Ian D. Clark

Bio: Ian D. Clark is an academic researcher from University of Ottawa. The author has contributed to research in topics: Permafrost & Groundwater recharge. The author has an hindex of 35, co-authored 183 publications receiving 7940 citations. Previous affiliations of Ian D. Clark include University of Paris-Sud & Federation University Australia.

Environmental Isotopes in Hydrogeology

Abstract: The Environmental Isotopes Environmental Isotopes in Hydrogeology Stable Isotopes: Standards and Measurement Isotope Ratio Mass Spectrometry Radioisotopes Isotope Fractionation Isotope Fractionation (a), Enrichment (e), and Separation (D) Tracing the Hydrological Cycle Craig's Meteoric Relationship in Global Fresh Waters Partitioning of Isotopes Through the Hydrological Cycle Condensation, Precipitation, and the Meteoric Water Line A Closer Look at Rayleigh Distillation Effects of Extreme Evaporation Precipitation The T - d18O Correlation in Precipitation Local Effects on T - d18O Ice Cores and Paleotemperature Groundwater Recharge in Temperate Climates Recharge in Arid Regions Recharge from River-Connected Aquifers Hydrograph Separation in Catchment Studies Groundwater Mixing Tracing the Carbon Cycle Evolution of Carbon in Groundwaters Carbonate Geochemistry Carbon-13 in the Carbonate System Dissolved Organic Carbon Methane in Groundwaters Isotopic Composition of Carbonates Chapter 6. Groundwater Quality Sulphate, Sulphide and the Sulphur Cycle Nitrogen Cycles in Rural Watersheds The "Fuhrberger Feld" Study Source of Chloride Salinity Landfill Leachates Degredation of Chloro-organics and Hydrocarbon Sensitivity of Groundwater to Contamination Summary of Isotopes in Contaminant Hydrology Identifying and Dating Modern Groundwaters The "Age" of Groundwater Stable Isotopes Tritium in Precipitation Dating Groundwaters with Tritium Groundwater Dating with 3H -3He Chlorofluorocarbons (CFCs) Thermonuclear 36Cl Detecting Modern Groundwaters with 85Kr Submodern Groundwater Age Dating Old Groundwaters Stable Isotopes and Paleogroundwaters Groundwater Dating with Radiocarbon Correction for Carbonate Dissolution Some Additional Complications to 14C Dating 14C Dating with Dissolved Organic Carbon (DOC) Case Studies for 14C dating with DOC and DIC Chlorine-36 and Very Old Groundwater The Uranium Decay Series Water-Rock Interaction Mechanisms of Isotope Exchange High Temperature Systems Low Temperature Water-Rock Interaction Strontium Isotopes in Water and Rock Isotope Exchange in Gas-Water Reactions High pH Groundwaters-The Effect of Cement Reactions Field Methods for Sampling Groundwater Water in the Unsaturated Zone Precipitation Gases Geochemistry References Index Each chapter has Problems sections.

