Re: testing a pond, river,creek for ph, diss co2 silica nitrites

Hi Susan-

That's a pretty broad question! If you're measuring pH in a creek, river and pond, it will vary depending on many things- including the chemical composition of the soils in the watershed, the mineral and chemical composition in the lake/stream bed, and the presence/absence of anoxia, for starts. Dissolved CO₂ tells you basically how much respiration has gone on, and silica (in lakes at least) can be a limiting nutrient for diatoms. Phosphate is typically the limiting nutrient in lakes, but in hypereutrophic lakes, it's possible for nitrate to become limiting if there is a lot of phosphate inputs (such as a pond near a farm that gets a lot of fertilizer runoff). I'd suggest you have a look at Robert G. Wetzel's "Limnology" (1983: Saunders), which has some excellent sections on lake chemistry.

Rob Campbell, MAD Scientist