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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Estoques e mecanismos de estabilização do carbono orgânico do solo em agroecossistemas de clima temperado e sub-tropical / Soil organic carbon stocks and stabilization mechanisms on temperate and sub-tropical climate agroecosystems

Nicoloso, Rodrigo da Silveira 21 June 2009 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Soil carbon (C) sequestration in agriculture soil is a low cost option to mitigate global climatic change. No-till (NT) associated with good husbandry practices could compensate up to 15% of the anthropogenic CO2 emissions by storing the C from atmosphere as soil organic carbon (SOC). To be fully accepted as a mitigation alternative, research must be conducted to improve the accuracy of soil C sequestration estimates on field experiments as well as those made by mathematical models at regional and local scales. Complementarily, is necessary to improve the knowledge about the SOC stabilization mechanisms, delimiting the real soil´s capacity into accumulate C, quantifying how much of the stored C could be re-emitted to the atmosphere by changes in soil management. The present work is divided in four chapters with the objective to answer these questions. The first chapter has the objective to discuss the importance of sampling depth (0-0.30, 0-0.60, and 0-0.90 m) and the definition of a reliable and adequate baseline for the calculation of the C sequestration rates. Two long-term field experiments from a temperate (Mollisol) and a sub-tropical (Oxisol) climate soil were selected for this research. The experiments tested soil tillage systems (conventional tillage (CT) and NT) (Mollisol and Oxisol) and sources and rates of nitrogen amendment on corn in the Mollisol (control without N, 168 kg N ha-1 as ammonium sulfate, and 168 kg N ha-1 as organic fertilizer) and different crop rotation systems in the Oxisol (R0:soybean-wheat, R1:soybean-wheat-soybean-oat, and R2:soybean-oat-soybean-oat+vetch-corn-radish-wheat). The increase of sampling depth provided limited contribution to the estimates of C sequestration rates due to the increase of the error on SOC stocks estimates at deeper soil depths. To improve the C sequestration rate estimates, SOC temporal dynamic analysis should be preferred rather than the comparison of the SOC stocks of paired plots at a unique time point. The second chapter had the objective to apply simple mathematical equations to describe the SOC dynamics and improve the estimates of C sequestration rates and also to understand the role of the macroaggregate formation on SOC accumulation and saturation. The use of linear and kinetic (exponential growth) equation was adequate to describe the SOC dynamics increasing the accuracy of the C sequestration rate estimates by reducing errors promoted by soil spatial variability. The SOC accumulation was a function of the amount of C input to the soil and the macroaggregate formation to protect SOC. The SOC saturation process occurred from the smaller to the larger aggregate size fraction, limiting the capacity of a given superficial soil layer to accumulate SOC. However, the SOC saturation at superficial soil layers did not indicate the end of C sequestration in the soil, since the SOC accumulation occurred at sub-superficial soil layers. In the third chapter, the mathematical approach to determine changes on SOC stocks and the SOC saturation-induced limitation for C sequestration were applied to improve the accuracy of the Hénin e Dupuís (1945) one- 8 compartmental mathematical model into predict future soil C sequestration rates. The long-term field experiment from the Mollisol was selected for this research because of the better data availability (sampling years) and also by the presence of two treatments under CT and NT with SOC saturated soil layers. The mathematical adjustment (by linear equations) of the SOC dynamic coefficients improved the adjustment of the model‟s predictions. The SOC saturation-induced restriction for SOC accumulation on the mathematical model avoided the overestimation of the soil‟s potential for C sequestration. The predictions of the mathematical models indicate that the Mollisol‟s superficial layer (0-0.05 m) under NT could maintain significant C sequestration rates for up to 50 years as a function of the amount of C input to the soil. For the fourth chapter, a detailed study of the SOC pools in water-stable aggregate size fractions by granulometric and densimetric fractionation was carried out. The objective was to identify the pools where SOC accumulation was occurring and what SOC stabilization mechanisms were present. This will provide estimates of the NT potential to promote long-term C sequestration. SOC accumulation occurred preferentially in the more stable and recalcitrant SOC fractions (Mollisol and Oxisol) or in microaggregate and macroaggregate physically protected fractions (Mollisol). In the Oxisol, the SOC enrichment occurred mostly in the mineral associated-SOC fractions extra-microaggregates occluded within meso- and macroaggregates, while in the Mollisol, the SOC accumulation occurred in both intra- and extra-microaggregate mineral associated-SOC fractions. More than 78 and 92% of the C sequestration verified in the Mollisol and Oxisol, respectively, were