Groundwater Geochemistry and Isotopes

Abstract: Groundwater Geochemistry and Isotopes Introduction Water, Rocks, and Solutes The Nature of Water Solutes in Water From Elements to Aquifers Problems Thermodynamics of Aqueous Systems Introduction Mass Action Ion Activity and Equilibrium Constants Electron Activity and Redox Speciation and Mineral Solubility Codes Mass Transfer Models Problems Geochemical Reactions Introduction Dissociation Reactions Redox Reactions Gases in Groundwater CO2 and Dissolved Inorganic Carbon Problems Isotope Reactions Introduction Stable Isotope Fractionation and Distillation Radioisotopes Problems Tracing the Water Cycle Introduction Temperature-delta18O Correlation in Precipitation Meteoric Water Line for delta18O and deltaD Temperature Effects in Precipitation Groundwater Recharge Isotope Effects of Evaporation Multicomponent Groundwater Mixing Rock-Water-Gas Interaction Problems CO2 and Weathering Introduction CO2 and the Carbon Cycle Soil CO2 and Weathering Carbonate Weathering Weathering in Silicate Terrains Weathering and 13C of Dissolved Inorganic Carbon Weathering and Alkalinity Advanced Chemical Weathering: Saprolites and Laterites Problems Geochemical Evolution Introduction Ion Exchange Surfaces in Aquifers Cation Exchange Sorption Redox Evolution in Groundwaters Salinity in Groundwater Graphical Presentation of Geochemical Evolution Problems Groundwater Dating Introduction Groundwater Age and Mean Residence Time Anthropogenic Tracers of Modern Groundwater Tritium-3He Dating Dating Submodern Groundwaters Radiocarbon Dating Old Groundwater Stable Isotopes and Noble Gases in Paleogroundwaters Dating Very Old Groundwater Problems Contaminant Geochemistry and Isotopes Introduction Nitrogen Species and Groundwater Contamination Organic Carbon Compounds Degradation of Fuel Oxygenates: MTBE and Ethanol Biodegradation of Organohalogens Abiotic Degradation of Organochlorine Compounds in Permeable Reactive Barriers Fugitive Gases Landfill Leachate Acid Mine Drainage Remediation Base Metals in Groundwater Salinity in Groundwater Arsenic Nuclear Waste Sampling and Analysis Introduction Field Measurements Temperature Electrical Conductivity pH Redox Potential Field Filtering Alkalinity Titrations Major Ion Geochemistry Major Anions (Cl-, F-, SO4-, NO3-, Br -) Major Cations, Minor and Trace Metals Nutrients Sulfate and Hydrogen Sulfid Isotopes in Water delta 18O and deltaD in Water Tritium Dissolved Carbon DOC and DOC Concentration and 13C Radiocarbon Nitrogen Species Isotopes NO3-- 15N and 18O NH4+- 15N Sulfur Species Isotopes SO4 2- - 34S and 18O H2S - 34S Isotopes of the Halides 37Cl 36Cl 81Br 129I Isotopes of Minor Elements Gases Effervescing Gases Dissolved Gases Analysis Noble Gases Water Samples Passive Gas Diffusion Samplers Analysis References Index

Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales

Abstract: [1] Ice-cored permafrost landscapes are highly sensitive to disturbance and have the potential to undergo dramatic geomorphic transformations in response to climate change. The acceleration of thermokarst activity in the lower Mackenzie and Peel River watersheds of northwestern Canada has led to the development of large permafrost thaw slumps and caused major impacts to fluvial systems. Individual “mega slumps” have thawed up to 106 m3of ice-rich permafrost. The widespread development of these large thaw slumps (up to 40 ha area with headwalls of up to 25 m height) and associated debris flows drive distinct patterns of stream sediment and solute flux that are evident across a range of watershed scales. Suspended sediment and solute concentrations in impacted streams were several orders of magnitude greater than in unaffected streams. In summer, slump impacted streams displayed diurnal fluctuations in water levels and solute and sediment flux driven entirely by ground-ice thaw. Turbidity in these streams varied diurnally by up to an order of magnitude and followed the patterns of net radiation and ground-ice ablation in mega slumps. These diurnal patterns were discernible at the 103 km2 catchment scale, and regional disturbance inventories indicate that hundreds of watersheds are already influenced by slumping. The broad scale impacts of accelerated slumping are indicated by a significant increase in solute concentrations in the Peel River (70,000 km2). These observations illustrate the nature and magnitude of hydrogeomorphic changes that can be expected as glaciogenic landscapes underlain by massive ice adjust to a rapidly changing climate.

Fast Tree: Computing Large Minimum-Evolution Trees with Profiles instead of a Distance Matrix

