Evapotranspiration (ET) can affect treatment performance in constructed wetlands by enhancing constituent transport through the hydrosoil where treatment reactions occur. Additionally, ET can decrease volumetric flow thereby increasing hydraulic retention time and increasing concentrations of dissolved constituents. This research aims to assess the net effects of water loss attributed to ET on constructed wetland performance and determine the significance of plant transpiration on vertical transport of constituents. A flowing wetland lysimeter constructed using 265-L storage containers filled with sand and Typha latifolia was used to record ET and determine crop coefficient during summer 2011. Results indicate that ET from the lysimeter was 2.5 times greater than calculated reference ET (K c = 2.5; R 2 = 0.96). The calculated crop coefficient was used in conjunction with a first-order tank-in-series model to predict removal of a conservative constituent (k = 0.2 d-1) and readily treatable constituent (k = 1.2 d-1) in a constructed wetland (20 cm and 40 cm water depths, 4-day nominal HRT, and 100 mg L-1 constituent loading) operating under a range of ET (0, 10, 20, and 30 mm d-1). The model predicts that removal efficiency of the conservative constituent decreases with increasing ET, while removal efficiency of the readily treatable constituent increases with increasing ET. In addition, eight vertical tracer tests were performed on wetland cells with either trimmed or untrimmed T. latifolia to measure transport time of tracer solution from the water surface to a depth of 5 cm. Mean tracer arrival time differed significantly (p = 1.2 x 10-8) between the untrimmed and trimmed cells (104 minutes versus 450 minutes, 3 respectively) demonstrating that plant transpiration contributes significantly to vertical flow through hydrosoil.

Detrital-zircon U-Pb geochronology documents a regional- to continental-scale drainage reorganization along the eastern Gulf Coastal Plain (USA) from the Late Cretaceous (Cenomanian) to the Paleocene–Eocene. We present detrital-zircon U-Pb ages and Th/U values from the Maastrichtian Ripley Formation to determine the sedimentary provenance and to provide spatiotemporal resolution of drainage reorganization. The Ripley Formation contains a 12.7% overall average abundance of detrital zircons with low (< 0.1) Th/U values relative to the underlying Cenomanian Tuscaloosa Group (3.6%), the overlying Paleocene–Eocene Wilcox Group (2.8%), an Appalachian foreland composite (2.1%), and the laterally equivalent McNairy Sandstone in the northern Mississippi Embayment (3.8%). Multidimensional scaling of detrital-zircon U-Pb spectra shows that the Ripley Formation is dissimilar from underlying and overlying Gulf Coastal Plain units, the McNairy Sandstone, and an Appalachian foreland composite sample because of differences in proportions of Appalachian (490–270 Ma) and Grenville (1250–900 Ma) zircons. We interpret the southern Appalachian Piedmont province as the principal sediment source region for the Ripley Formation to account for the elevated abundance of grains with low (< 0.1) Th/U values and unique detrital-zircon U-Pb age spectra. Results suggest a regional-scale (105 km2) drainage network, which delivered sediment to the Maastrichtian coast followed by northwestward littoral transport and eventual mixing with Appalachian foreland-derived sediment in the northern Mississippi Embayment. This study further brackets drainage reorganization along the eastern Gulf Coastal Plain and demonstrates how simple chemical–age relationships, such as zircon Th/U values coupled with U-Pb ages, can be used to evaluate sediment provenance.

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Here we isolate groundwater responses to atmospheric forcing of surface water levels by relating anomalies in coastal aquifer hydraulic head time‐series to weather events. Our results demonstrate that atmospheric forcing has a greater effect on groundwater exchange and extended residence time over astronomical tidal pumping at times. During winter, atmospheric groundwater forcing was associated with winter storm passage and had a recurrence interval of approximately 7 days. During summer, atmospheric groundwater forcing was limited to weak diurnal atmospheric convection and infrequent tropical cyclone activity. Because winter storms and tropical cyclones commonly produce precipitation, atmospheric groundwater forcing can synergize with the timing of meteoric recharge producing periods of intense submarine groundwater discharge.

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Constructed wetlands have been used to treat contaminants, including ammonia and nitrate, with varying degrees of success; however, no study has been performed to evaluate ammonia treatment performance of a constructed wetland specifically designed to promote biogeochemical conditions controlling nitrification and denitrification. Therefore, this research aims to improve the design of treating ammonia using constructed wetlands by targeting biogeochemical conditions needed for nitrification and denitrification. A pilot-scale constructed wetland was designed and constructed to meet targeted ranges of dissolved oxygen concentration, hydrosoil redox potential, pH, alkalinity, and organic carbon availability to enhance nitrification and denitrification. Design features included aeration, sucrose, and oyster shell addition. The constructed wetland decreased ammonia-N from *20 mg/L in inflow to nondetectable levels ( < 0.1 mg/L) in outflow during three of the four treatment months. Measured biogeochemical conditions indicate that nitrification continued to occur while hydrosoil redox potential, dissolved oxygen concentration, and pH were lower than the targeted ranges. Conversely, denitrification continued to occur while pH was lower than the targeted range, and dissolved oxygen concentration was higher than the targeted range. The success of the constructed wetland in removing ammonia and nitrate under conditions outside of target ranges was attributed to the existence of heterogeneous macro-and microenvironments within individual wetland cells that allow both reactions to occur simultaneously under a wider range of conditions than previously expected. Results from this study demonstrated the advantage of designing constructed wetlands to promote biogeochemical conditions for improved ammonia treatment and also provide the basis for treatment of ammonia-contaminated produced waters.

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