Darbo objektas - dirbtinių telkinių vandens savybės: nitratų (NO3-), nitritų (NO -2) jonų koncentracijos, organinių medžiagų kiekis (ChDS Mn), Karvių, girdytų dirbtinių telkinių vandeniu, pieno savybės: nitratų (NO3-), nitritų (NO -2) jonų koncentracijos. Darbo tikslas – įvertinti dirbtinių telkinių vandens,naudojamo gyvuliams girdyti taršą, ir jo įtaką pieno kokybei. Darbo metodas. Tyrimams pasirinktos centrinėje Lietuvos dalyje, Kauno rajone Poderiškių ir Mitkūnų kaimuose esančiose penkiose sodybose dirbtiniai vandens telkiniai. Vandens ėminiai iš dirbtinių vandens telkinių buvo imami kas mėnesį, nuo 2006 metų sausio mėnesio iki 2006 metų gruodžio mėnesio (imtinai). Ėminiai buvo imami rankiniu būdu. Pieno ėminiai buvo imami iš karvių, kurios buvo girdomos iš tirtų dirbtinių vandens telkinių tuo pačiu metu. Vandens ir pieno cheminės analizės buvo atliekamos LŽŪU Chemijos katedros neorganinės chemijos tyrimų laboratorijoje. Nitratų jonų koncentracija tiriamajame vandenyje buvo nustatoma jonometriniu metodu, nitritų jonu koncentracija - kolorimetriniu metodu, naudojant Griso reagentą. Nitratų ir nitritų koncentracijos piene buvo nustatytos pagal LST 1264 standartą. Atliktų analizių duomenys buvo vertinami pagal LR Sveikatos apsaugos ministro patvirtintą Lietuvos higienos normą HN 48:2001 Žmogaus vartojamo žalio vandens kokybės higieniniai reikalavimai . Darbo rezultatai. 2006 m. sausio – gruodžio mėnesiais atlikus tyrimus nustatyta, kad nitratų koncentracijos... [toliau žr. visą tekstą] / The object of the work is the properties of water in the artificial basins: concentration of (ChDS Mn), nitrate (NO¯3) and nitrite (NO¯2) ions. The properties of milk milked from the cows watered from artificial water basins: concentration of nitrate (NO¯3) and nitrite (NO¯2) ions. The goal of the work is to evaluate the contamination of water in the artificial water basins used for livestock watering and its effect on milk quality. The method of work. The artificial water basins located in five homesteads located in Poderiškiai and Mitkūnai villages in Kaunas district in the central part of Lithuania were chosen for the research. The water samples from artificial water basins were taken once per month January 2006 through December 2006. The samples were taken manually. The milk samples were taken from cows that at the same time had been watered from the artificial water basins under research. The chemical analysis of water and milk were made at the Inorganic Chemistry Research Laboratory of LUA. The concentration of nitrate ions in the water under research was determined by the ionometric method and the concentration of nitrite ions was determined by the colorimetric method using the Grees reagent. The concentrations of nitrates and nitrites in milk were determined in accordance with LST 1264 standard. The results of the analysis made were evaluated in accordance with the Lithuanian Hygiene Norm HN 48:2001 “Hygienic Requirements for Raw Water Quality Used by People”... [to full text]

Tyrimų tikslas. Ištirti kietakūnio apšvietimo, pagrįsto šviesą emituojančių diodų technologija, panaudojimo galimybes žalumyninių daržovių, želmenų ir daigintų sėklų vidinės kokybės rodikliams valdyti. Mokslinis naujumas. Pirmą kartą nustatyta, kad raudona 638 nm šviesa ir jos derinys su raudona 669 nm, mėlyna 447 nm ir tolimąja raudona 731 nm šviesa paskatina nitratų redukcijos procesus salotose ir kitose žalumyninėse daržovėse. Nustatyta, kad reikšmingam teigiamam efektui žalumyninių daržovių vidinei kokybei pasiekti pakanka jas švitinti didelio tankio fotosintetiškai aktyvios raudonos 638 nm spinduliuotės srautu ~72 h prieš planuojamą derliaus nuėmimą. Pirmą kartą įvertintas kietakūnio apšvietimo spektro efektas skirtingų lietuviškų javų želmenų, lapinių ridikėlių ir daigintų sėklų antioksidacinėms savybėms. Nustatytas teigiamas raudonų 638, 669 nm, mėlynos 447 nm ir tolimosios raudonos 731 nm bangų ilgių deriniui papildomų žalios 518 nm ir geltonos 595 nm šviesos efektas natūraliai aukštomis bioaktyvių medžiagų koncentracijomis audiniuose išsiskiriančių žalumyninių daržovių ir želmenų antioksidacinėms savybėms. Darbo praktinė svarba. Įvertintos originalios konstrukcijos kietakūnio apšvietimo įrenginių taikymo žalumyninių daržovių vidinei kokybei gerinti galimybės. Remiantis darbe nustatytais dėsningumais, parengtas ir patentuotas žalingų nitratų kiekio augaluose sumažinimo, apšvitinant kietakūnio šviestuvo sukuriamu šviesos srautu, metodas ir įrenginys. Atliktų tyrimų... [toliau žr. visą tekstą] / The aim of the research was to investigate the usability of the solid state lighting, based on light emitting diode technology, for the management of nutritional