Die Uferfiltration (UF) ist eine potentielle Alternative zur konventionellen Oberflächenwasseraufbereitung in Indien, da Trübstoffe, pathogene Mikroorganismen und organische Wasserinhaltsstoffe effektiv entfernt werden. In dieser Arbeit wurde erstmals ein umfangreicher Überblick zu bestehenden UF-Anlagen in Indien erarbeitet. Für die Standorterkundung und -bewertung wurde ein Konzept erarbeitet, das an drei Standorten entlang des Ganges getestet und weiterentwickelt wurde. Das Konzept umfasst vier Stufen: Standortvorerkundung, Bestimmung von Grundwasserleiterparametern, Erfassung von hydraulischen und Beschaffenheits-parametern sowie numerische Grundwasser-strömungsmodellierung. Entlang des oberen Flusslaufes des Ganges (Haridwar und Srinagar) wurden günstige geohydraulische Verhältnisse identifiziert (kf = 10E-4 bis 10E-3 m/s, Grundwasser leitermächtigkeit 11 bis 20 m). Entlang des unteren Flusslaufes (Patna) gibt es in Abhängigkeit von der Mächtigkeit der Sedimentablagerungen im Ganges nur bei erhöhter Schleppkraft im Monsun eine gute hydraulische Verbindung zwischen dem Fluss und dem Grundwasserleiter. In Haridwar wurde der Uferfiltratanteil im Rohwasser mittels Isotopenanalysen (δ18O) und Leitfähigkeitsmessungen im Fluss- und Rohwasser ermittelt. Der Uferfiltratanteil in den auf einer Insel und südlich davon gelegenen Brunnen liegt bei bis zu 90%. An den untersuchten Standorten wird durch die UF eine effektive Entfernung von E. coli um 3,5 bis 4,4 Log10 und der Trübung bis >2 Log10 Einheiten erreicht. Eine Entfernung von 3 Log10 Einheiten wurde bereits bei einer Fließzeit des Uferfiltrats von zwei Tagen beobachtet. Die erhöhte Anzahl an Coliformen in einigen Brunnen am Standort Haridwar resultiert aus Verunreinigungen des landseitigen Grundwassers. Bei Hochwässern und Starkregenereignissen muss eine Kontamination durch den direkten Eintrag von Wasser durch undichte Brunnenabdeckungen, Risse in den Schächten bzw. unsachgemäßen Brunnenbau berücksichtigt werden. Die Anwendung des angepassten Untersuchungskonzepts an 15 weiteren UF-Standorten in Indien hat gezeigt, dass die niedrigen DOC-Konzentrationen im Flusswasser (0,9 bis 3,0 mg/L) und im Brunnenwasser (0,4 bis 2,3 mg/L) günstig für die Anwendung der UF sind. Bei erhöhten DOC-Konzentrationen (Vormonsun) im Flusswasser konnte in Delhi und Mathura im Monsun eine 50%ige Verminderung erreicht werden. Bei der Erkundung neuer UF-Standorte in bergigen Gebieten sind die Grundwasserleitermächtigkeit mit geophysikalischen Erkundungsverfahren, die Strömungsverhältnisse in den alluvialen Ablagerungen sowie lokale Hochwasserrisiken zu untersuchen.:Abstract i (Seitenzahl / page number) Acknowledgements iii Table of contents v List of tables viii List of figures ix Abbreviations and symbols xi 1 Introduction 1 1.1 Problem description 1 1.2 Riverbank filtration and its potential in India 2 1.3 Motivation 3 1.4 Aims 4 2 Bank filtration in context to India’s water resources 5 2.1 Water budget of India and the Ganga River catchment 5 2.1.1 Water budget 5 2.1.2 The Ganga River catchment 6 2.2 Problems of surface water abstraction for drinking water production 8 2.2.1 Effect of low surface flows on the quantity of raw water abstraction 8 2.2.2 Effect of the monsoon on conventional drinking water treatment plants using directly abstracted surface water 9 2.2.3 Quality of surface water 10 2.2.4 Treatment of directly abstracted surface water for drinking 11 2.3 Sustainability issues of groundwater abstraction 11 2.4 Drinking water consumption in India 12 2.5 Bank filtration for water supply 14 2.5.1 Geohydraulic, siting and design aspects of bank filtration systems 14 2.5.2 Water quality aspects 15 2.5.3 Water quality aspects for bank filtration in India 15 2.5.4 Risks to riverbank filtration sites from floods 16 2.6 Hypotheses favouring the use of bank filtration and the need for a concept to investigate potential RBF sites in India 17 3 Study areas 18 3.1 Choice of study areas 18 3.2 Case study site Haridwar 19 3.3 Case study site Patna 20 3.4 Case study site Srinagar in Uttarakhand 21 3.5 Hypotheses favouring RBF at the selected study sites 22 4 Methodology for the investigation of the case study sites 24 4.1 Overview of methodology for investigating the case-study sites 24 4.2 Investigations at the case study site of Haridwar 25 4.2.1 Initial site-assessment 25 4.2.2 Basic site-survey and establishing monitoring infrastructure 26 4.2.2.1 Identification of specific locations for monitoring wells 26 4.2.2.2 Geodetic survey and inventory of existing on-site infrastructure 26 4.2.2.3 Construction of exploratory wells 27 4.2.3 Determination of hydrogeological parameters 27 4.2.3.1 Sediment analyses 27 4.2.3.2 Determination of hydraulic conductivity by pump tests on large-diameter wells 29 4.2.4 Water level and stable isotope measurements 30 4.2.4.1 Water level 30 4.2.4.2 Stable isotopes 31 4.2.5 Water quality monitoring 31 4.2.5.1 Initial investigations, screening and formulation of monitoring concept 31 4.2.5.2 Comprehensive and regular monitoring 2011 - 2013 33 4.3 Investigations at the case study site of Patna 34 4.3.1 Initial site-assessment, basic-site survey and monitoring 34 4.3.2 Sampling for water quality and isotope analyses 35 4.4 Investigations at the case study site of Srinagar in Uttarakhand 35 4.4.1 Basic site-survey and establishing monitoring infrastructure 35 4.4.1.1 Identification of a specific location for a new RBF well 35 4.4.1.2 Construction of production and monitoring wells and exploratory boreholes 37 4.4.2 Determination of hydrogeological parameters and monitoring 38 4.4.2.1 Sediment analyses and determination of hydraulic conductivity of the aquifer 38 4.4.3 Water quality