This research project was aimed at monitoring the quality of drinking water that is supplied to the inhabitants of small villages. The quality of drinking water produced by small waterworks in South Bohemia, in municipalities Mazelov, Ortvínovice, Doubravka and Rábín, was studied. Sanitary analyses of drinking water samples carried out by the waterworks operators in 2004-2009 showed some variability in the concentrations of free chlorine, nitrates, pH, turbidity and the content of Escherichia coli in all the waterworks during the investigated period. The hypothesis assuming that the quality of drinking water produced by water treatment from small water sources is stable and that it does not vary in some key indicators, such as nitrates, the contents of Escherichia coli etc., throughout the year was not confirmed. The other hypothesis assuming that the number of small water sources used for public drinking water supplies decreases during the period was confirmed. The causes of these changes depend on many factors, such as the location and source of drinking water, the type of treatment plant, and, last but not least, the quality of service and economic potential of the waterworks operators play a negative role.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T11:26:33Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T11:26:33Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta uma nova metodologia, simples e de baixo custo, para quantificação direta de urânio em compostos do ciclo do combustível nuclear, baseada na espectroscopia no infravermelho com transformada de Fourier (FTIR), utilizando a técnica de pastilhamento em KBr. Diferentes matrizes foram utilizadas para o desenvolvimento e validação analítica: nitrato de uranilo complexado com TBP (UO2(NO3)2.2TBP) em fase orgânica e nitrato de uranilo (UO2(NO3)2) em fase aquosa. O método para matriz de urânio em fase orgânica (UO2(NO3)2.2TBP em hexano/incorporado em KBr) apresentou linearidade (r = 0,9980) dentro da faixa analítica de 0,20% 2,85% de urânio na pastilha de KBr, LD de 0,02% e LQ de 0,03%, exatidão com recuperações acima de 101,0%, robustez e precisão (DPR < 1,6%). O método para matriz de urânio em fase aquosa (UO2(NO3)2/incorporado em KBr) apresentou linearidade (r = 0,9900) dentro da faixa analítica de 0,14% 0,29% de urânio na pastilha de KBr, LD de 0,01% e LQ de 0,02%, exatidão com recuperações acima de 99,4%, robustez e precisão (DPR < 1,6 %). Amostras de processo do ciclo do combustível nuclear foram submetidas a avaliação intralaboratorial e os resultados foram comparados estatisticamente por outras técnicas: Espectrometria de Fluorescência de Raios-X (FRX) e gravimetria. Os testes estatísticos (t-Student e Fischer) indicaram que a técnica por FTIR e as de referência são equivalentes, demonstrando que a nova metodologia pode ser empregada com sucesso nas análises de rotina para o controle de qualidade dos compostos nucleares. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

La maîtrise du transfert de nitrates sous les systèmes irrigués est un objectif primordial dans l’agriculture moderne. Celle-ci exige la recherche, surtout en plein champ, de conduire une stratégie optimale de fertigation. Dans ce but, un protocole expérimental sur une parcelle de 2 ha a été mis en oeuvre pour analyser le devenir de l’’azote sous différents scénarios d’irrigation et de fertilisation d’une culture de maïs. Dans l’articulation de ce travail, et pour pouvoir étudier la dynamique de l’azote en systèmes irrigués, nous avons tout d’abord réussi à définir et clarifier la relation ambigüe entre la méthode d’irrigation (irrigation gravitaire, par aspersion ASP, en goutte à goutte de surface GGS ou enterré GGE) et les différentes transformations de l’azote (Fixation, Minéralisation, Immobilisation, Nitrification, Dénitrification et Volatilisation). Cette relation, peu claire et non traitée dans d’autres études similaires, a été étudiée en mettant l’accent sur l’effet de certains facteurs, comme par exemple, l’humidité de sol et sa température, sur l’activité microbienne et donc sur les différentes transformations de l’azote (comme la minéralisation) et ce en mettant en avant la relation directe ou indirecte avec les méthodes d’irrigation. Une différence significative a été observée pour la minéralisation in situ entre les traitements sans aucun apport d’engrais menés sous les deux méthodes d’irrigation GGE et ASP. Une méthode manuelle d’analyse a été ensuite mise au point et validée pour déterminer la concentration en azote dans les échantillons de sol prélevés dans le cadre de ce