quality indices in green vegetables and sprouts. Scientific originality. It was determined for the first time, that red 638 nm light and its combination with blue 447 nm, red 669 nm and far red 731 nm light promoted nitrate reduction processes in lettuce and other green vegetables. It is enough to irradiate green vegetables with the high flux of photosyntheticaly active 638 nm red light for ~72 h before harvesting for the pronounced positive effect on their internal quality. The effect of the solid-state lighting spectra on antioxidant properties of Lithuanian cereal greens, leafy radish and sprouted seeds was evaluated for the first time. The positive effect of green 518 nm and yellow 595 nm light, supplemental for the red 638, 669 nm light, blue 447 nm and far red 731 nm light on the antioxidant properties of green vegetables and sprouts, naturally containing higher concentrations of bioactive compounds, was determined. Practical value of the work. Solid-state lighting application possibilities for the improvement of green vegetable internal quality were evaluated. According to defined trends, the method and apparatus for the reduction of harmful nitrates in plants, when irradiating plants with the light flux generated by semiconductor lighting unit, was designed and patented. The complex investigations and... [to full text]

Tyrimų tikslas. Ištirti kietakūnio apšvietimo, pagrįsto šviesą emituojančių diodų technologija, panaudojimo galimybes žalumyninių daržovių, želmenų ir daigintų sėklų vidinės kokybės rodikliams valdyti. Mokslinis naujumas. Pirmą kartą nustatyta, kad raudona 638 nm šviesa ir jos derinys su raudona 669 nm, mėlyna 447 nm ir tolimąja raudona 731 nm šviesa paskatina nitratų redukcijos procesus salotose ir kitose žalumyninėse daržovėse. Nustatyta, kad reikšmingam teigiamam efektui žalumyninių daržovių vidinei kokybei pasiekti pakanka jas švitinti didelio tankio fotosintetiškai aktyvios raudonos 638 nm spinduliuotės srautu ~72 h prieš planuojamą derliaus nuėmimą. Pirmą kartą įvertintas kietakūnio apšvietimo spektro efektas skirtingų lietuviškų javų želmenų, lapinių ridikėlių ir daigintų sėklų antioksidacinėms savybėms. Nustatytas teigiamas raudonų 638, 669 nm, mėlynos 447 nm ir tolimosios raudonos 731 nm bangų ilgių deriniui papildomų žalios 518 nm ir geltonos 595 nm šviesos efektas natūraliai aukštomis bioaktyvių medžiagų koncentracijomis audiniuose išsiskiriančių žalumyninių daržovių ir želmenų antioksidacinėms savybėms. Darbo praktinė svarba. Įvertintos originalios konstrukcijos kietakūnio apšvietimo įrenginių taikymo žalumyninių daržovių vidinei kokybei gerinti galimybės. Remiantis darbe nustatytais dėsningumais, parengtas ir patentuotas žalingų nitratų kiekio augaluose sumažinimo, apšvitinant kietakūnio šviestuvo sukuriamu šviesos srautu, metodas ir įrenginys. Atliktų tyrimų... [toliau žr. visą tekstą] / The aim of the research was to investigate the usability of the solid state lighting, based on light emitting diode technology, for the management of nutritional quality indices in green vegetables and sprouts. Scientific originality. It was determined for the first time, that red 638 nm light and its combination with blue 447 nm, red 669 nm and far red 731 nm light promoted nitrate reduction processes in lettuce and other green vegetables. It is enough to irradiate green vegetables with the high flux of photosyntheticaly active 638 nm red light for ~72 h before harvesting for the pronounced positive effect on their internal quality. The effect of the solid-state lighting spectra on antioxidant properties of Lithuanian cereal greens, leafy radish and sprouted seeds was evaluated for the first time. The positive effect of green 518 nm and yellow 595 nm light, supplemental for the red 638, 669 nm light, blue 447 nm and far red 731 nm light on the antioxidant properties of green vegetables and sprouts, naturally containing higher concentrations of bioactive compounds, was determined. Practical value of the work. Solid-state lighting application possibilities for the improvement of green vegetable internal quality were evaluated. According to defined trends, the method and apparatus for the reduction of harmful nitrates in plants, when irradiating plants with the light flux generated by semiconductor lighting unit, was designed and patented. The complex investigations and... [to full text]

