a. What is meant by the term accumulated elements when used to refer to the elem
ID: 233383 • Letter: A
Question
a. What is meant by the term accumulated elements when used to refer to the elements in seawater?
b. Which elements fall into this category?
H, O, Na, Mg, Ca, K, Sr, B,C, F, S, Cl and Br.
c. What are the most likely forms (chemical species) of these elements in oxygenated seawater?
The concentration of carbon is mainly found in carbonate, bicarbonate and CO2.
The concentration of sulfur is mainly found in sulfate.
The concentration of boron is mainly found in B(OH)3 and B(OH)4-
The rest of the major elements are dissolved ions in seawater.
d. Use this understanding of the speciation of these elements, together with any other necessary information, to explain why these particular elements fall into this category.
e. What has this to do with the concept of the constant composition of seawater.
Explanation / Answer
a) Accumulated elements are elements in which their concentrations are stable over time in the oceans.
b) Accumulated elements are- H,O,Na, Mg, K, B, F, S, Cl
elements that have minor non-accumulative behaviors are: Ca, Sr, C
d) An element is conservative or accumulative in seawater when its ratio to salinity is conserved. These major elements are conservative because they are in large concentration in sea water. Also they have very long replacement/ residence times in sea water compared to the mixing time of the ocean, which is less than a thousand years.
e) When an element is conservative or accumulative their concentrations are stable over time in the oceans and its ratio to salinity is conserved. Also the ratio of one conservative element to another is constant. This is known as The Law of Constant Proportions. These conservative elements have very low chemical reactivity in the ocean and their distributions in the ocean interior are decided only by currents and mixing.
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