Variation of dissolved of organic carbon concentration in stream water is a consequence of process changes in the surrounding terrestrial environment. This study will focus on 1) Identify significant environmental factors controlling the spatial and temporal variation of DOC in terrestrial ecosystems of a watershed southeast of Boston, Massachusetts; 2) Model the DOC leaching from different land cover and examine the relationship between leaching flux and in-stream DOC. Our hypothesis is variations of in stream DOC is closely related to watershed properties and environmental factors at annual, seasonal, and daily scales, especially land cover type, watershed size and hydrology. To explore the relationship of hydrology and DOC variation at ungauged sub-basin, we examined the effectiveness of using simulated stream flow from Soil Water Assessment Tool (SWAT) to study terrestrial DOC dynamics. Our results demonstrated that streamflow, drainage area, and percent of wetland and forest were particularly strong predictors in watersheds with a large proportion of developed area. The resulting linear model is able to explain about 70.2% (R2=0.702) and 65.1% (R2=0.651) of the variance of in-stream DOC concentrations at seasonal and annual scales respectively. Results also suggest that more frequent DOC sampling is necessary to establish the quantitative relationship between simulated stream flows from the SWAT and in-stream DOC concentrations at daily scale. The physically based ecosystem model developed in this study shows that DOC leaching from various land cover are highly correlated (up to 80%) with in-stream DOC by using ecological process with incorporated different hydrological pathways. It shows that leaching of DOC from soil is a significant contributor to the in-stream DOC. The production of DOC is largely controlled by the vegetation type and soil texture. Considering the hydrologic control on DOC transport with different pathways of water at finer spatial and temporal scale highlights the need to identify the quantitative relationships between water and carbon flux.

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No description available.

Snowmelt river systems exhibit seasonal fluxes in water chemistry, potentially affecting the water supply of one-sixth of the worlds population. In this study, we examined water chemistry of the upper Provo River, northern Utah, which supplies water to over two million people along the urban Wasatch Front. Seasonal changes in water chemistry were characterized by analyzing discharge and dissolved organic carbon (DOC) with dissolved trace metal and cation concentrations (La, Pb, Cu, Al, Be, Sr and K) over three consecutive water years 20142016, with intensive sampling during snowmelt runoff. To better understand links between metal movement and DOC, we sampled the river in three locations (Soapstone, Woodland, and Hailstone), snowpack, and ephemeral snowmelt channels. Concentrations of La, Pb, Cu, Al, and Be increased with discharge/snowmelt during the 2014, 2015 and 2016 water years. Over 90% of La, Pb, Cu, Al, Be and between 70-90% Sr and K loads occurred during the snowmelt season (April-June). In relation to discharge, concentrations of each element varied between the river sampling sites. At Soapstone, DOC, La, Pb, Cu, Al and Be increased slightly with discharge, but Sr and K remained chemostatic. At Woodland and Hailstone, DOC, La, Pb, Cu, Al and Be had sharp increases with discharge, and Sr and K were diluted. Hysteresis patterns showed that concentrations of DOC, La, Pb, Cu, Al, Be, Sr and K all peaked on the rising limb of the hydrograph at the higher elevation Soapstone site but patterns were variable at the lower elevation Woodland and Hailstone sites. Concentrations for ephemeral channels were significantly higher than river and snow concentrations in La, Pb, Cu and Al, suggesting soil water was a significant source of flushed metals and DOC to the upper Provo River. DOC was highly correlated with La (R2 = 0.94, P = < .0001), Pb (R2 = 0.76, P = < .0023), Cu (R2 = 0.83, P = < .0001), Al (R2 = 0.94, P = < .0001) and Be (R2 = 0.93, P = < .0005), and likely facilitating metal transport. More work is needed to determine the mechanisms of DOC and metal transport, and potential metal complexation. This study has implications for understanding water quality impacts from metal flushing during snowmelt in mountain watersheds.

