[Ambient pressure synthesis and characterization of silica aerogel as adsorbent for dieldrin].

Hydrophobic silica aerogels were prepared from cheap waterglass precursors via surface modification of wet gels and ambient pressure drying route. Its adsorption capacity of Dieldrin, a typical of persistent organic pollutants (POPs), was examined. It is characterized via BET, FTIR, and DSC-TGA. The silica aerogels were highly hydrophobic with contact angles of 135 degrees-142 degrees, and the hydrophobicity of the aerogels could be maintained up to the temperature of 380 degrees C. The silica aerogels were porous with, pore size distribution of 17.5-23.4 nm, porosity of 94.8%-95.6%, and surface area of 444-560 m2 x g(-1). The results of adsorption experiments indicated that the hydrophobic aerogels could remove 84% of dieldrin from aqueous solution within 4 h; the adsorption process followed the pseudo-second-order kinetics process. Based on the adsorption equilibrium results, the adsorption capacity of silica aerogel was 11 times bigger than by active carbon.

The inhibitory effects and removal of dieldrin in continuous upflow anaerobic sludge blanket reactors.

The inhibitory effects and removal efficiency of dieldrin (DLD) in anaerobic reactors were investigated. Anaerobic toxicity assay (ATA) experiments conducted in batch reactors revealed that 30 mg/l DLD had inhibitory effects on the unacclimated mixed anaerobic cultures. Continuous reactor experiments performed in a lab-scale two-stage upflow anaerobic sludge blanket (UASB) reactor system which was fed with ethanol as the sole carbon source, indicated that anaerobic granular cultures could be successfully acclimated to DLD. Chemical oxygen demand (COD) removal efficiencies were 88-92% for the two-stage system. The influent DLD concentration of 10 mg/l was removed by 44-86% and 86-94% in the second stage and overall UASB system, respectively. Biosorption of DLD on granular anaerobic biomass was found to be a significant mechanism for DLD removal in the UASB system. The maximum DLD loading rate and minimum HRT achievable for the first stage UASB reactor were 0.5 mg/lday (76 microg DLD/g VSS.day) and 10 h, respectively, which resulted in the overall COD removal efficiency of 85%.

Organochlorinated pesticides in the Argentine Antarctic sector and Atlantic coastline waters.

The presence of organochlorinated pesticides in water samples drawn in the Argentine Antarctic Sector and Atlantic coastline has been proved. In general, these samples showed quantities that varied between a few hundredths of a ppmm to slightly more than 1 ppmm, although in some cases and for certain pesticides, depending on the locations, the levels found were definitely higher. With the exception of Dieldrin, which appeared in only one sample/in what would seem to be its course few hundredths of a ppm, to slightly more than 1 ppmm, although in some cases and for certain pesticides found were the same as those reported in previous investigations. The isolated cases of high pesticide contents in water samples drawn at wharves and of snow in the vicinity of Almirante Brown Base show up clearly the influence of human activity on the contamination of the environment.