monitoring 40 4.5 Column experiments to determine the removal of bacteriological indicators under field conditions 40 5 Characterisation of the RBF system in Haridwar 42 5.1 Site and design aspects 42 5.1.1 Location of RBF wells 42 5.1.2 Design of RBF wells 44 5.1.3 Quantity of drinking water produced by RBF 45 5.2 Aquifer characterisation 47 5.3 Numerical groundwater flow model of RBF well field in Haridwar 49 5.3.1 Model set-up 49 5.3.2 Model calibration 50 5.4 Origin of water and mean portion of bank filtrate abstracted by RBF wells 52 5.5 Water quality 53 5.6 Analysis of presence of thermotolerant coliforms in RBF wells 56 5.7 Impact of regulated Upper Ganga Canal on RBF wells on Pant Dweep 58 5.8 Summary of case study site Haridwar 60 5.8.1 Aspects related to water quality 60 5.8.2 Benefit of groundwater flow modelling 60 6 Evaluation of the potential for RBF in Patna 62 6.1 Physiography and hydrogeology 62 6.1.1 South Ganga Plain 62 6.1.2 Patna 63 6.2 Ground and surface water levels 65 6.3 Ganga River morphology 66 6.4 Water quality 67 6.5 Numerical groundwater flow model of case study site Patna 68 6.5.1 Model geometry and initial conditions 68 6.5.2 Boundary conditions 69 6.5.3 Steady-state flow modelling 70 6.6 Isotope analyses 71 6.7 Summary of case study site Patna 71 7 Evaluation of the potential for RBF in Srinagar 73 7.1 Drinking water production and overview of geomorphology 73 7.2 RBF site characterisation 74 7.2.1 Aquifer geometry and material 74 7.2.2 Water levels 75 7.2.3 Hydraulic conductivity 76 7.3 Numerical groundwater flow model of case study site Srinagar 77 7.3.1 Model geometry and calibration 77 7.3.2 Origin of bank filtrate and travel time 78 7.4 Water quality 79 7.5 Discussion and summary of case study site Srinagar 81 8 Assessment of risks from floods and insufficient sanitary measures to RBF wells in Haridwar and Srinagar 82 8.1 Flood-risk identification from field investigations 82 8.1.1 Description of an extreme flood event in Haridwar 82 8.1.2 Description of an extreme flood event in Srinagar 82 8.1.3 Summary of identifiable risks 83 8.2 Assessment of risks to RBF wells 84 8.2.1 Design of wells and direct contamination 84 8.2.2 Field investigations on the removal of bacteriological indicators 85 8.2.3 Removal of coliforms under field conditions by column experiments 87 8.3 Proposals to mitigate risks at RBF sites Haridwar and Srinagar 89 8.3.1 Operational and technical aspects for a general risk management plan 89 8.3.2 Health aspects for a general risk management plan 89 8.3.3 Criteria for flood protection measures of RBF wells 90 8.3.4 Sanitary sealing of RBF wells 90 9 Application of initial site-assessment to investigate other RBF sites in India 92 9.1 Hydrogeology and system-design 92 9.1.1 RBF systems for small and large-scale urban water supply 92 9.1.2 “Koop” well RBF systems for small-scale rural water supply 98 9.2 Water quality parameters 98 9.2.1 Removal of bacteriological indicators by RBF 98 9.2.2 Removal of dissolved organic carbon and organic micropollutants by RBF 101 9.2.3 Inorganic parameters 102 10 Conclusions, recommendations and propagation of RBF 105 10.1 Hydrogeological and system-design considerations 105 10.2 Aspects for improvement of the concept for RBF site investigations 106 10.3 Policy and planning aspects for the propagation of RBF in India 108 References 110 Annexes 121 / Riverbank filtration or bank filtration (RBF / BF) is a potential alternative to the direct abstraction and conventional treatment of surface water by virtue of the effective removal of pathogens, turbidity, suspended particles and organic substances. A comprehensive overview of existing RBF systems in India has been compiled for the first time. To systematically select and investigate new and existing potential RBF sites in India, a methodological concept was developed and tested at three sites along the Ganga River. The four stages of the concept are: initial site-assessment, basic site-survey, monitoring of water quality and quantity parameters and determination of aquifer parameters and numerical groundwater flow modelling. Suitable geohydraulic conditions for RBF (hydraulic conductivity: 10E-4 to 10E-3 m/s, aquifer thickness: 11 to 20 m) exist along the upper course of the Ganga (Haridwar and Srinagar). Due to the presence of fine sediment layers beneath the river bed along the Ganga’s lower course (Patna), river-aquifer interaction occurs during increased shear stress on the riverbed in monsoon. The portion of bank filtrate abstracted by the wells in Haridwar was determined from isotope analyses (Oxygen 18) and electrical conductivity measurements of river and well water and is up to 90% for wells located on an island and between the river and a canal. The results were confirmed by groundwater flow modelling. A high removal of E. coli (3.5 to 4.4 Log10 units) and turbidity (>2 Log10 units) was observed at the investigated sites. An E. coli removal of 3 Log10 units was observed for short travel times of 2 days. Higher coliform counts in some wells occur due to contamination from landside groundwater. During floods and intense rainfall events, contamination of RBF wells from direct entry of flood water, seepage of surface runoff into the well through leaky covers, fissures in the well-heads / caissons and in-appropriately sealed well-bases has to be considered. The application of the adapted investigation concept to 15 other sites in India showed that the low DOC concentrations in river water (0.9 to 3.0 mg/L) and well-water (0.4 to 2.3 mg/L) are favourable for the application of RBF. A 50% decrease of the high (pre-monsoon) DOC concentration was observed during monsoon in Delhi and Mathura. For