A PORTABLE FLOW INJECTION ANALYZER FOR THE IN SITU DETERMINATION OF FILTERABLE REACTIVE PHOSPHORUS (FRP) IN FRESHWATER

The development and deployment of a portable flow injection analyzer for continuous, real-time monitoring of filterable reactive phosphorus (FRP) in the Tamar catchment is described. The optimized method can be used for the determination of FRP in freshwater systems (4-150gL-1 P) and is capable of sampling with high temporal resolution (up to 15 samples h-1). The analyzer, fitted with a pre-filter and an in-line membrane filter (0.45m, cellulose acetate), was used in situ (bank-side and shipboard deployment) to provide real-time FRP data and in the laboratory to determine FRP in freshwater samples. The portable FRP analyzer was reproducible (RSD5%; n=3) over the range 4-150gL-1 P and accurate, achieving good agreement with a laboratory based air-segmented continuous flow analyzer reference method for a range of freshwater samples from the Tamar catchment in SW England.