Wetlands water quality is influenced by the anthopogenic activities in the catchments’ areas. Wastewaters from the urban storm, agricultural runoff and sewage treatment often end up in wetlands before flowing to rivers, lakes and the sea. A lot of pollutants are readily transported in these wastewaters, thus subjecting the wetland ecosystem into a continuous resilience. Importantly, heavy metals like Cu, Zn, and Pb etc. are constituents of such pollutants in the wastewaters. The study has as a specific objective to investigate the effects of heavy metal Cu, Zn and Pb on denitrification, an important ecosystem process and service. In a wetland situation, denitrification is a permanent nitrogen removal process accounting for about 90% of the total nitrogen removal. The research was carried out in the laboratory and sediment samples were taken from a constructed wetland in Linkoping. We employed acetylene inhibition technique in obtaining N2O as a product resulting from nitrate reduction. The treatments (Cu, Zn and Pb) levels were 100 mg/kg, 250 mg/kg, 500 mg/kg and 1000 mg/kg of sediment, in three replicates and a control. Samplings of the assay were taken within 24hours. Gas chromatography was used to analyse and quantify N2O in the various samples. A linear regression analysis was carried out with Windows Excel and SPSS to compare the various treatments with the control at 95% confidence level. The results show that there were no inhibitions of denitrification at 100 mg/kg sediment treatment level for any of the element. Inhibition of denitrification was observed at treatment levels 500 mg/kg and 1000 mg/kg of sediment. The rate of nitrate reduction was compared from the slope of the regression curve. The rate for Cu at 500 mg and 1000 mg /kg of sediment was moderately related to that of the control, Zn shows a similar trend but a higher rate in some samples, while Pb shows more inhibition.

This study explores the use of N2O and its isotopic composition to investigate nitrogen processes in groundwater aquifers. Groundwater sampling was undertaken in 2008-2009 at two septic system sites (Long Point site and Lake Joseph site) and two agricultural sites (Strathroy site and Woodstock site). All of these four sites have been studied previously, and denitrification zones were identified by using NO3- isotopes. Extremely broad ranges of N2O-N concentrations are present at septic system sites (1 to 1071 μg/L at Long Point and 0.1 to 106 μg/L at Lake Joseph). N2O concentrations at the agricultural sites show lower levels and narrower ranges (0.1 to 3.3 μg/L at Strathroy and 14.6 to 40.5 μg/L at Woodstock site). However, N2O-N concentrations at four sites except Strathroy are higher than the atmospheric equilibrium values (0.27 to 0.37 μg/L at 8 to 17°C) as well as N2O-N values in surface water (0.2 to 1.2 μg/L, Grand River). This provides indication of N2O production in subsurface in both septic system sites and agricultural sites. Using reported enrichment factors and measured ranges for NH4+ and NO3- isotopic values, ranges were calculated for the isotopic composition expected for N2O produced by nitrification and denitrification. At Long Point site, δ15N-N2O and δ18O-N2O ranging from -43.9 to +24.9 ‰ and +20.6 to +89.4 ‰ indicates that nitrification is mainly responsible for N2O accumulation in both proximal shallow and deep zones while some N2O at the bottom of the aquifer is presumably produced from denitrification. After N2O is produced in the plume core, δ15N and δ18O in N2O reveal that N2O is further consumed to N2. Also, N2O isotopic values cleanly show seasonal N2O production shifted from mostly nitrification in early season to primarily denitrification in late season. At Lake Joseph, δ15N-N2O and δ18O-N2O varying from -4.4 to -43.2 ‰ and +24.7 to +56.7 ‰ reveal that nitrification N2O was mainly present in aerobic zone whereas denitrification zone was found in downgradient anaerobic area. At Strathroy site, δ15N-N2O (+1.7 to -29.7 ‰) and δ18O-N2O (+33 to +65 ‰) show that N2O in shallow aquifer (< 5m depth) is presumably derived from atmosphere and nitrification whereas in deep aquifer (>5m depth), N2O formation occurs during denitrification. At Woodstock site, δ15N-N2O (-4.7 to -15.9 ‰) and δ18O-N2O (+30.7 to +37.1 ‰) at Woodstock provide indication of N2O production from a mixing of denitrification N2O and tropospheric N2O. N2O isotopic signatures are highly useful to identify N2O sources which include nitrification, denitrification, and dissolution of atmospheric N2O at both septic system sites and agricultural sites. Further, at Lake Joseph site and Woodstock site, denitrification evidence from NO3- concentration/isotopes is lacking but N2O isotopes suggest the occurrence of denitrification. At Long Point site, N2O isotopes indicated N2O production was by denitrification occurred early in the season; however, no NO3- isotopic enrichment was t that depth until in late season. These sites provide evidence that N2O is an early and sensitive indicator of denitrification in groundwater at both septic system and agricultural sites. Additionally, N2O isotopes are valuable for detecting N2O consumption whereas NO3- isotopes cannot provide insight into this process.