considered as long-term by occurring in stable SOC fractions. / O seqüestro de carbono (C) em solos agrícolas é uma opção de baixo custo para mitigação das mudanças climáticas globais. O plantio direto (PD), associado a boas práticas agronômicas, pode compensar até 15% das emissões antrópicas de CO2 ao armazenar o C drenado da atmosfera na forma de carbono orgânico (CO) do solo. Para ser amplamente aceito como alternativa de mitigação, pesquisas devem ser conduzidas a fim de melhorar a precisão das estimativas de taxas de seqüestro de C em experimentos de campo, assim como as previsões feitas por modelos matemáticos em escalas regionais e locais. Complementarmente, é necessário aprimorar o conhecimento sobre os mecanismos de estabilização do CO, delimitando a capacidade real do solo em acumular C e quantificando quanto do C acumulado no solo pode ser re-emitido para atmosfera por mudança no manejo do solo. Desta maneira, o presente trabalho se divide em quatro capítulos com o objetivo de abordar estas questões. O primeiro capítulo tem por objetivo discutir a importância da profundidade de amostragem (0-0,30; 0-0,60; 0-0,90 m) e da definição de situações de linhas-base confiáveis a adequadas para o cálculo das taxas de seqüestro de C. Para isto, foram utilizados dois experimentos de longa duração sobre um solo de clima temperado (Mollisol) e outro de clima sub-tropical (Oxisol). Os experimentos testaram efeitos de sistema de preparo do solo (preparo convencional (PC) e PD) (Mollisol e Oxisol) e fontes e doses de nitrogênio para o milho no Mollisol (testemunha (T), 168 kg N ha-1 na forma de sulfato de amônia (AM) e 168 kg N ha-1 na forma de adubo orgânico (AO)) e diferentes sistemas de rotação de culturas no Oxisol (R0:soja-trigo, R1:soja-trigo-soja-aveia e R2:soja-aveia-soja-aveia+ervilhaca-milho-nabo-trigo). O aumento da profundidade de amostragem não contribuiu com a melhoria das estimativas de taxas de seqüestro de C devido ao aumento do erro nas estimativas dos estoques de CO nas camadas mais profundas de solo. Para melhoria das estimativas das taxas de seqüestro de C devem-se preferir análises temporais da dinâmica do CO no solo ao invés da comparação de estoques de CO em um único momento. O segundo capítulo tem por objetivo aplicar equações matemáticas simples para descrever a dinâmica do CO e melhorar as estimativas taxas de seqüestro de C e também entender o papel da formação de macroagregados no acúmulo e saturação de CO no solo. O uso de equações lineares e cinéticas (crescimento exponencial) foi adequado para descrever a dinâmica do CO, aumentando a precisão das estimativas de taxas de seqüestro de C ao reduzir os erros de estimativa por variabilidade espacial do solo. O acúmulo de CO no solo mostrou-se uma função da quantidade de C aportada ao solo por resíduos vegetais e a formação de macroagregados no solo para proteção do CO. O processo de saturação do solo ocorreu das menores para as maiores frações de agregados do solo, limitando a capacidade de uma 6 determinada camada de solo em acumular CO. No entanto, verificou-se que a saturação de camadas superficiais de solo não indica o fim do seqüestro de C neste solo, visto que o acúmulo de CO passa a ocorrer em camadas sub-superficiais. No terceiro capítulo, a aproximação matemática para determinar mudanças nos estoques de CO e a limitação na capacidade do solo em acumular CO promovida pelo processo de saturação dos agregados do solo foram aplicados para melhorar a precisão do modelo matemático uni-compartimental de Hénin e Dupuís (1945) em prever futuras taxas de seqüestro de C. O Mollisol foi escolhido para este estudo em função da maior disponibilidade de dados (anos de amostragem) e também pela presença de dois tratamentos em PC e PD com camada de solo saturada por CO. O ajuste matemático (por equações lineares) dos coeficientes da dinâmica do CO melhorou o ajuste das previsões do modelo com os dados observados. A restrição do modelo matemático quanto à capacidade do solo em acumular CO (saturação de CO) evitou a superestimação do potencial de seqüestro de C deste solo. As previsões do modelo matemático indicam que a camada superficial (0-0,05 m) do solo sob PD pode apresentar taxas significativas de seqüestro de C por até 50 anos, em função da quantidade de C adicionada ao solo. No quarto capítulo, foi realizado um estudo detalhado dos compartimentos do CO em função da sua distribuição em classes de tamanhos de agregados estáveis em água e o fracionamento granulométrico e densimétrico do CO. O objetivo foi identificar em quais compartimentos está ocorrendo o acúmulo de CO no solo, os mecanismos de estabilização do CO, estimando o potencial do PD em promover sequestro de C de longa duração. Verificou-se que o acúmulo de C ocorre preferencialmente em frações mais estáveis e recalcitrantes do CO (Mollisol e Oxisol) ou em frações protegidas fisicamente por micro e macroagregados (Mollisol). No Oxisol, o enriquecimento de CO ocorre principalmente nas frações de CO associadas aos minerais extra-microaggregados oclusas em meso e macroagregados de solo, enquanto que no Mollisol, o acumulo de CO ocorre tanto na fração intra como extra microagregados. Mais de 78 e 92% do seqüestro de C verificado no Mollisol e Oxisol, repectivamente, foi considerado de longa duração por ocorrer em frações estáveis do CO.
272

