The use of agricultural chemicals, such as nitrogen fertilizers in corn production, often results in water pollution. This research, comprising three parts, was designed to investigate the effects of nitrogen fertilizer application rates, water table management, and corn cropping systems on drainage water quality. The first part was a field study, to investigate the impact of two cropping systems and water table management on nitrate loss through tile drainage. The considered water table treatments were free drainage, and subirrigation with target water table depths at 0.5 m or 0.75 M below the soil surface. Corn (Zea mays L.) monoculture and corn intercropped with annual ryegrass (Lolium multiflorum Lam.) were investigated. The highest annual tile drainage losses of 21.9 kg N/ha were measured in monocropped, freely draining plots. Subirrigation with a water table depth of 0.5 m reduced tile drainage loss of N by over 70%, and intercropping corn with ryegrass under free drainage reduced leaching losses by 50%. / The second part of the research was a simulation study with the water quality model, DRAINMOD-N. The water quality impact of fertilizer application rate under free drainage, subirrigation and controlled drainage was evaluated. Leaching losses, denitrification and N accumulation in the soil profile were investigated. Using data obtained from the field experiment, the performance of DRAINMOD-N was evaluated. DRAINMOD-N assumes that denitrification follows first order kinetics, contrary to field measurements which showed little correlation between denitrification rate and NO$ sb3 sp-$-N concentration. Therefore, DRAINMOD-N was modified by replacing the original denitrification function with the Michaelis-Menten relationship. In so doing, denitrification is expressed as a first order process when NO$ sb3 sp-$-N concentration limits denitrification, and as a zero order process for non-limiting NO$ sb3 sp-$-N concentration. / For denitrification to be a decision making criterion of water table management, inexpensive but reliable measurement techniques are required. Thus, the purpose of the final part of this research was to formulate a technique for measuring real-time denitrification rate. Denitrification rate could be expressed as a function of soil redox potential (Eh) and temperature. Laboratory and field studies showed that factors such as soil nitrate and organic carbon had negligible effect on denitrification rate. Therefore, it can be concluded that for most agricultural soil, Eh and soil temperature will satisfactorily describe denitrification variation.

<p>The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation.</p>

Water table management (WTM), consisting of controlled drainage and subirrigation, can significantly reduce nitrate losses through subsurface drainage. However, recent research showed that this system could increase phosphorus (P) losses in tile drains. The cause of this increase, whether related to enhanced P solubility due to shallow water tables seen with WTM or to the addition of P by the subirrigation water, has not been investigated. / The goal of this research was to evaluate the impact of WTM on P losses and on soil P concentration, soil P saturation and soil pH with a field study. Furthermore, a laboratory soil column study was conducted to better understand the results of the field study. / The field study was carried out in 2004 and 2005 in Coteau-du-Lac (Quebec). The WTM system, with a design water table set at 0.60 m below the soil surface, was compared to conventional free drainage (FD). The results showed that WTM had no effect on the soil P concentration and saturation. However, soil pH was slightly increased in WTM plots, which may demonstrate a greater P solubility. Total outflow volumes from WTM plots were reduced by 19% and 27% in 2004 and 2005, respectively. However, P loads in drainage water from plots under WTM were greater than from FD plots due to increased P concentrations, which always exceeded Quebec's surface water quality standard of 0.03 mg/L. Of the total P concentration, around 96% was dissolved P in both treatments. / The laboratory soil column experiment, in which the two drainage treatments were simulated, also showed that P concentrations were greater under WTM than FD. This suggests that the increased P losses in the field with WTM were most likely caused by the increased P solubility due to a shallow water table rather than by the addition of P by the water used for subirrigation.

Subirrigation systems are generally used in humid areas to provide suitable moisture conditions for plant growth. These systems can also be used to reduce pesticide loadings from agricultural lands, since they tend to keep the discharging waters within farm boundaries for extended periods of time. This allows for greater pesticide microbial and chemical degradation. / A three-year field lysimeter study was initiated to investigate the role of subirrigation systems in reducing the risk of water pollution from the three most commonly used herbicides in Quebec, namely atrazine (2-chloro-4[ethylamino]-6[isopropylamino]-1,3,5-triazine), metribuzin (4-am ino-6(1,1-di meth yl eth yl)-3-(meth yl thio)-1,2,4-tria zin-5(4H)-one), and meto lach lor (2-chlo ro-N-(2-eth yl-6-methyl phen yl)-N-(2-meth oxy-1-meth yl eth yl)acet amide). Eighteen PVC lysimeters, 1 m tall x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Grain corn (Zea mays L.) and potatoes (Solanum tuberosum L.) were grown on lysimeters, and herbicides were applied each year at the locally recommended rates at the beginning of each summer. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Herbicides were extracted from soil and water samples and were analyzed using Gas Chromatography. / From the three years results (1993--1995), it has been concluded that all three herbicides were quite mobile in this sandy soil, as they leached to the 0.85 m depth below the soil surface quite early in the growing season. This suggests that if the drainage effluent or seeping waters from sandy soils of agricultural lands in southern Quebec drain freely, they may be considered to be a serious non-point source of pollution to the water bodies. The results have also shown that herbicide concentration decreased with soil depth as well as with time, meaning that the higher herbicide residues were found at top layers, and soon after the herbicide application. The herbicide mass balance study revealed that when the drainage effluent was kept within the lysimeters under the subirrigation setup, there was a statistically significant reduction of atrazine and metribuzin residues (shorter half lives) in the adsorbed and liquid phases. However, the reduction in metolachlor concentration under the subirrigation system was not statistically significant. These findings suggest that subirrigation, combined with certain herbicides can significantly reduce the herbicide loadings from corn and potato farms in southwestern Quebec, and become environmentally beneficial. / A computer simulation model (PRZM2), was used to simulate atrazine, metribuzin, and metolachlor leaching in the lysimeters, under subsurface drainage conditions. The simulated values for all three chemicals in most of the cases followed the leaching pattern of observed data. But the model either under- or over-estimated the herbicide concentrations in the soil. This could have been caused by simplistic instantaneous linear adsorption/desorption of herbicides, and inadequacy of conventional Darcian approach for the treatment of matrix flow.