the exploration of new RBF sites in hilly / mountainous areas, investigations of the aquifer thickness using geophysical methods, subsurface flow conditions in the alluvial deposits and the risk from floods should be conducted.:Abstract i (Seitenzahl / page number) Acknowledgements iii Table of contents v List of tables viii List of figures ix Abbreviations and symbols xi 1 Introduction 1 1.1 Problem description 1 1.2 Riverbank filtration and its potential in India 2 1.3 Motivation 3 1.4 Aims 4 2 Bank filtration in context to India’s water resources 5 2.1 Water budget of India and the Ganga River catchment 5 2.1.1 Water budget 5 2.1.2 The Ganga River catchment 6 2.2 Problems of surface water abstraction for drinking water production 8 2.2.1 Effect of low surface flows on the quantity of raw water abstraction 8 2.2.2 Effect of the monsoon on conventional drinking water treatment plants using directly abstracted surface water 9 2.2.3 Quality of surface water 10 2.2.4 Treatment of directly abstracted surface water for drinking 11 2.3 Sustainability issues of groundwater abstraction 11 2.4 Drinking water consumption in India 12 2.5 Bank filtration for water supply 14 2.5.1 Geohydraulic, siting and design aspects of bank filtration systems 14 2.5.2 Water quality aspects 15 2.5.3 Water quality aspects for bank filtration in India 15 2.5.4 Risks to riverbank filtration sites from floods 16 2.6 Hypotheses favouring the use of bank filtration and the need for a concept to investigate potential RBF sites in India 17 3 Study areas 18 3.1 Choice of study areas 18 3.2 Case study site Haridwar 19 3.3 Case study site Patna 20 3.4 Case study site Srinagar in Uttarakhand 21 3.5 Hypotheses favouring RBF at the selected study sites 22 4 Methodology for the investigation of the case study sites 24 4.1 Overview of methodology for investigating the case-study sites 24 4.2 Investigations at the case study site of Haridwar 25 4.2.1 Initial site-assessment 25 4.2.2 Basic site-survey and establishing monitoring infrastructure 26 4.2.2.1 Identification of specific locations for monitoring wells 26 4.2.2.2 Geodetic survey and inventory of existing on-site infrastructure 26 4.2.2.3 Construction of exploratory wells 27 4.2.3 Determination of hydrogeological parameters 27 4.2.3.1 Sediment analyses 27 4.2.3.2 Determination of hydraulic conductivity by pump tests on large-diameter wells 29 4.2.4 Water level and stable isotope measurements 30 4.2.4.1 Water level 30 4.2.4.2 Stable isotopes 31 4.2.5 Water quality monitoring 31 4.2.5.1 Initial investigations, screening and formulation of monitoring concept 31 4.2.5.2 Comprehensive and regular monitoring 2011 - 2013 33 4.3 Investigations at the case study site of Patna 34 4.3.1 Initial site-assessment, basic-site survey and monitoring 34 4.3.2 Sampling for water quality and isotope analyses 35 4.4 Investigations at the case study site of Srinagar in Uttarakhand 35 4.4.1 Basic site-survey and establishing monitoring infrastructure 35 4.4.1.1 Identification of a specific location for a new RBF well 35 4.4.1.2 Construction of production and monitoring wells and exploratory boreholes 37 4.4.2 Determination of hydrogeological parameters and monitoring 38 4.4.2.1 Sediment analyses and determination of hydraulic conductivity of the aquifer 38 4.4.3 Water quality monitoring 40 4.5 Column experiments to determine the removal of bacteriological indicators under field conditions 40 5 Characterisation of the RBF system in Haridwar 42 5.1 Site and design aspects 42 5.1.1 Location of RBF wells 42 5.1.2 Design of RBF wells 44 5.1.3 Quantity of drinking water produced by RBF 45 5.2 Aquifer characterisation 47 5.3 Numerical groundwater flow model of RBF well field in Haridwar 49 5.3.1 Model set-up 49 5.3.2 Model calibration 50 5.4 Origin of water and mean portion of bank filtrate abstracted by RBF wells 52 5.5 Water quality 53 5.6 Analysis of presence of thermotolerant coliforms in RBF wells 56 5.7 Impact of regulated Upper Ganga Canal on RBF wells on Pant Dweep 58 5.8 Summary of case study site Haridwar 60 5.8.1 Aspects related to water quality 60 5.8.2 Benefit of groundwater flow modelling 60 6 Evaluation of the potential for RBF in Patna 62 6.1 Physiography and hydrogeology 62 6.1.1 South Ganga Plain 62 6.1.2 Patna 63 6.2 Ground and surface water levels 65 6.3 Ganga River morphology 66 6.4 Water quality 67 6.5 Numerical groundwater flow model of case study site Patna 68 6.5.1 Model geometry and initial conditions 68 6.5.2 Boundary conditions 69 6.5.3 Steady-state flow modelling 70 6.6 Isotope analyses 71 6.7 Summary of case study site Patna 71 7 Evaluation of the potential for RBF in Srinagar 73 7.1 Drinking water production and overview of geomorphology 73 7.2 RBF site characterisation 74 7.2.1 Aquifer geometry and material 74 7.2.2 Water levels 75 7.2.3 Hydraulic conductivity 76 7.3 Numerical groundwater flow model of case study site Srinagar 77 7.3.1 Model geometry and calibration 77 7.3.2 Origin of bank filtrate and travel time 78 7.4 Water quality 79 7.5 Discussion and summary of case study site Srinagar 81 8 Assessment of risks from floods and insufficient sanitary measures to RBF wells in Haridwar and Srinagar 82 8.1 Flood-risk identification from field investigations 82 8.1.1 Description of an extreme flood event in Haridwar 82 8.1.2 Description of an extreme flood event in Srinagar 82 8.1.3 Summary of identifiable risks 83 8.2 Assessment of risks to RBF wells 84 8.2.1 Design of wells and direct contamination 84 8.2.2 Field investigations on the removal of bacteriological indicators 85 8.2.3 Removal of coliforms under field conditions by column experiments 87 8.3 Proposals to mitigate risks at RBF sites Haridwar and Srinagar 