Biodegradation of spilled diesel fuel in agricultural soil: effect of humates, zeolite, and bioaugmentation.

Possible enhancement of biodegradation of petroleum hydrocarbons in agricultural soil after tank truck accident (~5000 mg/kg dry soil initial concentration) by bioaugmentation of diesel degrading Pseudomonas fluorescens strain and addition of abiotic additives (humates, zeolite) was studied in a 9-month pot experiment. The biodegradation process was followed by means of analytical parameters (hydrocarbon index expressed as content of C10-C40 aliphatic hydrocarbons, ratio pristane/C17, and total organic carbon content) and characterization of soil microbial community (content of phospholipid fatty acids (PLFA) as an indicator of living microbial biomass, respiration, and dehydrogenase activity). The concentration of petroleum hydrocarbons (C10-C40) was successfully reduced by ~60% in all 15 experiment variants. The bioaugmentation resulted in faster hydrocarbon elimination. On the contrary, the addition of humates and zeolite caused only a negligible increase in the degradation rate. These factors, however, affected significantly the amount of PLFA. The humates caused significantly faster increase of the total PLFA suggesting improvement of the soil microenvironment. Zeolite caused significantly slower increase of the total PLFA; nevertheless it aided in homogenization of the soil. Comparison of microbial activities and total PLFA revealed that only a small fraction of autochthonous microbes took part in the biodegradation which confirms that bioaugmentation was the most important treatment.

Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes.

Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase.

A single-parameter logistic equation for fitting concentration-response curves from standard acute ecotoxicity assays.

A set of 69 concentration-response curves from 5 acute ecotoxicity assays was fitted with a 2-parameter logistic equation. High correlation between values of regression parameters suggested similar slopes of the curves. This enabled derivation of the empirical single-parameter logistic equation with the sole median effective concentration (EC50) parameter. Such an equation might be useful in the evaluation of lower-quality (preliminary) experimental data and for the reduction of the number of test organisms and of testing costs.

Estimation of the quantity of bacteria encapsulated in Lentikats Biocatalyst via phospholipid fatty acids content: a preliminary study.

The content of phospholipid fatty acids (PLFA) was determined in samples of polyvinyl alcohol lenses (Lentikats Biocatalyst, LB) with encapsulated Paracoccus denitrificans withdrawn during long-term denitrification experiments. The total PLFA content correlated highly with specific denitrification activities of LB as well as biomass estimation based on image analyses of microscopic photos. The results confirmed the applicability of PLFA determination for estimation of the amount of living encapsulated microbial biomass during biotechnological applications.

Removal of basic (Methylene Blue) and acid (Egacid Orange) dyes from waters by sorption on chemically treated wood shavings.

Spruce wood shavings from Picea abies were used for an adsorptive removal of both basic as well as acid dyes from waters. The sorption properties of the sorbents were modified with HCl, Na(2)CO(3) and Na(2)HPO(4). The treatment of the wood sorbents with alkaline carbonate solution as well as with phosphate solution increased the sorption ability for the basic dye (Methylene Blue), whereas the treatment with mineral acid decreased the sorption ability for Methylene Blue to some extent. The opposite is true for the sorption of the acid dye--Egacid Orange. The maximum sorption capacities estimated from the Langmuir-Freundlich isotherms ranged from 0.060 to 0.165 mmol g(-1) for Methylene Blue, and from 0.045 to 0.513 mmol g(-1) for Egacid Orange. The basic dye sorption decreased at low pH values in accordance with a presupposed ion-exchange mechanism of the sorption. The sorption of acid dye, on the other hand, decreased with increasing pH. The presence of inorganic salts as well as surfactants exhibited only minor effects on the dye sorption.

Reduction and immobilization of hexavalent chromium with coal- and humate-based sorbents.

Two kinds of the commercially available sorbents containing humic acids as active constituents were used for Cr(VI) reduction and removal, namely oxihumolite (naturally occurring weathered young brown coal) and iron humate (IH) (waste material produced during industrial manufacturing of humic substances). The mechanisms of the chromium removal involve the reduction of Cr(VI) (by humic substances or by Fe(II) ions) and subsequent binding of Cr(III) to a humic acid matrix. Other metal-binding mechanisms possibly effective in the process of Cr(VI) removal, e.g., coprecipitation or surface precipitation of Fe(III)/Cr(III) hydroxides, are also discussed. Oxihumolite was able to remove Cr(VI) from strongly acidic solutions with pH below ca. 2. IH, on the other hand, exhibited a maximum sorption capability in slightly acidic solutions with pH above ca. 3. Over the whole examined range (pH 1-5), however, IH was able to reduce Cr(VI) almost completely to its less toxic trivalent state. A sufficiently high sorption capacity (20 mg g(-1)) was found for chromium removal with IH in an unbuffered system, where the "natural" pH values governed by the buffering capacity of the sorbent itself ranged from 3.9 to 4.6. It follows from extraction studies with the loaded (spent) sorbents that chromium is bound strongly to the sorbent, and thus risks of its subsequent liberation into the environment are minimized. Similarity in the extraction behavior of the Cr(III)-loaded and Cr(VI)-loaded sorbents supported the above-mentioned mechanisms of the Cr(VI) removal.