Climate change impacts on production and dynamics of fish populations

Hedström, Per January 2016 (has links)
Ongoing climate change is predicted to increase water temperatures and export of terrestrial dissolved matter (TDOM) to aquatic ecosystems influencing ecosystem productivity, food web dynamics and production of top consumers. Ecosystem productivity is mainly determined by the rates of primary production (GPP) in turn controlled by nutrients, light availability and temperature, while temperature alone affect vital rates like consumption and metabolic rates and maintenance requirements of consumers. Increased level of TDOM causes brownification of water which may cause light limitation in algae and decrease GPP and especially so in the benthic habitat. Temperature increase has a been suggested to increase metabolic rates of consumers to larger extent than the corresponding effect on GPP, which suggest reduced top consumer biomass and production with warming. The aim of this thesis was to experimentally study the effects of increased temperature and TDOM on habitat specific and whole ecosystem GPP and fish densities and production. In a replicated large-scale pond experiment encompassing natural food webs of lotic ecosystems I studied population level responses to warming and brownification in the three- spined stickleback (Gasterosteus aculeatus). Results showed overall that warming had no effect on whole ecosystem GPP, likely due to nutrient limitation, while TDOM input decreased benthic GPP but stimulated pelagic GPP. In fish, results first of all suggested that recruitment in sticklebacks over summer was negatively affected by warming as maintenance requirements in relation to GPP increased and thereby increased starvation mortality of young-of-the-year (YOY) sticklebacks. Secondly, brownification increased mortality over winter in YOY as the negative effect on light conditions likely decreased search efficiency and caused lower consumption rates and starvation over winter in sticklebacks. Third, seasonal production of YOY, older, and total stickleback production was negatively affected by warming, while increased TDOM caused decreased YOY and total fish production. The combined effect of the two was intermediate but still negative. Temperature effects on fish production were likely a result of increased energy requirements of fish in relation to resource production and intake rates whereas the negative effect of TDOM likely was a result of decreased benthic resource production. Finally, effects of warming over a three-year period caused total fish density and biomass and abundance of both mature and old fish to decrease, while proportion of young fish increased. The main cause behind the strong negative effects of warming on fish population biomass and changes in population demographic parameters were likely the temperature driven increased energy requirements relative to resource production and cohort competition. The results from this thesis suggest that predicted climate change impacts on lentic aquatic ecosystems will decrease future densities and biomass of fish and negatively affect fish production and especially so in systems dominated by benthic resource production.
273

