Today… Hydrologic cycle Hydrologic cycle Reservoirs, fluxes, transient, steady state processes Reservoirs, fluxes, transient, steady state processes General origins of solutes General origins of solutes Atmospheric deposition, surface water, groundwater Atmospheric deposition, surface water, groundwater Other types of water… Other types of water…

Terminology - hydrologic cycle Reservoirs = location of mass: Reservoirs = location of mass: H 2 O cycle: glacier, lake, ocean, river etc. H 2 O cycle: glacier, lake, ocean, river etc. Gases (atmosphere) Gases (atmosphere) Solutes in water etc. Solutes in water etc. Flux = transfer of mass between reservoirs Flux = transfer of mass between reservoirs Water, other fluids, solutes Water, other fluids, solutes Units = mass per area per time ( e.g., m 3 /m 2 /yr) Units = mass per area per time ( e.g., m 3 /m 2 /yr) Requires physical transport – advection and diffusion, both water and solutes Requires physical transport – advection and diffusion, both water and solutes

Major H 2 O reservoirs Three phases (gas, liquid, solid) Three phases (gas, liquid, solid) Free H 2 O only (not hydrated minerals) Free H 2 O only (not hydrated minerals) 97% in oceans 97% in oceans 2% in ice (solid) 2% in ice (solid) Melting would raise sealevel by 2% (about 80 m) Melting would raise sealevel by 2% (about 80 m) Greenland alone would raise sealevel ~7 m Greenland alone would raise sealevel ~7 m 1% in ground water 1% in ground water 0.01% in streams and lakes 0.01% in streams and lakes 0.001% in atmosphere (vapor) 0.001% in atmosphere (vapor)

East AAIS (52 m) Gainesville (your house) elevation ~ masl West AAIS (5 m) Greenland IS (7m) Modern Sea level Continental ice sheets and sea level More or less to scale… including whale

Steady state system: Steady state system: One that has invariant concentrations through time One that has invariant concentrations through time Fluxes: Input = output Fluxes: Input = output Often can be described by equilibrium conditions (thermodynamics) Often can be described by equilibrium conditions (thermodynamics) Transient system: Transient system: Abundances within reservoirs variable with time Abundances within reservoirs variable with time Fluxes variable with time Fluxes variable with time

Transient systems Can be described by “Response time” Can be described by “Response time” The amount of time for mass to change to certain value The amount of time for mass to change to certain value Typically doubling or halving. Typically doubling or halving. Sometimes considered “e-folding time” Sometimes considered “e-folding time” Amount of time for exponentially growing quantity to increase by a factor of e. Amount of time for exponentially growing quantity to increase by a factor of e. Exponential decay = time to decrease by a factor of 1/e Exponential decay = time to decrease by a factor of 1/e

Transient conditions Transient systems described by kinetics Transient systems described by kinetics Much more complicated than equilibrium chemistry Much more complicated than equilibrium chemistry No real theoretical basis – largely empirical No real theoretical basis – largely empirical Based on reaction rate reaction coefficients Based on reaction rate reaction coefficients

Hydrologic cycle Hydrologic cycle = closed loop of the flux of water Hydrologic cycle = closed loop of the flux of water E.g., all reservoirs and all fluxes E.g., all reservoirs and all fluxes May be steady state or transient May be steady state or transient

Box models Three reservoir box model Three reservoir box model Fluxes and abundances of water Fluxes and abundances of water Does this model represent all fluxes/reservoirs? Does this model represent all fluxes/reservoirs? Convenient way to describe reservoirs and fluxes Convenient way to describe reservoirs and fluxes

More descriptive box model Same as previous model except finer resolution Same as previous model except finer resolution Provide more/better info on system Provide more/better info on system Harder to parameterize Harder to parameterize

Example: Sea level rise since LGM At these space and time scales, global hydrological cycle is transient At these space and time scales, global hydrological cycle is transient Smaller scale may be considered steady state Smaller scale may be considered steady state Lambeck et al., 2014, PNAS

Projected Greenland contributions to SL Clearly not steady state Clearly not steady state Surface mass balance and outflow projected for 21 st century Surface mass balance and outflow projected for 21 st century Red – mass loss; blue – mass gain Purple and green – equilibrium lines at start and end of 21 st century Insets – model estimates contributions from outlet glaciers & entire ice sheet IPCC, th AR

IPCC Global Carbon Cycle Solomon et al., (eds) IPCC report 2007  Black – fluxes and reservoirs - pre 1750  Red – Anthropogenic induced fluxes  Includes weathering – but limited to silicate minerals Perturbation

Residence Time Average time that material is in reservoir Average time that material is in reservoir Only systems in steady state Only systems in steady state Definition: Definition:  = A/J Where: A = abundance (not concentration) of material (units of mass) J = flux (in or out of reservoir) of material (units of mass/time)

