106molNO11 x 36 x 10161 yr1 072 x 1012 molNO yr1

The NO3- concentrations in some rivers have been increased by human activities to concentrations as high as 500 |mmoll-1, although the greatest changes have generally been in small rivers which make a small contribution to the total river flux to the oceans. If, as an extreme case, we suppose that 10% of the world river flow increased to this high concentration, we can calculate how long such a situation would take to double the oceanic NO- concentration, i.e. introduce 41 X 1015 mol. The calculation is simplified by ignoring NO3- removal to sediment. In reality, increased NO3- inputs would result in increased biological activity and increased NO3- removal from the oceans, since the main sink for nitrogen and phosphorus is burial in organic matter.

If 10% of the world's rivers have NO3- concentrations increased to 500 |mmoll-1, total riverine NO- inputs become:

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