NITRATES - LOSS PROCESSES IN RAW WATER
Report No DWI0630
Summary of main conclusions
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- Slight changes in the method used to prepare sediment slurries
can result in large changes in the measured nitrifying activity.
This makes comparisons between studies, using different methods,
- Methods to study sediment nitrification processes which do not
disrupt preformed substrate gradients within the sediment provide
the most reliable rate estimates.
- On an annual basis the nitrate load to Grasmere lake from the
catchment was 157 kg N/ha compared to nitrate produced by
nitrification within the lake of 80 kg N/ha. If these separate
nitrate loads were calculated on a monthly basis their relative imp
ortance to the total nitrate load to the lake showed considerable
- Rates of nitrification were greatest in the surface sediments of
the littoral zone. However, in terms of nitrate produced within the
lake the water column had most influence as the volume which could
support nitrification was 700 times greater than the active volume
- Increased eutrophication of lakes resulted in increased rates of
nitrification in the deeper waters and surface sediments of the
littoral zone. Such effects were not observed in profundal sediments
possibly due to inhibition by unknown mechanisms.