Tibetan pasture degradation under the impact of global change: Consequences for carbon and nutrient cycles and recovery strategies

Liu, Shibin 13 July 2017 (has links)
No description available.
274

Landscape partitioning and burial processes of soil organic carbon in contrasting areas of continuous permafrost

Palmtag, Juri January 2017 (has links)
Recent studies have shown that permafrost soils in the northern circumpolar region store almost twice as much carbon as the atmosphere. Since soil organic carbon (SOC) pools have large regional and landscape-level variability, detailed SOC inventories from across the northern permafrost region are needed to assess potential remobilization of SOC with permafrost degradation and to quantify the permafrost carbon-climate feedback on global warming. This thesis provides high-resolution data on SOC storage in five study areas located in undersampled regions of the continuous permafrost zone (Zackenberg in NE Greenland; Shalaurovo and Cherskiy in NE Siberia; Ary-Mas and Logata in Taymyr Peninsula). The emphasis throughout the five different study areas is put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Our results indicate large differences in mean SOC 0–100 cm storage among study areas, ranging from 4.8 to 30.0 kg C m-2, highlighting the need to consider numerous factors as topography, geomorphology, land cover, soil texture, soil moisture, etc. in the assessment of landscape-level and regional SOC stock estimates. In the high arctic mountainous area of Zackenberg, the mean SOC storage is low due to the high proportion of bare grounds. The geomorphology based upscaling resulted in a c. 40% lower estimate compared to a land cover based upscaling (4.8 vs 8.3 kg C m-2, respectively). A landform approach provides a better tool for identifying hotspots of SOC burial in the landscape, which in this area corresponds to alluvial fan deposits in the foothills of the mountains. SOC burial by cryoturbation was much more limited and largely restricted to soils in the lower central valley. In the lowland permafrost study areas of Russia the mean SOC 0–100 cm storage ranged from 14.8 to 30.0 kg C m-2. Cryoturbation is the main burial process of SOC, storing on average c. 30% of the total landscape SOC 0–100 cm in deeper C-enriched pockets in all study areas. In Taymyr Peninsula, the mean SOC storage between the Ary-Mas and Logata study areas differed by c. 40% (14.8 vs 20.8 kg C m-2, respectively). We ascribe this mainly to the finer soil texture in the latter study area. Grain size analyses show that cryoturbation is most prominent in silt loam soils with high coarse silt to very fine sand fractions. However, in profiles and samples not affected by C-enrichment, C concentrations and densities were higher in silt loam soils with higher clay to medium silt fractions. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
275

En resa tillbaka i tiden för att förstå framtiden : En undersökning av organiskt material i eoliska lössjordssediment på västra Grönland, Kangerlussuaq. / A Journey Back in Time to Understand the Future : A Study of Organic Material in Aeolian Loess Sediments in Western Greenland, Kangerlussuaq.

