Analytical approaches to the determination of phosphorus partitioning patterns in sediments

Three methods for phosphorus fractionation in sediments based on chemical extractions have been applied to fourteen aquatic sediment samples of different origin and characteristics. Two of the methods used different approaches to obtain the inorganic fractions. The Hieltjes and Lijklema procedure (HL) uses strong acids or bases, whereas the Golterman procedure (G) uses chelating reagents. The third one, the Standards, Measurements and Testing (SMT) protocol, was proposed in the frame of the SMT Programme (European Commission) which aimed to provide harmonisation and the validation of such methodologies. This harmonised procedure was also used for the certification of the extractable phosphorus contents in a sediment certified reference material (CRM BCR 684). Principal component analysis (PCA) was used to group sediments according to their composition and the three extraction methods were applied to the samples including CRM BCR 684. The data obtained show that there is some correlation between the results from the three methods when considering the organic and the residual fractions together. The SMT and the HL methods are the most comparable, whereas the G method, using a different type of reagent, yields different distribution patterns depending on sample composition. In relation to the inorganic phosphorus, the three methods give similar information, although the distribution between non-apatite and apatite fractions can be different.