7.11.1. Introduction
Lakes intercept the flow (and fluxes) in an area. The chemistry of lake water thus gives an integrated picture of the fluxes from atmospheric and terrestrial environments. Processes occurring in lakes, like net sedimentation, turnover and freeze-over in the northern latitudes, may change the concentrations in the water. Thus the retention of fluxes in lakes might affect the values in the output to some degree. Lakes as intermediate pools of element fluxes are important bodies for compound changes, which in turn might cause reactions in their hydrobiological nature. If a lake exists within an IM area the lake water chemistry should be monitored for the understanding of the effect of internal fluxes.
The parameters included on the mandatory list are those also mandatory in the ICP Waters programme and mainly related to acidification. The optional determinants are those also listed optional in the ICP Waters programme.
Mandatory parameters:
anions: alkalinity, sulphate, nitrate, chloride
organic: dissolved organic carbon
cations: pH, calcium, magnesium, sodium, potassium, inorganic (labile) aluminium 1)
nutrients: total nitrogen, ammonium
physical properties: specific conductivity
1) Difference between reactive (organic + inorganic) and non-labile (organic) aluminium. May be omitted at pH>5.5.
Optional parameters:
physical properties: water temperature
nutrients: total phosphorus, soluble reactive phosphate, total sulphur, silica, dissolved oxygen
metals: iron, manganese, cadmium, zinc, copper, nickel, lead, arsenic, chromium, molybdenum, total aluminium
other: fluoride, colour
7.11.2 Methods
7.11.2.1 Water chemistry samples
Establish a permanent lake water chemistry sampling site at the deepest point of the lake away from littoral influences. A bathymetric survey of the lake will help the allocation of sampling site. Lakes are sampled at depths of 0.5 m (or 1 m), 3 m, 5 m, halfway to the bottom and 1 m above the bottom. At the deepest point of the lake, a water profile should be established which should be followed up annually.
Lake water samples should be taken 2 - 6 times per year.
Use water samplers of the cylindrical open-top (e.g. Limnos) type, made of materials like teflon, polypropene and polyethylene. The sampler is hoisted up and down with a rope. A polyethylene sampler must be equipped with a plastic-embedded weight and a teflon sampler must have a sufficiently thick bottom in order to make it sink.
7.11.2.2 Handling of water chemistry samples
Please see Chapter 8.2 for details.
7.11.3 Analytical techniques
For a list of available standards, see Chapter 8.5.
7.11.4 Quality assurance/Quality control
See data quality management in Chapter 8.
7.11.5 Data reporting
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Mandatory parameters
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list
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unit
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PH
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DB
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pH
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COND
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DB
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specific conductivity at 25 oC
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mS/m
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NA
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DB
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sodium
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mg/l
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K
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DB
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potassium
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mg/l
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CA
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DB
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calcium
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mg/l
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MG
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DB
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magnesium
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mg/l
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ALL
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DB
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inorganic labile aluminium
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µg/l
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NO3N
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DB
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nitrate as nitrogen
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µg/l
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NH4N
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DB
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ammonium as nitrogen
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µg/l
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NTOT
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DB
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total nitrogen
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µg/l
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ALK 1)
|
DB
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alkalinity, GRAN plot
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mmol/l
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CL
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DB
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chloride
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mg/l
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SO4S
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DB
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sulphate as sulphur
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mg/l
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DOC
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DB
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dissolved organic carbon
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mg/l
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Optional parameters:
|
list
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|
unit
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O2D
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DB
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dissolved oxygen
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mg/l
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PO4P
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DB
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phosphate as phosphorous
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µg/l
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PTOT
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DB
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total phosphorous
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µg/l
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STOT
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DB
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total sulphur
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µg/l
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SIO2
|
DB
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silica (as silica)
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mg/l
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CNR
|
DB
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colour number
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Pt mg/l
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TEMP
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DB
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temperature
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oC
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F
|
DB
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fluoride
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mg/l
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|
FE
|
DB
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iron
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µg/l
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|
MN
|
DB
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manganese
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µg/l
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|
AL
|
DB
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total aluminium
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µg/l
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|
AS
|
DB
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arsenic
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µg/l
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CD
|
DB
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cadmium
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µg/l
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CR
|
DB
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chromium
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µg/l
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CU
|
DB
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copper
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µg/l
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MO
|
DB
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molybdenum
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µg/l
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NI
|
DB
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nickel
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µg/l
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PB
|
DB
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lead
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µg/l
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|
ZN
|
DB
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zinc
|
µg/l
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1) Please note the change of unit.
Important: if the titration is made to one single pH value (usually pH 4.5) it is necessary to indicate (using the correct determination code in DB list) whether the given value is adjusted to be the endpoint value or represents the total acid consumption to pH 4.5.
Example files
LC example Excel file
LC example ASCII file
- File identifier SUBPROG states the subprogramme.
- MEDIUM is left blank.
- LEVEL is given as sampling depth from the lake surface (cm).
- Spatial pool SPOOL refers to the number of sampling points.
- Monthly values are reported without status. Values for several sampling dates per month are reported as arithmetic averages with status flag X. For calculation of weighted means, please see Annex 7. General information on flags is given in Chapter 4.
- Sampling year and month are given as YYYYMM, day field is left blank.
7.11.6 References
ICP Waters Programme manual. Compiled by the the Programme Centre, Norwegian Institute for Water Research. Revised edition, Oslo.