89 8.3.1 Operational and technical aspects for a general risk management plan 89 8.3.2 Health aspects for a general risk management plan 89 8.3.3 Criteria for flood protection measures of RBF wells 90 8.3.4 Sanitary sealing of RBF wells 90 9 Application of initial site-assessment to investigate other RBF sites in India 92 9.1 Hydrogeology and system-design 92 9.1.1 RBF systems for small and large-scale urban water supply 92 9.1.2 “Koop” well RBF systems for small-scale rural water supply 98 9.2 Water quality parameters 98 9.2.1 Removal of bacteriological indicators by RBF 98 9.2.2 Removal of dissolved organic carbon and organic micropollutants by RBF 101 9.2.3 Inorganic parameters 102 10 Conclusions, recommendations and propagation of RBF 105 10.1 Hydrogeological and system-design considerations 105 10.2 Aspects for improvement of the concept for RBF site investigations 106 10.3 Policy and planning aspects for the propagation of RBF in India 108 References 110 Annexes 121

Student Number: 9503012G Master of Science. School of Geography, Archaeology and Environmental Studies / A brown haze which builds-up over Cape Town under calm and cold weather conditions causes public concern. The brown haze is thought to be due to the gaseous and particulate emissions from the city, industries, traffic and townships in the Cape Town region. Volatile organic carbon (VOCs) compounds are an important component of the haze layer particularly because of their reactivity. VOCs play an important role in the carbon budget and radiation balance, regional oxidant balance, and in the distribution of ozone and other reactive gases, both at the regional and global scale. In this study the variation in ambient VOC concentrations during brown and non-brown haze days over Cape Town during July and August 2003 were characterised. Ambient air samples were collected in evacuated stainless steel canistes from the South African Weather Service (SAWS) research aircraft (Aerocommander, ZS-JRB) and later analysed by gas chromotography equipped with a flame ionisation detector (GC-FID). Benzene, toluene, ethylbenzene and xylene (BTEX) were the specific VOCs targeted for this study. Comparable meteorology data was also collected to determine the effects of wind field and atmospheric stability on BTEX concentrations.

[pt] Este trabalho investiga a eficiência do Processo Oxidativo Avançado eletro-Fenton (EF) no tratamento de efluentes da indústria de celulose e papel previamente tratados por processo biológico. Utilizou-se planejamento fatorial em três variáveis e dois níveis, variando-se pH inicial (4 e 6), dosagem de H2O2:COD (1:1 e 2:1mol/mol) e densidade de corrente (j) (4 e 10mA/cm2). Experimentos foram realizados em reator de 1L com eletrodos de aço SAE1010, em regime de batelada, com tempo de reação de 60min. Avaliou-se também o processo Fenton convencional e realizou-se ensaios de controle com oxidação por H2O2, Eletrocoagulação e Fenton Zero, em 20min. Quanto ao EF, observou-se que um tempo de 40min foi suficiente para estabilização da remoção de cor e compostos lignínicos e 20min para remoção de carbono orgânico dissolvido (COD) nos processos com maior j e 40min, naqueles com menor j. A melhor configuração do EF foi com pH inicial 4, relação H2O2:COD 1:1mol/mol e menor j (4mA/cm2), alcançando-se remoção de 82 porcento de COD, 99 porcento de compostos lignínicos e 99 porcento de cor verdadeira, com consumo energético de 1.0 kWh/m3. Comparando-se os processos avaliados, todos no ponto central do plano fatorial, observou-se maior eficiência do EF na remoção de cor e compostos lignínicos e menor eficiência na remoção de COD, em relação ao processo Fenton convencional, contudo, com maior eficiência em sua melhor condição operacional. Conclui-se que o EF se mostra eficiente no polimento deste efluente para remoção da matéria orgânica e cor verdadeira remanescentes do processo biológico e que o parâmetro de maior influência neste processo é a densidade de corrente. / [en] This study investigates the efficiency of the Advanced Oxidation Process electro-Fenton (EF) in the wastewater treatment from pulp and paper industry, previously treated biologically. A factorial design of three factors and two levels was used, varying initial pH (4 and 6), H2O2:COD ratio (1:1 and 2:1mole/mole) and current density (j) (4 and 10mA/cm2). Experiments were made in a 1L reactor in batch mode with SAE 1010 steel electrodes, in 60min reaction time. The conventional Fenton process was also evaluated and control tests were carried out with direct oxidation by H2O2, Electrocoagulation and Zero-valent Fenton, with 20min. As for the EF process, it was observed that a 40min reaction time was enough to stabilize the colour and removal of the lignin compounds, and 20 minutes to remove dissolved organic carbon (COD) in the processes with higher j and 40min, in those with lower j. The best configuration for the EF process was initial pH 4, H2O2:COD ratio 1:1mole/mole and lower j (4mA/cm2), leading to 82 percent COD, 99 percent lignin compounds and 99 percent colour removal, with energy consumption of 1.0kWh/m3. Comparing the evaluated processes, all at the central point of the factorial design matrix, it was observed greater efficiency of the EF in the colour and lignin compounds removal and lower efficiency in COD removal in relation to the conventional Fenton, nevertheless, with greater efficiency in its best overall condition. It was concluded that the EF-process is efficient as a polishing step of this wastewater treatment to remove the remaining organic compounds and true color from the biological process and that the parameter of greatest influence in the EF-process is the current density.