travail. Cette méthode peu onéreuse pourrait être profitable aux agriculteurs. Les données issues de l’ensemble des traitements ont été utilisées pour modéliser les flux hydriques et azotés à l’aide de modèle HYDRUS-2D pour les systèmes par aspersion et en goutte à goutte enterré. L’analyse de sensibilité aux paramètres liés au transfert de nitrates du modèle de transfert a permis d’estimer la dynamique azotée pour d’autres contextes hydro-pédo-climatiques plus complexes. En conclusion, la présente thèse a permis d’améliorer la connaissance du fonctionnement de la fertigation en irrigation goutte à goutte enterré par comparaison avec l’aspersion, en milieu méditerranéen, en vue d’une diminution des entrants agrochimiques dans un contexte d’économie de la ressource en eau. / The main goal in modern agriculture is the control of nitrogen fluxes in agricultural soils under the irrigation techniques. This objective requires a lot of research, especially in the field, to escort an optimal strategy of fertigation. For this purpose, an experimental protocol has been applied to follow the soil nitrogen fate for various irrigation and fertilization scenarios, during two intensive field campaigns in maize plots. In the articulation of our work, and to be able to examine the nitrogen dynamics in unsaturated agricultural soils under irrigated systems, we succeeded firstly to determine and clarify the ambiguous relation between the irrigation techniques (flood irrigation, sprinkler irrigation, surface and subsurface drip irrigation) and the different nitrogen transformations (Fixation, Mineralization, Immobilization, Nitrification, Denitrification and Volatilization) in agricultural contexts. This relationship, which is unclear and untreated in other similar studies, has been reviewed by studying the impact of certain factors, such as soil moisture and soil temperature under different irrigation techniques, on microbial soil activity and therefore on the nitrogen transformations (such as mineralization). A significant difference of mineralization was observed in maize plots with no fertilizer application treatment between sprinkler irrigation and subsurface drip irrigation. The experimental data collected have been used to analyze the water and nitrogen fluxes for various initial conditions and fertilisation strategies under sprinkler and subsurface drip irrigation by using the HYDRUS-2D model. Analyzing the sensitivity of nitrogen fluxes parameters using HYDRUS-2D allowed to estimate the nitrogen dynamics under more complex agro-pedoclimatic contexts. In conclusion, the present study allowed to improve the fertilization knowledge under both the sprinkler and subsurface drip irrigation in a Mediterranean environment.

Devido ao seu elevado teor de nutrientes e potencial de neutralização da acidez do solo, a utilização de lodos de curtume em áreas agrícolas tem sido uma alternativa para disposição e reciclagem desses resíduos. Por outro lado, o aumento do pH e do teor de nitrogênio amoniacal no solo, quando da aplicação superficial do lodo de curtume, podem favorecer a perda de nitrogênio (N) por volatilização da amônia (NH3). Altos teores de nitrogênio inorgânico no solo podem gerar efeitos negativos, principalmente quando a amonificação e nitrificação não são sincronizadas com a absorção pelas plantas, possibilitando lixiviação e conseqüente contaminação das águas subsuperficiais. Um experimento de campo foi instalado em Rolândia (PR) com os objetivos de avaliar a perda de nitrogênio por volatilização da amônia, as alterações em alguns atributos microbiológicos do solo envolvidos no ciclo do nitrogênio e carbono, a lixiviação de nitrogênio mineral no solo, a produtividade da cultura de milho e o efeito residual, após a aplicação de doses crescentes de lodo de curtume no solo. O delineamento experimental foi de blocos completos casualizados, com quatro repetições. As doses de lodo foram calculadas em função do teor de N total contido no lodo de curtume. Os tratamentos foram: controle, 120, 480, 840 e 1200 kg ha-1 de N total adicionados via lodo de curtume, correspondendo, respectivamente, a 0, 3,4, 13,5, 23,6 e 33,7 Mg ha-1 de lodo de curtume (base seca). O lodo foi aplicado na superfície de um Nitossolo Vermelho distroférrico, muito argiloso, onde permaneceu por 89 dias, período em que foi determinada a perda de amônia por volatilização. Em seqüência, o lodo foi incorporado, com posterior semeadura da cultura de milho. Nesse momento foi instalado um tratamento adicional (Tratamento agronômico - 120 kg ha-1 N via uréia). Após a colheita do milho, a aveia preta foi