The Hydrosphere Flashcards

Question

What are the major ions in river water?

Answer 1

Cations: Mg²⁺, Ca²⁺, H⁺, Na⁺, K⁺, Fe³⁺ Anions: phosphates, nitrates, carbonates Rivers are pH 7.5-8 due to calcium carbonate H₂O + CO₃²⁺ \<--\> OH^- + HCO₃^-

Answer 2

N₂ = 78.08% O₂: 20.95% Ar: 0.93% All other gases: 0.04% - CO₂, N₂O, CH₄, O₃, H_2,He, Ne, Kr,Xe

Answer 3

Gas molecules are continually transfering between the water surface and the atmosphere For a gas at equilibrium between the atmosphere and in dissolved form in water: A_(g) \<----\> A_(aq) The concentration of a gas in water is related to the artial pressure of the gasin the atmosphere, P_A, by Henry's law: [A] = K_AP_A K_A = Henry's constant

Answer 4

Solutional formation: limestone dissolves in water which contains H₂CO₃ Dissolution occurs along joints and faults and planes Portions of a solutional cave that are below the water table will be flooded

Answer 5

Low temperature = more oxygen High pressure = more oxgen Dissolved salt = greater ionic strength = less oxygen Turbulence - increases surface area with which can come to equilibrium, draws part of the atmosphere down into the water body Contrast river with pond

Answer 6

Animals require oxygen for metabolic processes? Oxudative degredation of organic matter

Answer 7

Uses dissolved oxygen (CH₂O) + O₂ ---\> CO₂ + H₂O + Energy Other elements: N ---\> NO₃^- - good in moderation S ---\> SO₄^2- P ---\> PO₄^3- - good in moderation

Answer 8

Doesn't use oxidatio as energy source - use reduction Stringest in O₂ defincient water C ---\> CH₄ N ---\> NH₃ S ---\> H₂S P ---\> PH₃ These are toxic and kill off organisms

Answer 9

If water is rich in nitrates and phosphates = rapid algal growth = phytoplankton bloom During the day, high [O₂], water is saturated Bloom reduces light penetration, inhibiting photosynthesis + groqwth pf rooted vegetation Shirt lived - [O₂] decreases with decomposition Anaerobic decomposition (odourous breakdown of products Oxygen introduced again through turbulance, surface area and photosynthesis

Answer 10

March - even temp ≈ 4.5°C July - stratified - no mixing - top layer (epilimnion) = hot ca 18-19°C middle layer (thermocline) = warm Bottom layer (hypolimnion) = cold ca 6-7°C - removed from the atmosphere, doesn't equilibrate efficiently, aerobic + anearobic decomp form nutrients in cold area

Answer 11

November - even temperature - 4.5°C - mixing = overturn = mixes nutrients to top layers Jan - Epilimnion = ca. 0-1°C Hypolimnion ≈ 5 m down ≈ 3-4°C Ice provides thermal blanket

Answer 12

Almost no current - pollutants persist Organic broken down by oxidation If all oxygen used up = reduction used to break down material - anearobic / anoxic water Seasonal overturns

Answer 13

Interactions between the geosphere, atmosphere and hydrosphere The biosphere is intrinsically linked with this system while the cycles of matter are completed by tge alternatln snd / or uplift of sedimentary rocks

Answer 14

Surface ocean uniform temperature and salinity Strongly influenced by the atmosphere

Answer 15

50-1000m depth Preominent transition feature conditioning many physical, chemical, biological processes occurring in the oceanic upper layers If the vertcle constraints of salinity are small also defines the pycnocline (pycno = density) i.e. warmer less dense surface waters overlying colder more dense deep waters

Answer 16

Deep ocean water interior isolated from the atmosphere

Answer 17

Shallow ocean dynamics forced by winds Deep ocean dynamics forced by density variations

Answer 18

Essential part of dynamics In the northern hemisphere: Wind generates a clockwise surface circulation - drives water downwards Wind generates anticlockwise surface circulation - dirves water upwards Resulting dynamic pressure variations can be read by satellites that measure sea-surface height relative to the geoid

Answer 19

GEnerally temperature is high at the equator and low at the poles The inter-Tropical convergence zone is the pioint at which the trade winds converge, rainfall converges - This means freshwater is dropped in the Pacific not the Atlantic This is shown in the salinity of the oceans - Atlantic high salinity whereas the tropics are fresher Higher salinity makes the atlantic more dense

