Human effects on total ocean minor element budgets

3 Human effects on total ocean minor element budgets 

In the preceding sections we showed that riverine nutrient inputs impact regional seas. We also stated in Section 6.5.4 that the huge reservoirs of nutrients in the deep ocean mean that increases in, for example, the concentrations of NOf in riverwaters due to human activity have little effect on oceanic NO, concentration, assuming that NOf is effectively mixed throughout the ocean volume. We can now demonstrate that this is the case using some simple reasoning. 

The average NOf concentration in the oceans is 30pmoll 1. The total oceanic NO, inventory is calculated by multiplying this concentration by the volume of the oceans, i.e.  

It is difficult to estimate the natural pre-human NO 3 concentration in rivers, since most have now been affected by human activities to some extent. Nitrate concentrations in the Amazon are about 20pmoll 1 and are probably close to natural levels. Multiplying this NO3 concentration by the global river flux gives an estimate of the natural nitrate input to the oceans  

If 10% of the world s rivers have NOl concentrations increased to 500pmoll 1, total riverine NOl inputs become  

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