Decades of agricultural use of fertilizer and manure has resulted in nitrogen being the most common groundwater contaminant. Of the known processes for nitrogen attenuation, both denitrification and anammox produce a complete transformation of nitrogen species to dinitrogen gas (N2); however, denitrification is typically also associated with the release of N2O and CO2, both greenhouse gases. Anaerobic ammonium oxidation (Anammox), which has been recently discovered to be more prevalent in groundwater environments than previously thought, simultaneously removes NH4+ and nitrate (NO3-), does not require dissolved organic carbon (DOC), and does not produce greenhouse gas by-products. This study evaluates the natural occurrence of anammox in a manure lagoon plume, as well as the feasibility of enhancing anammox activity by mixing NH4+ rich groundwaters and NO3- rich groundwaters together. Fifteen experiments were undertaken with NH4+-N concentrations ranging between 5-100 mg/L, and a NO3--N ranging from 5-88 mg/L. These experiments suggest a nitrogen removal rate (based on NH4 + removal in anaerobic conditions) from anammox generally in the range of 0.1-0.2 mg/L/day. Based on an absence of dissolved oxygen (DO), and concomitant loss of NO3--N with associated 15N-NO3- enrichment (2.1-8.7‰ ) in 11 experiments, it is considered unlikely that nitrification was the cause of the NH4+ loss observed in these experiments. Concurrent 15NNH4+ enrichment of 4.1-11.5‰ was observed in these 11 experiments. Real-time quantitative polymerase chain reaction (qPCR) DNA analyses were used to show the presence of anammox bacteria and to demonstrate temporal population increases during the experiments (up to 16.3% anammox in total bacteria population) in the three experiments analyzed. Although anammoxrelated N removal rates were modest in these trials, such rates could be significant with respect to the multi-year residence times associated with most groundwater flow systems.

In der vorliegenden Arbeit werden Ergebnisse von Untersuchungen zur Denitrifikation in Grundwasserleitern vorgestellt. Dabei werden drei pleistozäne norddeutsche Grundwasser-leiter betrachtet. Grundlage der Untersuchungen im Labor bilden Sedimentproben, die aus Bohrungen mit einer maximalen Teufe von 60 m u GOK, gewonnen wurden. Der Gehalt an organischem Kohlenstoff und Sulfidschwefel erlaubt den Ablauf einer chemo-organotrophen und chemo-lithotrophen Denitrifikation. Die Laborversuche zeigen eine maximale Nitratelimi-nation von 0,2 mg∙kg-1∙d-1 N, hauptsächlich infolge chemo-lithotropher Denitrification. Für einige Sedimentproben wurde eine Sorption von Nitrat mit maximal 0,85 mg∙kg-1N nachge-wiesen. Im Feld wurde der Ablauf einer Denitrifikation anhand von N2- und Ar-Messungen nachgewiesen. Die Größenordnung der Denitrifikation im Aquifer wurde außerdem mit Ein-bohrloch-Tracerversuchen (Push&amp;amp;Pull-Tests) bestimmt. Diese Tracerversuche wurden in Teufen durchgeführt, aus denen Sedimentproben für Laboruntersuchungen gewonnen wor-den waren. Die Labor- und Tracerversuche lieferten vergleichbare Ergebnisse. Weiterhin wird ein Weg gezeigt, wie Punktinformationen zum N-Umsatz mittels stochastischer Simula-tion in die Fläche übertragen werden und somit in numerische Transportmodelle eingebun-den werden können. / This thesis shows results from investigations about denitrification, a possibility is shown in aquifers. The investigation areas are three pleistocene aquifers in northern Germany. The studies in laboratory are based on samples of drillings until a depth of 60 m. The content of organic carbon and sulphides allows both chemo-organotrophic and chem-lithotrophic deni-trification. The maximum of nitrate, that was eliminated, mainly by chemo-lithotrophic denitri-fication, was 0.2 mg N per kg sediment and day. In some samples a sorption of nitrate was detected at a maximum of 0.85 mg N per kg sediment. Denitrification in situ was detected by measurements of the gases N2 and Ar at some measurement wells. Denitrification in situ was also quantified by push&amp;amp;pull-tests (single-well-tracer tests). Push&amp;amp;pull-tests as well as labo-ratory studies were carried out with sediment samples of respective measurement-wells. Similar results were found for push&amp;amp;pull tests and batchtests. Further, a possibility is shown how point-data concerning nitrate-metabolism can be transferred into two dimensions by sto-chastic simulation. Thus one can implement point-data into numerical transport-models.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 45-54). Also available on the World Wide Web.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2002. / Vita. Includes bibliographical references (leaves 153-161).