Answer 20

Upper 1mm of water is blown in the same direction of wind Just below the surface the ocean deflects to the right and deflects more and more with depth eventually flowing in the opposite direction Average flow of water due to wind = 90° to wind This is to the right in the northern hemisphere and to the left in the southern hemsphere This is called Ekman pumping

Answer 21

Wind driven currents encircle large spinning gyres in subtropical oceans Subtropical gyres - clockwise in N h/s, anticlockwise in S h/s Dome of water in subtropics

Answer 22

When the wind blows parallel to the coat the ocean surface layer is blown 90° to the direction of the wind (offshore) - Ekman transport This means warmer waters are driven offshore and cooler waters upwell from below At the equator trade winds cause warmer water to be driven towards the poles and cooler water upwells from below This bring nutrients from below and so there is often lots of bio activity

Answer 23

Normal: surface winds blow stroingly from the east - Drives upwelling off south america - tilts thermocline towards the west - piles warmer water in a pool near indonesia with strong convection and rainfall above it - La Nina is extreme of this Weak trade winds = less tilting of the thermocline - reversing upwelling/downwelling patterns - displacement of warm water pool to central Pacific = drought in Asia, torential rans in America and failure of Peruvoan fisheries

Answer 24

Organic matter can be represented as CH₂O for fixed carbon and NH₃ for fixed nitrogen CO_2(g) + H₂O \<---\> CH₂O_(s) + O_2(g) NO₃^-_(aq) + H₂O + H⁺_(aq) \<---\> NH₃_(s) + 2O₂_(g) These reaction lie to the right in photosynthesis and to the left in respiration

Answer 25

Oceanic organic matter contains the elements C, N and P in nearly constant ratios - Redfield ratios C : 106 N : 16 P: 1 Seawater contains N and P in exactly the same ratio This imples: All N and P in shallow ocean comes from remineralisation of organic matter at depth so it is supplieed dto the cycle with Redfield ratio Life has evolved to optimally utilise available nutrients leaving neither in significant excess

Answer 26

Excess comes from weathering input Implies NO₃ is limitting but N₂ can befixed to NO₃ if Fe is present available - hence ideas about Fefertilisation of ocean and CO₂ sequestration [PO₄] indicates where upwelling is providing nutrients and hence where primary productivity occurs in the ocean These locations are where diatoms are makibg SiO₂shells that rain out to form siliceous sediments

Answer 27

Previously defined as Total amount of dissolved material in gams in one kg of seawater - this is a simple concept but impossible to meaure Currently salinity is based on conductivity - dimentionless easy and precise measurements found with conductib=vity meters

Answer 28

We use a CTD - conductivity, temperature and depth Actually measures conductivty, temperature and pressure Depth is calculated from the pressure and density The instrument can be deployed by itself on a wire or attached to a larger frame equipped with water sampling bottles

Answer 29

Density is a function of temperature, salinity and pressure Seawater density (ρ) quated in kg m^-3 - usually close to 1000 Often quoted as relative density (σ): σ = ρ -1000 Cold water is more dense than warm water - temp down, pressure up, σ up Salt water is more dense than fresh water - salinity up, pressure up, σ up

Answer 30

traditionally thught of as the global deep water circulation of the oceans driven by differences in ocean density which is itself a function of both temperature and salinity The overturning or internal mixing time

Answer 31

By their temperature and salinity whih are properties or signatures T and S a=properties are set at boundaries of ocean - exchange if heat and freshwater with atmosphere In the ocean interior T and S are conservative propoerties of seawater - do not change unless mixed with waters of differing properties As mixing is slow T and S can be used to trace movements of water masses - track deep ocean circulation

Answer 32

Very slow: driven by deep water formation and isopycnal flow All southwards in the Atlantic Ocean, northwards in Indian and Pacific Oceans; steered western boundary of each ocean Must be compensated by return flow in shallow ocean but this is small compared ti wind driven motions above thermocline

Answer 33

Transports large amounts of warm water into he North Atlantic and keeps Northern Europe warmer than it would otherwise be