semeada em sistema direto, sendo conduzida até o estádio de florescimento. Durante todo o período experimental foram realizadas coletas de solo nas camadas de 0-10, 10-20, 20-40, 40-60 cm e solução do solo nos tratamentos controle, 120 e 1200 kg ha-1 N total via lodo, a 1,2 m de profundidade. A volatilização da amônia foi mais intensa nos 30 primeiros dias após a aplicação, decaindo depois desse período. A fração volatilizada como NH3 correspondeu, em média, a 17,5% do N total contido no lodo de curtume. A densidade dos grupos funcionais de microrganismos, respiração do solo e atividade enzimática apresentaram aumentos transientes após aplicação de lodo de curtume. Dentre os atributos avaliados, as enzimas glutaminase, urease e asparaginase mostraram maior atividade em resposta à aplicação de lodo de curtume. A dose 120 kg ha-1 de N via lodo de curtume não apresentou risco de contaminação do lençol freático, enquanto que na maior dose (1200 kg ha-1 N total) o teor de nitrato na solução do solo coletada a 1,2 m foi até 12 vezes maior que no controle. A dose de 521 kg ha-1 de N total proporcionou ganhos de produtividade de grãos de 13% e 11% em relação ao controle e ao tratamento agronômico, respectivamente. Foi observado efeito residual sobre a massa de matéria seca da parte aérea da aveia preta 390 dias após a aplicação do lodo. Ou seja: Doses elevadas de lodo de curtume (equivalentes a altas doses de N), aplicadas ao solo, podem resultar em poluição do ar e das águas subsuperficiais. / Due to its high nutrient content and its neutralizing potential for soil acidity, the utilization of tannery sludge in agricultural areas can be an alternative for its disposal and recycling. On the other hand, the pH and ammonia nitrogen content increase in soil as a result of surface tannery sludge application and may induce the loss of nitrogen (N) by ammonia (NH3) volatilization. The high N content in soils can generate negative effects, mainly when the organic N ammonification and nitrification does not coincide with the plant N uptake, allowing the nitrate to leach through the soil profile to the groundwater. A field experiment was installed in Rolândia (Paraná State, Brazil). The aims of this experiment were to evaluate the N loss through ammonia volatilization, changes in soil microbial attributes that are linked to the carbon and N cycles, mineral N leaching through the soil profile, corn yield and the residual effect as affected by tannery sludge application on the soil surface. A randomized complete block design was used with four replicates. The tannery sludge treatments were: control, 120, 480, 840 and 1200 kg ha-1 total N applied as tannery sludge, equivalent to 0, 3.4, 13.5, 23.6 and 33.7 Mg ha-1 tannery sludge (dry weight). The tannery sludge was surface applied on a clayey Rhodic Kandiudult. The tannery sludge was left on the soil surface for 89 days, and during this period the N loss through NH3 volatilization was determined. Afterwards, tannery sludge was incorporated and the corn was sown. At this moment, an additional treatment (agricultural treatment - 120 kg ha-1 N as urea) was applied. After the corn harvest, black oat was sown and carried on until flowering. Soil samples were taken at the following depths: 0-10, 10-20, 20-40 and 40-60 cm for all treatments. Soil solution was extracted at 1.2 m soil depth only in the control, 120 and 1200 kg ha-1 total N treatments. NH3 volatilization was more intense during the beginning of the experiment (30 days). The volatilized fraction as NH3 corresponded in average to 17.5% of the total N of the tannery sludge. The functional microorganism density, soil respiration and enzyme activity showed transient increases after tannery sludge application. The glutaminase, urease and asparaginase enzymes showed a more pronounced increase in activity in response to tannery sludge application. The lowest dose of 120 kg ha-1 total N did not show a contamination risk to the groundwater, while in the highest dose (1200 kg ha-1 total N), the amount of nitrate detected at 1.2 m was 12 times higher than in the control. The dose of 521 kg ha-1 total N corresponded to the maximum corn yield and caused increases of 13% and 11%, when compared to the control and to the agricultural treatment, respectively. Even after 390 days, a residual effect of tannery sludge application was observed as an increase in shoot dry matter of black oat. In short: it was demonstrated that high doses of tannery sludge (equivalent to high doses of total N), applied to soil, result in prohibitively high values of air and ground water pollution.