Example: Example: What is  of students if 6 students/hr enter room with 6 students? What is  of students if 6 students/hr enter room with 6 students?  = 6 students/6 students/hr = 1 hour  = 6 students/6 students/hr = 1 hour

Global hydrologic and solute cycling Hydrologic cycle depends on processes transferring water to and from reservoirs Hydrologic cycle depends on processes transferring water to and from reservoirs Solute cycles depend on the compositions of water Solute cycles depend on the compositions of water Thus… useful to think about what controls concentrations within reservoirs of the hydrologic cycle Thus… useful to think about what controls concentrations within reservoirs of the hydrologic cycle

Fluxes in hydrologic cycle – this figure is for water. How would dissolved mass be included in this? Precipitation Recirculated seawater/MOR Sublimation Solutes? Constant composition? Reaction zones

Water chemistry and the hydrologic cycle Atmosphere Atmosphere Rain + other depositional processes Rain + other depositional processes Starting point – what controls composition? Starting point – what controls composition? Streams & Groundwater Streams & Groundwater Water/rock interactions – greatest amount of alteration Water/rock interactions – greatest amount of alteration Meteoric vs non-meteoric water Meteoric vs non-meteoric water Oceans – constant salinity, constant composition for some solutes Oceans – constant salinity, constant composition for some solutes

Composition of Water Begin to quantify changes in composition – kinetics & thermodynamics Begin to quantify changes in composition – kinetics & thermodynamics Langmuir, 1997 Chemical composition of water A = # of moles V = volume dN A = fluxes of A in and out Reaction: A = B

Importance Importance Dissolution of gases (e.g., CO 2 ) Dissolution of gases (e.g., CO 2 ) Dissolution of solid phases – porosity Dissolution of solid phases – porosity Precipitation of solid phases – cements Precipitation of solid phases – cements Coupled with hydrologic cycle - controls flux of material Coupled with hydrologic cycle - controls flux of material Controls on rainfall compositions, dN A Controls on rainfall compositions, dN A

Rain water chemistry Na + concentrations Cl - concentrations What might be the most likely source for Na and Cl? What might be the most likely source for Na and Cl? How could you test to see if this hypothesis is true? How could you test to see if this hypothesis is true? What are implications if this is true, e.g. what and where are other sources? What are implications if this is true, e.g. what and where are other sources?

Ca Concentration Sources of Ca other than marine aerosols

Relative concentrations, Rainfall Pollution – H 2 SO 4 Gypsum dust SO 4 matches Ca SO 4 matches pH – H 2 SO 4 SO 4 marine influence – dimethyl sulfide Close to ocean composition but still modified Note – total concentrations differ between samples

Temporal variations During storm During storm Rain starts salty, becomes fresher during storm as moves from ocean – ultimate source of water/aerosols Rain starts salty, becomes fresher during storm as moves from ocean – ultimate source of water/aerosols O and H isotopes also change during storm O and H isotopes also change during storm Snow melt initially saltier & lower pH Snow melt initially saltier & lower pH change in melting temperature change in melting temperature

Fractionation factor, F c Determine amount of dissolved mass from sea spray and aerosols Determine amount of dissolved mass from sea spray and aerosols Where: Where: C is dissolved component, Cl is chloride composition of sample or seawater C is dissolved component, Cl is chloride composition of sample or seawater Similar idea (ratio of ratios) in isotopes Similar idea (ratio of ratios) in isotopes

Other atmospheric sources Rainfall is not the only mechanism to deposit material from atmosphere to land surface Rainfall is not the only mechanism to deposit material from atmosphere to land surface Aerosol – suspension of fine solid or liquid in gas (e.g. atmosphere) Aerosol – suspension of fine solid or liquid in gas (e.g. atmosphere) Examples – smoke, haze over oceans, air pollution, smog Examples – smoke, haze over oceans, air pollution, smog

Dry deposition – aerosols Dry deposition – aerosols Sedimentation of large aerosols by gravity Sedimentation of large aerosols by gravity Occult deposition Occult deposition More general term - Dry deposition plus deposition from fog More general term - Dry deposition plus deposition from fog Dry and Occult deposition difficult to measure Dry and Occult deposition difficult to measure

Atmospheric deposition of material called “Throughfall” Atmospheric deposition of material called “Throughfall” Sum of solutes from precipitation, occult deposition, and dry deposition Sum of solutes from precipitation, occult deposition, and dry deposition A working definition A working definition Data Available Data Available National Atmospheric Deposition Program National Atmospheric Deposition Program

Compositional changes resulting from throughfall – NE US Open boxes – throughfall composition Shaded boxes – incident precipitation composition Note – only H + greater in precipitation

Surface and Groundwater Atmospheric deposition leads to surface and ground water Atmospheric deposition leads to surface and ground water Variety of processes alter/move this water: Variety of processes alter/move this water: Gravity Gravity Evaporation Evaporation Transpiration (vegetative induced evaporation) Transpiration (vegetative induced evaporation) Evapotranspiration Evapotranspiration