Answer 34

Significant cooling in Northern hemisphere - shut down of the thermohaline circulation triggered by large melting of northern ice - introduce fresh water Paleo-oceanographic evidence shows Younger dryas event was marked by a prolonged shut-down of the thermohaline circulation, which is likely to have triggered by the release of melt water

Answer 35

Particulates - \> 0.2 μm : sand, clay, detrital matter: excreta, molts, dead tissue, aggregates / marine snow - experience gravtational settling Dissoled: gases: N_2,O₂, Ar, CO₂, N₂O, DMS, CH₂I₂ Major ions: Na⁺, Cl^-, Mg²⁺, SO₄^2-, Ca²⁺, HCO₃^-, Br^- Minor ions: NO₃^-, NH₄⁺, PO₄^3- Trace metals: Fe, Zn, Co, Cd, Mn, Pb Organic compounds: amino acids, humic acids Not impacted by gravity Major constituents - major ionic - contribte to salinity significantly to salinity and are conservative or near conservative

Answer 36

Depends on both chemical properties and physical properties that transport water and particles and lead to transfer of material from one part of the system to another

Answer 37

Diffusion: Movement of constituents within the medium - In the presence of a concentration gradient net movement from high to low concentration In non turbulnt medium diffusion coefficient ≈ 10^-5 - 10^-6cm²s^-1 Turbulent diffusion (eddy diffusion) generally dominant - Oceanic vertical eddy diffusion coefficients typically 10⁵ times larger than molecular diffusion

Answer 38

Flow of water (wind driven and density driven circulation of oceans) In advection a dissolved constituent undergoes no change in concentration

Answer 39

Oceans formed relatively early in Earth's history - 4400 Ma Water transport mainly riverine transfers material from continuents to oceans Thousands of millions pf years of erosion transporting salts to the sea Oceans are not saturated - (must be transport out) Seawater doesn't look like river water - transport must ne different for different continuents

Answer 40

Mean ocean residence time = amount in ocean / input or output τ = A / δA/δt A = amount in resevoir The MORT of a dissolved constituent is usually calculated with respect to the riverine input because this is usually the dominant input and it is the best qualified of all inputs or outputs from the ocean We assume a well mixed ocean

Answer 41

The concentration of a constituent is assumed to be constant over time Evidence from the sedimentary record and evaporite deposits tell us that the broad characteristics of the ocean have been in steady state over the last 600 million years Inputs amnd outputs may have been out of balance over certain periods but on long geological timescles they are balanced

Answer 42

Tells us the tendency of that cinstituet to change phase - how likely a dissolved constituent will change to a solid These can be biologically mediated - e.g. incorporation of calcium carbonate into shells

Answer 43

Elements with low geochemical reactivity - B, Br, Cl, Cs, F, K, Li, Mg, Mo, Na, Rb, S, Tl, U MORT_A \> MORT_water (\>10⁶ years) Accumilate in ocean = conservative behaviour MORT \>\> mixing time of the ocean = well mixed Simple ions, inert gases - not biogeochemically active

Answer 44

e.g. C, Ca, N, P, Si, Zn Biological uptake removes nutrient elements from surface seawater Detrital material sinks, decomposing and releasing nutrients Biological cycling involves transformations Typically MORT_A ≈ 10⁴ - 10⁵ yr

Answer 45

e.g. Al, Bi, Ce, Co, Hg, Mn, Pb, Sn, Te, Th If MORT \< MORT_water(MORT ≤ 10³ years) Depleted in oceans - particle reactive (adsorption, precipitation, biological uptake) River inputs are lagely removed by estuarine processes - Atmosphere inputs to open ocean A has been depleted in the oceans and has high geochemical recativity

Answer 46

Riverine inout is higher into the atlntic than the pacific Deposits of sand from the sahara into the atlantic

Answer 47

Upwelling in the thermohaline cycle happens faster in the atlantic In the Pacific nutrients have more time to dissolve

Answer 48

Temperature - colder water greater solubility Salinity: higher salinity lower solubility Other factors: atmospheric pressure, humidity, surface consition (wave action/bubblr bursting) Solubility becomes non-linear as T and S increase Accurate empirical equations have been derived to predict gas solubility as a functionof T and S

Answer 49

No significant changes in concentration occur other than by mixing with other water bodies with a different gas concentration - conservative behaviour e.g. Ar, Xe, He Excellent tracers