Snowmelt river systems exhibit seasonal fluxes in water chemistry, potentially affecting the water supply of one-sixth of the worlds population. In this study, we examined water chemistry of the upper Provo River, northern Utah, which supplies water to over two million people along the urban Wasatch Front. Seasonal changes in water chemistry were characterized by analyzing discharge and dissolved organic carbon (DOC) with dissolved trace metal and cation concentrations (La, Pb, Cu, Al, Be, Sr and K) over three consecutive water years 2014”2016, with intensive sampling during snowmelt runoff. To better understand links between metal movement and DOC, we sampled the river in three locations (Soapstone, Woodland, and Hailstone), snowpack, and ephemeral snowmelt channels. Concentrations of La, Pb, Cu, Al, and Be increased with discharge/snowmelt during the 2014, 2015 and 2016 water years. Over 90% of La, Pb, Cu, Al, Be and between 70-90% Sr and K loads occurred during the snowmelt season (April-June). In relation to discharge, concentrations of each element varied between the river sampling sites. At Soapstone, DOC, La, Pb, Cu, Al and Be increased slightly with discharge, but Sr and K remained chemostatic. At Woodland and Hailstone, DOC, La, Pb, Cu, Al and Be had sharp increases with discharge, and Sr and K were diluted. Hysteresis patterns showed that concentrations of DOC, La, Pb, Cu, Al, Be, Sr and K all peaked on the rising limb of the hydrograph at the higher elevation Soapstone site but patterns were variable at the lower elevation Woodland and Hailstone sites. Concentrations for ephemeral channels were significantly higher than river and snow concentrations in La, Pb, Cu and Al, suggesting soil water was a significant source of flushed metals and DOC to the upper Provo River. DOC was highly correlated with La (R2 = 0.94, P = <<> .0001), Pb (R2 = 0.76, P = <<> .0023), Cu (R2 = 0.83, P = <<> .0001), Al (R2 = 0.94, P = <<> .0001) and Be (R2 = 0.93, P = <<> .0005), and likely facilitating metal transport. More work is needed to determine the mechanisms of DOC and metal transport, and potential metal complexation. This study has implications for understanding water quality impacts from metal flushing during snowmelt in mountain watersheds.

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In this dissertation I describe how coupled internal cycling and external forcing from the atmosphere and climate can regulate the dynamics of nitrogen (N) loss from forest watersheds. I address three major gaps in our understanding of the global N cycle: 1) the role of dissolved organic N (DON) in internal N cycling in low-N ecosystems; 2) The influence of atmospheric pollution on DON production and loss from forests; and 3) the inherent climate sensitivity of forest N cycling and loss. In chapter 2, I present the results of a study of DON spiraling that showed enormous capacity for stream microorganisms to immobilize and transform organic nutrients. Although most DON in surface waters is highly refractory products of SOM dissolution, this study revealed very tight internal cycling of DON at the sediment interface and suggested significant production of DON in the hyporheic zone. Most remarkably, this DON was not expressed in stream waters, supporting the idea that watershed DON losses would have been higher in the absence of pronounced benthic demand. The experiments also suggested that coupled dynamics between DOC and DON spiraling may be altered under conditions of elevated N supply. Chapter 3 challenges the idea that soil organic matter (SOM) and its dissolved products are stoichiometrically static as N pools accumulate. Using a broad geographic survey of forest streams, I show that DON losses increase as a consequence of N pollution and that this occurs through a disproportionate enrichment of N on dissolved organic matter rather than alteration of soil and dissolved carbon dynamics. These results have implications for N limitation in forests and aquatic systems. In particular, DOC: DON ratios of DOM draining N-saturated forests were strikingly low suggesting possible increases in DOM bioavailability with increasing N supply. Chapter 4 provides insight into how local forest nutrient cycles may be organized by synchronous global-scale climate-atmosphere dynamics. This study of long term (30 yr) hydro-chemistry from reference forest watersheds provides an integrated example of the overall climate sensitivity of N cycling and underscores the importance of complex synergies between simultaneous vectors of global change. Results from this study argue that the combined influence of N pollution and warming are likely to have pronounced long-term effects on ecosystems globally. / Ph. D.

