Adsorption characteristics of selected pharmaceuticals and an endocrine disrupting compound-Naproxen, carbamazepine and nonylphenol-on activated carbon

The adsorption of two representative pharmaceutically active compounds (PhACs) (naproxen and carbamazepine) and one endocrine disrupting compound (nonylphenol) were evaluated on two types of activated carbon. When determining their isotherms at environmentally relevant concentration levels, it was found that at this low concentration range (10-800 ng/L), removals of the target compounds were contrary to expectations based on their hydrophobicity. Nonylphenol (log K(ow) 5.8) was most poorly adsorbed, whereas carbamazepine (log K(ow) 2.45) was most adsorbable. Nonylphenol Freundlich isotherms at this very low concentration range had a much higher 1/n compared to isotherms at much higher concentrations. This indicates that extrapolation from an isotherm obtained at a high concentration range to predict the adsorption of nonylphenol at a concentration well below the range of the original isotherm, leads to a substantial overestimation of its removals. Comparison of isotherms for the target compounds to those for other conventional micropollutants suggested that naproxen and carbamazepine could be effectively removed by applying the same dosage utilized to remove odorous compounds (geosmin and MIB) at very low concentrations. The impact of competitive adsorption by background natural organic matter (NOM) on the adsorption of the target compounds was quantified by using the ideal adsorbed solution theory (IAST) in combination with the equivalent background compound (EBC) approach. The fulfilment of the requirements for applying the simplified IAST-EBC model, which leads to the conclusion that the percentage removal of the target compounds at a given carbon dosage is independent of the initial contaminant concentration, was confirmed for the situation examined in the paper. On this basis it is suggested that the estimated minimum carbon usage rates (CURs) to achieve 90% removal of these emerging contaminants would be valid at concentrations of less than 500 ng/L in natural water.     

Molecular criteria for discriminating adipose fat and milk from different species by NanoESI MS and MS/MS of their triacylglycerols: application to archaeological remains

A new multistep analytical methodology is described in this paper for the precise identification of triacylglycerols, which are biomarkers of dairy products and subcutaneous fats, that may be chemically identified in archaeological pottery. It consists of the analysis of the total lipid extract from different kinds of fats by high-temperature gas chromatography, performed in order to select the ceramic vessels in which animal fats are well preserved, followed by nanoelectrospray QqTOF mass spectrometry that allows for distinguishing the specific origins of the lipids detected (namely, cow, sheep, or goat). The analysis of model samples, cow and goat dairy products and cow and sheep adipose fats, was successfully achieved. The fatty acid composition of each triacylglycerol was identified, which allowed for the discrimination of subcutaneous fats and dairy fats and distinguishing between cow and goat milk. This methodology was then applied to archaeological samples, and the presence of goat milk, cow milk, and possibly sheep subcutaneous fat was assessed based on the discriminating criteria found on modern fats.     

Low-temperature fabrication of layered self-organized Ge clusters by RF-sputtering

In this article, we present an investigation of (Ge + SiO₂)/SiO₂ multilayers deposited by magnetron sputtering and subsequently annealed at different temperatures. The structural properties were investigated by transmission electron microscopy, grazing incidence small angles X-ray scattering, Rutherford backscattering spectrometry, Raman, and X-ray photoelectron spectroscopies. We show a formation of self-assembled Ge clusters during the deposition at 250°C. The clusters are ordered in a three-dimensional lattice, and they have very small sizes (about 3 nm) and narrow size distribution. The crystallization of the clusters was achieved at annealing temperature of 700°C.     

Incorporation of an unnatural amino acid in the active site of porcine pancreatic phospholipase A2. Substitution of histidine by l,2,4-triazole-3-alanine yields an enzyme with high activity at acidic pH

The effect of the substitution of the active site histidine48 by the unnatural 1,2,4-triazole-3-alanine (TAA) amino acidanalogue in porcine pancreas phospholipase A₂ (PLA₂) was studied.TAA was introduced biosynthetically using a his-auxotrophicEscherichia coli strain. To study solely the effect of the substitutionof the active site histidine, two nonessential histidines (i.e.His17 and His 115) were replaced by asparagines, resulting ina fully active mutant enzyme (His-PLA₂). In this His-PLA₂ thesingle histidine at position 48 was substituted by TAA withan incorporation efficiency of about 90%, giving a mixture ofHis-PLA₂ and TAA-PLA₂. Based on the charge difference at acidicpH, both forms could be separated by FPLC, allowing for thepurification of TAA-PLA₂ free from His-PLA₂. At pH 6, TAA-PLA₂has a fivefold reduced activity compared with His-PLA₂. Thisreduced activity paralells a reduced rate of covalent modificationwith p-nitrophenacyl bromide of TAA-PLA₂ compared with His-PLA₂.Competitive inhibition gave comparable IC₅₀ values for WT-PLA₂,His-PLA₂ and TAA-PLA₂. These results indicate that the reductionin activity is not caused by a different affinity for the substrate,but more likely results from a reduced k_cat value in TAA-PLA₂.The enzymatic activities for native and mutant PLA₂s were measuredat different pH values. For WT-PLA₂ and His-PLA₂ the activityis optimal at pH 6 and is strongly deminished at acidic pH,with no observable activity at pH 3. In contrast, TAA-PLA₂ isas active at pH 3 as at pH 6. Most likely, the decrease in activityobserved for WT-PLA₂ and His-PLA₂ is caused by the protonationof the active site His48, which is the general base involvedin the activation of the nucleophilic water molecule. In TAA-PLA₂,however, the active site residue TAA48 is unprotonated at bothpH 3 and 6 as a result of the low pK_a of TAA compared with histidine.     

Dissolved oxygen, COD, nitrogen and phosphorus profiles in a continuous sand filter used for WWTP effluent reclamation

Continuous sand filtration (CSF) offers interesting potential for the extensive treatment of wastewater treatment plant (WWTP) effluents for water reclamation and/or restrictive discharge. Research on concentration profiles over the height of the CSF shows that most bacteriological conversions are restricted to the lower part of the filter bed. Dissolved oxygen (DO) rapidly decreases to below 1 mg/L in the first 0.4 m of the filter bed, applying hydraulic velocities of 12.9 ～ 14.9 m/h and 10 ～ 20 mm/min sand velocities, independent of the methanol dosage. The DO decrease agrees with the observed decrease in chemical oxygen demand (COD). At the given operational conditions, NO(x)-N and N-total removal is dedicated to the first 0.9 m of the filter bed. Results show that by optimising the CSF operational conditions the very restrictive effluent N and P values of 2.2 and 0.15 mg/L, respectively, as described in the European Water Framework Directive, can be met.