No description available.

Increased use of fertilisers and pesticides has raised levels of agricultural pollution in surface and ground waters. Organism using these water sources are at risk of exposure to ammonium nitrate fertiliser. The effects of ammonium nitrate on spawn, larva and adult common frogs was investigated using ammonium nitrate fertiliser in solution and granular form at various stages of frog development. The concentrations used, up to 100mgIL NO-3-N used reflect nitrate concentrations on agricultural land in the United Kingdom in water bodies located within and adjacent to agricultural land at times when common frogs are actively breeding or developing. Nitrate concentrations in frog breeding ponds were high (> 1OOmgIL NO-3-N) during the frog breeding season, especially when water entered from field drains, but significantly lower (<25 mglL) for the remainder of the year. Frogs did not show a selective preference for ponds with low nitrate concentrations. Frog spawn swelled when exposed to ammonium nitrate and its viability was reduced (87% survival in controls; 63% at 80 mgIL NH\NO-3). The 96 hour LCso for frog larvae was 781 mglL (95% confidence intervals of 587 to 942) and the 48 hour ECso was 399 mgIL (95% Cl = 234 to 546). Long term exposure to 100 mgIL NW4NO-3 in a flow through system reduced larval survival from 85% (controls) to 53% after 96 days, with most mortality occurring during the three weeks prior to metamorphosis. Larval growth was affected marginally but with some evidence of enhanced mass in the treated larvae, especially at the lowest nitrate concentration of 25 mWL NH\NO-3. Metamorphosis in this group was earlier than in the other groups; by day 80, 48% of the metamorphs had emerged, by comparison with 38, 34 and 24% for the controls and those exposed to 50 and 100 mgIL NW4NO'3 respectively. Furthermore, the mass of emergent metamorphs in the 25 mgIL treatment group was significantly higher than that of the controls.

No description available.

The Western Boreal Forest exhibits complex hydrogeology juxtaposed with rapid resource development. Predicting surface water chemistry to assess the influence of landuse and climate change is needed. The research purpose was to test if a global model (Gibbs), used to assess water chemistry relative to precipitation, geologic and evaporative processes can be applied to mid-continental locations; and test if regional to local scale controls of surface-groundwater interactions can be used to refine predictions where geologic processes dominate water chemistry. The global model applied to many ponds, but failed in dilute and saline ponds. Caution is necessary, as the model assumes chloride-dominated precipitation, and continental to regional scale groundwater systems influence water chemistry, independent of evaporative processes. Bedrock geology influenced ion composition, TDS and pH via mineral dissolution and scale of flow. Surficial geology influenced TDP, TDN, DOC, pH and TDS, and wetland connection influenced TDP, TDN and DOC via flowpath. To assess water chemistry and the influence of landuse and climate change, regional to local controls of surface-groundwater interactions prove valuable over the global assessment of chemistry in heterogeneous and complex landscapes. / Ecology

No description available.

A common water quality issue is an excess of nutrients which can lead to problems such as eutrophication. Stream restoration is one method by which improvements in water quality may be attempted. One strategy is increasing hyporheic zone flow at baseflow by addition of instream structures. The hyporheic zone can be an area of increased biogeochemical activity, with potential enhancement of reactions such as denitrification. However, the comparative effects of various instream restoration techniques, as well as the role of watershed setting and corresponding environmental characteristics in which restoration occurs (e.g., hydraulic conductivity, stream slope), are still poorly understood. In this study we numerically modeled groundwater and surface water interaction in a 200 m second order stream reach in southwestern Virginia using MIKE SHE. We calibrated the model to hydrologic and tracer data available during field tests of restoration techniques. We then simulated different types of instream restoration techniques (e.g., fully and partially channel-spanning weirs and buried structures), and varied hydrologic and biogeochemical controlling factors driven by watershed setting. The measured effects for this sensitivity analysis were direction and magnitude of surface water-groundwater exchange and amount of denitrification. We found that factors related to watershed setting had the greatest effect on surface water-groundwater exchange and on denitrification, including streambed hydraulic conductivity, natural or background stream topography and slope, and groundwater levels. Type and number of instream structures also influenced surface water-groundwater exchange and denitrification, but to a lesser degree, and the effect of structures was in turn controlled by watershed setting. Watershed setting was thus the largest control, both on exchange overall, and the effectiveness of structures. Human effects on watersheds such as agriculture and urbanization therefore likely play a role in whether reach-scale restoration practices succeed in achieving water quality goals. More broadly, restoration efforts at the watershed scale itself, such as reducing fertilizer use or improving stormwater management, may be necessary to achieve ambitious water quality goals. Nevertheless, reach-scale restoration efforts such as in-stream structures may play a useful role in certain watershed settings. Furthermore, other reach-scale restoration techniques that affect streambed topography, such as addition of pool-riffle sequences, may be more effective, and bear investigation. / Master of Science

No description available.

Over the last few decades increasing attention has been paid to the effects of land use activities and land management on stream water quality. Recent research has largely focused on dominant land uses such as urban development and agricultural cropland. The relative effect of land use activities and management on stream chemistry in sub-tropical rangeland ecosystems, where much of the land use is converted to pasture and agriculture is largely unknown. This study examined stream water quality and land use in a sub-tropical watershed in Northeast Texas largely dominated by rangeland. The study site, White Oak Creek Watershed located in the Sulphur River Basin, has been identified as an impaired stream due to low dissolved oxygen concentrations and subsequently listed on the Texas Commission for Environmental Quality's 303d list (TCEQ). In an attempt to determine potential sources of the low dissolved oxygen concentrations, twenty different chemical constituents were analyzed at 18 different sample sites in the tributaries of White Oak Creek and also along the main stem from April 2010 to March 2011. Dissolved oxygen concentrations over the study period were consistently above the minimum standard required by TCEQ and showed no indication of impairment. Correlation analysis did not show any clear correlation between dissolved oxygen and any specific land use, or any chemical constituent. Some nutrients and suspended sediment concentrations were significantly different among the sub-catchments of White Oak Creek. Urban land uses were significantly and positively correlated to electrical conductivity, ammonium-N, magnesium, calcium, and dissolved organic carbon. Agricultural land use was significantly and positively correlated to orthophosphate-P, dissolved organic nitrogen, total suspended solids, and turbidity. Forests were inversely and significantly related to nitrate-N, orthophosphate-P, sulfate, dissolved organic carbon, total suspended solids, and turbidity. The study suggested that by maintaining a relatively high proportion of forested land in a watershed that water quality can be improved.

Wetland systems have been widely studied and found to have enhanced capacity to transform meaningful amounts of nitrate (NO3-N) from shallow subsurface water before the improved-quality water is delivered to lake, river, and groundwater systems. Wetland are characterized by the abundant presence of electron donors and acceptors (i.e., organic carbon & NO3-N, respectively) as well as anoxic and reducing conditions which are crucial for supporting denitrification processes and the reduction of excessive nitrate levels in the environment. When favorable conditions within the wetland systems are not present, denitrification is often limited to the biofilm-protected bacteria hosted on the sediment surfaces. However, there is still a need to determine if floodplain wetlands are being utilized to their maximum potential in excess nitrate removal.

No description available.