Soil spectroscopy in the visible-to-near infrared (VNIR) and mid-infrared (MIR) is a cost-effective method to determine the soil organic carbon content (SOC) based on predictive spectral models calibrated to analytical-determined SOC reference data. The degree to which uncertainty in reference data and spectral measurements contributes to the estimated accuracy of VNIR and MIR predictions, however, is rarely addressed and remains unclear, in particular for current handheld MIR spectrometers. We thus evaluated the reproducibility of both the spectral reflectance measurements with portable VNIR and MIR spectrometers and the analytical dry combustion SOC reference method, with the aim to assess how varying spectral inputs and reference values impact the calibration and validation of predictive VNIR and MIR models. Soil reflectance spectra and SOC were measured in triplicate, the latter by different laboratories, for a set of 75 finely ground soil samples covering a wide range of parent materials and SOC contents. Predictive partial least-squares regression (PLSR) models were evaluated in a repeated, nested cross-validation approach with systematically varied spectral inputs and reference data, respectively. We found that SOC predictions from both VNIR and MIR spectra were equally highly reproducible on average and similar to the dry combustion method, but MIR spectra were more robust to calibration sample variation. The contributions of spectral variation (ΔRMSE < 0.4 g·kg−1) and reference SOC uncertainty (ΔRMSE < 0.3 g·kg−1) to spectral modeling errors were small compared to the difference between the VNIR and MIR spectral ranges (ΔRMSE ~1.4 g·kg−1 in favor of MIR). For reference SOC, uncertainty was limited to the case of biased reference data appearing in either the calibration or validation. Given better predictive accuracy, comparable spectral reproducibility and greater robustness against calibration sample selection, the portable MIR spectrometer was considered overall superior to the VNIR instrument for SOC analysis. Our results further indicate that random errors in SOC reference values are effectively compensated for during model calibration, while biased SOC calibration data propagates errors into model predictions. Reference data uncertainty is thus more likely to negatively impact the estimated validation accuracy in soil spectroscopy studies where archived data, e.g., from soil spectral libraries, are used for model building, but it should be negligible otherwise.

In this research, five different coagulants were evaluated to determine their effectiveness at removing turbidity, color and dissolved organic carbon (DOC) from a surface water in Sarasota County, Florida. Bench-scale jar tests that simulated conventional coagulation, flocculation, and sedimentation processes were used. Iron-based coagulants (ferric chloride and ferric sulfate) and aluminum-based coagulants (aluminum sulfate, polyaluminum chloride (PACl) and aluminum chlorohydrate (ACH)) were used to treat a highly organic surface water supply (DOC ranging between 10 and 30 mg/L), known as the Cow Pen Slough, located within central Sarasota County, Florida. Isopleths depicting DOC and color removal efficiencies as a function of both pH and coagulant dose were developed and evaluated. Ferric chloride and ACH were observed to obtain the highest DOC (85% and 70%, respectively) and color (98% and 97%, respectively) removals at the lowest dose concentrations (120 mg/L and 100 mg/L, respectively). Ferric sulfate was effective at DOC removal but required a higher concentration of coagulant and was the least effective coagulant at removing color. The traditional iron-based coagulants and alum had low turbidity removals and they were often observed to add turbidity to the water. PACl and ACH had similar percent removals for color and turbidity achieving consistent percent removals of 95% and 45%, respectively, but PACl was less effective than ACH at removing organics. Sludge settling curves, dose-sludge production ratios, and settling velocities were determined at optimum DOC removal conditions for each coagulant. Ferric chloride was found to have the highest sludge settling rate but also produced the largest sludge quantities. Total trihalomethane formation potential (THMFP) was measured iv for the water treated with ferric chloride and ACH. As with DOC removal, ferric chloride yielded a higher percent reduction with respect to THMFP.