Groundwater affects the development of soil in many ways. Due to the natural relationship between soil and groundwater this study was aimed at determining whether soils affect the water table depth, episaturation occurs, and hydric soils exist at the study site. The three soils studied include Pewamo (poorly drained), Blount (somewhat poorly drained) and Glynwood (moderately well drained).Water table data were collected in 1994 and 1995 at the Hults Environmental Learning Center in Albany, Indiana. Soil, by itself, was not found to be significant in affecting water table depth whereas position (horizon), soil by position and Julian date were all found to be highly significant. Soils were affected by existing drainage tile found in Pewamo that acted to lower the water table. Blount and Glynwood were found to have a period of episaturation whereas Pewamo was found to be endosaturated. The soils were not found to be hydric based on the depth to the water table only. / Department of Natural Resources and Environmental Management

Understanding the gas phase flow and transport of volatile organic compounds (VOCs) in unsaturated zones is indispensable to develop effective environmental remediation strategies, to create precautions for fresh water protection, and to provide guidance for land and water resources management. Atmospheric pressure and water table fluctuations are two important natural processes at the upper and lower boundaries of the unsaturated zone, respectively. However, their significance has been neglected in previous studies. This dissertation systematically investigates their influence on the gas phase flow and transport of VOCs in soil and ground water remediation processes using analytically and numerically mathematical modeling. New semi-analytical and numerical solutions are developed to calculate the subsurface gas flow field and the gas phase transport of VOCs in active soil vapor extraction (SVE), barometric pumping (BP) and natural attenuation taking into account the atmospheric pressure and the water table fluctuations. The accuracy of the developed solutions are checked by comparing with published analytical solutions under extreme conditions, newly developed numerical solutions in COMSOL Multiphysics and field measured data. Results indicate that both the atmospheric pressure and the tidal-induced water table fluctuations significantly change the gas flow field in active SVE, especially when the vertical gas permeability is small (less than 0.4 Darcy). The tidal-induced downward moving water table increases the depth-averaged radius of influence (ROI) for the gas pumping well. However, this downward moving water table leads to a greater vertical pore gas velocity away from the gas pumping well, which is unfavorable for removing VOCs. The gas flow rate to/from the barometric pumping well can be accurately calculated by our newly developed solutions in both homogeneous and multi-layered unsaturated zones. Under natural unsaturated zone conditions, the time-averaged advective flux of the gas phase VOCs induced by the atmospheric pressure and water table fluctuations is one to three orders of magnitude less than the diffusive flux. The time-averaged advective flux is comparable with the diffusive flux only when the gas-filled porosity is very small (less than 0.05). The density-driven flux is negligible.

Thesis (Ph.D.) -- Flinders University, School of Chemistry, Physics and Earth Sciences. / Typescript (bound). Includes bibliographical references (leaves 265-281). Also available online.

Thesis supervisor: You-Kuan Zhang. Includes bibliographic references (p. 158-172).