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Uppsalas dricksvattenförsörjning baseras på konstgjord grundvattenbildning som innebär att vatten från Fyrisån får rinna ned till grundvattnet från infiltrationsbassänger. Detta examensarbete syftar till att undersöka vad som händer med naturligt organiskt material (NOM) i Uppsalaåsen vid konstgjord grundvattenbildning. De viktigaste processerna för minskning av NOM är biologisk avskiljning genom nedbrytning, fysikalisk-kemisk avskiljning genom sorption till metalloxider samt utspädning genom inblandning av naturligt grundvatten. Arbetet bestod av tre delar: 1) analys av vattenkemidata från grundvattenprover, 2) analys av extraktion av TOC, Al och Fe från jordprover för att undersöka utfällning av NOM med metalloxider samt 3) ett inkuberingsexperiment för att utvärdera potentialen för biologisk nedbrytning i löst organiskt material (DOC). Jordproverna hämtades från borrkärnor som tagits på fem platser längs åsen under sommaren 2014. Grundvattenprover togs i 19 brunnar minst en gång per månad från november 2014 fram till april 2015. TOC-halten i grundvattnet är som högst vid infiltrationsbassängerna, ca 15 mg/l. TOC- minskar med 30 % de första 200 metrarna i flödesriktningen men minskningen avtar under grundvattentransporten. I den omättade zonen avskiljs mindre än 10 %. Vattnet i Fyrisån har en varierande sammansättning över ett år, vilket också observerades i provtagningspunkter som ligger närmast infiltrationsanläggningarna. Analys av uran och stabila isotoper visar att dispersion i åsen utjämnar dessa variationer. Analys av UV-absorbans och fluorescens tyder på att det organiska materialet i grundvattnet byter karaktär i den mättade zonen och blir hydrofilt. Resultaten från extraktionerna i jordprover visar på god korrelation mellan Fe och TOC. Bidning till järnoxider antas därför vara den viktigaste avskiljningsmekanismen i åsen. Resultaten indikerar på anrikningar av humuskomplex i de ytligaste jordlagren under sandfiltren samt precis under grundvattenytan i närheten av bassängerna. Inkuberingsexperimentet utfördes genom att grundvatten från fem olika provpunkter sterilfiltrerades. 15 vattenprover tillsattes med inockulat innehållande mikroorganismer och övriga 15 sterila prover användes som referenser. TOC undersöktes varannan vecka på samtliga vattenprover under 1,5 månader. Efter två veckor minskade halten TOC i samtliga prover och referenser med cirka 25 % och var därefter relativt konstant. Sammanfattningsvis sker en snabb minskning av NOM i grundvattnet nära infiltrationsbassängerna. Det antas bero på adsorption till metalloxider och fasta partiklar och biologisk nedbrytning. Minskningstakten av NOM avtar med transportsträckan. Längre bort antas inblandning av naturligt grundvatten vara den viktigaste orsaken till att halten NOM minskar. / The drinking water supply in Uppsala is based on this technique which involves surface water from Fyrisån percolating to the ground water through an infiltration basin. This master thesis aims to evaluate the fate of natural organic matter (NOM) in the Uppsala esker during artificial groundwater recharge. The most important processes for the removal of NOM are biological degradation, physical-chemical sorption to metal complexes and dilution by mixing with natural ground water. The work consisted of three parts: 1) analysis of water chemistry data from groundwater samples, 2) analysis of extractions of TOC, Al and Fe from soil samples to evaluate deposition of NOM with metal oxides, and 3) an incubation test to evaluate the potential for biological degradation in dissolved organic carbon (DOC). Soil samples were collected from drill cores taken from five locations along the Uppsala esker in the summer of 2014. Ground water was sampled in 19 wells at least once every month from November 2014 to April 2015. The levels of TOC in ground water are highest at the infiltration basins, about 15 mg/l. The TOC levels drop by 30 % the first 200 meters in the flow direction, but the removal rate decreases during the ground water transport. Less than 10 % is removed in the unsaturated zone. The water in Fyrisån has a variation in composition during a year, which is also observered in sampling points close to the infiltration basins. Analysis of uranium and stable isotopes shows that dispersion in the esker evens these variations. The analysis of absorbance and fluorescence shows that the NOM changes character in the saturated zone and becomes less humificated and becomes hydrophilic. The results from the extractions in the soil samples show a good correlation between Fe and TOC. Complexes of NOM and iron oxides are thought to be the most important complex in the Uppsala esker. The extractions also indicate that enrichments of humus complexes in the uppermost soil of the infiltration basins and right below the ground water table in several locations near the basins. The incubation test was done by sterilization filtering of ground water from five different locations. Inoculate with microorganisms was added to 15 of these samples, while 15 without inoculate was used as reference samples. Analysis of TOC was done every two weeks during 1,5 months. The levels of TOC decreased by 25 % after two weeks in all samples and reference samples, and were stable afterwards. In summary, a quick decrease of NOM occurs in the groundwater close to the infiltration basins. This is mainly caused by sorption and biological degradation. The removal rate of NOM decreases with distance. Further away from the basins, the most important process for decrease of NOM is mixing with local ground water.