Rain gardens are low impact developments designed to mitigate a suite of issues associated with urban stormwater runoff. The site for this study was a Denton City rain garden at the Denton Waste Water Treatment Plant. Nitrogen and phosphorus removal was examined in light of two overflow events comprised of partially treated wastewater from an upslope anaerobic digester pond. Nitrate removal efficiency was examined across differing dry spell intervals of 5, 8, and 12 d, displaying a moderate negative correlation (r2 = 0.59). Continued phosphorus removal capacity was assessed, showing phosphorus removal in cases where P was in excess of 0.8 mg/L, reflecting an equilibrium phosphorus concentration. A high expanded shale component in the soil media (25%) was likely a factor in the continued removal of phosphorus. Overall the rain garden proved to be a large source of nitrate (+425%) and total nitrogen (+61%) by mass. The study showed that while the rain garden intercepted a large volume of partially treated wastewater during the overflow events, preventing it from reaching a nearby creek, the mitigation of an acute event has extended to a chronic one as nitrogen is gradually processed and flushed from the system as nitrate.

The aim of the diploma thesis is generation of active particles in plasma activated water (PAW) using a low-temperature plasma discharge. In this work I focus on the determination of hydrogen peroxide, nitrites and nitrates as active particles. The practical part is focused on a specific case of use of a plasma discharge in selected electrolytes dissolved in an aqueous solution. Here, three phosphates, differing in the number of acidic hydrogens, were selected for each experiment, and sodium chloride and tap water were compared for comparison. Phosphates were selected for their stable pH during plasma discharge in solution to monitor the effect of pH. The experiments were focused on investigating the stability of active particles in PAW, under which conditions is the highest production rate of these particles and what effect the pH value has on the result. It was found that hydrogen peroxide is generated the most in an alkaline environment but shows better stability in neutral. The concentration of generated nitrites is not high, but it shows stability, regardless of the polarity of the main electrode used for PAW generation. Nitrites were generated the most in alkaline environment and nitrates in acidic environment. One of the conclusions is that nitrates are not a very stable particle in PAW. Thanks to the activation and oxidation properties of plasma activated water, this method can be used in medicine or agriculture

Un dispositif en sol nu comprenant trois parcelles (90 m²) et six cases lysimétriques (4 m²) instrumentées a permis d’étudier l’influence d’apports répétés d’une boue de station d’épuration (BOUE) et de la même boue compostée avec des déchets verts (DVB) sur (i) les modifications des propriétés physico-chimiques et hydriques du sol ; (ii) le transport des ions bromures ; (iii) la dynamique de minéralisation du carbone et de l’azote organiques dans le sol. Finalement, le calage des paramètres hydrodynamiques et de décomposition de la matière organique dans le sol, propres à chaque horizon des profils de sols instrumentés, a permis une description satisfaisante de la dynamique hydrique et du transport des ions bromures et nitrates observés expérimentalement. Ces résultats aideront à l’adaptation de scénarios agronomiques sur le long terme pour répondre plus efficacement aux problématiques liées aux nouvelles exigences de recyclage des déchets et de protection de l’environnement. / An instrumented experimental bare soil site including three plots (90 m²) and six lysimeters (4 m²) has enabled to study the influence of repeated sewage sludge (SS) applications, as well as the same sewage sludge composted with green waste (SGW), on (i) the soil physicochemical and hydric properties ; (ii) the transport of bromide ions ; (iii) the organic carbon and nitrogen mineralization dynamics in soil. Finally, fitting the governing hydraulic parameters and the organic matter decomposition parameters in each soil horizon allowed a satisfying description of the experimentally observed water and bromide and nitrate ions transport in soil. These results will help conceive long-term agronomical scenarios aimed at providing more efficient answers to the new requirements of environmental protection and waste recycling policies.

This study utilized GIS and statistical methods to map the spatial variability of nitrate and related groundwater constituents in 30 counties above the Seymour Aquifer, analyze temporal patterns of nitrate pollution, identify probable sources of pollution, and recommend water development strategies to minimize exposure to nitrate and reduce future aquifer contamination. Nitrate concentrations in excess of 44 mg/L (US EPA limit) were commonly observed in the Seymour Aquifer region, especially in the central agricultural belt. Data indicated that this is an ongoing problem in the Seymour Aquifer and that agricultural activity and rural septic systems are the likely sources of the nitrate. Inconclusive results emphasized the need for a more comprehensive spatial and temporal water quality monitoring.

