OSX-2004 DA Revision Cards

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  • Created by: Rachelezy
  • Created on: 11-01-22 18:44

Estuarine Environments

Services of healthy estuaries:

> Store and recycle nutrients

> Trap sediments

> Form a buffer between coastal and marine environments

> Trap and detoxify pollutants (act as natural water filters)

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Vulnerability of Estuaries - Basics

Human activites that influence estuaries:

  • Production forestry
  • Land clearance
  • Sewage
  • Sediments, nutrients, pollutants
  • Agriculture
  • Introduced species
  • Marine farming
  • Road Building
  • Infilling and Reclamation
  • Marinas
  • Channel Dredging
  • Fishing
  • Coastal Settlement
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Vulnerability of Estuaries - Living

Sewage Waste DIsposal:

  • Impacts Sedimentological, Biological and Chemical processes
  • Smothering, deoxygenation, eutrophication, bacterial & viral contamination, marine litter

Urban Waste Water Runoff:

  • Impacts Physical, Biological and Chemical processes
  • Increase in FW runoff, due to infiltration. Urban chemical runoff

Removal of grass/trees:

  • Impacts Physical, Sedimentological and Biological processes
  • Reduced tidal volume, loss of tidal flood area for sedimentation
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Vulnerability of Estuaries - Working

Industrial Waste Disposal in Estuaries:

  • Impacts Chemical and Biological processes
  • Contamination/pollution, death of organisms. May transfer to man

Fishing:

  • Impacts Biological and Sedimentological processes
  • Reduction of fish stocks and seabed disturbance

Harbours/Marinas:

  • Impacts Chemical, Biological, Sedimentological and Physical processes
  • Changes in tidal volume, chemical inputs and sediment redistribution by dredging

Agriculture Waste Disposal Runoff:

  • Impacts Chemical and Biological processes
  • Contamination and pollution. Eutrophication
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Vulnerability of Estuaries - Recreation

Water Sports:

  • Impacts Physical, Chemical and Biological processes
  • Changes from barrages/marinas, sewage & anti-fouling paint

Wild Fowling:

  • Impacts Bioloical processes
  • Dead birds

Barrages for Water Sports/Marinas:

  • Impacts Physical, Chemical, Sedimenotological and Biological processes
  • Changes in physical and sediment dynamics, sediment retention and loss of habitat

Visiting and Looking:

  • Impacts Sedimentological and Biological
  • Litter and marine litter
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Vulnerability of Estuaries - Power Generation

Tidal Power:

  • Physical, Chemical, Sedimentological and Biological impacts
  • Drastic change in estuarine water dynamics and water quality

Hydro-Power:

  • Physical, Chemical, Sedimentological and Biological Impacts
  • Change in estuarine water dynamics & quality, due to reduced FW flow (if upstream)

Nuclear Power Cooling Water:

  • Physical, Chemical and Biological Impacts
  • Discharge of warm, chlorinated water into the marine environment
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Estuarine Chemistry

  • River water coming in one end, seawater coming in from the other. Causes salinity gradients through the water column. If seawater stronger than river, a vertical salinity gradient can occur
  • Chemical differences between FW and SW inputs, where behaviour of dissolved constituents changes during estuarine mixing
  • Estuarine Divisions - Lower = SW dominant, Upper = FW dominant (still subjected to tidal influence). Middle is where most of the mixing occurs

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Riverine Input

Elevated Concentration by Local Inputs (From riverine end):

  • Industry
  • Discharge
  • Human Waste
  • Street Runoff

Elevated Concentrations by Activities in the River Catchment:

  • Agriculture
  • Fertiliser Application
  • Rainfall
  • Runoff
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River vs Seawater

pH = River water tends to be acidic, with pH being lower in river water than seawater (RW = 5-7. SW = 8.3)

(Seawater contains ~300 times more dissolved salts than average river water. i.e. you are mixing a really strong solution with a really weak solution within an estuary)

Concentrations greater in River Water:

  • HCO3
  • H4SiO4

Concentrations greater in Sea Water:

  • Cl-
  • Na+
  • Mg2+
  • SO4-2
  • Ca2+
  • K+
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Dynamic Nature of Estuaries

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Conservative & Non-Conservative Behaviour

Conservative Behaviour:

  • DO NOT REACT (concentration controlled by simple physical mixing of two water masses)
  • River concentration LOWER in SW for: Sodium (Na2+), Potassium (K+), Calcium (Ca2+) and Sulphate (SO42-)
  • River concentration HIGHER than in SW for: Phosphate (PO43-), Nitrate (NO3-) and Manganese (Mn2+)

Non-Conservative Behaviour:

  • If estuarine mixing causes a physical change, or chemical reaction to occur
  • Includes both gain and loss of constituion (e.g. loss of constituent through aggregation of colloids, also known as flocculation/aggregation)
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Flocculation

> Can remove 'dissolved' ions from the sollution

> When colloids hit water, their ionic strength inceeases and they start cumping together (Colloidal form where flocculation occurs in the presence of water)

> Particles can be remobilised by bacterial activity in the sediment

> Returns colloids to overlying water column as dissolved constituents

Colloids = Very small particles that remain suspended in aqueous solutions

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Adsorption & Desorption

Adsorption:

  • Binding of molecules or particles to a surface
  • Weak and reversible
  • Promoted by high particle load and high riverine phosphate concentration

e.g. River Rhine. 1) Estuary filters out copper and zinc. 2) Element adsorbed when colloidal flocculation occurs. 3) Copper and zinc transfered to solid phase (particle) and can be deposited, and stored, in underlying sediment

Desorption:

  • Substance released from surface of a solid (opposite of adsorption)
  • Often temporary and can be reversed = re-adsorption
  • Solubilises elements - Leads to higher concentraions of constituent than estimated by the theoretical distribution line
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Additive Mechanisms

> Non-conservative behaviour may be caused by new sources to estuarine waters

Anthropogenic Additions:

> Hard to determine concentration when looking at anthropogenic conditions of chemicals (Are there high concentrations close to a source or is it just fine-grained sediment?)

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Element Behaviour

Phosphate Behaviour Example:

1) Flushing time ~2 weeks

  • High riverine concentration and High suspended particle load

2) Flushing time ~1 day 

  • Low riverine concentration and low suspended particle load

3) Flushing time ~2 weeks

  • Low riverine concentration and low suspended particle load

(3 = Non-conservative behaviour, 2 = Conservative behaviour)

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Behaviour of Trace Metals

(In European estuaries)

Manganese (Mn)

> Often found in removal

> Found in removal at low salinity, with mid-estuary addition

> Conservative in small estuaries

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Algal Blooms

(Additional removal mechanism for estuarine nutrients - autotrophic - and an additional source of dissolved O2)

> E.g. Phosphate showing non-conservative behaviour, with less than estimated, could be due to adsorption or plankton taking phosphate out of the solution for growth (or both)

Lower Turbidity, Higher Light Penetration:

  • Very large algal blooms can develop in estuaries, especially where there is high nutrient loads (Human activites can lead to high nutrient conc. in rivers that run into estuaries)

Harmful Algal Blooms (HABs):

  • Known as 'Red tides'. May not be toxic to the shellfish that accumulate there. However, they are toxic to humans that eat them, even when present in low concentrations
  • Phaeocystis (nuisance algae) - Ability to form floating colony with hundred of cells, embedded in a polysaccharide gel matrix that can multiply during blooms (Have been occurring more frequently within recent years)
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Human Activities Affecting Estuaries

Human Activities affecting Estuaries:

  • High concentrations of nutrients into rivers that run into estuaries
  • Raised number of phytoplankton cells = phytoplankton bloom
  • Phytoplankton die and some accumulate in underlying sediment. This mass of dead phytoplankton is intensely colonized by bacteria (~10^9 bacteria per cm3) that decompose organic matter, using oxygen (O2)
  • Use up crucial oxygen that may result in oxygen depletion/sea hypoxia
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Bacterial Respiration

  • 1. Dead organic matter intensively colonized by bacteria (~10^9 bacteria per cm3)
  • 2. Aerobic resouration lower O2 concentrations in overlying water column
  • When respiration is dominant, nitrate, phosphate etc. can be released back into the water column, producing non-conservative behaviour
  • More organic matter in the sediment, the thinner the oxygenated later, the more sediment is thus anoxic, creating dead zones
  • Oxic = O2 present throughout sediment
  • Suboxic = O2 present (intermediate)
  • Anoxic = No O2 present throughout sediment

Rate of Bacterial Respiration increase with:

  • Increasing temperature
  • Organic matter availability
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Sediment Sources & Composition

Estuarine-Generated:

  • Inorganic & organic flocculants, Precipitates, and both living and non-living Particulate Organic Matter (POM)

Ocean-Transported (Marine):

  • Inorganic solids from weathering and marine biogenous components (skeletal debris, organic matter etc.)

River-Transported (Fluvial):

  • Crustal weathering products (Terrestrial organic component, clay minerals, anthropogenic solids and quartz)

Atmospherically Transported:

  • Volcanic ash, Ash/debris of anthropogenic origin
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Sediment Grain Size

Normalisation:

  • Enrichment Factor: EF = (Xs / Als) / (Xb/Alb)
  • EF <= 1.5 = Natural
  • EF > 1.5 = Artifical Contamination

(Xb = background value that can be rocks, such as crustal rocks weathered by the estuary. Xs = X being metal concentration and s being sample. Al = natural metal that varies with grain size. i.e. a constant)

Geochemical Accumulation Index:

(0-1 = unpolluted, 1-2 moderately polluted, 2-3 moderately/strongly polluted, >3 = strongly polluted)

  • Used to evaluate level of contamination by directly grading contamination level of sediments. Takes away role of the natural analogy Al. Is not as sophisticated but is cheaper
  • If both potential contaminant and Al are high = natural grain size effect. If contaminant is high and Al low = artificial contamination, perhaps close to a source
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Case Study: Ribble Estuary

Experiment:

> Determining time spent by dog walkers each day, walking on contaminated sediments

Calculations:

How long a person spends in contact with the radioactive sediment

  • Data collected by interviewing
  • Dose to group assessed by: Time spent over it and amount of radioactivity

> How reactive sediment is

Grain size & concentration of radionuclide were measured

  • 50 sediment samples
  • 137Cs (caesium -137)

> Relationship determined between rain size and radionuclide conc. Found higher radiation doses above fine-grained sediments

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