Morin, Caroline, Sundman, Jessica January 2021 (has links)
Today's changing climate on Earth makes climate research more important than ever. By providing an understanding of the Earth's history and in particular places where large-scale climate change is taking place, for example Greenland, can one get an understanding about how the Earth will react in the future. In this report has eolian loess deposits been analyzed from the permafrost region on Greenland, near the city Kangerlussuaq (Hällberg 2018). The eolian sediment can contain organic carbon that shows climate conditions during the time when the sedimentation occurred. In this report, the organic carbon has been measured using loss of ignition (LOI). The method is well-tried and measures the loss of weight in the samples, which answers to the loss of organic carbon (Dean 1974). The samples were heated to 100°C and thereafter burned at 550°C. The results from the LOI have been analyzed and compared to other data from the same location. This includes data from carbon-14 dating, X-ray fluorescence, grain size and magnetic susceptibility. The final data set has been mapped in the geographical information system. The maps gave an overview of the changes in the area. Results shows that there are connections between organic carbon and climate change in Greenland, which also is proved by correlation to other studies. / Det rådande klimathotet och det föränderliga klimatet på jorden gör att klimatstudier är viktigare än någonsin. Genom att få en förståelse för jordens historia i synnerhet på platser där stora klimatförändringar sker, så som på Grönland, kan en uppfattning fås om hur vår jord kommer påverkas. I uppsatsen har eoliskt avsatt lössjord analyserats från permafrostområdet på Grönland, nära staden Kangerlussuaq (Hällberg 2018). Det eoliska sedimentet innehåller organiskt material som avspeglar klimatförhållanden på platsen för tiden då sedimentationen inträffade. I arbetet har innehållet av organiskt material undersökts genom metoden Loss of Ignition (LOI). Metoden är välbeprövad och går ut på att mäta förlust i vikt vilket motsvarar förlust av organiskt material (Dean 1974). Proverna har torkats i 100°C och därefter bränts i 550°C. Resultatet som gavs av LOI har analyserats och jämförts med annan data från samma lokaler. De innefattar kol 14-metoden, röntgenfluorescens, kornstorlek och magnetisk susceptibilitet. Den slutgiltiga datauppsätningen har genom kartverktyget Geografisk Informationssystem karterats. Kartorna gav övergripande bild på de rumsliga förändringarna i området. Resultaten visar att det finns samband mellan organiskt material och klimatet på Grönland vilket även bevisas av korrelation med andra studier.
276

Effects of a forested state park on stream dissolved organic carbon and total suspended solid concentrations in an agriculturally dominated watershed in SW Ohio

Rintsch, Eileen Tabata 26 July 2021 (has links)
No description available.
277

Investigating Soil Quality and Carbon Balance for Ohio State University Soils

Burgos Hernández, Tania D. 13 November 2020 (has links)
No description available.
278

Effect of Conservation Agriculture on Organic Matter Stratification and Hydro-Physical Properties of Soil Under Intensive Cereal-based Cropping Systems

