Abstract
Transfer of the elements metallic traces in the
soil-plant system and assessment of the risks of contamination of the food
chain (survey of the cases in the city of Lubumbashi, DR Congo
Two tests of survey of the behavior of 4 vegetable species on
soils contaminated in elements metallic traces (ETMs) (notably in copper,
cobalt, zinc, cadmium and lead) and on soils of the gardens have been achieved
to value the influence of the ETMs on the one hand on the growth of the plants
and on the other hand their bioaccumulation (transfer). The first test achieved
with the cultures of A. hybridus, D. carota and S. oleracea,
had for objective the survey of the behavior of these species on different
samples of soil (soils of the gardens and soils contaminated in ETMs of the GCM
district) of the city of Lubumbashi and to value the soil-plant transfer of the
ETMs. For this test, the plants of spinach all as the seeds of carrot and
amaranth have been put in containing pots each 1 kg of soils. The second test,
that had for objective to value the influence of the increasing doses of lime
(CaCO3) on the behavior of B. chinensis and the bioaccumulation of the
ETMs, has been achieved with plants of cabbage of dyes exits of the sprouter
that have been put in containing pots each 1 kg of soils.
The gotten results showed that:
1. The lime brought to soil contaminated of the
Gécamines (SC) encouraged the resumption and the growth of cabbage of
dyes in relation to soil contaminated of the Gécamines on which one
didn't apply the lime; and reduced the transfer of the ETMs of soil
considerably toward the plant (notably lead and the cadmium), what avoids to
the consumers all danger of poisoning by the ETMs; It would probably be owed to
the decrease of the mobility of the ETMs following the elevation of the pH.
Otherwise, the strong mortality observed from the 30th day would be due to the
elevation of the temperature that increased the impact of the illnesses.
However critical concentrations made of copper have been raised in the roots
(T0 and T2).
2. No meaningful difference has been raised for all parameters
observed at spinach. This plant seems to tolerate the strong concentrations of
the ETMs in soils and even reduced their transfer in the organs. It means that
the risks of poisonings in the ETMs are reduced among the consumers, except for
the copper and the cadmium. Otherwise, he/it proves to be that this plant can
be cultivated on soils contaminated in ETMs, nevertheless a contribution of
limes and/or the organic matters would be to wish to permit a better
development of the plants and a production of the leaves with values
supportable of ETMs.
3. For the amaranth, some differences were revealed between
the plants having pushed on the soils of the gardens and those that pushed on
soils contaminated in ETMs for observed most parameters. However, the compact
structure of soils (SJ and SE) led a bad development of the plants and to
caused their death even following the conditions of hypoxie. otherwise, the
amaranth seemed, of a general manner, especially accumulated of the strong
doses of the ETMs, what presents some very elevated risks of poisoning for the
consumers, with regard to the copper. Nevertheless, only plants that pushed on
the soils of the gardens, and on the one of the sediments with organic matter
(), could show a good performance.
4. For the carrot, only the plants having pushed on the soils
of the gardens had a good performance in relation to those that pushed on the
contaminated soils (excepts on the sediments with thick plant table setting);
besides a meaningful difference has been observed for most parameters. This
plant didn't resist the strong concentrations of the ETMs and the compact
structure of some among these soils (SJ and SE).
5. Most soils of the gardens used for the tests presented some
concentrations in copper superior to the normal values (toxic for the plants)
(except EN4, and SCE) and of others as EN5 and EN6 presented some contents in
zinc and cobalt superior to the normal values outside of the contents raised in
copper.
KEY WORDS: elements metallic traces, bioavailability,
bioaccumulation, mobility, soil-plant transfer, contaminated soil,
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