Inputs to Estuarine and Coastal Systems

Question 1

Rivers

Answer 1

Major source of most chemical elements to the ocean
- regulates ocean chemistry, PP
Chemical weathering regulates concentration of atmospheric carbon dioxide
- feedback between weathering and climate

Question 2

Atmospheric inputs

Answer 2

Material supplied by dry or wet deposition
Inputs high in coastal zone as most particles from land
- dust generated by wind erosion
- sea salt
- anthropogenic inputs

Question 3

Atmospheric N inputs

Answer 3

Mainly from:
- combustion sources to the atmosphere, forming nitrate
- agricultural emissions which release ammonia
Dispersed through coastal zone, not a point source
Fluxes highly variable in space and time

Question 4

Atmospheric sampling, bermuda

Answer 4

Tower 23m
Different instruments at the top
only samples when wind blows over ocean
Power supplied from containers at the bottom

Question 5

Inputs of toxic metals

Answer 5

Measurable increase in surface ocean water lead concs due to combustion of leaded petrol, now falling
Atmospheric deposition:
- volatile element, mainly deposited as Hg2+
- global atmospheric burden has increased by factor of 5 in last 200 years as a result of human activities

Question 6

Trace gases

Answer 6

estuaries and coastal seas are an important source of some climatically active trace gases
Directly or indirectly biological in origin

Question 7

Methane

Answer 7

Produced by anaerobic microbial processes
Contributes ~15% global radiative forcing
Mainly comes from sediments but may be produced at pycnocline
Oxygenated surface waters on coastal shelves supersaturated with methane, the methane paradox
Contribution from coastal waters ~3% of total emissions or ~10% if natural methane emissions doesn’t account for bubble fluxes

Question 8

Penlee point

Answer 8

Plymouth marine lab
measures sulphur dioxide , carbon dioxide and methane in air
Trace metals

Question 9

Ship Plumes

Answer 9

Large increase in pollution from ship fuel
Monthyl averaged sulphur dioxide mixing ratios which represent ships emissions
After policy for reduction is sulphate emissions, inputs to coastal regions was reduced

Question 10

Nitrous oxide

Answer 10

Nitrous oxide contributes ~6% of global radiative forcing
By product of microbial nitrification and intermediate during microbial denitrification
Mean surface saturation in shelf ~109%, estuaries ~600%

Question 11

Submarine ground water discharge

Answer 11

Water can move in and out of sediments by tides
creates mixing zones of varying salinities of water which increase with depth in the sediments
Significant impact on biogeochemical cycling
Slow diffuse flow but can be found as large point sources in certain terrains
Both freshwater and saltwater components
Composition may be modified by chemical reactions in the aquifer.

Question 12

Components of SGD

Answer 12

Meteoric water (fresh)
Recirculated sea water (salt)
Connate waters (v salty)

Question 13

Detecting and quantifying SGD

Answer 13

IR imaging:
- at high lats, SGD warm relative to ocean
- at low lats, tends to be cooler
Direct measurements:
- seepage meters
Tracer techniques:
- natural using radiotracers
- artificial dyes

Question 14

Tracers

Answer 14

Radium
224Ra. 3.66d
223Ra. 11.6d
228Ra, 5.75y
226Ra, 1600y.
226 most often used as it is integrated over a larger time period and able to see how significant the flow is into the ocean

Question 15

226Ra tracer

Answer 15

Less effective in fresh SGD as Ra is bound to particles in fresh water

Question 16

Water and chemical fluxes

Answer 16

estimates of water flux from SGD is mostly 6-10%
Total dissolved salts contributed to SGD may be as much as 50% of that contributed by rivers
Conc of nutrients, trace metals, organic C, methane and carbon dioxide may be considerably higher

Question 17

Reactions in estuary

Answer 17

Oxidation of organic C adds carbon dioxide, results in calcite dissolution
high levels of nutrients due to water rock interactions and anthropogenic inputs
Removal of nitrate by denitrification in low O groundwaters
Removal of dissolved iron at fresh-salt water interface and scavenging of other components

Question 18

Glacial inputs

Answer 18

Input of Fe from melting sufficient to fuel a phyto bloom
Meltwaters supply Fe in solution as nanoparticles

Question 19

Benthic sources

Answer 19

Sediments are a sink for elements and particles introduced to marine waters.
But. active recycling of many elements at the benthic interface and longer timescale release of materials into water column

Question 20

DMS

Answer 20

Dimethylsulfide produced by phaeocystis, coccos and dinos, some diatoms are also important
Oxidised in troposhere, contribute to atmospheric acidity and cloud condensation nuclei formation.