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EC number: 231-718-4
CAS number: 7699-45-8
Natural background in surface waters
Data on natural background of zinc in surface waters in the EU
were discussed in the RAR (ECB 2008). Based on values reported for a
number of EU countries, incl. NL, D, F, SF and others, two values were
selected for total background concentration, to be used in the
-3 µg Zn/l which is the lower limit of the range reported by the
member states in the risk assessment process,
-12 µg Zn/l which is the geometric mean value of an extensive EU
database on Zn concentrations in lowland brooks in unpolluted areas in
N-Europe, (10P and 90P in this review are 4 and 35 µg totalZn/l
resp. - Zuurdeeg 1999).
-Using a Kpsuspof 110,000 l/kg (RA; ECB 2008) and a
default particulate matter content of 15 mg/l, these values are
equivalent to 4.44 µg dissolved Zn/l, and 1.11 µg dissolved Zn /l,
Due to geochemical differences, the natural background
concentrations in surface waters will differ throughout Europe. It is
thus not appropriate to set one value for the whole of the EU. Recently,
an extensive database has become available on a.o. zinc background
values in surface waters, covering the whole of the EU (FOREGS 2005).
The 10P and 90P values for dissolved zinc following from this
analysis performed also on non-polluted head waters (cfr Zuurdeeg 1999)
are 0.7 and 18 µg dissolved zinc /l, resp. (http://www.gtk.fi/publ/foregsatlas/maps/Water/w_icpms_zn_edit.pdf);the
median value of 2.7 µg dissolved Zn/l corresponds well with the one used
in the RAR (ECB 2008).
The FOREGS study thus confirms the data reported in the EU RAR and
the Zuurdeeg (1999) analysis. It confirms that the value of 12 µg total
Zn/l – 4.44 µg dissolved Zn/l can be seen as the median value for zinc
background in European freshwaters.
Regarding the sediment, the RAR concluded, based on reported data
from a number EU countries, incl NL, D, F, N, SF, SW, that the range of
the background data for sediment was more or less in the same order of
magnitude (range 70-175 mg/kg dwt). Based on the data from several
EU-regions the value of 140 mg/kg dwt was set for use as a natural
background for correcting the EU sediment monitoring data.
It was noted that, if available monitoring data can unequivocally
be linked with a particular natural background value in an area,
preference should be given to that specific background value (ECB 2008).
For comparison, FOREGS (2005) reports for zinc in sediments 10P
and 90P values of 18 and 270 ppm, resp., demonstrating the big
variation, due to local geology. The median value is 65 ppm. Because of
the great variability, more localised assessments are preferred.
Natural background in the terrestrial compartment
The natural zinc concentrations in soils are highly variable and
dependent on soil type and soil properties. The EU RAR concluded from
the available soil data for a number of EU countries that there is a
large variation in the natural zinc background concentrations. This
variation is related to the native soil material and the present soil
characteristics like humus and lutum. The RAR observed a clear
relationship between natural background levels and various soil
parameters, but noted that a quantification of the exact natural
background level for a specific EU soil type is at present still an
extremely difficult and complex issue. The RAR mentioned zinc
backgrounds usually in the range 50-100 mg Zn/kg DW, which is confirmed
by data from the more recent FOREGS database, reporting 10P, 50P and 90P
zinc concentrations of 8, 52, and 140 mg/kg DW, respectively in
unpolluted soils throughout Europe. Important to note is that, due to
the high variability on the data, the RAR concluded that it was only
possible to use monitored soil data for risk characterisation when it
was possible to make a correction with the natural zinc background
concentration(s) typical for that soil type.
Recent monitored data on zinc concentations in water,
sediment and soil in the EU member states are reported under IUCLID
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