Construction is one of the largest consumers of natural resources and a major
contributor to greenhouse gas emissions, primarily due to cement production. To reduce
environmental impacts, green concrete is being developed, in which part of the aggregate
or cement is replaced with waste materials, among which biochar has proven particularly
promising for substituting a proportion of cement in concrete. Such concrete typically
exhibits improved mechanical, rheological, and durability properties; however, despite
these advantages, a key question remains regarding how materials with added biochar
affect the environment and, consequently, organisms under various conditions. The aim
of this master’s thesis was to investigate the effects of leachates from conventional and
green concrete containing biochar on four different organisms: duckweed (Lemna minor),
water flea (Daphnia magna), onion (Allium cepa), and white mustard (Sinapis alba). For
duckweed, frond and root growth as well as the production of photosynthetic pigments
were observed; for water fleas, mobility was monitored; for onion and white mustard,
root length was measured.
Results from duckweed tests showed that leachates from green concrete at higher
concentrations more strongly inhibited frond growth, whereas at the lowest concentration
they contributed more markedly to enhanced growth compared to conventional concrete.
Regarding root growth and total chlorophyll content, green concrete proved to be less
problematic, while conventional concrete did not reach toxic levels. A similar pattern of
low environmental impact was confirmed for water fleas, which exhibited negligibly low
inhibition at all concentrations of both types of concrete. For white mustard, root length
increased with decreasing concentrations of green concrete, while an opposite trend was
observed for conventional concrete; nonetheless, inhibition did not exceed 50 % in either
case. Onion showed the lowest level of impact, as it responded stimulatively in all
samples, with the strongest response observed in the presence of green concrete.
Despite differences in the responses of individual test organisms, the results indicate that
green concrete is less toxic than conventional concrete, except for frond growth in
duckweed. Leachates from both green and conventional concrete proved less toxic to
terrestrial organisms (onion and white mustard) than to aquatic organisms (water fleas
and duckweed).
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