Made available in DSpace on 2014-12-17T14:36:19Z (GMT). No. of bitstreams: 1 AnadjaMGB.pdf: 857520 bytes, checksum: c6897422096f7f137e3648055b5bcc74 (MD5) Previous issue date: 2006-06-19 / Esta tesis (desarrollada en la Base de Pesquisa, Forma??o e Profissionaliza??o Docente da UFRN) concentra su ?mbito de inter?s en el problema de la formaci?n, de la profesionalizaci?n del pensamiento del profesor, buscando investigar las Teor?as Impl?citas de los estudiantes del Curso de Pedagog?a sobre la docencia en los a?os iniciales de la Ense?anza Fundamental. La emergente necesidad de t?rminos acceso a las Teor?as Impl?citas de estudiantes de Pedagog?a (futuros profesores) sobre la docencia en los a?os iniciales de la Ense?anza Fundamental, a trav?s de un instrumento de pesquisa que posibilite su aplicaci?n en varios contextos formativos para contribuir con su proceso de profesionalizaci?n docente, constituye el problema analizado. La pesquisa tiene como objetivo elaborar un instrumento investigativo para estudiar las Teor?as Impl?citas de los profesores sobre la docencia en los a?os iniciales de la Ense?aza Fundamental. La complejidad del estudio nos ha llevado a integrar diferentes procedimientos metodol?gicos, seg?n orientaci?n del paradigma sociocultural, tales como: estudios exploratorios, a trav?s de la revisi?n bibliogr?fica de la literatura especializada y t?cnica de trabajo creativo en grupo; t?cnicas normativas y psicom?tricas. A trav?s de los estudios exploratorios identificamos y configuramos tres teor?as profesionales de la docencia en los a?os iniciales de la Ense?anza Fundamental, las cuales presentan una importante relaci?n con el Estado: la docencia como actividad laica, la docencia como actividad t?cnica y la docencia como actividad profesional. Para la configuraci?n de la teor?as, definimos siete subdominios estructurales de la docencia: funci?n docente, concepci?n de aluno, contenidos de ense?anza, gesti?n de aula de clase, proceso formativo, condiciones de trabajo y naturaleza del grupo profesional. El cuestionario normativo ha sido el instrumento orientado para investigar las representaciones de los estudiantes a nivel de conocimientos establecidos y reglamentados por la cultura, como condici?n b?sica para investigar sus Teor?as Impl?citas sobre a docencia. El estudio ha constatado que los subdominios determinados para la comprensi?n del objeto de estudio est?n presentes, de manera reincidente, en la literatura especializada como los son representativos en las identificaciones de los estudiantes investigados. Hemos concluido que las teor?as configuradas para caracterizar la profesi?n docente en los a?os iniciales de la Ense?anza Fundamental hacen parte de la estructura de conocimientos de los estudiantes sobre la docencia, aunque los enunciados de las teor?as, como actividad laica y como actividad t?cnica, no presente ?ndice de tipicidad y de polaridad muy significativo cuanto aquellos relativos a la teor?a de la docencia como actividad profesional. Las Teor?as Impl?citas de los estudiantes ense?an que ellos comparten elementos o rasgos de todas las teor?as de la docencia, aunque se revelen m?s predispuestos a la docencia como actividad profesional. El estudio orienta la aplicaci?n del cuestionario reglamentado a un grupo de profesores actuantes en el nivel de ense?anza en cuesti?n, para que averig?emos si los enunciados que hacen