The objective of this study was to use an applied tracer to study lateral ground water flow paths in the top ~0.5 m of clay settling areas (CSA) in order to gain better understanding of hydrologic connectivity of CSAs to the surrounding hydrologic systems. The study site was located on the non-operational Mosaic Fort Mead Mine property in Fort Meade, Polk County, Florida. This lateral tracer test study is a follow up from a vertical tracer test study performed at the same site location in 2007. The CSA is generally composed of a well developed, clay rich, subangular-blocky surface layer ~0-1.0m, which exhibits abundant desiccation cracks plus other macropores underlain by a massive, saturated, clay-rich sublayer from ~1.0-2.5 m. A bromide tracer was applied into an injected trench. All 60L of the applied tracer flowed out of the down gradient face of the trench quickly, over an eleven minute period. The Bromide tracer was rapidly transported laterally and was detected as far as 16 m from the starting point just 24 hours after application, as well as in the inundated north pond adjacent to the study area. Bromide concentration distribution was not uniform over the study area during any time period, with an initial disorganized bromide pulse followed by secondary pulse concentrated on the north side of the sampling area. This spatial-temporal distribution of bromide indicates preferential flow through desiccation cracks or other macropores. Bromide concentrations in the north pond increased over time while pond stage fluctuated due to this shallow lateral macropore dominated flow in and out. Although it is most likely true that flow paths from the CSA to the adjacent hydrologic landscape during the wet season is dominated by rapid shallow lateral flow through macropores, specific flow paths, macropore length, diameter and distribution and fluxes still remain unquantified. Therefore, how the hydrology of CSAs affects the adjacent hydrologic landscape still remain unquantified.

The objective of this study was to use applied and naturally-occurring geochemical tracers to study the hydrology of clay settling areas (CSAs) and the hydrological connectivity between CSAs and surrounding hydrological landscapes. The study site is located on the Fort Meade Mine in Polk County, Florida. The surface of the CSA is covered in desiccation cracks which swell and shrink in response to wetting and drying. Bromide was used as an applied tracer to study hydrological processes in the upper part of the CSA. Bromide infiltrated rapidly and perched on an uncracked massive sublayer. Bromide concentrations attenuated in the upper part of the profile without being translated vertically down through the lower part of the profile suggesting that bromide was lost to lateral rather than to vertical downward transport. Infiltration and lateral flow were rapid suggesting that preferential flow through desiccation cracks and other macropores likely dominates flow in the upper part of the profile. Naturally-occurring dissolved constituents and stable isotopes of hydrogen and oxygen were used as naturally-occurring tracers to study the hydrological connectivity between the CSA and the surrounding hydrological landscape. The relative contributions of source waters were determined using a two-end, mass-balance mixing model with sodium as a conservative natural tracer. On average, water samples downgradient from the CSA were ~80% rainfall/ambient water and ~20% CSA water. Discharge from the CSA to the surrounding surface water bodies and surficial aquifer occurs laterally over, through, and/or under the berms and/or vertically through the thick uncracked massive sublayer. However, the precise flowpaths from the CSA to the surrounding hydrological landscape are unclear and the fluxes remain unquantified, so the effects of CSAs on the hydrology of the surrounding and underlying hydrological landscape also remain unquantified.

Here we report vertical profiles of dissolved (0.2 um filtered) Aluminum (Al) for eight stations in the Beaufort Sea in the Canadian Arctic, six of which are along a transect extending from the coastal shelf northeast of the Mackenzie River delta out to the Beaufort Sea. Sampling was performed aboard the CCGS Sir Wilfrid Laurier in September 2007 and all analyses were performed in a Class 100 clean space at the University of Victoria. Vertical profiles of dissolved Al in the water column displayed surface maxima, subsurface minima and a general increase in concentration with depth as is characteristic of a “scavenged” trace element in seawater. Concentrations of dissolved Al for the upper 1000 m were generally low ranging from the < 1 nmol kg-1 observed in the sub-surface minimum corresponding to the Pacific inflow layer and increasing to ~6-10 nmol kg-1 with depth. The surface maxima at stations for Al was associated with relatively fresh surface water (26-30 PSS) that is believed to be the result of seasonal sea-ice melt. This correlation suggests that the melting of sea-ice with entrained sediments may be an important mechanism for the delivery of Al and associated trace metals to the water column of the Beaufort Sea. We also report measurements of “total Al” (unfiltered and acidified to pH 1.7 for two year prior to analysis) for the Arctic Ocean which indicate that a significant proportion of Al in the water column is present in the > 0.2 um fraction. These measurements and the hydrographic data along the transect indicate the transport of a cold, saline, metal enriched water mass off of the continental shelf into the Canada Basin. This water mass appears to reflect the return of cold, high salinity slope water originally emplaced on the shelf by upwelling favourable winds. Alternatively, this water mass may be the product of brine exclusion from sea-ice formation during the previous winter that was unable to vacate the shelf due to the persistent upwelling observed throughout 2007. This finding suggests that the convection of cold, dense shelf water may be a mechanism for supplying the deep waters of the Arctic with an injection of water containing a significant Al content. In addition, a low volume sequential injection analysis (SIA) method is proposed for determination of elevated concentrations of Al, like those typically observed in coastal and river waters. A thorough optimization of the chemistry and instrumental parameters was performed along with an extensive investigation into potential interferents. The method was found to be largely free of interferents at environmentally relevant concentrations and was determined to have a detection limit of 24 nM. The precision of the method was reported to be 2% at 75 nmol kg-1 and analysis of the SLRS-4 certified reference material validated the accuracy of the method. Analysis of several samples that were previously analyzed via flow injection analysis (FIA) and standardized with consensus values of an open ocean reference material indicated the method returned comparable values for the Al concentration in the samples. Development and optimization of the SIA has resulted in an accurate and precise low-cost method of analysis that is both sensitive and relatively free from interference for the detection of nano-molar levels of Al in coastal and natural waters.