environmental chemistry

• what is the biomarker for eucarya?


  sterols
• what is the biomarker for bacteria?

  hopanoids and isorenieratene (green sulfur bacteria)
• what does CPI of 5.3 mean?

  >1 where high odd over even predominance. n-alkanes are plant derived (immature)
• how can 13C be used to analyse samples?

  n-alkanes from C3 plants have different composition than C4 plants
• what is PLFA? and what is ir a marker for?

  phospholipid fatty acid and a marker for living biomass
• is terrestrial or marine OM better preserved?

  terrestrial - contains more resistant lipid material. marine is built up of labile protein and carbohydrate OM
• what does O2 represent in the water column?

  direct impact on the amount of material that makes it to sediments. short O2 exposure time = more C preserved
• what is the impact of O2 exposure time on the remineralisation of OM in the water column?

  more OM is preserved in anoxic conditions. longer exposure time = lower amounts of OM preserved in sediments
• why be careful with hopanes to determine the maturity of peat sediments?

  isomerisation in peats is influenced by acidity. OM may be immature but hopanes may suggest high level of maturity
• what is the problem of early diagenetic sulfurisation of OM?

  sulfurised OM is more resistant against bacterial degradation and better preserved in kerogen. labile OM (carbohydrates) is preserved through sulfurisation
• how to determine the influx of isorenieratene is formed out of isorenieratene?

  isorenieratene is enriched in 13C compared to algae derived OM. specific compounds in kimmerridge clay show similar enrichment to algae biomarkers
• what biomarker is used to determine the relative input of fucoxanthin?

  loliolide
• why do HMW n-alkanes produced by C3 and C4 plants differ σ13C values?

  use different pathways to fix CO2 and produce n-alkanes
• what pathway does C3 use?

  calvin-benson: bulk of plants around globe
• what pathway does C4 use?

  hatch slack: dry conditions
• are carbohydrates or lipids more enriched in 13C?

  carbohydrates are 16%
• why is it important to know if an organism uses MVA or MEP pathway to synthesis a sterol?

  different carbon atoms with different isotopic compositions end up in the sterol synthesised based on pathway used. synthesised sterol will have different isotopic composition
• what does the isotopic composition depend on?

  c-isotope composition of carbon atoms in glucose
• what is the origin of 24-ethylcholesterol?

  diatoms or higher plants
• what does σ13C values of -80‰ for a biomarker in a marine sediment indicate?

  organism that produced this biomarker used methane as carbon source
• what are the natural influences that impact atmospheric 14C composition?

  variations in solar activity and earth's geomagnetic field strength, climate induced variations, volcanic activity
• what are the anthropogenic influences that impact atmospheric 14C composition?

  suess effect (manmade equilvant of volcanic eruption) and bomb spike (nuclear bomb testing)
• how can be CRSA be used?

  study transport mechanism in marine sediments, study if microbes can use fossil carbon as a carbon source, determine the origin of an environmental contamiant
• what are the advantages of using marine samples compared to soils when getting paleo information from the terestrial environment?

  homogeneous, long term
• what are the disadvantages of using marine samples compared to soils when getting paleo information from the terestrial environment?

  hard to get, buried deeply (catagensis/oil window)
• where does most terrestrial OM end up?

  remineralised in water column and buried on continental margins and in deltas
• what does a C organic/N ratio measure?

  6 is marine, >15 is terrestrial
• limitations of C/N

  diagenetic influences and inorganic N source
• what does σ13C TOC measure?

  common land plants (C3 photosynthesis), tropical grasses (C4 photosynthesis), marine phytoplankton
• what are the limitations of σ13C TOC?

  contributions of C4 plants, marine end member value constant over time, selective preservation of lipids over proteins/carbohydrates
• what is the biomarker for sitosterol?

  higher plant marker - terrestrial
• what is the biomarker for adenosylhopane?

  soil bacteria marker
• where do dinosterol come from?

  dinoflagellates - marine
• where can crenarchaeol be found?

  marine environment (pelagic) and small quantities in soils
• what is the marker for dinosterol?

  marine
• what is the marker for camposterol?

  higher plant (terrestrial) biomarker?
• where can marine biomarkers: isorenieratene and chlorobactene be used for?


  green sulfur bacteria and anoxia in photic zone
• what can marine biomarker: alkenones be used for?

  sea surface temperature reconstruction
• what is the distribution of branched GDGTs in sediments?

  mainly transported by the river - highest sediments in the outflow or river
• what is the distribution of HMW n-alkanes in sediments?

  highest in sediments in path of prevailing wind direction