Hi Jose,

It depends on whether you are considering human or ecosystem health? I assume ecosystem health as you are interested in P. The WHO stipulates thresholds for human health for most contaminants. For ecosystem health the thresholds should be specific to the particular ecosystem type and the sensitivity of that ecosystem. I'm not sure you can stipulate a global threshold for ecosystems other than relatively general maxima? Other members may be able to help with this. 

Hello

I will direct you on the internet which the address is :www.fne.asso.fr/documents/eau/fichesthematiques/c_fiche_6_nitratesmilieuaquatiques.pdf

You will probably find answers to your questions.

Best regards

Hi,

According US EPA nitrate levels below 90 ppm do not show any effects on warm water fish. Apparently, warm fish also can survive if nitrite levels are below 0.5 ppm. Nonetheless, cold water fish are more sensitive having threshold levels 0.06 ppm for nitrite. 

In case of phosphorus, total phosphate levels should be ranged between 0.01-0.03 ppm in order to keep water bodies free from contamination.

Reference:

Quality Criteria for Water, U.S. Environmental Protection Agency, EPA#440/5-86-001, 1986.

The WFD approach is specific for each tipology of water body. The good ecological status is assessed by comparison between the actual status of the water body (or typology of water body) and the reference (pristine) consitions. So there are different limits for every typology. In Italy physico-chemical parameters for ecological status asessement concur to define an overall index which is callde LIM. Look at the tables 4.1.2/a and b of the attached document (in Italian, pages 65-67) and 4.2.2a for the lakes (page 78 and following)

Hello

There is not really an international standard defined on concentrations of nitrates and phosphates in their lakes and rivers. By cons there is a recognized estimate that the waters of rivers and lakes should not exceed the following concentrations:

- 05 mg per liter for nitrates;

- 0.1 mg per liter for phosphates.

In dams nitrate concentration should not exceed 50 mg per liter  

 Best regards

To avoid eutrophication in rivers the Western Canadian Guidelines are 0.05mg/L for soluble phosphate. The corresponding guideline for lakes is 0.03mg/L. Nitrate is not generally a concern but I had one situation where the denitrification system in a wastewater treatment plant was incomplete and toxic nitrite releases were measured.