Οι διεργασίες βιολογικής απομάκρυνσης του αζώτου μέσω της νιτροποίησης και της απονιτροποίησης βρίσκουν σήμερα ευρεία εφαρμογή στην επεξεργασία τόσο των αστικών και των βιομηχανικών υγρών αποβλήτων όσο και στην προεπεξεργασία του πόσιμου νερού. Η νιτροποίηση (βιολογική οξείδωση της αμμωνίας) υλοποιείται από δύο διαφορετικές κατηγορίες αυτότροφων βακτηριών. Η πρώτη ομάδα (νιτρωδοποιητές) μετατρέπει την αμμωνία (+4 NH) σε νιτρώδη (−2NO) και στη συνέχεια η δεύτερη ομάδα, οι νιτρικοποιητές, οξειδώνει περαιτέρω το ενδιάμεσο προϊόν (νιτρώδη) σε νιτρικά. Η απονιτροποίηση είναι η βιολογική διεργασία, η οποία ευθύνεται για την απομάκρυνση του αζώτου με τη μορφή των νιτρικών και/ή νιτρωδών από τα απόβλητα μέσω μετατροπή τους σε αέριο άζωτο. Τα τελευταία χρόνια, γίνεται σημαντική ερευνητική προσπάθεια για να παρακαμφθεί το στάδιο της νιτρικοποίησης. Είναι επιθυμητό η αμμωνία να οξειδώνεται σε νιτρώδη και μετά απευθείας να λαμβάνει χώρα η απονιτροποίηση, παρά να γίνεται πρώτα η μετατροπή σε νιτρικά στα συστήματα απομάκρυνσης αζώτου. Θεωρητικά εξοικονομείται περίπου 25% σε δέκτη ηλεκτρονίων (οξυγόνο) και 40% σε δότη ηλεκτρονίων, ενώ επίσης ο ρυθμός απονιτροποίησης αυξάνεται κατά 63% με μικρότερη παραγωγή βιομάζας, οφέλη ιδιαίτερα σημαντικά από οικονομικής πλευράς, καθώς μειώνεται αρκετά το κόστος λειτουργίας της μονάδας επεξεργασίας αποβλήτων. Η παράκαμψη αυτή συνήθως επιτυγχάνεται ρυθμίζοντας κατάλληλα τη συγκέντρωση του διαλυμένου οξυγόνου, το pH και τη θερμοκρασία. Ο σκοπός της παρούσας εργασίας ήταν η εύρεση του βέλτιστου τρόπου λειτουργίας αντιδραστήρα SBR για την απομάκρυνση του αζώτου από τα λύματα με παράκαμψη της παραγωγής των νιτρικών μέσω κατάλληλης ρύθμισης του πλήθους και της διάρκειας των αερόβιων και ανοξικών φάσεων λειτουργίας του. Η παράκαμψη της νιτρικοποίησης επιτεύχθηκε για λειτουργία του συστήματος με 12ωρο κύκλο, με 3 ζεύγη αερόβιας/ανοξικής φάσης και αναλογία φάσεων 2:3. Η μείωση της διάρκειας του κύκλου λειτουργίας σε 8 ώρες οδήγησε σε εξίσου ικανοποιητική απόδοση, ταυτόχρονα όμως επιτρέπει την επεξεργασία μεγαλύτερου όγκου αποβλήτου στο ίδιο χρονικό διάστημα. / -