Indiana University-Purdue University Indianapolis (IUPUI) / Canines are regularly utilized by law enforcement agencies to detect explosives. However, the mechanism by which canines respond to explosive vapors is not well understood, leading to difficulties in canine training and testing. It is known that the amount of vapor generated from explosive compounds is dependent upon several factors including sample amount, vapor pressure, and the degree of confinement. Underlying these factors is the basic process of evaporation of an unconfined explosive, which is rucial to understanding how explosive vapors behave in other, more confined, systems. In Stage One of this study, evaporation rates were determined for several explosive liquids using an analytical balance. These rates were compared to one another as well as to theoretical models for the evaporation of liquids. In general and as expected, mass decreased linearly with time and evaporation rates decreased logarithmically as boiling point increased. Several examples of solvent “pinning” on a metal surface were also observed. While an empirical model for the evaporation of unconfined explosive liquids was developed, a comprehensive model for the escape of explosive vapors from sealed containers (i.e., a suitcase, knapsack, or IED container itself) is needed. The second part of Stage One of this study was to determine that the flow rate of explosive vapors escaping from relatively large orifices does not conform to Fick’s Law of Diffusion. Fick’s model states that the flow rate is linearly dependent upon the cross sectional area of the orifice and the material’s diffusion coefficient. Instead, the flow rate was found to be linearly dependent upon the diameter of the orifice due to the tendency of the flow to diffuse outwards from its circular edge. A clear relationship between flow rate and diffusion coefficient was seen, however. Additional uncertainty arises concerning the complexity of the odor generated from explosive compounds. Because explosive vapors are often complex (they consist of multiple chemical compounds), confusion exists regarding the cause of canine alert; that is the “odor compound” that allows for canine detection of various explosives. Although 2, 4- dinitrotoluene (DNT) has been explored as a potential odor compound, the possibility of a nitrated explosive inherently producing nitrated gas upon decomposition has not. Stage Two of this study focused on evaluating nitrate as a potential cause of canine alerts. An LC/MS method for the detection of nitrate ions in Composition C-4 and flake trinitrotoluene (TNT) was developed and tested. Instrumental analysis was not successful in detecting nitrate ions in any of the explosives tested. The lack of nitrate was confirmed using a diphenylamine color test for nitrates, thus eliminating nitrate as an odor compound and cause of canine alert to nitroaromatic compounds. 2, 4-DNT has been introduced as a potential odor compound of TNT, however, the mechanisms behind its vapor emission have not been thoroughly explored. More specifically, due to the “sticky” nature of the 2, 4-DNT isomer, the effects of surface adhesion to container walls are of concern. In particular, whether the amount of material lost to surface adhesion is significant enough to effect canine detection of TNT. A second focus of Stage Two explored this concern. A GC/MS method for the detection and separation of TNT and DNT isomers in liquid extracts was developed and the amount of 2, 4-DNT residues adhering to container walls was quantified. These values, compared to the amount 2,4-DNT expected to saturate each container (determined by the Ideal Gas Law), showed a significant preference of 2,4-DNT in the solid phase as opposed to in the gas phase. The amount of residue adhering to the walls of a gallon can differed from expected values by nearly 70%. The amount of material extracted from a quart can exceeded expected values by 137%. The apparent sticky nature of 2, 4-DNT resulted in a significant loss of material needed to fully saturate a container and thus canine detection success may be affected. In the final stage of this study, theories regarding odor compounds and odor availability of nitromethane, TNT, and Composition C-4 were tested using certified explosives-detecting canines. These trials included thirty-three canine-handler teams from eight government agencies. The odor availability of nitromethane was tested by placing varying volumes of nitromethane in containers with differing degrees of confinement and studying