Le réservoir de carbone de sol est un élément clé du cycle global du carbone et donc du système climatique. Les sols et le carbone organique qu'ils contiennent constituent le plus grand réservoir de carbone des écosystèmes terrestres. Ce réservoir est également responsable du stockage d'une grande quantité de carbone prélevé de l'atmosphère par les plantes par la photosynthèse. C'est pourquoi les sols sont considérés comme une stratégie de mitigation viable pour réduire la concentration atmosphérique de CO2 dûe aux émissions globales de CO2 d'origine fossile. Malgré son importance, des incertitudes subsistent quant à la taille du réservoir global de carbone organique de sol et à ses dynamiques. Les modèles de biosphère terrestre sont des outils essentiels pour quantifier et étudier la dynamique du carbone organique de sol. Ces modèles simulent les processus biophysiques et biogéochimiques au sein des écosystèmes et peuvent également simuler le comportement futur du réservoir de carbone organique de sol en utilisant des forçages météorologiques appropriés. Cependant, de grandes incertitudes dans les projections faite par les modèles de biosphère terrestre sur les dynamiques du carbone organique de sol ont été observées, en partie dues au problème de l'équifinalité. Afin d'améliorer notre compréhension de la dynamique du carbone organique de sol, cette recherche visait à optimiser les paramètres du schéma de carbone de sol contenu dans le modèle de schéma canadien de surface terrestre incluant les cycles biogéochimiques (CLASSIC), afin de parvenir à une meilleure représentation de la dynamique du carbone organique de sol. Une analyse de sensibilité globale a été réalisée pour identifier lesquels parmis les 16 paramètres du schéma de carbone de sol, n'affectaient pas la simulation du carbone organique de sol et de la respiration du sol. L'analyse de sensibilité a utilisé trois sites de covariance des turbulences afin de représenter différentes conditions climatiques simulées par le schéma de carbone de sol et d'économiser le coût calculatoire de l'analyse. L'analyse de sensibilité a démontré que certains paramètres du schéma de carbone de sol ne contribuent pas à la variance des simulations du carbone organique de sol et de la respiration du sol. Ce résultat a permis de réduire la dimensionnalité du problème d'optimisation. Ensuite, quatre scénarios d'optimisation ont été élaborés sur la base de l'analyse de sensibilité, chacun utilisant un ensemble de paramètres. Deux fonctions coûts ont été utilisées pour l'optimisation de chacun des scénarios. L'optimisation a également démontré que la fonction coût utilisée avait un impact sur les ensembles de paramètres optimisés. Les ensembles de paramètres obtenus à partir des différents scénarios et fonctions coûts ont été comparés à des ensembles de données indépendants et à des estimations globales du carbone organique de sol à l'aide de métrique tel la racine de l'erreur quadratique moyenne et le bias, afin d'évaluer l'effet des ensembles de paramètres sur les simulations effectuées par le schéma de carbone de sol. Un ensemble de paramètres a surpassé les autres ensembles de paramètres optimisés ainsi que le paramétrage par défaut du modèle. Ce résultat a indiqué que la structure d'optimisation était en mesure de produire un ensemble de paramètres qui simulait des valeurs de carbone organique de sol et de respiration du sol qui étaient plus près des valeurs observées que le modèle CLASSIC par défaut, améliorant la représentation de la dynamique du carbone du sol. Cet ensemble de paramètres optimisés a ensuite été utilisé pour effectuer des simulations futures (2015-2100) de la dynamique du carbone organique de sol afin d'évaluer son impact sur les projections de CLASSIC. Les simulations futures ont montré que l'ensemble de paramètres optimisés simulait une quantité de carbone organique de sol 62 % plus élevée que l'ensemble de paramètres par défaut tout en simulant des flux de respiration du sol similaires. Les simulations futures ont également montré que les ensembles de paramètres optimisés et par défaut prévoyaient que le réservoir de carbone organique de sol demeurerait un puits de carbone net d'ici 2100 avec des sources nettes régionales. Cette étude a amélioré globalement la représentation de la dynamique du carbone organique de sol dans le schéma de carbone de sol de CLASSIC en fournissant un ensemble de paramètres optimisés. Cet ensemble de paramètres devrait permettre d'améliorer notre compréhension de la dynamique du carbone du sol. / The soil carbon pool is a vital component of the global carbon cycle and, therefore, the climate system. Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems. This pool stores a large quantity of carbon that plants have removed from the atmosphere through photosynthesis. Because of this, soils are considered a viable climate change mitigation strategy to lower the global atmospheric CO2 concentration that is presently being driven higher by anthropogenic fossil CO2 emissions. Despite its importance, there are still considerable uncertainties around the size of the global SOC pool and its response to changing climate. Terrestrial biosphere models (TBM) simulate the biogeochemical processes within ecosystems and are critical tools to quantify and study SOC dynamics. These models can also simulate the future behavior of SOC if carefully applied and given the proper meteorological forcings. However, TBM predictions of SOC dynamics have high uncertainties due in part to equifinality. To improve our understanding of SOC dynamics, this research optimized the parameters of the soil carbon scheme contained within the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC), to better represent SOC dynamics. A global sensitivity analysis was performed to identify which of the 16 parameters of the soil carbon scheme did not affect simulated SOC stocks and soil respiration (Rsoil). The sensitivity analysis used observations from three eddy covariance sites for computational efficiency and to encapsulate the climate represented by the global soil carbon scheme. The sensitivity analysis revealed that some parameters of the soil carbon scheme did not contribute to the variance of simulated SOC and Rsoil. These parameters were excluded from the optimization which helped reduce the dimensionality of the optimization problem. Then, four optimization scenarios were created based on the sensitivity analysis, each using a different set of parameters to assess the impact the number of parameters included had on the optimization. Two different loss functions were used in the optimization to assess the impact of accounting for observational error. Comparing the optimal parameters between the optimizations performed using the different loss functions showed that the loss functions impacted the optimized parameter sets. To determine which optimized parameter set obtained by each loss function was most skillful, they were compared to independent data sets and global estimates of SOC, which were not used in the optimization using comparison metrics based on root-mean-square-deviation and bias. This study generated an optimal parameter set that outperformed the default parameterization of the model. This optimal parameter set was then applied in future simulations of SOC dynamics to assess its impact upon CLASSIC's future projections. These future simulations showed that the optimal parameter set simulated future global SOC content 62 % higher than the default parameter set while simulating similar Rsoil fluxes. The future simulations also showed that both the optimized and default parameter sets projected that the SOC pool would be a net sink by 2100 with regional net sources, notably tropical regions.

No description available.