This study explores the use of N2O and its isotopic composition to investigate nitrogen processes in groundwater aquifers. Groundwater sampling was undertaken in 2008-2009 at two septic system sites (Long Point site and Lake Joseph site) and two agricultural sites (Strathroy site and Woodstock site). All of these four sites have been studied previously, and denitrification zones were identified by using NO3- isotopes. Extremely broad ranges of N2O-N concentrations are present at septic system sites (1 to 1071 μg/L at Long Point and 0.1 to 106 μg/L at Lake Joseph). N2O concentrations at the agricultural sites show lower levels and narrower ranges (0.1 to 3.3 μg/L at Strathroy and 14.6 to 40.5 μg/L at Woodstock site). However, N2O-N concentrations at four sites except Strathroy are higher than the atmospheric equilibrium values (0.27 to 0.37 μg/L at 8 to 17°C) as well as N2O-N values in surface water (0.2 to 1.2 μg/L, Grand River). This provides indication of N2O production in subsurface in both septic system sites and agricultural sites. Using reported enrichment factors and measured ranges for NH4+ and NO3- isotopic values, ranges were calculated for the isotopic composition expected for N2O produced by nitrification and denitrification. At Long Point site, δ15N-N2O and δ18O-N2O ranging from -43.9 to +24.9 ‰ and +20.6 to +89.4 ‰ indicates that nitrification is mainly responsible for N2O accumulation in both proximal shallow and deep zones while some N2O at the bottom of the aquifer is presumably produced from denitrification. After N2O is produced in the plume core, δ15N and δ18O in N2O reveal that N2O is further consumed to N2. Also, N2O isotopic values cleanly show seasonal N2O production shifted from mostly nitrification in early season to primarily denitrification in late season. At Lake Joseph, δ15N-N2O and δ18O-N2O varying from -4.4 to -43.2 ‰ and +24.7 to +56.7 ‰ reveal that nitrification N2O was mainly present in aerobic zone whereas denitrification zone was found in downgradient anaerobic area. At Strathroy site, δ15N-N2O (+1.7 to -29.7 ‰) and δ18O-N2O (+33 to +65 ‰) show that N2O in shallow aquifer (< 5m depth) is presumably derived from atmosphere and nitrification whereas in deep aquifer (>5m depth), N2O formation occurs during denitrification. At Woodstock site, δ15N-N2O (-4.7 to -15.9 ‰) and δ18O-N2O (+30.7 to +37.1 ‰) at Woodstock provide indication of N2O production from a mixing of denitrification N2O and tropospheric N2O. N2O isotopic signatures are highly useful to identify N2O sources which include nitrification, denitrification, and dissolution of atmospheric N2O at both septic system sites and agricultural sites. Further, at Lake Joseph site and Woodstock site, denitrification evidence from NO3- concentration/isotopes is lacking but N2O isotopes suggest the occurrence of denitrification. At Long Point site, N2O isotopes indicated N2O production was by denitrification occurred early in the season; however, no NO3- isotopic enrichment was t that depth until in late season. These sites provide evidence that N2O is an early and sensitive indicator of denitrification in groundwater at both septic system and agricultural sites. Additionally, N2O isotopes are valuable for detecting N2O consumption whereas NO3- isotopes cannot provide insight into this process.

Coastal sediments continuously interact with the overlying water column, collecting and decomposing the incoming rain of organic detritus into inorganic nutrients, and consuming oxygen in the process. This thesis compares the ability of two qualitatively different sediment models, a two-layer and a multi-layer model, to quantify the biogeochemical transformations that occur when detritus is decomposed in the sediment. Using sediment flux observations from a mesocosm eutrophication experiment, selected model parameters and different parameterizations for depositional fluxes of organic matter have been optimized using an evolutionary algorithm and a gradient descent algorithm respectively. Simulations with constant depositional fluxes outperformed simulations where deposition was dependent on proxies of biomass concentration in the overlying water. With these constant inputs, both sediment models produced similar nutrient fluxes across the sediment-water interface, however the multi-layer model was better able to adapt to new environments. / Opimization of the Sediment Flux Model (DiToro 2001) and the multi-layer model described in Soetaert et al. (1996).

Agriculture management including tillage and crop residues impact the functioning of soil microbiota. Soil microbiota cycle nutrients, with greenhouse gases being a byproduct within the cycle. The main objectives of this thesis were to 1) assess tillage and corn residue impact on N-cycling soil microorganisms and N2O emissions in situ (Chapter 3); and 2) evaluate N-cycling soil microorganisms in situ relative to N2O flux during a spring thaw cycle (Chapter 4). In situ sampling addresses how changing field conditions influence soil bacterial processes. Results indicated tillage and removal of corn residue declined soil microbial abundance and increased N2O emissions. These responses were dependent on local environmental conditions; moisture, carbon and nitrogen availability. The spring thaw study highlighted N-cycling microorganisms were present and active over the spring thaw event, and delayed nosZ denitrifier activity was related to the timing of significant N2O emission events, suggesting new evidence of de novo denitrification. / Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and Natural Science and Engineering Research Council (NSERC)