The factors affecting the accumulation of nitrate in kikuyu grass pastures and the effect of elevated nitrate levels upon digestion in the ruminant were investigated. A high potassium level in the soil seems to be the major factor stimulating the accumulation of excessive amounts of nitrate in kikuyu grass, when the nitrate content of the soil is also high. The continuous elongation of kikuyu grass tillers allows constant exposure of high nitrate containing stem tissue to the grazing ruminant. Digestibility studies in vitro showed that nitrite, formed during the assimilatory reduction of nitrate to ammonia, reduces cellulose digestion, but the degree of reduction also depends upon the presence of readily available carbohydrates and protein in the digest. Studies in vivo showed that the microbial population can adapt to metabolise high concentrations of nitrate (500 mg% N, m/m) in fresh kikuyu grass, without the accumulation of nitrite in the rumen. However, introduction into the rumen of nitrite in excess of the capacity of the nitrite reducing microbes, causes nitrite accumulation. Nitrite has no direct effect upon rumen cellulase activity. Due to the affinity of rumen carbohydrases for the substrate, attempts to isolate these enzymes by means of isoelectric focusing and other separation techniques met with limited success. Nitrite strongly reduces the xylanolytic, total and cellulolytic microbial numbers with a concomitant decrease in xylanase and cellulase activity of the digest. Decreased microbial numbers could not be .attributed to a less negative redox potential of the digest in the presence of nitrite, nor could the effect upon the cellulolytic microbes be attributed to an effect of nitrite on branched chain fatty acid synthesis required for cellulolytic microbial growth. A study of the effect of nitrite upon the specific growth rate of pure cultures of the major cellulolytic bacteria, Ruminococcus flavefaciens strain FDI, Butyrivibrio fibrisolvens strain Ce 51, Bacteroides succinogenes strain S 85 and Ruminococcus albus strain 22.08.6A and the non-cellulolytic bacterium Selenomonas ruminantium strain ATCC 19205 revealed the extreme sensitivity to nitrite of some of these bacteria and the relative insensitivity of others. Growth inhibition seems to depend primarily upon the extent to which these microbes derive their energy from electron transport-mediated processes. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.

The commencement of in vitro differentiation is mediated by genetic changes that result in selective expression of genes and a shift in metabolism. The role of nitrate reductase, a key enzyme of nitrate assimilation, during differentiation was examined in this study using an in vitro Nicotiana tabacum (tobacco) callus culture system. In particular, the effects of nitrogen and light/dark regimes on callus differentiation and nitrate reductase were investigated. Methodology required for the analysis of nitrate reductase regulation during in vitro tobacco callus differentiation was established. Optimised in vivo, in situ and in vitro nitrate reductase assays yielded similar values and patterns during tobacco callus culture development, and the in vivo assay was selected for nitrate reductase activity measurement during subsequent experiments. Western blot analysis of tobacco callus acetone-extracted protein after sodium dodecyl sulfate-polyacrylamide gel electrophoresis using a spinach polyclonal nitrate reductase antibody yielded major bands at 71 and 48 kD, with numerous minor bands. Extraction of callus protein in the presence of various protectants did not prevent cleavage of putative nitrate reductase polypeptide. Slot blot detection of nitrate reductase mRNA using a [32p]- labelled nitrate reductase cDNA probe isolated from the plasmid pBMC102010 was not possible due to non-specific binding to nitrocellulose filters. Northern blotting of RNA fractionated by agarose gel electrophoresis using a [32p]-labelled nitrate reductase cDNA probe identified a single mRNA species at 3.5 kb, the expected size of tobacco nitrate reductase mRNA. In vitro tobacco callus differentiation on 60 or 120 mM nitrogen regimes and under light/dark (16/8 h), continuous dark or continuous light treatments were comparable in terms of fresh weight, protein and nitrate uptake. Higher levels of in vivo nitrate reductase activity were observed prior to visible shoot primordia in all treatments, suggesting that the developmental status of callus mediated the regulation of nitrate reductase. Putative nitrate reductase protein levels were not correlated with in vivo nitrate reductase activity during initial stages of tobacco callus differentiation under various light treatments; nitrate reductase mRNA levels could not be ascertained. These results suggested that post-translational control mechanisms were involved in nitrate reductase regulation during in vitro tobacco callus differentiation. / Thesis-(M.Sc.)-University of Natal, Durban, 1993.