Abstract: Gene families are growing rapidly, but standard methods for inferring phylogenies do not scale to alignments with over 10,000 sequences. We present FastTree, a method for constructing large phylogenies and for estimating their reliability. Instead of storing a distance matrix, FastTree stores sequence profiles of internal nodes in the tree. FastTree uses these profiles to implement neighbor-joining and uses heuristics to quickly identify candidate joins. FastTree then uses nearest-neighbor interchanges to reduce the length of the tree. For an alignment with N sequences, L sites, and a different characters, a distance matrix requires O(N^2) space and O(N^2 L) time, but FastTree requires just O( NLa + N sqrt(N) ) memory and O( N sqrt(N) log(N) L a ) time. To estimate the tree's reliability, FastTree uses local bootstrapping, which gives another 100-fold speedup over a distance matrix. For example, FastTree computed a tree and support values for 158,022 distinct 16S ribosomal RNAs in 17 hours and 2.4 gigabytes of memory. Just computing pairwise Jukes-Cantor distances and storing them, without inferring a tree or bootstrapping, would require 17 hours and 50 gigabytes of memory. In simulations, FastTree was slightly more accurate than neighbor joining, BIONJ, or FastME; on genuine alignments, FastTree's topologies had higher likelihoods. FastTree is available at http://microbesonline.org/fasttree.