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The models based on spatially distributed processes describe erosion and sediment yield using a physical approach of the mechanisms. In general, these models require high quality input data, description of the landscape, insertion of the physical processes involved, among others. Thus, it is not uncommon to find models that due to some operational difficulty do not fit well in the natural processes. Therefore, the objective of this study was to understand the hydrological and sedimentological dynamics of the Arvorezinha/RS experimental catchment in order to set the constraints of mathematical modeling that generate the overestimation in modeling the suspended sediment concentration (SSC) and sediment yield (SY). The study took place in the Arvorezinha experimental catchment, located in southern Brazil, which possesses a total drainage area of 1.23km2. Along with hidrossedimentological monitoring, there was an insertion of solute analysis through dissolved silicon (Sid) and particulate during and between precipitation events. This was carried out to understand the hydrological behavior of the catchment as well as assist in flow separation. The mathematical modelling of the erosive process was done with the LISEM model for the nine events monitored with Sid. In addition, we conducted an analysis of extreme events and variables responses, especially for SY, between 2010 and 2015. The years of 2014 and 2015 were the wettest since 2010, which had around 2.500mm of rain. The events monitored with Sid led us to conclude that the sub-surface flows have the biggest contribution during the event of precipitation, especially in events that take place in autumn-winter and low-average magnitude. Furthermore, it was possible to observe the effect of dilution that occurs during the events, that is, as liquid discharge increases, the concentration of Sid reduces. This is reflected in the suspended sediment concentration, because, as the event occurs, the SSC resulting from the surface flow will be diluted in the subsurface flow. Because, according to the present study, these water movements with lower speeds have a very important role in the hydrograph (it was higher than or close to 50% of the total volume). Therefore, the modeling of the erosive process is significantly influenced by the contribution of the slow flows (subsurface and groundwater flow), given that the model simulates the quick flow (superficial). In this way, LISEM model usage in areas with lower flow speeds can be limited; consequently, a greater level of care is required when concluding on the use of the model and their capacity to represent the hidrossedimentological processes. / Os modelos baseados em processos espacialmente distribuídos descrevem a erosão e a produção de sedimentos utilizando uma abordagem física dos mecanismos. Em geral, esses modelos exigem alta qualidade nos dados de entrada, descrição da paisagem, inserção dos processos físicos envolvidos, entre outros. Assim, não é raro encontrarmos modelos que, por alguma dificuldade operacional, não se ajustem bem aos processos naturais. Dessa forma, o objetivo do estudo foi compreender a dinâmica hidrológica e sedimentológica da bacia experimental de Arvorezinha/RS, para definir os condicionantes da modelagem matemática que geram a superestimava na modelagem da concentração de sedimentos em suspensão e da produção de sedimentos (PS). O estudo ocorreu na bacia experimental de Arvorezinha, sul do Brasil, com área de drenagem de 1,23km2. Juntamente ao monitoramento hidrossedimentológico, houve a inserção da análise de solutos por meio do silício dissolvido (Sid) e particulado durante eventos e entre eventos de precipitação. O monitoramento com Sid foi realizado para compreender o comportamento hidrológico da bacia hidrográfica, bem como auxiliar na separação dos escoamentos. A modelagem matemática do processo erosivo foi realizada com o modelo LISEM para os nove eventos monitorados com Sid. Além disso, foi realizada uma análise dos eventos extremos e das variáveis respostas, principalmente a PS, entre 2010 e 2015. Os anos de 2014 e 2015 foram os mais chuvosos desde 2010, com, aproximadamente, 2.500mm ao ano. Os eventos monitorados com Sid permitiram concluir que os escoamentos subsuperficiais possuem a maior contribuição de água no hidrograma durante o evento de precipitação, principalmente em eventos que ocorrem no outono-inverno e de baixa-média magnitude. Além disso, pôde-se verificar o efeito de diluição que ocorre durante os eventos, isto é, com o aumento da descarga líquida, a concentração de Sid reduz. Isso reflete-se na concentração de sedimentos em suspensão (Css), pois, havendo o evento, a Css de origem do escoamento superficial será diluída nos escoamentos subsuperficiais, uma vez que, conforme o estudo aqui realizado, esses movimentos de água mais lentos apresentam um papel muito importante no hidrograma (foi superior ou próximo a 50% do volume total). Portanto, a modelagem do processo erosivo na bacia experimental de Arvorezinha é significativamente influenciada pela contribuição dos fluxos lentos (subsuperficial e subterrâneo), uma vez que o modelo simula o escoamento rápido (superficial). Desse modo, o uso do modelo LISEM em áreas com a presença de escoamentos de menor velocidade pode ser limitado; por isso, é necessário cuidado ao obter conclusões sobre o uso do modelo e a capacidade do mesmo em representar os processos hidrossedimentológicos.