Bioaccumulation of total mercury in the earthworm Eisenia andrei

Earthworms are a major part of the total biomass of soil fauna and play a vital role in soil maintenance. They process large amounts of plant and soil material and can accumulate many pollutants that may be present in the soil. Earthworms have been explored as bioaccumulators for many heavy metal species such as Pb, Cu and Zn but limited information is available for mercury uptake and bioaccumulation in earth- worms and very few report on the factors that influence the kinetics of Hg uptake by earthworms. It is known however that the uptake of Hg is strongly influenced by the presence of organic matter, hence the influence of ligands are a major factor contribut - ing to the kinetics of mercury uptake in biosystems. In this work we have focused on the uptake of mercury by earthworms ( Eisenia andrei ) in the presence of humic acid (HA) under varying physical conditions of pH and temperature, done to assess the role of humic acid in the bioaccumulation of mercury by earthworms from soils. The study was conducted over a 5-day uptake period and all earthworm samples were analysed by direct mercury analysis. Mercury distribution profiles as a function of time, bioac- cumulation factors (BAFs), first order rate constants and body burden constants for mercury uptake under selected conditions of temperature, pH as well as via the dermal and gut route were evaluated in one comprehensive approach. The results showed that the uptake of Hg was influenced by pH, temperature and the presence of HA. Uptake of Hg 2 + was improved at low pH and temperature when the earthworms in soil were in contact with a saturating aqueous phase. The total amount of Hg 2 + uptake decreased from 75 to 48 % as a function of pH. For earthworms in dry soil, the uptake was strongly influenced by the presence of the ligand. Calculated BAF values ranged from 0.1 to 0.8. Mercury uptake typically followed first order kinetics with rate constants determined as 0.2 to 1 h ? 1 .Scopus 201

Temperature dependence of electron attachment to CHCl

Dissociative electron attachment (DEA) to CHCl2Br has been studied in a crossed electron/molecular beams experiment in the electron energy range between 0 and 8 eV and in the gas temperature range from 321 to 478 K. The two negative fragment ions Cl- and Br- are formed from a prominent low energy resonant feature close to zero eV and at comparatively weaker resonances at about 0.38 eV, 2.2 eV and 5.5 eV. In contrast to swarm experiments [7], the bihalogen ion Cl$_{2}^{-}$ was not detected in our experiment. The absolute partial cross-sections for Br- and Cl- reaction channels have been estimated. We find that in the low electron energy range ($\approx$0 eV) the overall DEA cross-section as well as the partial DEA cross-section for Br- formation slightly decrease with increasing gas temperature whilst the partial cross-section for the Cl- channel is temperature independent

Speciation of inorganic selenium and selenoamino acids by an HPLC-UV-HG-AFS system

For the on-line speciation of selenocystine (SeCys), selenomethionine (SeMet), selenoethionine (SeEt), selenite (Se(IV)) and selenate (Se(VI)), a high-performance liquid chromatography-UV irradiation-hydride generation-atomic fluorescence spectro- metric method is described. Separation was carried out on a conventional reversed-phase C18 column modified with didodecyl- dimethylammonium bromide with gradient elution applying two concentrations of ammonium acetate as the mobile phase. UV irradiation and hydride generation parameters were optimized. The obtained detection limits for SeCys, SeMet, SeEt, Se(IV) and Se(VI) were 0.31, 0.43, 0.7, 0.44 and 0.32 ng ml(−)1, respectively, using a 100-wl loop. The method was tested with spiked mineral water and two volunteers' urine samples