This paper reviews current knowledge on
sampling, storage and analysis of phosphorus (P) in river waters. Potential
sensitivity of rivers with different physical, chemical and biological
characteristics (trophic status, turbidity, flow regime, matrix chemistry) is
examined in terms of errors associated with sampling, sample preparation,
storage, contamination, interference and analytical errors. Key issues
identified include:
- The need to tailor analytical reagents and concentrations
to take into account the characteristics of the sample matrix.
- The effects of matrix interference on the colorimetric
analysis.
- The influence of variable rates of phospho-molybdenum blue
colour formation.
- The differing responses of river waters to physical and
chemical conditions of storage.
- The higher sensitivities of samples with low P
concentrations to storage and analytical errors.
Given high variability of river water characteristics in space
and time, no single standardised methodology for sampling, storage and analysis
of P in rivers can be offered. ‘Good Practice’ guidelines are suggested,
which recommend that protocols for sampling, storage and analysis of river water
for P is based on thorough site-specific method testing and assessment of P
stability on storage. For wider sampling programmes at the regional/national
scale where intensive site-specific method and stability testing are not
feasible, ‘Precautionary Practice’ guidelines are suggested. The study
highlights key areas requiring further investigation for improving
methodological rigour.
Keywords: phosphorus, orthophosphate, soluble reactive, particulate, colorimetry,
stability, sensitivity, analytical error, storage, sampling, filtration, preservative,
fractionation, digestion |