Patra, Sridhar 13 May 2022 (has links)
Although, the potential of management induced changes of soil organic matter, soil hydraulic properties (SHPs) and soil physical quality has been studied particularly in relation to tillage, few studies have evaluated combined effect of tillage, crop residue retention and cropping sequence, which are essential components of conservation agriculture (CA), on stratification and storage of soil organic matter, its effect on near-saturated soil hydraulic properties and soil physical quality in intensive cereal based irrigated cropping systems. Hence, the present study critically analyses the effects of CA on organic matter and hydro-physical properties of soil in a long-term CA field trial in NWIGP, India, which is one of the most fragile agro-ecosystems in the world. The objectives were (I) to investigate the stratification of soil organic carbon (SOC), total nitrogen (TN), C/N ratio and evaluate SR as an indicator of storage of SOC and TN and soil quality for different CA practices, (II) to assess the long-term effect of CA practices and short-term effect of crops on near-saturated soil hydraulic conductivity and water transmission properties, and (III) to assess the effect of CA practices on soil physical quality using capacitive and dynamic indicators. There were four treatments: (1) conventionally tilled rice-wheat cropping system (CT-RW), (2) reduced till CA-based rice-wheat-mungbean system (RT-RWMB), (3) no-till CA-based rice-wheat-mungbean system (NT-RWMB), and (4) no-till CA-based maize-wheat-mungbean system (NT-MWMB). To achieve these objectives, soil bulk density, SOC and TN were measured in an increment of 5 cm up to 30 cm soil depth. Furthermore, the effects of CA were also evaluated in terms of soil hydro-physical properties. Soil physical properties such as bulk density and soil aggregate distribution were evaluated in two cropping seasons along with near saturated hydraulic properties. Steady state infiltration rates were obtained at four pressure heads by hood infiltrometer consecutively over two cropping seasons, i.e. during harvest season of rice/maize (October 2017) and maximum crop growth stage of wheat (February 2018). Data were analysed in terms of soil hydraulic conductivity, k(h), flow weighted mean pore radius (r0), hydraulically active porosity (ε) and threshold pore radius (rbp), a new pore measure indicative of macropore stability derived by substituting soil’s bubble pressure in the capillary equation. Finally, the effects of CA on soil physical quality in terms of both capacitive and dynamic indicators, derived from soil moisture retention curve and field measured hydraulic conductivity, respectively, were assessed and related with crop yield to infer which indicator better represented the soil physical quality and its effect on crop yield under irrigated intensive cereal based cropping systems. Results showed that CA had profound impacts on distribution of SOC and TN in the soil profile. Significantly higher proportion of both SOC and TN were observed in the top soil in the CA-based treatments as compared with conventional intensive tillage-based treatment. The mean stratification ratio of both SOC and TN were found > 2 in CA-based treatments whereas the same was < 2 in intensive tillage-based treatment. Storage of SOC and TN in the 0-30 cm were found higher in CA-based treatments as compared with the intensive tillage-based treatment. These results on vertical distribution and storage of SOC and TN indicated a relatively better soil carbon sequestration and soil quality in CA-based treatment. The higher concentrations and storage of soil organic matter in CA-based treatments were, however, not translated into significantly (p < 0.05) lower bulk density due to probable compaction effect of no-tillage and harvest machinery and hydraulic pressure exerted by the flooded irrigation water. However, the increased soil organic matter in the top soil in CA-based treatments improved the soil aggregation significantly which helped in enhancing soil structural quality. Improvement in soil structure was reflected in relatively higher near saturated hydraulic conductivity in CA-based treatments. Irrespective of crop seasons, higher k(h) was observed under CA due to formation of macropores with better continuity, greater size and numbers as compared with conventional intensive tillage treatment. Moreover, higher r0 values were observed for a given k(h) for CA treatments suggesting that interaggregate pores are the dominant pathways of infiltration in CA. A relatively smaller temporal variation of rbp was indicative of a more stable macropore system established by rice-based CA as compared with maize-based CA. CA also enhanced hydraulically active macropores as compared with intensive tillage based conventional agriculture. Results also indicated that crops play an important role in relative distribution of the hydraulically active macropores in the root zone. The impact of CA on soil organic matter stratification and soil hydraulic properties were found to be expressed in terms of changes in soil physical quality. Soil moisture retention curves and pore size distributions under different treatments suggested higher soil water storage in structural pores in CA as compared with intensive tillage-based conventional agriculture. The impact of CA on soil physical quality and consequent effect on crop yield was found to be more expressed through dynamic indicators such as hydraulically active porosity rather than capacitive indicators derived from soil moisture retention curve. Overall, this study reveals that conservation agriculture has great potentials to reverse the intensive tillage induced degradation of soil resources in Indo-Gangetic Plains of India by improving the soil hydro-physical properties and soil physical quality.:Table of Contents Declaration i Declaration of Conformity ii Acknowledgements iii Table of Contents v List of Figures vii List of Tables xi List of Symbols, Abbreviations and Acronyms xiv Abstract xvii 1 Introduction and Background 1 1.1 General Overview 1 1.2 Statement of the Research Problem 5 1.3 Objectives 6 1.4 Research Flow and Chapter Description 7 2 Materials and Methods 9 2.1 Study Area Description 9 2.1.1 Study site 9 2.1.2 Climate 9 2.1.3 Soil 10 2.1.4 Treatments 10 2.1.5 Field Campaigns and Measurement/Analysis 14 2.2 Methods and Theoretical Considerations 14 2.2.1 Soil Sampling and Analysis 14 2.2.1.1 Calculation of Stratification Ratio 15 2.2.1.2 Calculation of SOC and TN Storage 15 2.2.1.3 Aggregate Size Distribution 16 2.2.2 Infiltration Measurements 16 2.2.3 Soil Moisture Retention Experiments 17 2.2.4 Derivation of Hydraulic Properties from Steady State Infiltration Rates 18 2.2.4.1 Near-Saturated Hydraulic Conductivity 18 2.2.4.2 Flow Weighted Mean Pore Radius 20 2.2.4.3 Equivalent Threshold pore Radius 21 2.2.4.4 Hydraulically Active Porosity 21 2.2.5 Determiation of Soil Moisture Charachtristics and Pore Size Distribution 22 2.2.6 Derivation of Soil Physical Quality Indicators 23 2.3 Statistics 25 3 Results and Discussion 26 3.1 Stratification and Storage of Soil Organic Matter 26 3.1.1 Bulk Density 26 3.1.2 Concenrations of SOC 27 3.1.3 Concentrations of TN 28 3.1.4 C/N Ratio 29 3.1.5 Stratification Ratio of SOC, TN and C/N Ratio 30 3.1.6 Storage of SOC and TN 33 3.1.7 Discussion 34 3.1.8 Summary of Results 39 3.2 Soil Hydro-Physical Properties 40 3.2.1 Soil Physical Properties 40 3.2.2 Near-Saturated Hydraulic Conductivity 43 3.2.3 Soil Pore Characteristics-Conductivity Relationship 47 3.2.4 Hydrailically active Porosity 51 3.2.5 Summary of Results 54 3.3 Soil Physical Quality (SPQ) 56 3.3.1 Soil Moisture Retention Curve (SMRC) 56 3.3.2 Soil Pore Size Distribution (SPSD) 58 3.3.3 Capacitive Indicators 59 3.3.4 Dynamic Indicators 60 3.3.5 Relationship between capacitive indicators of SPQ with dynamic indicators of SPQ and long-term crop yield 60 3.3.6 Relationship between dynamic indicator of SPQ (hydraulically active porosity) and Long-term Crop Yield 62 3.3.7 Summary of Results 64 4 Synthesis and Conclusions 65 5 Implications and Outlook 69 References 71
279

