Originally Posted by wbuffetjr
One more question... What is the relation between phosphate and phosphorus in water?? A water sample I took from my spring had .06 mg/l of Phosphate. That was straight out of the ground. A google search says natural waters contain .02ppm of phosphorus. Mine is 3x that right out of the ground if phosphate = phosphorus.

Great question - and beyond my ability (limited chemistry) to answer. I can tell you that I looked at several studies /articles on that subject and it is complicated. We need a good water chemistry expert. I will add a few things I found - they are not answers. Bill would be a better source on this topic.

PO4 (phosphate) Almost all of the inorganic phosphorus (P) in water is in the form of phosphate (PO4). Units of measure for phosphorus may be as phosphate (mg/L) or based only on the phosphorus ion (mg P/L). Thus, 1.000 mg/L of phos phate is equivalent to 0.326 mg P/L. Much of the phospho rus in surface water is bound to living or dead particulate matter. It can be stored in the bottom sediments of ponds. Phosphorus is an essential plant nutrient and, because it is often in limited supply, adding phosphorus to water will stimulate plant and algae growth. This growth of algae can be undesirable, as in the case of pristine clear-water streams and lakes, or desirable, as in ponds for fish culture. The typical range for surface waters is 0.005 to 0.5 mg/L. Groundwater in certain aquifers may contain significant concentrations of phosphorus because of local geology. Ponds in watersheds fertilized with poultry litter or livestock manure may be fertile (or excessively fertile) because of the influx of phosphorus from animal wastes. Similarly, in urban settings, phosphorus from lawn fertilizers or leaking septic systems can cause algal growth in waters.

The geochemistry, availability and abundance of different forms of phosphorus in soil, water and sediments are reviewed. The present knowledge of phosphorus pathways in ecosystems and their regulation is discussed.
In a drainage basin, anthropogenic phosphorus is brought into the system mainly as fertilizers and detergents. Sewer systems and outwash processes transfer the phosphorus from the terrestrial environment to the aquatic part of the ecosystem where an accumulation occurs in the sediments of the watercourse.
A great part of the phosphates in soil is sorbed to soil particles or incorporated into soil organic matter. The release and export of phosphorus from uncultivated soil is a function of the geology and soil composition, but also of the air temperature, precipitation and the hydrological condition, pH etc.
The solubility of phosphates is controlled by either sorption-desorption or precipitation-dissolution reactions depending on the environment in the soil or sediments. In soil and sediments with large amounts of iron and aluminium hydrous oxides, sorption-desorption reactions are largely responsible for determining the level of orthophosphate in the solution at equilibrium.
Algal availability of phosphorus associated with soil-derived materials present in aquatic systems deserves more research. In addition, processes responsible for transport of phosphorus from cropland to aquatic systems and chemical and microbial transformations of phosphorus in lakes and streams deserve more attention.



An exchange mechanism exists in lake water between phosphate and plankton, but the excretion of an organic phosphorus compound by the plankton is also a significant process. It results in the extracellular formation of a colloidal substance, and most of the nonparticulate phosphorus in lake water is in this form.






The change in concentrations of four phosphorus fractions (total phosphorus, total dissolved phosphorus, total reactive phosphorus and dissolved reactive phosphorus) commonly measured in natural waters were measured in two lake water samples after storage at 4°C. After 4 h only total phosphorus had not significantly changed. The other phosphorus fractions showed decreases of between 25 and 54%.

Last edited by ewest; 09/28/21 05:40 PM.