Introduction
The standard ISO DIS 20079 “ Water quality – Determination
of the toxic effect of water constituents and waste water to
duckweed (Lemna minor) – Duckweed growth inhibition test
“ is a new standard developed to test growth inhibiting
response of substances and mixtures contained in water, treated
municipal waste water and industrial effluents. This will allow
for the first time to use a short (7 days) test with a higher
plant as ISO standard. During development the test was very
successfully used with a broad variety of applications. The
test is already used in a large number of countries.
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Aim
of the ring test
The ring test should provide final performance data and validation
for the reference toxicant 3,5-Dichlorophenol as mentioned in
the standard. Each lab will see how its values are in the range
of many other participants.
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Standard
used
LemnaTec will send out the relevant actual text of the standard
to all participants. No other regulation except for this standard
and its references are relevant for test performance and calculation
of results.
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Organisation
The ring test is organised by LemnaTec in agreement with the
German mirror committee NAW I.3 of the German Standards Institute
(DIN. All questions and registrations should be addressed to:
Matthias
Eberius
Tel. +49 (0) 2405 / 4126-15
Fax. +49 (0) 2405 / 4126-26
eberius@lemnatec.com
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Chemical
to be used
Reference chemical for all tests will be 3,5-Dichlorophenol
(CAS-No. 591-35-5). Each lab shall provide its own chemical
as far as possible as this will be the same in later testing
too. The substance should have analytical purity.
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Duckweed
sources
The ISO guideline just defines Lemna minor to be used. Thus
all Lemna minor clones are allowed to be used in the ring test.
Please take into consideration that it may be difficult in some
cases even to distinguish between Lemna minor and Lemna gibba
used in OECD and ASTM, USEPA standards. Some strains show despite
constant lab conditions high perennial changes in growth.
For this reason the clone Lemna minor ST is recommended informally.
In all cases a good documentation of the source is necessary
and of high interest for the study results. LemnaTec can provide
cultures of Lemna minor ST. All labs that have obtained a duckweed
culture at any time before by Lemnatec have Lemna minor ST.
Detailed description of origin of this strain can be provided
by LemnaTec. The lab will have to bear only the transportation
costs if such a culture is needed. For countries with special
regulations for importing plants all costs related to this have
to be paid by the lab. To accelerate provision cultures of Lemna
minor St, can also be obtained from US and Canadian sources
as mentioned in the annex of the guideline.
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End
of the practical ring test phase
While late registration is no problem the decisive thing is
provision of data. All data must be provided till 30 May 2004.
For labs facing severe problems with this date please contact
LemnaTec as fast as possible. Reason for this date is the finalisation
of the ISO FDIS Version.
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Costs
The costs include all organisation, provision of plant material
(except sending costs), provision of data sheets, recalculation
and the provision of the final report including a special statement
of participation of the lab including its own values, the code
number of the lab in the report and the range of EC-values later
included in the standard.
A total of 150 Euro should be paid to the following account:
Dr. Schmidt Ringversuche, Deutsche Bank Leverkusen, Account
no.734643001, BLZ (code no) 375 700 64. Code word: “RV-Lemna”
(important!!) While
all material and data sheets are sent out after registration
to avoid any delay, the final report will only be sent out after
payment.
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Test
design
3,5-Dichlorophenol is tested in at least 5 concentrations with
6 replicates. Preliminary tests showed ErC50 values in the range
of 1,8 mg/l and 3,6 mg/l. As the concentration-response curve
is very steep it is recommended to test concentrations especially
in the range between 0.5 and 6 mg/L to find inhibition values
between <5 and 75 % of growth rate. The values mentioned
here are just informal recommendations. Final spacing just have
to fulfil requirements of §10.1 while the “intended
ErCx” values are x=5,10,20,25,50.
Wherever
possible 3 independent tests should be made to allow calculation
on variances within one lab.
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Test
media
The Steinberg medium should be used as primary general test
medium as described in the guideline. If some labs decide to
use the OECD medium, because this would be the main routine
use with the standard, it would be strongly recommended to make
3 independent tests and add at least one test with main test
and pre-culture in Steinberg medium.
The option to use of the APHA test medium is included in the
standard to cover special regulatory requirements in some countries.
This use of this medium should be restricted to environmental
samples containing primarily heavy metals. Thus, this medium
would not normally be chosen for testing the reference substance
DCP. Nevertheless it would be of high value if labs in those
countries that will do such APHA test in routine would provide
APHA data with DCP additionally to Steinberg data. The same
is true for data of KCl tests. KCl is not tested in this ring
test but labs who have data with KCl produced under ISO standard
conditions are invited to provide them.
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Document
transfer:
All relevant documents will be sent out by e-mail after registration.
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Registration
for ringtest participation
The ringtest registration will end on 15th of April. For all
participants who need duckweed or have other problems registration
should be made as fast as possible. For registration please
fill out the form
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Registration
Hereby we confirm our participation in the ringtest of ISO 20079
Duckweed.
