sediments

Question 1

sediments basic principles

Answer 1

• settling particles transport pollutant into lakes/lake sediments
• in undisturbed sediments, depth represents time scale
• to interpret data, we must know smth about sedimentary processes (ex redox, stability..)

Question 2

components of sediments

Answer 2

• solid (detrital material, non dtrital material OM, 2ndary mrnls)
• • pore water (may occupy >95% of volume)

Question 3

chemical analysis of solid sediment

Answer 3

toal analysis : all mineral phases dissolved in one step in a strong acid, gives total elt C°
sequential leaching of sediment : dissolved in several steps using diff reagents, each one dissolves different solid components

Question 4

oxic/anoxic sediments

Answer 4

oxic sediemnts : where oxygen is dissolved in the pore water, top mm/cm = Brown Fe and Mn are stare here

anoxic = no oxygen, consumed in decomposition of OM? Sulphites are stables, black sediments (FeS)

Question 5

sediment rates

Answer 5

• mg accumulate sediment/cm2/year
• mm accumulated sediment/year=> affected by the compaction of the sediments with increasing depth

Question 6

depletion rate

Answer 6

• if mg/cm2:year : D =S * C
• if mm/year : D = S(1-n)phoC
• S = sedimentation rate, C = C° in sedimenting material, pho = density, n = porosity

Question 7

diffusion in pore waters

transport of elts in pore water

Answer 7

Fick’s first law:
J = -nD*deltaC/deltaZ

J in ug/cm2/year, n = porosity, D = diff coeff (cm2/year) delta = C° gratient in pore water (ug/cm2)

diffusion of elt always from higher to lower C°

Question 8

sediments as environmental archives prerequisites

Answer 8

• cst and known sedimentatio accumulation rate
• sediment must be undisturbed by bottom currents
• investigated elt mut be immobile, not diff in pore waters