parte de la estructura de conocimientos de los profesores son los mismos que componen la estructura de conocimiento de los estudiantes, de modo a fortalecer la validaci?n de nuestro instrumento de pesquisa / Esta tese (desenvolvida na Base de Pesquisa, Forma??o e Profissionaliza??o Docente da UFRN) centra seu ?mbito de interesse no problema da forma??o, da profissionaliza??o e do pensamento do professor, procurando investigar as Teorias Impl?citas dos estudantes do Curso de Pedagogia sobre a doc?ncia nos anos iniciais do Ensino Fundamental. A emergente necessidade de termos acesso ?s Teorias Impl?citas de estudantes de Pedagogia (futuros professores) sobre a doc?ncia nos anos iniciais do Ensino Fundamental, atrav?s de um instrumento de pesquisa que possibilite sua aplica??o em v?rios contextos formativos para contribuir com o processo de profissionaliza??o docente, constitui o problema analisado. A pesquisa tem como objetivo elaborar um instrumento investigativo para estudar as Teorias Impl?citas dos professores sobre a doc?ncia nos anos iniciais do Ensino Fundamental. A complexidade do estudo nos levou a integrar diferentes procedimentos metodol?gicos, conforme orienta??o do paradigma s?cio-cultural, tais como: estudos explorat?rios, atrav?s da revis?o bibliogr?fica da literatura especializada e a t?cnica de trabalho criativo em grupo; t?cnicas normativas e psicom?tricas. Atrav?s dos estudos explorat?rios identificamos e configuramos tr?s teorias profissionais da doc?ncia nos anos iniciais do Ensino Fundamental, as quais apresentam uma importante rela??o com o Estado: a doc?ncia como atividade leiga, a doc?ncia como atividade t?cnica e a doc?ncia como atividade profissional. Para a configura??o das teorias, definimos sete subdom?nios estruturantes da doc?ncia: fun??o docente, concep??o de aluno, conte?dos de ensino, gest?o da sala de aula, processo formativo, condi??es de trabalho e natureza do grupo profissional. O question?rio normativo foi o instrumento orientado para investigar as representa??es dos estudantes ? n?vel de conhecimentos estabelecidos e normatizados pela cultura, enquanto condi??o b?sica para investigar suas Teorias Impl?citas sobre a doc?ncia. O estudo constatou que os subdom?nios determinados para a compreens?o do objeto de estudo est?o presentes, de maneira reincidente, na literatura especializada assim como s?o representativos nas identifica??es dos estudantes pesquisados. Conclu?mos que as teorias configuradas para caracterizar a profiss?o docente nos anos iniciais do Ensino Fundamental fazem parte da estrutura de conhecimentos dos estudantes sobre a doc?ncia, embora os enunciados das teorias, como atividade leiga e como atividade t?cnica, n?o apresente um ?ndice de tipicidade e de polaridade t?o significativo quanto aqueles relativos ? teoria da doc?ncia como atividade profissional. As Teorias Impl?citas dos estudantes mostram que eles compartilham elementos ou tra?os de todas as teorias da doc?ncia, embora se revelem mais propensos ? doc?ncia como atividade profissional. O estudo recomenda a aplica??o do question?rio normativo a um grupo de professores atuantes no n?vel de ensino em foco, para averiguarmos se os enunciados que fazem parte da estrutura de conhecimento dos professores s?o os mesmos que comp?em a estrutura de conhecimento dos estudantes, de modo a fortalecer a valida??o do nosso instrumento de pesquisa