Impact of Peat Bogs on the Brownification of River Storån and Lake Bolmen

Onyegbule, Peter Nnamdi January 2020 (has links)
Freshwater bodies have been long observed to become browner within the northern hemisphere. This brownification, has made drinking water production difficult, since increased organic content in freshwaters requires higher dosages of chemicals during water treatment.  Changes in land use through increased industrial forestry, decreased sulphur deposition from reduced industrial emissions, changing patterns of hydrological and meteorological parameters resulting from climate change, including recently highlighted increase in iron concentrations have been proposed to explain brownification. Drained peat bogs are man-made source of brownifying substances, capable of causing brownification in the rivers and lakes where the water ends up. This research is aimed at investigating dissolved organic matter, total organic carbon, iron, phosphorous, nitrogen and colour in bog ditches draining into the Storån River and Lake Bolmen in southern Sweden, in order to answer these research questions: (1) What are the differences in the level of water quality parameters, pH, conductivity, temperature, DOM, TOC, total phosphorous, total nitrogen, Fe and colour, between bog ditches and Storån River? And what could be the outcome of Colour absorbance comparison, between bog ditches, Storån and lake Bolmen as a single control sample? (2) Is there any association among the different water quality parameters, pH, conductivity, temperature, DOM, TOC, total phosphorous, total nitrogen, Fe and colour within the bog ditch water? Water samples from bog ditches and their corresponding Storån River locations, were used in the analysis. DOM and flow showed significant differences, after statistical test for difference. Conductivity, DOM, total nitrogen and total phosphorous exhibited significant correlations with pH.  TOC also had a correlation with DOM., while colour correlated and depended strongly on Fe, within the bog ditches. Therefore, the bog ditch has behaved to contribute some amount of the brownification, found in Southern Swedish Lakes and Rivers. This knowledge might be useful in future, for more studies and control of Swedish fresh water brownification.
280

Effects of diverse plant species on the bioavailability of contaminants in soil

Nguyen, Thi Xuan Trang 12 1900 (has links)
No description available.

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