is a primary source of groundwater in northeastern Arizona. One of the largest commercial users of water from the C-aquifer in Apache County, Arizona, is Springerville Generating Station, a coal-fired power plant owned and operated by Tucson Electric Power. The area surrounding the power plant, located between the cities of Springerville and St. Johns, Arizona (the Springerville-St. Johns area), is geologically complex: it contains the Cedar Mesa anticline, an underlying CO2 reservoir, extensive travertine deposits, and several faults, including the Coyote Wash fault. The Coyote Wash fault and Cedar Mesa anticline play a significant role in the relationships between the St. Johns CO2 gas field, groundwater flow, and the travertine deposits. Yet, the interaction between the structures and the effect they have on groundwater flow is poorly constrained. By mapping the subsurface geology utilizing borehole records and by creating a groundwater model of the area, this study determined that the Cedar Mesa anticline acts as a partial horizontal barrier to groundwater flow, whereas the Coyote Wash fault does not act as such a barrier. Particle tracking for the model indicates that despite the reduced water volume in the aquifer after decades of groundwater extraction, flow still occurs across the hinge of the Cedar Mesa anticline, accelerated by active pumping wells located west of the anticline axis. The model indicates that prior to the activation of the pumping wells, outflow from the C-aquifer would have occurred with greater frequency to Lyman Lake and along the extent of the Little Colorado River located downstream from the lake. The study also identified a zone of high hydraulic conductivity located between the Cedar Mesa anticline and the Coyote Wash fault that continues west of the Coyote Wash fault and may align with the Buttes anticline. This model of groundwater flow conditions improves the understanding of the complex subsurface geology and groundwater flow dynamics in the area.

Climate change and increasing sea level elevation are predicted to increase salinity in estuarine tidal wetlands in the Southeastern United States. Since much of the ecosystem function in these areas is predicated upon salinity regimes, many fundamental changes are likely to occur as a result. The influence of salinity and SO4 2- reduction on PO4 3- release from tidal wetland soils was evaluated along a salinity gradient at three sites in The St. John’s River, Florida using both field and laboratorybased methods. Porewater was sampled over the course of 10 months to determine ambient levels of SO4 2- and PO4 3-. Lab-based experiments, soils samples were subjected to seawater and SO4 2- treatments in an attempt to induce PO4 3- release. Salinity was lowest at Sixmile Creek (0.45 ± 0.1 g kg-1) and Goodby’s Creek (2.05 ± 2.3 g kg-1) and much higher at Sister’s Creek (27.81 ± 3.1 g kg-1). The organic content of soils was highest (82.35% ± 5.11) at Sixmile Creek, intermediate at Goodby’s Creek (64.45% ± 7.02) and lowest at Sister’s Creek (32.11% ± 9.61). Total soil P was highest at the freshwater Sixmile Creek (1101.64 ± 220.2 μg g-1), intermediate at the brackish Goodby’s Creek (719.61 ± 114.3 μg g-1) and lowest at the Sister’s Creek saltmarsh (475.85 ± 110.9 μg g-1). Porewater PO4 3- was higher at Sixmile and Goodby’s Creek sites (9.44 ± 15.6, 8.99 ± 14.7 !g L-1, respectively) compared to Sister’s Creek (0.6 ± 3.1 !g L-1). Porewater SO4 2- was lower at Sixmile (70.73± 57.58 !g L-1) and Goodby’s Creeks (124.35 ± 152.5 !g L-1) compared to Sister’s Creek (1931.41 ± 557.82 !g L-1). Temporal and spatial trends indicated that SO4 2- and PO4 3- in porewater was likely due to floodwater content and that direct reaction between analytes in soils was unlikely. The addition of aerated seawater failed to cause PO4 3- release from any sites. The incubation of soils under anaerobic conditions, in the presence of Na2SO4 induced SO4 2- reduction, but inhibited PO4 3- flux from both Sixmile and Goodby’s Creek, which is attributed here to likely S- toxicity (Roychoudhury et al., 1999). PO4 3- flux from Sister’s Creek increased in association with Na2SO4 concentration, likely due to more Fe availability to mitigate Stoxicity. Ambient seawater additions to soils under anaerobic conditions followed a similar trend, but the results were not statistically conclusive. Overall, both field and labbased data indicated that Tidal wetland porewater PO4 3- likely originates from floodwaters and that increased salinity and SO4 2- reduction did not directly enhance soil PO4 3- fluxes.