Explanation of total constituent analyses performed on National Stream Quality Accounting Network and Hydrologic Benchmark Network water-quality samples
[The total form reflects different characteristics of the analytical methods and the water-suspended sediment mixture of the samples. Explanations are modified from USGS annual State data reports]
_____________________________________________________________________________
Term Explanation Applicable
constituents
_____________________________________________________________________________
Total The total amount of constituent in a representative Nitrogen1,
water-suspended sediment sample, regardless of the phosphorus,
constituent's physical or chemical form. The Kjeldahl
analytical procedure assures measurement of at least (organic plus
95 percent of the constituent present in both the ammonia)
dissolved and suspended phases of the sample. nitrogen, and
carbon.
"Total" The determination represents the amount of a consti- Nitrite,
tuent in a water sample present in the "dissolved" nitrate plus
form. The analytical method was performed on water- nitrite2,
suspended sediment samples "decanted" in the ammonia, and
laboratory (Skougstad and others, 1979) to avoid orthophosphate
measurement interferences associated with particulate
material. The results of these analyses are not
statistically separable from analytical results based
on "dissolved" samples obtained by filtering a water-
suspended sediment sample in the field using a 0.45
micrometer membrane filtration device (see memorandum
QW93_04).
Total The amount of a given constituent remaining in solu- Trace elements
recov- tion after a representative suspended-sediment
erable sample has been digested by a method (usually using
a dilute acid solution) that results in dissolution
of only readily soluable substances. Complete dis-
solution of all particulate matter is not achieved
by the digestion treatment, and the determination
represents quantities that are less than 95 percent
of the total amount.
_____________________________________________________________________________
1 Total nitrogen is calculated as the sum of total Kjeldahl nitrogen
and "total" nitrate+nitrite determinations.
2 In cases where "total" nitrate+nitrite laboratory analyses were not
performed (i.e., beginning on 10-1-94), the results of laboratory analyses
of dissolved nitrate+nitrite were automatically substituted by the U.S.
Geological Survey's water-quality data storage and retrieval system, the
National Water Information System.