6 research outputs found
Toxicity of cadmium to soil microbial activity: effect of sewage sludge addition to soil on the ecological dose
10 pages, 4 figures, 4 tables.Cadmium has a toxic effect on soil microbial activity which plays an important role in nutrient cycling and, therefore, in maintaining soil fertility. In addition, the mobility of this heavy metal in soil is affected by the addition of urban wastes such as sewage sludge. This study was conducted to determine the effect of sewage sludge amendment of a semiarid soil, previously polluted with Cd, on the toxic effect of this heavy metal on soil microbial biomass and its activity. Dehydrogenase activity, ATP content, microbial soil respiration and microbial biomass carbon were used as bioindicators of the toxic effect of Cd. The inhibition of microbial activity and biomass by different Cd concentrations ranging from 0 to 8000 mg Cd kgâ1 soil was described by three mathematical models in order to calculate three ecological doses of Cd: ED50, ED10, and ED5. In general, higher ED values were calculated for the sewage sludge amended soil than for unamended soil. Thus the Cd toxicity to microbial activity of the sewage sludge amended soil can be considered lower than that of the unamended soil. Moreover, increased ED values with time after soil Cd contamination were observed.Peer reviewe
Toxicity of cadmium to soil microbial activity: effect of sewage sludge addition to soil on the ecological dose
Le magmatisme basique hercynien et post-hercynien du SystÚme central espagnol: essai de caractérisation des sources mantelliques
Les manifestations du magmatisme basique dans le SystĂšme central espagnol sâĂ©talent de façon sporadique sur une pĂ©riode de
140 Ma. Les données géochimiques suggÚrent des sources mantelliques variables pour les cinq suites magmatiques reconnues.
Une contribution crustale significative est mise en Ă©vidence dans les magmas Gb1 Ă Gb3, mis en place en liaison avec
lâorogĂ©nĂšse hercynienne. Elle tĂ©moigne de processus dâhybridation intracrustal et/ou du recyclage de matĂ©riaux dâorigine
continentale dans le manteau. En revanche, le magmatisme post-collisionnel ultérieur montre une empreinte crustale négligeable
dans la suite lamprophyrique alcaline Gb4, extraite dâun rĂ©servoir source de type OIB. La suite tholĂ©iitique Gb5 pourrait
tĂ©moigner dâun manteau source mĂ©tasomatisĂ© par un composant dâorigine crustale
[ABSTRACT]
Hercynian and post-Hercynian basic rocks from the Spanish Central System: estimates of Central Spain subcontinental
mantle. Basic magmatism in central Spain occurred sporadically during a long period of ca. 140 Ma. The geochemical data
on representative samples from the five igneous episodes show that different mantle reservoirs were tapped. Crustal involvement
(via recycling in mantle sources or by hybridization at emplacement levels) was important in the basic magmas related to the
Hercynian orogeny (Gb1 to Gb3 suites). Samples occurring as later dykes have signatures ranging from OIB-like values (Gb4
alkaline lamprophyres) to those of a formerly enriched subcontinental lithospheric mantle (tholeiites Gb5