Microalgal communities epibiontic on the marine hydroid <Emphasis Type="Italic">Eudendrium racemosum</Emphasis> in the Ligurian Sea during an annual cycle

The microalgal community associated with Eudendrium racemosum, a marine hydroid widely distributed in the Mediterranean Sea, was studied during an annual cycle, at monthly frequency, in a coastal station of the Ligurian Sea. Microalgae were represented mainly by diatoms, which exhibited higher abundance and biomass values between autumn and spring (max 46,752 cells mm⁻² and 1.94 μg C mm⁻², respectively), while during summer a significant decrease was observed (min 917 cells mm⁻² and 0.013 μg C mm⁻²). High levels of abundance of filamentous cyanobacteria were observed in summer. Spatial distribution of epibiontic microalgae showed a markedly increasing gradient from the basal to the apical part of hydroid colonies. Considering the growth forms of diatom communities, motile diatoms (mainly small naviculoid taxa) were the most abundant in all the periods. Adnate (Amphora and Cocconeis spp.) were distributed mainly in the basal and central part of hydroid colonies and showed two peaks (autumn and summer). Erect forms (mainly Tabularia tabulata, Licmophora spp., Cyclophora tenuis) were mainly distributed in the apical part of the colonies and showed their maximum densities in spring–summer. Tube-dwelling (Berkeleya rutilans, Parlibellus sp.) were observed at low densities throughout the study period, without any significant temporal or spatial variability. Comparing the microalgal communities on marine hydroid to those grown on mimic substrata placed in the sampling station during summer, significantly higher values of abundance were observed in the hydroid, suggesting that microalgae may benefit from the polyp catabolites. This fact was particularly evident for the adnate diatoms, whose temporal trend paralleled the cycle of hydroid host.     

PCB in soils and estimated soil-air exchange fluxes of selected PCB congeners in the south of Sweden

PCB concentrations were studied in different soils to determine the spatial variation over a region of approximately 11 000 km(2). PCB congener pattern was used to illustrate the spatial differences, as shown by principal component analysis (PCA). The relationship to different soil parameters was studied. PCB concentrations in soil showed a large variation between sampling-areas with median concentrations ranging between 2.3 and 332 ng g(-1) (dw). Highest concentrations were found at two sites with sandy soils, one with extremely high organic carbon content. Both sites were located on the west coast of southern Sweden. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with congener patterns almost site-specific. PCB in air and precipitation was measured and the transfer of chemicals between the soil and air compartments was estimated. Soil-air fugacity quotient calculations showed that the PCBs in the soil consistently had a higher fugacity than the PCBs in the air, with a median quotient value of 2.7. The gaseous fluxes between soil and air were estimated using standard modelling equations and a net soil-air flux estimated by subtracting bulk deposition from gaseous soil-air fluxes. It was shown that inclusion of vertical sorbed phase transport of PCBs in the soil had a large effect on the direction of the net soil-air exchange fluxes.     

Accumulation of perchlorate in tobacco plants: development of a plant kinetic model

Previous studies have shown that tobacco plants are tolerant of perchlorate and will accumulate perchlorate in plant tissues. This research determined the uptake, translocation, and accumulation of perchlorate in tobacco plants. Three hydroponics growth studies were completed under greenhouse conditions. Depletion of perchlorate in the hydroponics nutrient solution and accumulation of perchlorate in plant tissues were determined at two-day intervals using ion chromatography. Perchlorate primarily accumulated in tobacco leaves, yielding a substantial storage capacity for perchlorate. Mass balance results show that perchlorate degradation was negligible in plants. Tobacco plants were shown to effectively accumulate perchlorate over a wide range of initial concentrations (10 ppb to 100 ppm) from the hydroponics solution. Results suggest that plants are potential plants for the phytoremediation of perchlorate. A mathematical model was developed to describe the distribution of perchlorate in tobacco plants under rapid growth conditions. The Plant Kinetic (PK) model defined a plant as a set of compartments, described by mass balance differential equations and plant-specific physiological parameters. Data obtained from a separate hydroponics growth study with multiple solution perchlorate concentrations were used to validate predicted root, stem, and leaf concentrations. There was good agreement between model predictions and measured concentrations in the plant. The model, once adequately validated, can be applied to other terrestrial plants and inorganic chemicals currently used for both phytoremediation and ecological risk assessment.     

Carbon turnover and ammonia emissions during composting of biowaste at different temperatures

The effects of different process temperatures (40, 55, and 67 degrees C) during composting of source-separated household waste were studied in a 200 L compost reactor at an oxygen concentration of 16%. The overall decomposition measured as carbon mineralization, decomposition of different carbon constituents, and the dynamics of nitrogen mineralization and the microbial community, are reported. Ammonia emissions at 67 degrees C were more than double those at lower temperatures, and they were lowest at 40 degrees C. The decomposition rate, measured as CO2 emission, was highest at 55 degrees C. Decomposition of crude fat was slower at 40 degrees C than at 55 and 67 degrees C. The peak in microbial biomass was largest in the run at 40 degrees C, where substantial differences were seen in the microbial community structure and succession compared to thermophilic temperatures. Biowaste composting can be optimized to obtain both a high decomposition rate and low ammonia emissions by controlling the process at about 55 degrees C in the initial, high-rate stage. To reduce ammonia emissions it seems worthwhile to reduce the temperature after an initial high-temperature stage.     

Gender impact on first trimester markers in Down syndrome screening

The influence of fetal gender on the level in the first trimester of the serological markers alpha-fetoprotein (AFP), pregnancy-associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotropin (βhCG) and on nuchal translucency is described for 2637 singleton pregnancies with normal outcome. Mean log MoM values for pregnancies with female and male fetuses were calculated using regression of log marker values on gestational age expressed as crown rump length and on maternal weight. A pronounced gender impact was found for free βhCG, being 16% higher for female than for male fetuses. Copyright © 2002 John Wiley & Sons, Ltd.     

Use of reference chemicals to determine passive uptake rates of common indoor air VOCs by collocation deployment of active and passive samplers

Passive samplers have become more popular in their application in the measurement of airborne chemicals. For volatile organic compounds, the rate of a chemical's diffusivity is a determining factor in the quantity of the chemical being collected for a given passive sampler. While uptake rate of a chemical in the passive sampler can be determined either by collocation deployment of both active and passive samplers or use of controlled facilities such as environmental chambers, a new approach without a need for accurate active flow rate in the collocation experiment was demonstrated in this study. This approach uses chemicals of known uptake rates as references to calculate the actual flow rate of the active sampling in the collocation experiment. The active sampling rate in turn can be used in the determination of the uptake rates of all other chemicals present in the passive samplers. The advantage of such approach is the elimination of the errors in actual active sampling rate associated with low flow employed in the collocation experiment. Using this approach, passive uptake rates of more than 80 volatile organic compounds commonly present in indoor air were determined. These experimentally determined uptake rates correlate well with air diffusivity of the chemicals, indicating the regression equation describing such correlation might be useful in predicting the uptake rates of other volatile organic chemicals in indoor air based on their air diffusivity.