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Phosphorus in Runoff Assessed by Anion Exchange Resin Extraction and an Algal Assay
Author(s) -
Uusitalo Risto,
Ekholm Petri
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.6330
Subject(s) - phosphorus , eutrophication , extraction (chemistry) , surface runoff , chemistry , molybdate , algae , environmental chemistry , chromatography , nutrient , botany , ecology , biology , inorganic chemistry , organic chemistry
Eutrophication of surface waters can be accelerated by agricultural inputs of phosphorus (P), provided that P is in a form that can be utilized by aquatic algae. We studied anion exchange resin (AER) extraction and a dual culture algal assay (DCAA) for the determination of potentially algal‐available P in water samples without sediment preconcentration. Our material consisted of agricultural and forest runoff and wastewaters. The results obtained by the two methods were essentially equal when the samples contained only small amounts of particulate phosphorus (PP) in relation to dissolved molybdate‐reactive phosphorus (DRP). However, in turbid agricultural runoff, P extracted with AER averaged 72% ( n = 17) of the P yield of the 3‐wk DCAA ( R 2 = 0.94). When the runoff samples were diluted for the AER extraction in the same manner as for the DCAA, the AER‐P yield increased to 85% ( n = 5) of DCAA‐P. The minimum detectable value was greater for the AER test (41 μg L −1 AER‐extractable P) than for the DCAA (7 μg L −1 DCAA‐P). At concentrations greater than about 50 μg L −1 AER‐P or DCAA‐P, the accuracy of the methods was satisfactory, with the coefficient of variation in replicated analyses being less than 10% for the AER test and less than 20% for the DCAA. Other anions competing for the exchange sites of the AER decreased P recovery by 15 to 20% when their equivalent concentration exceeded about 4 mmol c L −1 , and this effect was relatively constant over a large concentration range. We consider that AER extraction is a suitable low‐cost method to estimate the algal availability of P in runoff samples.