The urgent ongoing contemporary climate change is drastically changing the Earth as we know it. In the Arctic, the climate is changing more drastically than the global average, and temperatures are rising significantly more. The phenomenon, known as Arctic amplification, is believed to happen by a combination of albedo reduction, cloud-feedback, and temperature inversion. Another important, but often overlooked, factor in Arctic climate change is dust. Dust does not only cause albedo reduction but has also been found to host syngenetic permafrost in Adventdalen, Svalbard. As permafrost is both a sensitive and important carbon reserve, holding twice as much carbon as currently available in the atmosphere, it is of great importance to understand the carbon storage mechanism of it. This study shows not only a correlation between cryostructures and organic carbon content but presents aeolian sedimentation rate as a possible cause of it. The results show that for syngenetic permafrost in Adventdalen, a high sedimentation rate yields structureless permafrost with low organic content. Inversely, a low sedimentation rate yields well defined cryostructures with high organic content. This shows that aeolian dust activity and loess deposits are vital to understand, in order to properly assess the cryostratigraphy and carbon content. / Den brådskande samtida klimatförändringen omarbetar dramatiskt vår värld. Arktis klimat förändras mer drastiskt än på resten av jorden och temperaturen stiger avsevärt snabbare. Fenomenet kallas förArktis förstärkning, eller Arctic Amplification, och antas ske på grund av synergier mellan minskning av albedo, molnfeedback och temperaturinversion. Damm är en annan viktig, men ofta underskattad faktor i klimatförändrarna i Arktis. Damm bidrar inte bara till en ökad reduktion av albedo utan dammavlagringar i Adventdalen Svalbard fungerar som en viktig grogrund för syngenetisk permafrost. Kolsänkan i permafrost är lika skör som den är viktig, då permafrost förvarar dubbelt så mycket kol som för nuvarande finns i atmosfären, men samtidigt stadigt tinar. Därför är det ytterst viktigt att förstå hur permafrost fungerar, själva mekanismerna bakom förvarandet av organisk kol. Detta arbete visar inte bara ett samband mellan kryostrukturer och organiskt kol i permafrost, utan föreslår att sedimentationshastighet är orsaken till det. Resultaten av LOI (loss on ignition) och kryostratigrafi tyder på att en hög sedimentationshastighet skapar en strukturlös permafrost som endast har låga halter av organisk materia. I det omvända fallet ger en låg sedimentationshastighet välformade kryostrukturer, och en permafrost med hög andel organisk materia. Detta visar på att sedimentationshastighet i loess är en viktig aspekt för att bedöma lagring av kol i permafrost, vilket är en avsevärd kolsänka att förstå i dagens klimatförändringar.

Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C₃ Prosopis veleruina (mesquite) trees, whereas the burned plots are open C₄-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant -available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C₃ shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C₄ grasses to C₃ shrubs in surface soil layers. δ¹³C(SOM) values indicate that the Holocene and Late Pleistocene were dominated by C₄ grasslands, and the pre-Late Pleistocene vegetation was a C₄-grass savanna with abundant C₃ plants.

Les proliférations nuisibles de la cyanobactérie filamenteuse benthique Lyngbya wollei qui forme des tapis déposés sur les sédiments ont augmenté en fréquence au cours des 30 dernières années dans les rivières, lacs et sources de l'Amérique du Nord. Lyngbya wollei produit des neurotoxines et des composés organiques volatils (géosmin, 2-méthylisobornéol) qui ont des répercussions sur la santé publique de même que des impacts d'ordre socioéconomiques. Cette cyanobactérie est considérée comme un habitat et une source de nourriture de piètre qualité pour les invertébrés en raison de sa gaine robuste et de sa production de toxines. Les proliférations de L. wollei ont été observées pour la première fois en 2005 dans le fleuve Saint-Laurent (SLR; Québec, Canada). Nous avons jugé important de déterminer sa distribution sur un tronçon de 250 km afin d'élaborer des modèles prédictifs de sa présence et biomasse en se basant sur les caractéristiques chimiques et physiques de l'eau. Lyngbya wollei était généralement observé en aval de la confluence de petits tributaires qui irriguent des terres agricoles. L’écoulement d’eaux enrichies à travers la végétation submergée se traduisait par une diminution de la concentration d’azote inorganique dissous (DIN), alors que les concentrations de carbone organique dissous (DOC) et de phosphore total dissous (TDP) demeuraient élevées, produisant un faible rapport DIN :TDP. Selon nos modèles, DOC (effet positif), TP (effet négatif) et DIN :TDP (effet négatif) sont les variables les plus importantes pour expliquer la répartition de cette cyanobactérie. La probabilité que L. wollei soit présent dans le SLR a été prédite avec exactitude dans 72 % à 92 % des cas pour un ensemble de données indépendantes. Nous avons ensuite examiné si les conditions hydrodynamiques, c'est-à-dire le courant généré par les vagues et l'écoulement du fleuve, contrôlent les variations spatiales et temporelles de biomasse de L. wollei dans un grand système fluvial. Nous avons mesuré la biomasse de L. wollei ainsi que les variables chimiques, physiques et météorologiques durant trois ans à 10 sites le long d'un gradient d'exposition au courant et au vent dans un grand (148 km2) lac fluvial du SLR. L'exposition aux vagues et la vitesse du courant contrôlaient les variations de biomasses spatiales et temporelles. La biomasse augmentait de mai à novembre et persistait durant l'hiver. Les variations interannuelles étaient contrôlées par l'écoulement de la rivière (niveau d'eau) avec la crue printanière qui délogeait les tapis de l'année précédente. Les baisses du niveau d'eau et l'augmentation de l'intensité des tempêtes anticipées par les scénarios de changements climatiques pourraient accroître la superficie colonisée par L. wollei de même que son accumulation sur les berges. Par la suite, nous avons évalué l'importance relative de L. wollei par rapport aux macrophytes et aux épiphytes. Nous avons examiné l'influence structurante de l'échelle spatiale sur les variables environnementales et la biomasse de ces producteurs primaires (PP) benthiques. Nous avons testé si leur biomasse reflétait la nature des agrégats d'habitat basées sur l'écogéomorphologie ou plutôt le continuum fluvial. Pour répondre à ces deux questions, nous avons utilisé un design à 3 échelles spatiales dans le SLR: 1) le long d'un tronçon de 250 km, 2) entre les lacs fluviaux localisés dans ce tronçon, 3) à