Formation of polycyclic aromatic hydrocarbons in the smoke from heated model lipids and food lipids.

The contents of polycyclic aromatic hydrocarbons (PAHs) in the smoke from model lipids and food lipids during heating were determined and the mechanism of PAH formation was studied. A Rancimat oil stability analyzer was used as a model system for heating model lipids and food lipids at 220 degrees C for 2 h and for adsorption of smoke. The various lipid degradation products and PAHs in the smoke were identified and quantified by a GC/MS technique. Results showed that model lipids were more susceptible to smoke formation than food lipids during heating, but the PAH levels were lower for the former than latter. Methyl linolenate produced the highest amount of PAHs, followed by methyl linoleate, methyl oleate, and methyl stearate. Also, soybean oil generated a larger amount of PAHs than canola oil or sunflower oil. Benzene-like compounds were found to be possible precursors for PAHs formation. Several PAH derivatives were also present in heated model lipids and food lipids.     

Determination of glufosinate ammonium and its metabolite (AE F064619 and AE F061517) residues in water by gas chromatography with tandem mass spectrometry after ion exchange cleanup and derivatization

An analytical method for the determination of glufosinate ammonium and its principal metabolites, AE F064619 and AE F061517, in water of two different hardnesses (5 and 30 DH, French hardness) has been developed and validated. Samples were spiked at different levels (0. 05 and 0.5 microgram/L) and were purified by column chromatography on ion-exchange resins. After derivatization with glacial acetic acid and trimethylarthoacetate mixture, the derivatives were quantified by using capillary gas chromatography with an ion-trap tandem mass spectrometric detector. Analytical conditions for MS/MS detection were optimized, and the quantification was carried out on the areas of the most representative ions. The limit of quantification was validated at 0.05 microgram/L for each compound. The mean recovery value and the relative standard deviation (n = 20) were 92.0% and 17. 8% for glufosinate ammonium, 90.2% and 15.8% for AE F064619, and 89. 7% and 12.7% for AE F061517.     

Quantitative extraction of macro-invertebrates from temperate and tropical leaf litter and soil: efficiency and time-dependent taxonomic biases of the Winkler extraction

Winkler extractors, a simple device presumed to extract macro-invertebrates efficiently from soil and litter samples, is being used increasingly in ecological surveys and functional studies of soil macro-invertebrate communities. In this study the extraction efficiency and taxonomic bias of the Winkler extraction are evaluated for extraction periods of 3 h up to 7 weeks, calibrated by hand-sorting after 7 weeks. The method extracts most macro-invertebrates completely or to a proportion of over 90% except Isopoda, Diplopoda and Mollusca. However, for an exhaustive result, a long extraction period of several weeks is necessary. For the most speciose group (adult beetles) and for the commonly most abundant group (ants), a short extraction of 3 days was sufficient to get 70% of the individuals and nearly all species. Three days was also sufficient to recover the rank abundance order of beetle families, while for ‘higher taxa’ and for Chilopoda species, 4 and 3 weeks were necessary, respectively. Optimum extraction times for the abundant macro-invertebrate groups and possible adjustment factors for the soil macro-invertebrates of temperate woodlands are proposed to compensate the taxonomic bias caused by short extraction periods. However, for recording an accurate snapshot of the soil and litter fauna at a particular time, shorter extraction periods are advisable because of the short life cycle of many soil invertebrates causing emergence of later stages or a second generation during longer extraction periods. The problem of contamination of samples is also discussed.     

Snowmelt in a boreal forest site: an integrated model of meltwater quality (SNOQUALI)

An integrated model (SNOQUALI) for the simulation of meltwater quality has been developed for a boreal forest site (Lake Laflamme, Québec). The model consists of a physical module and a chemical module; it has been validated for H⁺, NO₃ and SO₄ ^2? concentrations in discharge from the snowcover during the spring melt of 1984. Good agreement of simulated ion concentrations with those measured in the field were obtained for the strong acid anions NO₃ ^? and SO₄ ^2?. Greater deviations of simulated concentrations from observed concentrations were recorded in the case of H+. These are attributed to ion exchange reactions between the ion and the organic debris which is deposited continously onto the snowcover from the forest canopy during the winter season.     

Volatilization of ketones from water

The overall mass-transfer coefficients for the volatilization from water of acetone, 2-butanone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone, 2-heptanone, and 2-octanone were measured simultaneously with the oxygen-absorption coefficient in a laboratory stirred water bath. The liquid-film and gas-film coefficients of the two-film model were determined for the ketones from the overall coefficients, and both film resistances were important for volatilization of the ketones. The liquid-film coefficients for the ketones varied with the 0.719 power of the molecular-diffusion coefficient, in agreement with the literature. The liquid-film coefficients showed a variable dependence on molecular weight, with the dependence ranging from the ?0.263 power for acetone to the ?0.378 power for 2-octanone. This is in contrast with the literature where a constant ?0.500 power dependence on the molecular weight is assumed. The gas-film coefficients for the ketones showed no dependence on molecular weight, in contrast with the literature where a ?0.500 power is assumed.     

