Phosphorus Holding Time

Water sample holding times at appropriate temperature, filtering, and storage conditions for accurate analysis of soluble reactive phosphorus

Phosphorous (P) loss to surface water contributes to eutrophication and harmful algal blooms and restricts water use for fisheries, recreation, industry, and human consumption. When P becomes soluble, it can include small amounts of organic particulates and purely inorganic forms of orthophosphate anion (P043-, HPO42-, and H2PO4-), depending on soil pH. Sorption-desorption is arguably the most important chemical process governing the retention-release of the orthophosphate, PO43- in the soil solution. Our objective was to investigate the temporal impact of two combinations of sampling-filtering analysis and storage-filtering analysis on the soluble reactive phosphorus (SRP) concentration. Determined SRP concentrations of the temporal sampling-filtering revealed a significant concentration reduction of SRP in water samples filtered. They analyzed immediately compared with other water samples taken and analyzed after 24 hours, 7 days, and 14 days. The temporal combination of filtering- storage of water samples taken and analyzed within 24 hours at four successive weeks and re-analyzed after filtering for 28 days revealed a constant concentration of SRP stored in the refrigerator compared to those stored in the freezer, which lost up to 40-60% of their SRP concentrations, although they were filtered.