2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
L13 APPLICATION OF NEEDLES AS
bIOINDICATORS FOR ThE EVALuATION
OF PERSISTENT ORGANIC POLLuTANTS
ENVIRONMENTAL CONTAMINATION LEVEL
M. VáVROVá a,b , R. LánA a , M. HROCH a , J.
ČáSLAVSKý a , I. HLAVáČKOVá a and B. TREMLOVá b
a Brno University of Technology, Faculty of Chemistry; Purkyňova
118, 612 00 Brno, Czech Republic
b University of Veterinary and Pharmaceutical Sciences Brno,
Faculty of Veterinary Hygiene and Ecology,
vavrova@fch.vutbr.cz
Introduction
Bioindicators are living organisms in which concentrations
of organic pollutants considerably exceed those found
in air, water, sediments, or soil. Bioindicators, which are
frequently used in monitoring studies and screenings, should
allow selective and specific determination of contaminants
not only in all compartments of the environment, but also
in all links of food chains of species living in the area under
study. Contaminants detectable by the use of bioindicators
include also PCB indicator congeners 28, 52, 101, 118, 138,
153, 180 which rank with priority pollutants monitored in the
Czech Republic 1 . Plant bioindicators are used in environmental
studies of agrarian ecosystems in our country where they
can yield information for both conventional monitoring and
biomonitoring. The most frequently used plant species are
alfalfa, cereals, and oil plants 2 . The source of contamination
is of great importance. Monitoring of PCBs can often identify
long-distance transport as one of the contamination sources.
Airborne volatile PCBs can originate from various sources
including agricultural production 3 . Thus, PCBs penetrate into
plant tissues and influence the contamination level. Papers
dealing with the contamination of crops by xenobiotics are
rather scarce. Most of the respective investigations were carried
out in fodder plants and were oriented rather on effects of
feeding of contaminated crops to farm animals 1 .
Of all above-mentioned plant bioindicators, coniferous
plants except for larch have the greatest informative value
when the leaf analysis method is used. needles do not fall
off every year as compared to deciduous trees, and one may
monitor a degree of burden using different methods such
as the discoloration of assimilatory organs, sudden changes
in coloration, excessive leaf-fall, crown thinning, partial or
complete dieback of trees, and particularly the above-mentioned
methods of leaf analysis.
Knowledge of the level of contamination of this link of
the food chain is therefore necessary for studies of xenobiotic
transfer 1,4 . Comprehensive studies of plant contamination
were completed in Moravian areas affected by disastrous floods
in 1997 and 1998. Effects of floods on the contamination
of soil and vegetation by persistent organic substances are
summarized in the „Report on the 1998 Monitoring Results
- Hazardous Substances within Food Chains and Influencing
s328
Imputes published by the Ministry of Agriculture of the
Czech Republic in 1998 2 .
Synthetic xenobiotics are included in persistent organic
pollutants (POPs) group; they represented a significant risk to
the environment owing to their physico-chemical and toxicological
properties.
PBDEs are aromatic substances whose structures resemble
that of PCBs (see Fig. 1.).
Fig. 1. PbDEs and PCbs
The numbering of individual PBDE congeners, whose
total sum is 209, complies with the IUPAC nomenclature
used in the numbering of PCBs.
P h y s i c o c h e m i c a l P r o p e r t i e s o f
P B D E s
Tri- (major congener 28), tetra- (47), penta- (99, 100),
hexa- (153, 154), hepta- (183) and deka-(209) are the most
commonly used PBDE groups which also occur most
frequently in the environment.
PBDEs are lipophilic and persistent substances that
show low solubility in water. Because of their high resistance
against acids, bases, heat, light, and redox reactions, they
pose a significant risk to the environment. When they enter
the environment, they remain there for a prolonged period
of time due to their physical-chemical properties. The octanol/water
partition coefficient (log K ow ) is another important
characteristic of these compounds. The values of their log K ow
vary in a range of 5.98 (28)–9.97 (209), which indicates that
these substances are highly hydrophobic.
Upon excessive heating and burning, PBDEs will
decompose to very toxic substances such as polybrominated
dibenzo-p-dioxins (PBDD) and dibenzofuranes (PBDF).
The melting point of PBDEs varies from 64 °C (BDE 28) to
302.5 °C (BDE 209) whereas many congeners are liquids at
standard conditions.
PBDEs are used as fire retardants. In this application the
ideal situation is when a retardant decomposes at a temperature
by about 50 °C lower than that of a polymer – PBDEs
meet this requirement with a number of polymers.
P r o d u c t i o n
The industrial synthesis of PBDEs usually proceeds through
catalytic reaction between a diphenyl ether and bromine,
yielding a mixture of different isomers. Alternatively,
PBDE may also be prepared from phenolate and bromobenzene
or by allowing diphenyliodonium salt to react with bromophenolate.