BS EN 17136 pdf free download

BS EN 17136-2019 pdf free download.Water quality – Guidance on field and laboratory procedures for quantitative analysis and identification of macroinvertebrates from inland surface waters.
guaranteed by the manufacturer attestation or control, providing metrological traceability. It should regularly visually be inspected for visible damage before every use
For DNA-based studies the removal of larger, visible contaminants by washing the equipment in water only is not sufficient. Instead sieves should be cleaned preferably with an appropriate bleach solution for each consecutive sample location.
5.2 Microscope
A low-power stereo-zoom microscope (typical magnification —lOx to 60x) can be used for accurate quantitative sorting and most identifications. For the species identification of specific groups like Chironomidae and Oligochaeta a compound microscope (typical magnification 40x to 400x) should be used.
5.3 Fixatives and preservatives
5.3.1 General
There is a distinct difference between fixation and preservation. In general, fixation is preferred for morphological analysis. Within the context of freshwater macroinvertebrate analysis ethanol as a preservative is the most often used chemical for preserving samples for quantification and identification. When ethanol is used as a preservative formaldehyde fixation can be left out for macroinvertebrate analysis.
WARNING — Formaldehyde Is hazardous to humans (CMR substance, see ECHA) even at very low concentrations in air. Formaldehyde fixation should be avoided as much as possible.
Preservation by ethanol and formaldehyde fixation affects the estimation of biomass. Although weight loss by ethanol is considered to be more significant than by formaldehyde no unambiguous scientific data are available on the exact effect of either preservative. Therefore, prior to estimating biomass on the basis of preserved organisms the bias by using preserved material should be assessed for the specific taxonomic groups under investigation and the relevant conditions of sampling and preservation.
After the fixative or preservative has been added the sample should be gently turned to disperse the preservative.
5.3.2 Formaldehyde, 37 % (volume fraction)
Formaldehyde 37 % should be added to an undrained sample with a final concentration of 4 % to
6 %. This concentration provides a good fixation of organisms (avoiding damaging and shrinking).
Formaldehyde is not a suitable fixative for DNA analysis. Formaldehyde samples should always be
thoroughly rinsed with water on a sieve prior to processing.
Long-term storage in formaldehyde can seriously affect the colour of specimens and dissolves the shells of Mollusca (if not buffered). To prevent this, formaldehyde fixed samples can be transferred to 70 % ethanol. Transferring the sample to ethanol can already be done after 24 h of fixation. The sample should be thoroughly rinsed with water to remove the free formaldehyde before adding the ethanol.
5.3.3 Ethanol, C2H5OH
Before addition of ethanol the sample should be drained to minimize the dilution with excess sample water. In most cases ethanol 96 % should be added to compensate for dilution by the residual sample water. In samples with absorbing material and/or relatively large organisms (e.g. numerous molluscs) the initial 96 % ethanol should be replaced after a few days to ensure a permanent concentration of approximately 70 % in the sample. The sample container should not be filled for more than one third with material. Ethanol should be added until the sample is completely immersed and the container is filled to achieve a concentration of 75 %. Ethanol concentrations well above 70 % will harden many organisms rendering them difficult to manipulate and identify. Ethanol concentrations below 70 % will lead to tissue degradation.
Initial ethanol concentrations should be checked sample-wise with an alcohol meter.
Unfixed macroinvertebrate samples preserved with ethanol can be stored for several years.
Macroinvertebrate samples used for DNA studies or DNA-based identification that need to be stored for extended times before analysis (e.g. DNA barcoding) should be placed within two days of sampling in  90 % ethanol and preferably stored In a cool and dark place. At concentrations below 80 % DNA will degenerate.
5.4 Reagents for examination using compound microscopes
5.4.1 General
Many chemicals are known to enhance the microscope image quality in order to be able to accurately describe diagnostic features. The most relevant chemicals including mounting media can be found in group specific identification literature. Koenike and Laevulose syrup, presented below, are the most often used reagents. Koenike can also be used as a preservative for Arachnida (mites).
5.4.2 Koenike
Mix 50 ml of glycerol with 30 ml of water and add 20 ml of acetic acid. This clear solution can be stored at room temperature for an unlimited period of time.
5.4.3 Laevulose syrup
Dilute 25 g D(-)Fructose in 25 ml water by proper stirring (magnetic stirring bar). The solution can he slightly heated. Thereafter add 25 ml of lactic acid and stir again. This clear solution can be stored at room temperature for an unlimited period of time
6 Pre-laboratory procedure
6.1 General
The pre-laboratory procedure starts with a visual inspection of the sample to assess the amount of matrix material (silt, clay, sand, macrophytes) and the number of organisms. With this information the right procedure for pre-treatment and sorting can be selected. It can be done in the field directly after sampling or in the laboratory.
The general objective is to select the organisms in the most effective way (least amoLint of time). If sub- sampling is necessary it should be done in a random way. When not all organisms have to be identified selectivity in sorting of taxa should be avoided.
Before collecting the organisms the sample should be rinsed and cleaned and/or sub-divided in smaller portions.
In case of unpreserved samples macroinvertebrates are collected alive in larger trays with the naked eye or with the use of a magnifying glass.
In case of preserved samples the macroinvertebrates with the remaining matrix are transferred to small trays and collected with the use of a stereo-zoom microscope.
Each collected organism is first sorted to its main taxonomic group (see Table 1). In a second step, the organisms are identified per taxonomic group to the desired taxonomic level.
Generally the smallest mesh size for collecting the macroinvertebrates during the analysis is 500 m (e.g. sampling EN ISO 10870) as for most waters it is the best combination for trapping the macroinvertebrates and at the same time allowing effective rinsing. In specific situations (e.g. clear stony rivers) a smaller mesh size for maximum trapping of small macroinvertebrates can be selected.BS EN 17136 pdf download.