120 research outputs found
Evaluation of composts and liming materials in the phytostabilization of a mine soil using perennial ryegrass
A microcosm experiment was carried out to evaluate the effects of municipal solid waste
compost (MSWC) or garden waste compost (GWC), and liming materials in the rehabilitation
of a soil affected by mining activities, and to study the use of perennial ryegrass (Lolium
perenne L.) for phystostabilization. The performance of the amendments was assessed by
soil chemical parameters, total and bioavailable metals (Cu, Pb and Zn), soil enzymatic
activities, and plant relative growth and mineral composition. In general, both composts
corrected soil acidity and increased the total organic matter content of the soil, although
with a better performance in the case of MSWC, especially when considering total N and
available P and K levels in the amended soil. The application of both composts and liming
materials led to a decrease in the mobile fractions of Cu, Pb and Zn, but mobilisable fractions
of Cu and Zn increased with MSWC application. Plant biomass increased more than three
times in the presence of 50 Mg MSWC haâ1 and with the combined use of 25 or 50 Mg MSWC
haâ1 and CaO, but no significant differences were observed when GWC was applied. Plant
tissue analysis showed that the treatments did not significantly reduce Cu, Pb and Zn
uptake by the plant. Dehydrogenase, and the enzymes related to the N-cycle, urease and
protease, had increased activities with increasing MSWC application rate. Conversely, the
enzymatic activities of both enzymes related to the C-cycle, cellulase and ÎČ-glucosidase,
were only positively affected by GWC application, a compost obtained from raw materials
rich in C. Principal component analyses evidenced this clear separation between the effect
of MSWC on soil enzymes related to the N-cycle and of GWC on soil enzymes related to the
C-cycle. This study indicates that MSWC (50 Mg haâ1, limed or unlimed) can be used
successfully in the remediation of a highly acidic metal-contaminated soil, allowing the
establishment of perennial ryegrass
Organic residues as immobilizing agents in aided phytostabilization: (I) Effects on soil chemical characteristics
A greenhouse experiment was conducted to evaluate the effect of three different organic residues, sewage
sludge (SS), municipal solid waste compost (MSWC), and garden waste compost (GWC), as immobilizing
agents in aided phytostabilization of a highly acidic metal-contaminated soil, affected by mining
activities, using perennial ryegrass (Lolium perenne L.). The organic residues were applied at 25, 50 and
100 Mg ha 1 (dry weight basis), and their effects on soil chemical characteristics and on relative plant
growth and metal concentrations were assessed. All the organic residues tested immobilized Cu, Pb
and Zn, decreasing their mobile fractions. This was corroborated by negative correlations obtained
between mobile Cu, Pb and Zn and other soil chemical characteristics, which rose as a consequence of
the amendments applied (i.e., pH, electrical conductivity, organic matter, nitrogen content, available P
and available K), and by the multivariate exploratory techniques performed that showed an inverse correlation
between these groups of variables. The greatest increase in ryegrass relative growth (more than
three times) was obtained in the presence of 50 Mg MSWC ha 1, followed by SS at the same application
dosage. GWC did not contribute to an increase in shoot growth, due to its small capacity to correct soil
acidity and to supply essential macronutrients (N, P, K). No extractant was able of demonstrating by a
linear correlation the uptake of Cu, Pb and Zn by ryegrass. This plant was therefore not a good ââindicatorâ
of Cu, Pb and Zn availability in the soil. The results obtained in this study suggest that ryegrass can be
used in aided phytostabilization for this type of mine contaminated soils and that MSWC, and to a minor
extent SS, applied at 50 Mg ha 1, were effective in the in situ immobilization of metals, improving soil
chemical properties and leading to a large increase in plant biomas
Evaluation of tests to assess the quality of mine-contaminated soils
An acid metal-contaminated soil from the
Aljustrel mining area (a pyrite mine located in SW
Portugal in the Iberian Pyrite Belt) was subjected to
chemical characterisation and total metal quantiWcation
(Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals
were determined and a sequential extraction
procedure was used to investigate metal speciation.
Two bioavailable metal fractions were determined: a
mobile fraction and a mobilisable fraction. Soil ecotoxicity
was studied using a battery of bioassays:
plant growth test and seed germination with cress
(Lepidium sativum L.), earthworm (Eisenia fetida)
mortality, E. fetida avoidance behaviour, luminescent
inhibition of Vibrio Wscheri and Daphnia magna
immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/
kg dry matter, respectively), these metals were mostly
structurally bound (87% for Cu, 81% for Zn and 89%
for Pb) and, therefore, scarcely bioavailable. Nonetheless,
the D. magna immobilization test using soil
leachate showed an EC50 (48 h) of 36.3% (v/v), and
the luminescent inhibition of V. Wscheri presented an
EC20 (15 min) of 45.2% and an EC20 (30 min) of
10.7% (v/v), suggesting a considerable toxic eVect. In
the direct exposure bioassays, E. fetida avoided the
mine soil at the highest concentrations (50%, 75%
and 100% v/v). At the same soil concentrations, cress
showed negligible growth. The results suggest the
need to use a battery of toxicity tests, in conjunction
with chemical methods, in order to assess the quality
of mine-contaminated soils correctly
Language of Lullabies: The Russification and De-Russification of the Baltic States
This article argues that the laws for promotion of the national languages are a legitimate means for the Baltic states to establish their cultural independence from Russia and the former Soviet Union
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