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / The Campus of UFSM (Universidade Federal de Santa Maria) is supplied mainly by groundwater, captured at outcrop zones (ZA) of the Guarani Aquifer System (GAS). In this sense, the present study aimed to fill the lack of quantitative information of groundwater in the UFSM Basin Campus School. The aims of this study were: 1) Perform recharge estimation of water table in single-well, using the Water Table Fluctuation method. 2) Execute statistical analysis on weekly data levels, monitored since May 2010, identifying possible correlations with rainfall data s and analysis on weekly data levels, and 3) Quantify the areas sealed in bowl using ArcGIS software and Google Earth images of 2007 to 2010. The results of the study indicated a 17.0% to 48.0% infiltration rate of the total precipitation in FATEC old well, whereas an average of 36.0% of rainfall contributes to aquifer recharge. The investigation of soil sealing, performed with data from 2007 to 2014 showed an increase of 24.32 ha in the sealed area during the study period. In the static analysis of correlation of weekly levels with volumes of rain, it was observed that the rains recorded in the measurement date were those of major influences on monitored levels, indicating the replacement level. Regarding the fluctuating levels trends from a total of eight wells monitored, two had drawdown trend. The seasonal analysis showed that levels of the seasons of winter and autumn were those with more water stored in the aquifer, while in summer and spring the opposite happened. As a conclusion, despite the sealed areas had a significant and rapid growth for the Basin, wherein this growth has not specified losses in volumes of recharges groundwater. Once the correlation data between rain and water levels were positive, the level variation trends indicated two of the eight wells with loss of water volume during the monitoring. / O Campus da UFSM (Universidade Federal de Santa Maria) é abastecido principalmente por águas subterrâneas, captadas em Zona de Afloramentos (ZA) do Sistema Aquífero Guarani (SAG). Nesse sentido, o presente estudo objetivou analisar quantitativamente às águas subterrâneas na Bacia Escola do Campus da UFSM. Para tanto, os objetivos específicos desse trabalho foram: 1) Elaborar estimativas de recarga do lençol freático em poço único, utilizando o método da flutuação do nível da água/WTF (Water Table Fluctuation). 2) Realizar análises estatísticas em dados de medições semanais de níveis da água (NA), monitorados no Campus da UFSM desde maio de 2010, identificando-se possíveis correlações com os dados de precipitações e as flutuações do nível da água. Ainda analisou-se a sazonalidade de variação desses níveis e, 3) Mapear a variação das áreas impermeabilizadas na Bacia com uso do programa ArcGIS e de imagens do Google Earth do ano de 2007 a 2010. Os resultados do trabalho apontaram para uma taxa de infiltração na área da Bacia de 17,0 a 48,0% da precipitação total, em média 36% das chuvas contribuem para a recarga do aquífero. As modificações no uso da terra mostrou que houve um crescimento de 24,32 ha, na área impermeabilizada no período avaliado. Na análise da correlação dos níveis da água semanais com os volumes de chuvas, evidenciou-se que as chuvas registradas na data da aferição foram aquelas de maiores influências nos níveis monitorados, acusando reposição no nível. Quanto à tendência de flutuação dos níveis, de um total de oito poços monitorados, dois apresentaram tendência de rebaixamento. A análise sazonal dos níveis mostrou que as estações do inverno e outono são aquelas que recarregam o aquífero, enquanto que no verão e na primavera acontece o contrário. Conclui-se que apesar das áreas impermeabilizadas apresentarem um crescimento significativo e rápido para a Bacia, esse crescimento ainda não forneceu prejuízos nos volumes das recargas das águas subterrâneas. Uma vez que os dados de correlação entre a chuva e os níveis da água foram positivos e as tendências de variação de nível indicaram dois dos oitos poços com perda de volume de água ao longo do monitoramento..

Orientador: Chang Hung Kiang / Banca: Everton de Oliveira / Banca: Holger Weiss / Banca: Luis Tadeu Furlan / Banca: Miguel Alfaro Soto / Resumo: Vazamentos acidentais de derivados de petróleo podem ocorrer em refinarias, dutos, postos de serviços e no transporte rodoviário ou ferroviário, ocasionando diversos impactos ambientais. Este trabalho teve por objetivo avaliar o comportamento de uma pluma de fase livre de querosene, presente em uma área industrial no município de Paulínia (SP), e estudar a recuperação de querosene em resposta à variação sazonal das chuvas. A área de estudo apresentou seis litotipos de origem fluvial, destacando-se a presença de paleocanais preenchidos por areias grossas. Verificou-se que as grandes variações nos níveis d'água proporcionam o fenômeno de trapeamento/destrapeamento do querosene, afetando diretamente o processo de remediação. A área apresenta altas taxas de recarga, variando de 370 mm a 550 mm em um ano. Após 40 meses de remediação, em que se procedeu ao bombeamento de oito poços, foram recuperados 176.000 litros de querosene. O período de maior recuperação foi de outubro a janeiro. Cálculos efetuados a partir dos índices físicos do solo, das propriedades físicas do querosene e da espessura observada de fase livre, em dezembro de 2008, permitiram estimar um volume remanescente recuperável de 192.000 litros de querosene no subsolo / Abstract: Accidental spills of petroleum products may occur in refineries, pipelines, and service stations, as well as during roadway and railway transportation, causing environmental damages. The main objective of this thesis is to evaluate the behavior of a kerosene free phase plume in an industrial area of the municipality of Paulinia, and evaluate the role of water table fluctuation on hydrocarbon recovery. Six lithofacies deposited in fluvial environment were identified, in particular paleochannels filled by coarse grain sands. An important finding was large water table fluctuation induce entrapment/release of kerosene, greatly affecting aquifer remediation. The studied aquifer underwent high recharge rates of 370 mm to 550 mm per year. Throughout 40 months of remediation, in which eight submersible pumps were employed, 176.000 liters of kerosene were recovered. The largest period of kerosene recovery was in the interval comprising October to January. Calculations using soil physical indexes, physical properties of kerosene and the observed thickness of free phase, as measured in December of 2008, allowed to estimate a volume of 192.000 liters of recoverable remnant kerosene yet in the ground / Doutor