Conclusion:
Due to population growth and the associated agricultural developments
and upland soil erosion, western rivers discharging in Urmia Lake
release massive quantities of P-loaded water and sediment. This is the
main reason for eutrophication of wetlands at this lake. In this
investigation, a selection of extraction methods was considered in their
capability to extract sediment-bound P. The extracted quantities
appeared to vary significantly between these methods, even though most
methods showed a good correlation with each other. The extracted P was
also compared with algae growth in a bio-assay, for the algaeSelenastrum capricornutum . Correlations with algal growth were
modest, except for the Colwell-P that correlated very well. For
sediments as discharged into Urmia Lake, where pH and EC appears to have
an effect on algae growth, the Colwell-P extraction therefore looks as
the best option. Because of dense algal bloom in lower research areas,
withholding fertilizer application for building up crop requirement is
recommended in susceptible land for erosion.