Movement across/through land surface Movement across/through land surface Overland flow – heavy flow on land surface Overland flow – heavy flow on land surface Interflow – flow through soil zone Interflow – flow through soil zone Percolate into ground water Percolate into ground water

Conceptualization of water flow Through- fall Important to consider how each of these flow paths alter chemical compositions of water

Examples of changing chemistry Plants Plants Provide solutes, neutralize acidity, extract N and P species Provide solutes, neutralize acidity, extract N and P species Soil/minerals Soil/minerals Dissolve providing solutes Dissolve providing solutes Evaporation Evaporation Increase overall solute concentrations Increase overall solute concentrations Elevated concentrations lead to precipitation Elevated concentrations lead to precipitation Salts/cements Salts/cements

Stream Hydrology Baseflow Baseflow Ground water source to streams Ground water source to streams Allow streams to flow even in droughts Allow streams to flow even in droughts Augmentations of baseflow Augmentations of baseflow Interflow, overland flow, direct precipitation Interflow, overland flow, direct precipitation Result in flooding Result in flooding Chemical variations in time Chemical variations in time caused by variations in compositions of sources caused by variations in compositions of sources

Bank storage Bank storage Flooding causes hydraulic head of stream to be greater than hydraulic head of ground water Flooding causes hydraulic head of stream to be greater than hydraulic head of ground water Baseflow direction reversed Baseflow direction reversed Water flows from stream to ground water Water flows from stream to ground water Hyporheic flow Hyporheic flow Exchange of water with stream bed and stagnant areas of stream Exchange of water with stream bed and stagnant areas of stream Nutrient spiraling – chemical changes in composition because changing reservoir Nutrient spiraling – chemical changes in composition because changing reservoir

Stream compositions Generally little change downstream Generally little change downstream Short residence time in stream Short residence time in stream Little contact with solids Little contact with solids Changes usually biologically mediated Changes usually biologically mediated Nutrients (N, P, Si) uptake and release (Nutrient spiraling) Nutrients (N, P, Si) uptake and release (Nutrient spiraling) Pollutants Pollutants Chemistry changes with discharge Chemistry changes with discharge Chemistry changes with exchange of GW and SW Chemistry changes with exchange of GW and SW

Diel stream variations Example from Ichetucknee River Example from Ichetucknee River Clear water – high solar radiation Clear water – high solar radiation Solar radiation changes Solar radiation changes Nutrient and DO change Nutrient and DO change SpC, pH and Ca change SpC, pH and Ca change All sub-aqueous plant mediated All sub-aqueous plant mediated De Montety et al., 2011, Chem. Geol.

Stream water composition USGS provide stream water quality data across US USGS provide stream water quality data across US URL is URL is

Ground water Unconfined example Unconfined example Porosity – fraction of total solid that is void Porosity – fraction of total solid that is void Porosity filled w/ water or water + gas Porosity filled w/ water or water + gas Vadose zone – zone with gas plus water (unsaturated – can be confusing term) Vadose zone – zone with gas plus water (unsaturated – can be confusing term) Phreatic zone – all water (saturated zone) Phreatic zone – all water (saturated zone) Water table – separates vadose and phreatic zone Water table – separates vadose and phreatic zone

Groundwater flow Flow through rocks controlled by permeability Flow through rocks controlled by permeability Water flows from high areas to low areas Water flows from high areas to low areas Head gradients Head gradients Water table mimics land topography Water table mimics land topography Flow rate depends on gradient and permeability Flow rate depends on gradient and permeability

Confined aquifers Regions with (semi) impermeable rocks Regions with (semi) impermeable rocks Confining unit Confining unit Confined aquifers have upper boundary in contact with confining unit Confined aquifers have upper boundary in contact with confining unit Water above confining unit is perched Water above confining unit is perched Level water will rise is pieziometric surface Level water will rise is pieziometric surface Hydrostatic head Hydrostatic head

Effects of confinement GW withdrawal lowers head Perched aquifers, springs, water table mimic topography

Other types of water Meteoric water – rain, surface, ground water Meteoric water – rain, surface, ground water Water buried with sediments in lakes and oceans Water buried with sediments in lakes and oceans Formation waters Formation waters Pore waters Pore waters Interstitial water/fluids Interstitial water/fluids Typically old – greatly altered in composition Typically old – greatly altered in composition

Other water sources Dehydration of hydrated mineral phases Dehydration of hydrated mineral phases Clays, amphiboles, zeolites Clays, amphiboles, zeolites Metamorphic water Metamorphic water Water from origin of earth – mantle water Water from origin of earth – mantle water Juvenile water Juvenile water Both small volumetrically; important geological consequences Both small volumetrically; important geological consequences