Community composition of ammonia-oxidizing bacteria in the rhizosphere of intercropped wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.), maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.), and faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

Cereal/cereal and cereal/legume intercropping systems are popular in the north, northwest, and southwest of China and often result in yield increases compared to monocropping. Rhizosphere interactions may play a significant role in the yield increases, particularly with respect to nutrient availability. The aim of this study was to investigate the effects of intercropping on N availability and community composition of ammonia-oxidizing bacteria in the rhizosphere of wheat, maize, and faba bean at different growth stages. Denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA genes was used to analyze the community composition of bacterial ammonia oxidizers belonging to β-proteobacteria. The results showed that intercropping with faba bean significantly increased nitrate concentrations in the rhizosphere of wheat and maize at the second sampling time (20 June) compared to monocropping or intercropping between maize and wheat. Intercropping significantly affected the community composition of ammonia-oxidizing bacteria in the rhizosphere compared to monocropping, and the effects were most pronounced in the maize/faba bean and wheat/maize intercropping systems when faba bean and wheat were at anthesis and maize was in seedling stage. In wheat/faba bean intercropping, the effects of intercropping on community composition of ammonia-oxidizing bacteria were less pronounced at the seedling stage of the two species but were significant at anthesis.     

Antioxidant activity and phenolic compounds in selected herbs.

The antioxidant capacities (oxygen radical absorbance capacity, ORAC) and total phenolic contents in extracts of 27 culinary herbs and 12 medicinal herbs were determined. The ORAC values and total phenolic contents for the medicinal herbs ranged from 1.88 to 22.30 micromol of Trolox equivalents (TE)/g of fresh weight and 0.23 to 2.85 mg of gallic acid equivalents (GAE)/g of fresh weight, respectively. Origanum x majoricum, O. vulgare ssp. hirtum, and Poliomintha longiflora have higher ORAC and phenolic contents as compared to other culinary herbs. The ORAC values and total phenolic content for the culinary herbs ranged from 2.35 to 92.18 micromol of TE/g of fresh weight and 0.26 to 17.51 mg of GAE/g of fresh weight, respectively. These also were much higher than values found in the medicinal herbs. The medicinal herbs with the highest ORAC values were Catharanthus roseus, Thymus vulgaris, Hypericum perforatum, and Artemisia annua. A linear relationship existed between ORAC values and total phenolic contents of the medicinal herbs (R = 0.919) and culinary herbs (R = 0.986). High-performance liquid chromatography (HPLC) coupled with diode-array detection was used to identify and quantify the phenolic compounds in selected herbs. Among the identified phenolic compounds, rosmarinic acid was the predominant phenolic compound in Salvia officinalis, Thymus vulgaris, Origanum x majoricum, and P. longiflora, whereas quercetin-3-O-rhamnosyl-(1 --> 2)-rhamnosyl-(1 --> 6)-glucoside and kaempferol-3-O-rhamnosyl-(1 --> 2)-rhamnosyl-(1 --> 6)-glucoside were predominant phenolic compounds in Ginkgo biloba leaves.     

The effect of alkaline dust decline on the precipitation chemistry in northern Japan

The precipitation chemistry in northern Japan, especially Hokkaido, has been investigated since 1982. This area has often been found to have high concentrations of alkaline road dust (asphalt dust) in the air, caused by the use of studded tires during the winter. It is well known that the composition of precipitation in these areas is often dominated by asphalt dust including calcium bicarbonate. However, recently the concentration of asphalt dust in the air has decreased owing to a ban on the use of studded tires. Simultaneously, in precipitation, the lowering of pH values and the increase of hydrogen ion depositions have been occurring owing to the decrease of non-sea-salt calcium ions (nss-Ca²⁺) concentrations and depositions derived from asphalt dust. In addition, we found that a decrease of nss-Ca²⁺ firstly leads to a decrease of bicarbonate ions (HCO₃ ^?), the counter ion to nss-Ca²⁺ in asphalt dust. Therefore, the increase of H⁺ concentrations and depositions was great in comparison with the decrease of nss-Ca²⁺ concentrations and depositions in areas where the HCO₃ ^?concentrations, varied by pH, and depositions had been low. Furthermore, this variation was mainly observed in the ionic composition of snow cover and snowfall at sites along the Japan Sea in northern Japan during winter. In this area, the Acid Shock effect may become a serious problem from the decline of pH values in melting snow. Moreover, we found that ammonium ions and non-sea-salt sulfate ions depositions have also been decreasing in response to a decrease of nss-Ca²⁺ depositions, derived from asphalt dust. It seems that this phenomenon is caused by the decrease of asphalt dust concentrations in the air.     

Improved storage stability of model infant formula by whey peptides fractions

The purpose of this study was to evaluate the shelf-life stability (6 months) of model infant formula with whey protein hydrolysates or peptidic fractions as carrageenan replacers. Whey protein hydrolysates were prepared with trypsin and followed by ultrafiltration of the hydrolyzed mixture, and peptidic fractions were isolated from the ultrafiltered tryptic hydrolysate by anion- or cation-exchange chromatography. The stability of the model infant formula was evaluated using a stratification method based on fat content differences between the top and bottom strata of the samples. With protein hydrolysate-based formulations, the creaming rate of the fat in the product was slightly higher than in the standard formulation (with carrageenan), which is indicative of lower storage stability. The addition of cationic fractions to model infant formula also resulted in lower product stability, whereas the fat creaming rate was retarded in anionic fraction based formulations. The physicochemical characteristics of certain peptides combined with the reported high emulsifying properties of peptidic sequences found within these fractions may account for their ability to act as carrageenan replacers.