Karst Hydrogeology and Geomorphology

Abstract: CHAPTER 1. INTRODUCTION TO KARST. 1.1 Definitions. 1.2 The Relationship Between Karst And General Geomorphology And Hydrogeology. 1.3 The Global Distribution Of Karst. 1.4 The Growth Of Ideas. 1.5 Aims Of The Book. 1.6 Karst Terminology. CHAPTER 2. THE KARST ROCKS. 2.1 Carbonate Rocks And Minerals. 2.2 Limestone Compositions And Depositional Facies. 2.3 Limestone Diagenesis And The Formation Of Dolomite. 2.4 The Evaporite Rocks. 2.5. Quartzites And Siliceous Sandstones. 2.6 Effects Of Lithologic Properties Upon Karst Development. 2.7 Interbedded Clastic Rocks. 2.8 Bedding Planes, Joints, Faults And Fracture Traces. 2.9 Fold Topography. 2.10 Paleokarst Unconformities. CHAPTER 3. DISSOLUTION: CHEMICAL AND KINETIC BEHAVIOUR OF THE KARST ROCKS. 3.1 Introduction. 3.2 Aqueous Solutions And Chemical Equilibria. 3.3 The Dissolution Of Anhydrite, Gypsum And Salt. 3.4 The Dissolution Of Silica. 3.5 Bicarbonate Equilibria And The Dissolution Of Carbonate Rocks In Normal Meteoric Waters. 3.6 The S-O-H System And The Dissolution Of Carbonate Rocks. 3.7 Chemical Complications In Carbonate Dissolution. 3.8 Biokarst Processes. 3.9 Measurements In The Field And Lab Computer Programs. 3.10 Dissolution And Precipitation Kinetics Of Karst Rocks. CHAPTER 4. DISTRIBUTION AND RATE OF KARST DENUDATION. 4.1 Global Variations In The Solutional Denudation Of Carbonate Terrains. 4.2 Measurement And Calculation Of Solutional Denudation Rates. 4.3 Solution Rates In Gypsum, Salt And Other Non-Carbonate Rocks. 4.4 Interpretation Of Measurements. CHAPTER 5. KARST HYDROLOGY. 5.1 Basic Hydrological Concepts, Terms And Definitions. 5.2 Controls On The Development Of Karst Hydrologic Systems. 5.3 Energy Supply And Flow Network Development. 5.4 Development Of The Water Table And Phreatic Zones. 5.5 Development Of The Vadose Zone. 5.6 Classification And Characteristics Of Karst Aquifers. 5.7 Applicability Of Darcy's Law To Karst. 5.8 The Fresh Water/Salt Water Interface. CHAPTER 6. ANALYSIS OF KARST DRAINAGE SYSTEMS. 6.1 The 'Grey Box' Nature Of Karst. 6.2 Surface Exploration And Survey Techniques. 6.3 Investigating Recharge And Percolation In The Vadose Zone. 6.4 Borehole Analysis. 6.5 Spring Hydrograph Analysis. 6.6 Polje Hydrograph Analysis. 6.7 Spring Chemograph Interpretation. 6.8 Storage Volumes And Flow Routing Under Different States Of The Hydrograph. 6.9 Interpreting The Organisation Of A Karst Aquifer. 6.10 Water Tracing Techniques. 6.11 Computer Modelling Of Karst Aquifers. CHAPTER 7. SPELEOGENESIS: THE DEVELOPMENT OF CAVE SYSTEMS. 7.1 Classifying Cave Systems. 7.2 Building The Plan Patterns Of Unconfined Caves. 7.3 Unconfined Cave Development In Length And Depth. 7.4 System Modifications Occurring Within A Single Phase. 7.5 Multi-Phase Cave Systems. 7.6 Meteoric Water Caves Developed Where There Is Confined Circulation Or Basal Injection Of Water. 7.7 Hypogene Caves: (A) Hydrothermal Caves Associated Chiefly With Co2. 7.8 Hypogene Caves: (B) Caves Formed By Waters Containing H2s. 7.9 Sea Coast Eogenetic Caves. 7.10 Passage Cross-Sections And Smaller Features Of Erosional Morphology. 7.11 Condensation, Condensation Corrosion, And Weathering In Caves. 7.12 Breakdown In Caves. CHAPTER 8. CAVE INTERIOR DEPOSITS. 8.1 Introduction. 8.2 Clastic Sediments. 8.3 Calcite, Aragonite And Other Carbonate Precipitates. 8.4 Other Cave Minerals. 8.5 Ice In Caves. 8.6 Dating Of Calcite Speleothems And Other Cave Deposits. 8.7 Paleo-Environmental Analysis Of Calcite Speleothems. 8.8 Mass Flux Through A Cave System: The Example Of Friar's Hole, W.Va. CHAPTER 9. KARST LANDFORM DEVELOPMENT IN HUMID REGIONS. 9.1 Coupled Hydrological And Geochemical Systems. 9.2 Small Scale Solution Sculpture - Microkarren And Karren. 9.3 Dolines - The 'Diagnostic' Karst Landform? 9.4 The Origin And Development Of Solution Dolines. 9.5 The Origin Of Collapse And Subsidence Depressions. 9.6 Polygonal Karst. 9.7 Morphometric Analysis Of Solution Dolines. 9.8 Landforms Associated With Allogenic Inputs. 9.9 Karst Poljes. 9.10 Corrosional Plains And Shifts In Baselevel. 9.11 Residual Hills On Karst Plains. 9.12 Depositional And Constructional Karst Features. 9.13 Special Features Of Evaporite Terrains. 9.14 Karstic Features Of Quartzose And Other Rocks. 9.15 Sequences Of Carbonate Karst Evolution In Humid Terrains. CHAPTER 10.THE INFLUENCE OF CLIMATE, CLIMATIC CHANGE AND OTHER ENVIRONMENTAL FACTORS ON KARST DEVELOPMENT. 10.1 The Precepts Of Climatic Geomorphology. 10.2 The Hot Arid Extreme. 10.3 The Cold Extreme: 1 Karst Development In Glaciated Terrains. 10.4 The Cold Extreme: 2 Karst Development In Permafrozen Terrains. 10.5 Sea Level Changes, Tectonic Movement And Implications For Coastal Karst Development. 10.6 Polycyclic, Polygenetic And Exhumed Karsts. CHAPTER 11. KARST WATER RESOURCES MANAGEMENT. 11.1 Water Resources And Sustainable Yields. 11.2 Determination Of Available Water Resources. 11.3 Karst Hydrogeological Mapping. 11.4 Human Impacts On Karst Water. 11.5 Groundwater Vulnerability, Protection, And Risk Mapping. 11.6 Dam Building, Leakages, Failures And Impacts. CHAPTER 12. HUMAN IMPACTS AND ENVIRONMENTAL REHABILITATION. 12.1 The Inherent Vulnerability Of Karst Systems. 12.2 Deforestation, Agricultural Impacts And Rocky Desertification. 12.3 Sinkholes Induced By De-Watering, Surcharging, Solution Mining And Other Practices On Karst. 12.4 Problems Of Construction On And In The Karst Rocks - Expect The Unexpected! 12.5 Industrial Exploitation Of Karst Rocks And Minerals. 12.6 Restoration Of Karstlands And Rehabilitation Of Limestone Quarries. 12.7 Sustainable Management Of Karst. 12.8 Scientific, Cultural And Recreational Values Of Karstlands.

Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001.

Abstract: Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.