Final Study Guide Flashcards
Write the chemical equation for the dissolution of CaCO3 in seawater.
CaCO3 -> Ca 2+ + CO3 2-
The K’sp for CaCO3 (calcite) in the ocean at 25°C and 1 m depth is 4.8 x 10-7. If the Ca2+ concentration in seawater is 0.01 mol/kg, what would be the [CO32-] in the ocean if the saturation index (omega) was 0.9? Write the equation for the K’sp expression.
What would be the [CO32-] in this water if the saturation index (omega) was 2.5 instead of 0.9? Assume the Ca2+ concentration and K’sp are the same.
= 4.3x10-5
[CO32-] = 1.2x10-4
The average concentration of Si in river water is 190 µmol/kg and the residence time of Si in seawater is 10,000 years. What is the total amount of Si in the ocean? Assume that the input of river water to the ocean is 1 Sverdrup (1 Sv = 106 m3/sec), and that 1000 kg = 1 m3 seawater. Show your work and units.
1.7x10^18 g Si in the ocean.
What is the Redfield Ratio? Why is it nearly the same in all particulate matter in the ocean?
The Redfield Ratio is the proportion of C:N:P in organic matter in the ocean. It is approximately 106:16:1. It was thought to be the same in particulate matter in the ocean, because there is a mixture of proteins (N-rich), carbohydrates and lipids (both C-rich) and organic P in all particles. This has been shown to not really be the case in the ocean afterall.
Name three components of dissolved organic phosphorous.
• Nucleic acids (DNA, RNA) and nucleotides
• Phosphosugars
• Phospholipids (an important component of cell walls)
What is the main source to and the main sink from P in ocean water?
The main source is rivers, and the main sink is sedimentation to the ocean sediment as organic P.
P recycling in the ocean is very extensive. Each P atom in the surface ocean resides in __ different plankton before being exported to deep ocean.
10
True or False: the remineralization of phospholipid fatty acids yields inorganic phosphate PO4 3-
True
What are the approximate pool sizes (in Gt C, where 1 Gt C = 1015 g C) of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the ocean?
DOC: ~ 640 GtC
POC: ~ 30 GtC
What are the two major types of particulate organic matter that fall through the water column most quickly?
Fecal pellets and marine snow
Give an example of a biomarker and how is it used to study a pathway in marine chemistry.
The presence of the sterol “dinosterol” (a lipid) in ocean sediments indicates production by the marine plankton called dinoflagellates.
How do scientists collect sinking POC in the water column and what is the range of flux of POC in the deep sea? How do they collect suspended POC in the water column?
Sediment traps are deployed in the water column to collect POC that falls into cups located at the bottom of the trap. To collect suspended POC, pumps are deployed to a specific depth in the water column, and allowed to pump water through a filter that collects the POC.
How does DOC concentration change in the transit of deep water from the N Atlantic to the N Pacific (does it increase or does it decrease)? Why?
The DOC concentration decreases with distance from the N Atlantic (45µmol/kg) to the N Pacific (37µmol/kg). This is the result of microbial remineralization of DOC along the conveyor belt of the deep sea.
How does dissolved inorganic carbon (DIC) concentration ([DIC]) change in the water column as deep water travels from the North Atlantic to the North Pacific? What process is responsible for this change?
The DIC concentration increases with distance from the N Atlantic (2000µmol/kg) to the N Pacific (2400µmol/kg). This is the result of microbial remineralization of DOC.
What is the Feq (flux, in mol/m2/yr) of Ar into seawater at 0°C?
Known: z=50 µm, D=4.0x 10-5 cm2/sec at 0°C and Salinity=35psu.
[Ar]gas=0.01 atm, KH=gas solubility constant=1.83 mmol/kg/atm.
Density of seawater=1.0kg/1000 cm3
= 44 mol/m^2/yr