the effects on canine detection success. The odor availability trial showed no significant effect of sample amount or degree of confinement on canine detection so long as the sample volume was sufficient to saturate its container. In this study that volume was determined to be < 1 mL. Detection of 2, 4-DNT, TNT-NESST (Non-Hazardous Explosives for Security Training and Testing), and flake TNT were also studied using certified canines. The purpose of this was to identify the odorant responsible for canine alert to the explosive TNT. These trials showed a significant response to 2, 4-DNT compared to TNT and its training aid; this suggests that 2, 4-DNT is the primary cause of canine alerts to TNT. Additionally, Composition C-4 and RDX-NESTT were tested along with potential odor compounds that included the manufacturing solvent, cyclohexanone, the energetic “taggant” 2, 3-dimethyl-2.3-dinitrobutane (DMNB), the plasticizer dioctyladipate (DOA) and its degradation product 2-ethyl-1-hexanol. While some response to DMNB and cyclohexanone was seen, the most significant response was to the actual Composition C-4. This suggests that the cause of canine alert to Composition C-4 is the explosive mixture as a whole and not a single chemical component of the mixture

Titre de l'écran-titre (visionné le 29 février 2024) / Dans la vallée du Fraser en Colombie-Britannique, l'élevage intensif de vaches laitières produit d'importantes quantités de fumier. Le maïs ensilage (*Zea mays* L.), cultivé en rotation avec d'autres plantes fourragères telles que le ray-grass (*Lolium perenne* L.), représente la principale source d'aliments pour cet élevage intensif. Cet agroécosystème permet de recycler le fumier riche en nutriments comme le phosphore (P). Cependant, la culture du maïs ensilage dans la vallée du Fraser implique d'importantes applications de fumier et d'engrais de démarrage. Ceci entraine une accumulation de P dans les sols, augmentant le risque de perte de P vers les sources d'eau. De plus, le risque de mobilisation et de transport de P peut aussi être accéléré par les conditions hydriques des sols, notamment l'engorgement en eau, du fait des fortes précipitations qui s'accumulent dans les parcelles agricoles à cause du mauvais drainage des sols. Cette thèse, qui se déroule sur un sol riche en P dans la zone humide de la vallée du Fraser en Colombie Britannique, a pour objectif d'évaluer l'impact de régime d'humidité du sol, de la fertilisant en P sous forme de lisier de vache laitière, et de l'ajout de nitrate de fer sur (i) les rendements du raygrass et les exportations de P, (ii) la réduction de Fe$^\textup{3+}$ en Fe$^\textup{2+}$ et la solubilité et la mobilité du P, (iii) les activités microbiennes et les émissions de gaz à effet de serre, (iv) les activités enzymatiques, et (v) les pertes de P par lessivage. Dans les sols engorgés, le rendement en matière sèche du raygrass et l'exportation du P étaient inférieurs par rapport aux sols à capacité au champ. Une baisse du potentiel redox dans les sols engorgés a réduit le Fe$^\textup{3+}$ en Fe$^\textup{2+}$, entrainant une augmentation du pH du sol en 120 jours. Cette augmentation du pH est due à la consommation des ions H$^\textup{+}$ pendant la réduction microbienne des cations métalliques. Cette réduction de Fe$^\textup{3+}$ en Fe$^\textup{2+}$ dans les sols engorgés a libéré du P, du carbone organique dissous et de l'azote total dissous, reflétée par la diminution du P extractible à l'eau (Pw), du P extractible à la solution Mehlich-3 (P$_\textup{M3}$) et de l'indice de saturation en phosphore, mais une augmentation de la biomasse microbienne du C, du N (avant 120 jours) et des émissions de CO₂ et N₂O. L'ajout de nitrate de Fe$^\textup{3+}$ a inhibé la réduction de fer tout en stimulant les émissions de N₂O, indiquant la préférence du NO₃$^\textup{-}$ sur le Fe$^\textup{3+}$ comme accepteur d'électrons en conditions inondées. La réduction du fer et la libération des éléments tels que le P et le Fe dans les sols engorgés étaient plus marquées à la surface du sol qu'en profondeur. La libération accrue de carbone organique dissous et d'ions phosphatés dans les sols engorgés a diminué la demande en enzymes de 399 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ pour la β-glucosidase et de 1646 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ pour la phosphomonoestérase acide à la surface du sol (0-5 cm). Les conditions de l'engorgement ont cependant augmenté l'activité de la N-acétyl-β-glucosaminidase de 50.5 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ et accru l'azote total dissous de 9.1 mg kg$^\textup{-1}$ à travers toutes les profondeurs. L'apport de lisier au sol engorgé a diminué les activités enzymatiques extracellulaires, suggérant un apport suffisant en C, N, et P. Les activités enzymatiques et la biomasse microbienne étaient principalement confinées dans la couche superficielle du sol qui a été plus affectée par l'engorgement par rapport à la couche profonde. En conclusion, les conditions d'engorgement dans les sols entraînent des changements significatifs dans la chimie du P dans le sol et l'activité microbienne, conduisant à une diminution du rendement des cultures, à une modification de la dynamique des nutriments, et à une augmentation des pertes de nutriments et des émissions de gaz à effet de serre. La diminution des activités enzymatiques dans les sols engorgés et lors de l'application de lisier souligne la nécessité d'une gestion intégrée des nutriments et de l'eau dans les pratiques agricoles. / In the Fraser Valley of British Columbia (BC), intensive dairy farming produces large amount of manure. Silage corn (*Zea mays* L.), grown in rotation with other forage plants such as ryegrass (*Lolium perenne* L.), is the primary feed source for this intensive farming. This agroecosystem allows the recycling of nutrient-rich manure, like phosphorus (P). However, growing silage corn in the Fraser Valley involves significant applications of manure and starter fertilizers. This results in a buildup of P in the soils, increasing the risk of P loss to water sources. Additionally, the risk of mobilization and transport of P might be accelerated by soil water conditions, especially waterlogging, due to heavy rainfall accumulating in farmland because of poor soil drainage. This thesis, conducted on a P-rich soil in the humid area of the Fraser Valley, BC, aims to evaluate the impacts of soil moisture regime, P fertilizer levels in the form of dairy slurry, and iron nitrate addition on (i) ryegrass yields and P uptake, (ii) reduction of Fe$^\textup{3+}$to Fe$^\textup{2+}$and P solubility and mobility, (iii) microbial activities and greenhouse gas emissions, (iv) soil enzyme activities, and (v) P leaching. In waterlogged soils, ryegrass dry matter yield and exportation of P were lower compared to field capacity soils. A decrease in redox potential in the waterlogged soils reduced Fe$^\textup{3+}$ to Fe$^\textup{2+}$, leading to an increase in soil pH in 120 days. This increase in soil pH is due to the consumption of H$^\textup{+}$ ions during microbial reduction of metallic cations. This reduction of Fe$^\textup{3+}$ to Fe$^\textup{2+}$ in waterlogged soils released P, dissolved organic carbon (DOC), and total dissolved nitrogen (TDN), reflected by a decrease in water-extractable P (Pw), Mehlich-3 extractable P (P$_\textup{M3}$), and P saturation index (PSI) but an increase in microbial biomass C, N (before 120 days), and CO₂ and N₂O emissions. The addition of Fe$^\textup{3+}$ nitrate inhibited iron reduction while stimulating N₂O emissions, indicating the preference of NO₃$^\textup{-}$ over Fe$^\textup{3+}$ as an electron acceptor under waterlogged conditions. Iron reduction and the release of elements such as P and Fe in waterlogged soils were more pronounced at the topsoil than subsoil. The increased release of dissolved organic carbon and phosphate ions in waterlogged soils decreased the enzyme demand by 398.5 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ for β-glucosidase and by 1646.1 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ for acid phosphomonoesterase at the topsoil (0-5 cm). Waterlogged conditions on the other hand increased the activity of N-acetyl-β-glucosaminidase by 50.5 nmol MUF g$^\textup{-1}$ soil h$^\textup{-1}$ and raised the total dissolved nitrogen by 9.1 mg kg$^\textup{-1}$ across all depths. The application of slurry to waterlogged soil decreased extracellular enzymatic activities, suggesting a sufficient supply of C, N, and P. The activities of soil enzyme and microbial biomass were primarily confined to the topsoil, which was more affected by waterlogging compared to the subsoil. In conclusion, waterlogged conditions in soils lead to significant shifts in soil P chemistry and microbial activity, resulting in decreased crop yield, altered nutrient dynamics, and increased nutrient losses and greenhouse gas emissions. The decreased enzymatic activities under waterlogged soils and upon slurry application emphasize the need for integrated nutrient and water management in agricultural practices.