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Re: water quality reports
A M Moore asked:
>
> Could someone advise me of exactly which elements are the important ones I
> should be looking for on my Water Quality Report and what levels they should
> be ? I can then adjust my PMDD etc accordingly.
>
Well, that's a tall order.
> My report gives Min, Max & Mean values for many, many different compounds.
> Which are the ones I should be bothered about ?
>
I don't know what your analysis lists, so I'll just describe what I've
seen reported before.
Nine solutes comprise the vast majority of all minerals dissolved in most
water. These are Ca++, Mg++, Na+, K+, HCO3-, Cl-, SO4--, NO3-- and SiO2.
The means of reporting these values varies from laboratory to laboratory.
Usually concentrations are reported in milligrams per liter or ppm. For
most waters there is no practical distinction between these units of
measure.
Ca++ and Mg++ taken together (usually along with very much smaller
amounts of Sr++ and Ba++) comprise hardness. HCO3- (possibly with
CO3-- if your pH high) comprise the alkalinity. Hardness and alkalinity
are usually reported in terms of an equivalent amount of CaCO3. The
values might be in ppm, mg/l, degrees (German or English) or in the US,
grains per gallon (sometimes called American degrees).
Nitrate (NO3--) is generally reported as nitrate plus nitrite. Ammonia or
ammonium may also be reported. It is most common these days to report all
of the nitrogen species in terms of the amount of nitrogen they contain.
This allows easy comparison between the concentrations of different
nitrogen-containing solutes. It also allows the results from different
methods of analysis to be cross-compared.
TKN or Total Kejldahl Nitrogen (sp?) is another often-reported nitrogen
measure. It is the total of all dissolved nitrogen species - including
nitrogen bound in organic molecules.
SiO2 may be reported as H4SiO4.
I don't know of any freshwater plant or algae that *must* have
sodium (Na+), but all of the other major constituents are essential to
something.
The water also contains milligram per liter levels of dissolved gases -
nitrogen, oxygen, argon and carbon dioxide mostly. The gas concentrations
are far too variable to be captured by normal sampling methods, and would
vary greatly at the point of use, as well. Generally noone reports
dissolved gases.
In addition to the major constituents there are a large number of minor
constituents that might also be reported. The most common that come to my
mind are iron (Fe), manganese (Mn) and phoshorus (P). These may be
reported in milligrams or micrograms per liter or parts per billion (ppb).
They may also be reported as an oxide, i.e. total iron might be reported
as FeO. Phosphorus may be reported as total P, or as a phosphate (PO4);
its concentration may be as P or as PO4. That is highly variable.
The list above covers most of what you need to be concerned with. You
will want to measure pH yourself, as the value is highly variable.
There's a lot said on this list about how much you need of different
components, and I won't try to summarize it. For my own thinking, I
divide the minerals into two categories; those that are important mostly
as electrolytes and those that are metabolized into organic molecules.
Some components (like magnesium, I think, might fall in both categories).
The metabolized components can be ranked by their concentrations in plant
material and this provides some measure of the relative concentrations
needed in their environment (not necessarily all in the water). In
decending order, I think we have C (CO2, HCO3-) > N (NH4, NO3-) > S
(SO4--) > P (H2PO4-, HPO4--) > Fe (Fe++ I think) > Mg (Mg++). I might
have these last two reversed. Can't recall for sure.
The electrolytes include K+, Ca++, Mg++, Cl- in (I think) that order.
Hydrogen might also be considered as an essential electrolyte.
Certainly if someone else wants to change this list or flesh it out, feel
free.
The analysis might include a lot of other things...
There's a very large number of trace elements that might be reported.
Many trace elements are essential (at trace levels) for plant growth. The
most commonly reported concentrations are for metals - copper (Cu),
chromium (Cr) and lead (Pb) are commonly reported. Arsenic, selenium and
boron are sometimes reported as well. These are generally reported as
micrograms per liter. Some might be reported in picograms per liter. The
reported concentrations of trace metals are (in my experience) usually
wrong, so don't worry about them too much.
pH is often reported. There are also a number of physical parameters
commonly reported, including temperature, turbidity and color.
There's an enormous number of organic compounds potentially present in
tap water - usually in the microgram per liter range. The only ones
commonly reported are the toxic or carcinogenic contaminants.
Trihalomethanes are often reported. So might be various forms of benzene,
toluene, ethylene, and/or xylene. A large number of solvents -
especially chlorinated solvents like trichloroethane - might also be
reported.
Then there's the biological parameters. Coliform bacteria is very
commonly reported. Giardia and cryptosporidium are getting increasingly
reported in the US. There might be other measures too, including algae,
fungus, spores, insect parts (oh wait, that's flour, not water) and a few
other odds and ends.
> I still plan to pre-filter my water through an activated Carbon block - will
> this reduce/take out any of these important elements ?
>
Activated charcoal removes mostly organic compounds from the water and
will have little effect on inorganic plant nutrients.
Have fun,
Roger Miller