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.