l'intérieur de chaque lac fluvial. Les facteurs environnementaux (conductivité et TP) et la structure spatiale expliquent 59% de la variation de biomasse des trois PP benthiques. Spécifiquement, les variations de biomasses étaient le mieux expliquées par la conductivité (+) pour les macrophytes, par le ratio DIN:TDP (+) et le coefficient d'extinction lumineuse (+) pour les épiphytes et par le DOC (+) et le NH4+ (-) pour L. wollei. La structure spatiale à l'intérieur des lacs fluviaux était la plus importante composante spatiale pour tous les PP benthiques, suggérant que les effets locaux tels que l'enrichissement par les tributaire plutôt que les gradients amont-aval déterminent la biomasse de PP benthiques. Donc, la dynamique des agrégats d'habitat représente un cadre général adéquat pour expliquer les variations spatiales et la grande variété de conditions environnementales supportant des organismes aquatiques dans les grands fleuves. Enfin, nous avons étudié le rôle écologique des tapis de L. wollei dans les écosystèmes aquatiques, en particulier comme source de nourriture et refuge pour l'amphipode Gammarus fasciatus. Nous avons offert aux amphipodes un choix entre des tapis de L. wollei et soit des chlorophytes filamenteuses ou un tapis artificiel de laine acrylique lors d'expériences en laboratoire. Nous avons aussi reconstitué la diète in situ des amphipodes à l'aide du mixing model (d13C et δ15N). Gammarus fasciatus choisissait le substrat offrant le meilleur refuge face à la lumière (Acrylique>Lyngbya=Rhizoclonium>Spirogyra). La présence de saxitoxines, la composition élémentaire des tissus et l'abondance des épiphytes n'ont eu aucun effet sur le choix de substrat. Lyngbya wollei et ses épiphytes constituaient 36 et 24 % de l'alimentation in situ de G. fasciatus alors que les chlorophytes, les macrophytes et les épiphytes associées représentaient une fraction moins importante de son alimentation. Les tapis de cyanobactéries benthiques devraient être considérés comme un bon refuge et une source de nourriture pour les petits invertébrés omnivores tels que les amphipodes. / Harmful proliferations of the filamentous cyanobacterium L. wollei forming conspicuous benthic mats on the bottom sediment have been reported with increasing frequency in the last 30 years in rivers, lakes, and springs in North America. It is a known producer of neurotoxins and volatile organic compounds (geosmin, 2-methylisoborneol) thus exerting socioeconomic and public health impacts. Lyngbya wollei is also considered a poor nutritional source for invertebrates because of its robust sheath and toxin production. Proliferation of L. wollei in St. Lawrence River (SLR; Quebec, Canada) was first noticed in 2005. We deemed important to determine its distribution over a 250 km stretch of the SLR to elaborate predictive models of its presence and biomass based on chemical and physical characteristics. Lyngbya wollei was generally found downstream of the inflow tributaries draining farmlands. As enriched waters flowed slowly through submerged vegetation, dissolved inorganic nitrogen (DIN) concentration dropped but dissolved organic carbon (DOC) and total dissolved phosphorus (TDP) remained high, leading to a low DIN:TDP ratio. Models identified DOC (positive effect), TP (negative effect), and DIN:TDP (negative effect) as the most important variables explaining L. wollei distribution. The risk of L. wollei occurrence in the SLR was correctly forecasted in 72%-92% of all cases with an independent data set. We then examined if hydrodynamic conditions, namely currents generated by waves and river flow, control spatial and temporal variations of L. wollei biomass in a large river system. We measured L. wollei biomass together with meteorological, physical, and chemical variables over three years at 10 sites along a gradient of exposure to current and wind in a large (148 km2) fluvial lake of SLR. Wave exposure and current velocity controlled spatial and temporal biomass variations. Biomass increased from May to November and persisted during winter. Interannual variations were primarily controlled by river flow (water level) with spring discharge dislodging mats from the previous year. As anticipated under climate change scenarios, drops in water level and rising storm intensity may lead to an increase in the areas colonized by L. wollei, together with more frequent episodes of mat disruption and beach fouling. Additionally, we evaluated the relative importance of L. wollei with respect to macrophytes and epiphytes. We assessed the influence of the spatial scale in structuring environmental variables and biomass of these benthic primary producers (PP). We also test to which extent their biomass reflected the nature of patches based on ecogeomorphology or the river continuum. To address these two questions, we used a nested design at 3 spatial scales within the SLR: 1) along a 250-km-long upstream-downstream river stretch, 2) among three fluvial lakes located within that river stretch and 3) within each fluvial lake. Environmental factors (conductivity and TP) and spatial structure together explained 59% of the variability in biomass of all three benthic PP. Spatial variability of biomass was best explained by conductivity (+) for macrophytes, DIN:TDP ratio (+) and water extinction coefficient (+) for epiphytes and DOC (+) and NH4+ (-) for L. wollei mats. Within-lake structure was the most important spatial component for all benthic PP, suggesting that local effects, such as enrichment by the inflow of tributaries, rather than upstream-downstream gradients, determined the biomass and composition of benthic PP. Therefore patch dynamics represents a general framework which adequately covers the spatial variability and wide variety of environmental conditions experienced by aquatic organisms found in large rivers. Finally, we investigated the ecological role of L. wollei mats in aquatic ecosystems, especially as a food source and shelter for the amphipod Gammarus fasciatus. We offered amphipods a choice between mats of L. wollei and either chlorophytes or an artificial mat made of acrylic wool in laboratory experiment. Moreover, we reconstructed in situ amphipod diet using mixing model (δ13C and δ15N). Gammarus fasciatus selected the substratum offering the best light refuge (Acrylic > Lyngbya = Rhizoclonium > Spirogyra). Presence of saxitoxins, tissue elemental composition and epiphyte abundance had no significant effect on substratum choice. Lyngbya wollei and its epiphytes constituted 36 and 24% of the in situ diet of G. fasciatus whereas chlorophytes, macrophytes and associated epiphytes represented a less important fraction of its diet. Benthic cyanobacterial mats should be considered a good shelter and food source for small omnivorous invertebrates such as amphipods.