Delayed filtration and preservation of surface water samples collected for nutrient analysis

摘要

Two sample collection techniques were compared using several typical water quality parameters. The two collection techniques compared involved 1) field filtration and preservation of samples as currently required by USEPA and FDEP; and 2) collection of large grabs, refrigeration and return to the laboratory for filtration and preservation. Samples were collected at three locations: the Sebastian River, the Indian River Lagoon and Sebastian Inlet. Analytical parameters included orthophosphorus, silica, and dissolved and total (filtered and unfiltered) phosphorus and organic nitrogen. Analyses were conducted at detection levels expected to have environmental significance. 0.0lmg/L for phosphorus fractions and 0.lmg/L for nitrogen fractions. Analytical results from the collected samples were compared by two way ANOVA. Nutrient data, with the exception of dissolved nitrogen, demonstrated no differences between sample means between collection techniques. This collection techniques provides a sharp contrast to the labor and cost intensive "clean collection / clean analysis" techniques required for extremely low level samples. In our experience "field grab / laboratory process" technique provide labor savings of 40% over field sample processing collection schemes and appear to be equally effective when routine, non-trace detection requirements are employed. Additionally, error around mean values for laboratory processed samples was observationally lower than error around field processed means perhaps indicating a more uniform analysis can be expected from the laboratory processing approach.