An Introduction to Environmental Chemistry

6.4 Chemical cycling of major ions The concept of residence times was introduced when discussing atmospheric gases (see Section ...

The residence times in Box 6.3 are based on riverwater being the only input of ions to the oceans. This is a simplification as t ...

Identifying removal mechanisms for a specific component is difficult because removal processes are usually slow and occur over l ...

Despite these complications, the main removal mechanisms of major ions from seawater are known (Table 6.2). Quantifying the impo ...

eqn. 6.4). With continued evaporation and an approximately four-fold increase in salinity, CaSO 4 .2H 2 O (gypsum) precipitates: ...

however, thought to be double the long-term values due to the effects of abnor- mally high postglacial suspended-solid input rat ...

bonate (CO 32 - ). Measured Ca^2 +and CO 32 - ocean surface concentrations are 0.01 and 0.000 29 mol l-^1 respectively and thus ...

198 Chapter Six Box 6.4 Ion interactions, ion pairing, ligands and chelation Ions and water When ionic salts dissolve in water, ...

The Oceans 199 O C H 2 C O– H 2 C C O O– N: O H 2 C CH 2 :N CH 2 CH 2 C O– C O– O + M+ EDTA O C H 2 C O H 2 C C O O N O H 2 C CH ...

Allowance for ion pairing indicates that about 90% of the calcium in seawater is present as the free ion with the remainder pres ...

eqn. 6.11 The difference between the Wvalues in equations 6.9 and 6.11 is mainly due to the effects of ionic strength, which are ...

202 Chapter Six Box 6.5 Abiological precipitation of calcium carbonate Where a skeletal source cannot be identified, calcium car ...

The Oceans 203 shallow, saline waters where these deposits are found favour increased concentrations of carbonate ions (CO 32 - ...

204 Chapter Six (a) (b) Fig. 6.10(a) Planktonic coccolithophore Emiliania huxleyi, a very common species in the modern oceans. T ...

Modern surface seawater is demonstrably supersaturated with respect to CaCO 3 , and the presence of carbonate sediments in rocks ...

tation rates are high, associated with nutrient-rich upwelling waters and polar seas, particularly around Antarctica (Fig. 6.9). ...

available as electron acceptors in marine sediments, their importance is small in comparison with SO 42 - , which is abundant in ...

CaCO 3 (eqn. 6.6). This allows CaCO 3 to precipitate as nodules (concretions) in the sediment. These are not quantified in the g ...

source warms the water, causing it to expand and become less dense, forcing it upward again through the crust in a huge convecti ...

cloud of iron, zinc, lead and copper sulphides and iron oxides on injection into cold, oxic oceanic bottom waters. This sulphidi ...