Answer 50

If significant changes in concentration occur due to reactivity the gas shows non-conservatiuve behaviour O₂ - used biologically CO₂ - reacts with water

Answer 51

O₂ usually supersaturated in surface waters due to: phytoplankton (photosynthesis) Wzaveaction + bubble bursting

Answer 52

O₂ profiles generally mirroe those for nutrients High in surface waters screasing t a minimum at 1000m as O₂ is consumed during recycling Oxygen increases with depth below the oxygen minimum because it is supplied by relatuiveky young ventilated water When productivity is very high or supply is cut off, deep waters may be cme anoxic e.g. Black sea, Gulf of Mexico

Answer 53

Important greenhouse gas - control planetary climate CO₂ is the raw material used to build organic matter CO₂ controls pH of the oceans Distribution of CO₂ species affects calcification and preservation of CaCO₃ on the sea floor

Answer 54

TCO₂ = CO₂\*+ HCO₃^- + CO₃^2-

Answer 55

The sea contains anions of weak acids delivered by weathering processes These associate with H+ ions and buffer seawater against incerase in pH On short term the sea is buffered by its alkalinity On long term the sea is buffered by balance between carbonate precipitation and amd dissolutions

Answer 56

Carbonate alkalinity (CA): total alkalinity can be converted to CA CA = [HCO₃^-] + [2CO₃^2-]

Answer 57

Speciation curve shows dominant species is HCO₃^- TCO₂ = CO_2(aq) + H₂CO₃ + HCO₃^- + CO₃^2- = CO₂\* + HCO₃^- + CO₃^2- TCO₂ ≈ HCO₃^- + CO₃^2- As pCO₂ increases: TCO₂ up, pH down, CO₂\* up, HCO₃^- up, CO₃^2- down

Answer 58

The solubility pump - combined influence of physical and chemical processes on ocean concentrations of dissolved CO₂ and air sea exchange The biological pump - transport of carbon from the surface to the deep ocean by biological processes Both pumps act to store carbon in the deep ocean

Answer 59

Surface ocean - photosynthesis and carbonate precipitation consume TCO₂ and CA Deep ocean - recycling (respiration of C_organd dissoluton of CaCO₃) release CO₂ and CA

Answer 60

Source strength (production) and Degree of preservation (extent if dissolution) Resuklts in sediment distribution which shows strong relationship with depth Abyssal clays found in deep ocean basins Calcaerous oozes abundant on ocean ridges and rises Siliceous oozes aew found beneath areas of high biologic productivity

Answer 61

K_SPis the stochiometric solubility product for the equilibrium reaction: CaCO_3(s)⇔ Ca²⁺ + CO₃^2- K_SP = [Ca²⁺][CO₃^2-] The precipitation and dissolution of calcium carbonate is controlled by the saturation _state of seawater with repect to CaCO₃_ (Ω) Ω = [Ca²⁺]_SW[CO₃^2-]_SW / K_SP [Ca²⁺]_SW and[CO₃^2-]_SW are actual concs of calcium and carbonate ions in seawater If Ω= 1 SW at equilibrim is saturated wrt CaCO₃

Answer 62

Determined by [CO₃^2-] The saturation of carbonate ion concentration increases with depth because CaCO₃ is more soluble at T decreases and pressure increases If [CO₃^2-] ions lie to the right of the saturation curve then CaCO₃ will not dissolve The saturation curve for araonite lies to the right of that of calcite as it is less stable and dissolves more readily

Answer 63

The depth at which Ω = 1 The point at which dissolution of CaCO₃ in sediment becomes significant is called the lysoclne (can be significantky below the horizon) - slow dissolution kinetics The point at which CaCO₃ becomes a minor sediment component is called the carbonate compensation depth \*(defined as where carbonate skeletal material falls below 20% of the total sediment)

Answer 64

Increased TCO₂: Shift the carbomnate equilibria in favour of HCO₃^- and lower pH Overall effect is to lower [CO₃^2-] and therefore the CaCO₃ compensagion depth and the hysocline will shoal The high-CO₂ low pH Ocean: ocean pH is predicted to decrease by 0.3 units by 2100 - massive implications for ocean biology

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The Hydrosphere Flashcards

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