Estuaries, the interface of interaction of fluvial discharge and marine action serve as temporary repositories of materials (solid and dissolved) before finally exporting them to sea. This interchange of material is dependent on a range of factors such as tidal range, prism, and symmetry; fluvial flows and estuarine morphodynamics. The efficacy of transfer of materials to the marine environment is important for estuarine health particularly in estuaries located in highly developed areas such as the major coastal metropolitan areas of many countries. This study assesses the efficacy of the export of nitrates from three estuaries of the eThekwini Municipality of the city of Durban, South Africa which maintain an open mouth status, ensuring tidal exchange throughout the year. The focus of this study was to determine and analyze the net flux of nitrates between the Isipingo, Mgeni, and Tongati estuaries of the eThekwini Municipality, and their adjacent nearshore environments. It questioned whether the Isipingo, Mgeni, and Tongati estuaries were efficient at exporting nitrates to their adjacent marine environments. The abovementioned estuaries are classified as temporarily open/closed estuaries, and were chosen for this study, as they maintain an open mouth status for most of the year. An open mouth condition was critical in order to conduct this study, as tidal exchange, and the resulting nitrate fluxes, could occur. The net flux of nitrates was measured for these estuaries on a seasonal basis for both spring and neap tides. Measurements were taken over the tidal cycle, ensuring that the peak high and low tides were sampled. To determine the values of net flux, the cross-sectional area of the estuary mouths were measured; average flow velocities of water were measured; and average concentrations of nitrates were obtained. Results indicate that although there is a net export of nitrates to the nearshore environment, there were instances, particularly on the spring tide, when a net import of nitrates into the estuary occurred. The origin of the latter is likely derived from nearshore upwelling; unusually high biotic decomposition at sea and/or the longshore drift transport of decomposing sewage outfall. This creates an added dimension for consideration in estuarine management plans. Taking all three estuaries studied into consideration, a net export of nitrates for all seasons for the eThekwini Municipality was measured with a clear seasonal influence detected where high rainfall seasons led to greater export as a consequence of greater fluvial flows, erosion and leaching of agricultural lands and longer ebb duration. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Darbo tikslas – įvertinti šachtinių šulinių geriamojo vandens kokybę ir jo gerinimo galimybes Pakruojo rajone. Uždaviniai: 1. Įvertinti šachtinių šulinių geriamojo vandens kokybės rodiklius. 2. Nustatyti nėščių moterų ir moterų, kurios augina kūdikius iki 6 mėn. amžiaus, požiūrį į naudojamo vandens kokybę ir tyrimo rodiklius. 3. Įvertinti šachtinių šulinių geriamojo vandens kokybės gerinimo galimybes. Tyrimo metodika. Anketinė nėščių moterų ir kūdikius iki 6 mėn. amžiaus auginančių moterų (n=167, atsako dažnis 100 proc.) apklausa. Šachtinių šulinių geriamojo vandens kokybės rodiklių tyrimo protokolų analizė (n = 270) ir visuomenės sveikatos centro ir biuro specialistų, rajono ekologo (n=3, atsako dažnis 100 proc.) interviu. Apklausos duomenys analizuoti „SPSS 15.0 for Windows“ programa. Hipotezės tikrintos, taikant χ² testą, nustatčius reikšmingumo lygį p<0,05. Rezultatai. Tyrimo metu buvo nustatyta, kad respondentės, naudojančios užterštų šachtinių šulinių vandenį, dažniausiai gyvena kaimo vietovėse, turi mažas metines pajamas, yra bedarbės. 95,8 % respondenčių gavo informaciją apie šachtinių šulinių vandens kokybę ir patarimus, kaip apsaugoti save ir kūdikius. Moterys, turinčios žemesnį išsilavinimą, informavus apie vandens tyrimo rezultatus bei riziką sveikatai, vartoja užterštą geriamąjį vandenį nitratais ir nesiima jokių veiksmų jo kokybei gerinti. Netinkamai tvarkoma šulinio aplinka, kuri gali sąlygoti užteršimą: apie šulinį auginami augalai, kurie yra tręšiami... [toliau žr. visą tekstą] / The Aim of the study. To asses the quality of the possibilities of improving of water quality. Objectives : 1. Estimate the quality of drinking water. 2. Evaluate the attitude of pregnant women and the women growing up babies sunder the age of six (6) months to the wells water quality indicators. 3. Estimate the opportunities for improvements of quality of drinking water. Research methods. Questionnaire of pregnant women and the women raising infants under six months (n=167), response rate -100 percent. The analysis of the wells for drinking water quality indicators (n=270) was done by the public health center. Interview of the public health professionals of the region: (n=3, response rate 100 percent). Survey data, was analyzed at “SPSS15.0 for Windows” program. The Hypothesis is verified by using the test χ2 , significance level p<0,05. Results. 95.8 % of respondents have received enough information concerning the quality of the water in their wells. The women with lower education were informed about the test results of their water, about health risks using the water, but they still are using contaminated by nitrates drinking water and don’t take any actions to improve it’s quality. Improperly maintenance of wells and their environment may lead to contamination of drinking water: the plants growing near the wells are fertilized with organic fertilizers, sewage is loaded on the ground. The pregnant women with higher education show better knowledge for improvement of water... [to full text]

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Geological Sciences, 2007. / Includes bibliographical references.