Using non-equilibrium biosorption column modelling for improved process efficiency

An unsteady-state biosorption column model in one space variable is considered in this paper. The theoretical study is motivated by the need for predicting the dependent variables of biosorption columns for removal of heavy metals from wastewater, which is potentially an important technology in cleaner production. Pollutant concentrations in the bulk phase, in the liquid filling the pores and in the solid biomass along the axial coordinate of the column were evaluated for a wide range of physical and chemical parameters of the global process. In particular, the assumption of instantaneous chemical reactions is replaced by a more realistic expression taking into account chemical kinetics and fluid advection time scales separately. The resulting system of partial differential equations was solved by means of a reliable numerical algorithm based on the method of lines. The data obtained using the model described in this paper are compared with published experimental data and an estimation of the increased efficiency is made.     

Influence of large-spectrum environmental contamination on the micro-meiobenthic assemblages in harbour sediments of the ligurian sea (W Mediterranean)

The concentration of a large spectrum of environmental contaminants (PCBs, PAHs, pesticides and metals) was assessed in surface sediments of two Ligurian harbours (Sanremo and Alassio, NW Mediterranean Sea, Italy) and their relative impact on micro-meiobenthic assemblages was analysed. Concentration, distribution and relative importance of the different contaminants varied considerably between harbours in relation to the different anthropic activities and contamination sources. Results from Principal Component Analysis indicated that high levels of contaminants were typically correlated with low micro-meiobenthic abundance in the sediment. Heavy metals and the organic enrichment were the main factors affecting the distribution and abundance of the bacterial and meiofaunal assemblages in Alassio harbour, whereas hydrocarbons and pesticides played a major role in Sanremo sediments. Neither the bacteria density nor the meiofauna abundance were dependent on sediment grain size, suggesting that micro-meiobenthic parameters may be under the influence of other variables. Our results suggest that high concentrations of contaminants independently from their source or typology are responsible for the impact observed on micro-meiobenthic assemblages in these harbours.     

Review and assessment of models for predicting the migration of radionuclides through rivers

The present paper summarises the results of the review and assessment of state-of-the-art models developed for predicting the migration of radionuclides through rivers. The different approaches of the models to predict the behaviour of radionuclides in lotic ecosystems are presented and compared. The models were classified and evaluated according to their main methodological approaches. The results of an exercise of model application to specific contamination scenarios aimed at assessing and comparing the model performances were described. A critical evaluation and analysis of the uncertainty of the models was carried out. The main factors influencing the inherent uncertainty of the models, such as the incompleteness of the actual knowledge and the intrinsic environmental and biological variability of the processes controlling the behaviour of radionuclides in rivers, are analysed.     

Assessment of state-of-the-art models for predicting the remobilisation of radionuclides following the flooding of heavily contaminated areas: the case of Pripyat River floodplain

The performances of models are assessed to predict the wash-off of radionuclides from contaminated flooded areas. This process should be accounted for in the proper management of the aftermath of a nuclear accident. The contamination of the Pripyat River water following the inundation of a floodplain heavily contaminated by (90)Sr and (137)Cs of Chernobyl origin is used as the basis for modelling. The available experimental evidence demonstrated that remobilisation of radiostrontium is an important process implying a significant secondary radioactive load of water flowing over the contaminated floodplain. On the contrary, there is no empirical evidence of a similar behaviour for radiocaesium. In general, state-of-the-art models properly predicted the remobilisation of strontium, whereas they significantly overestimated radiocaesium concentrations in water. The necessary model improvements for a more accurate prediction of radiocaesium contamination levels include a reassessment of the values of the model parameters controlling the remobilisation process.     

Randomized clinical trial of transabdominal versus transcervical chorionic villus sampling methods

The relative advantages and disadvantages of transabdominal (TA) and transcervical (TC) chorionic villus sampling (CVS) in terms of fetal risks and efficacy were evaluated in a clinical trial conducted on 1194 women randomized at 7–12 weeks' gestation. The results of the study indicate that, if any, the relative risk of fetal loss following either procedure is less than double that of the alternative technique when performed by a skilled operator. Overall, the fetal loss rate (spontaneous abortions following randomization, terminations of pregnancy, and perinatal deaths) is 16.5 and 15.5 per cent, respectively, among women allocated to TA- and TC-CVS. The two procedures are equally effective, although TA-CVS is associated with a significantly lower rate of repeat device insertions; on the other hand, a higher weight of chorionic tissue is obtained, on average, with TC-CVS. Bleeding is more common following TC-CVS, while peritoneal reaction developed only after TA-CVS. No diagnostic problems specifically related to one sampling technique were identified.     

Prenatal karyotyping in malformed fetuses

Experience with prenatal karyotyping of 237 fetuses with sonographic evidence of malformation is reported. Abnormal karyotype was found in 40 cases (16-8 per cent): chromosomal aberrations were found in 19 of the 178 fetuses with an isolated structural anomaly (10-6 per cent) and in 21 of the 59 fetuses with multiple malformations (35-6 per cent). Detailed cytogenetic and morphological information concerning fetuses affected by omphalocele, duodenal atresia, hydrocephalus, multicystic kidney, unilateral hydronephrosis and cystic hygroma is reported. The need for a very careful ultrasound evaluation of fetal anatomy in these pregnancies is stressed, as the risk of a chromosomal anomaly depends mainly on the existence of more than one ultrasonically diagnosed structural defect.     

Occurrence of PCDD/Fs in urban air before and after the ban of leaded gasoline

The source of PCDDs and PCDFs in automotive exhaust is not yet fully explained. The chlorinated hydrocarbons used in the formulation of lead-alkyl additives were suspected as a possible major source. Based on this, the decreasing use of leaded gasoline followed by its final ban (occurred on 1/1/2002, in Italy) should have resulted in a decreasing presence of PCDD/Fs in urban air and possibly some differences in their profile. To investigate these aspects, we monitored PCDD/Fs for one year starting in September 2001, at a medium-traffic road site in Rome, with weekly frequency. Results were then compared with those obtained in a previous study performed before the ban (from February 2000 to January 2001) at the same site. As compared with the previous study, the yearly-averaged overall PCDD/F concentration, as toxic equivalent of 2,3,7,8-TCDD, decreased from 60 to 50 fg m(-3) I-TEQ; it remained unchanged, however, if one sample with a particularly high PCDD/F content was excluded from each data set. The monthly trend confirmed the one found in the former study. On an annual basis, the two mean congener profiles were almost identical. The concentration levels and the constancy of profiles, as calculated for the two periods, do not support the hypothesis of a major role of leaded gasoline, substantially different from unleaded one, in contributing to PCDD/F air pollution.     

Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts,Mediterranean Sea)

To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By contrast, the lowest polluted zones showed a high population density and the highest percentages of epiphytes. Epiphytes were abundant where a Posidonia oceanica meadow was present and decreased in the most polluted zones. Sediments of the Gulf of Termini and Lampedusa exhibited high percentages of benthic foraminifera typical of well-oxygenated waters and low concentrations of metals, with the exception of sites located near sewage outfalls and harbour areas. Furthermore, even though deformed tests are commonly known in natural stressed environmental conditions, this study shows that in the most polluted zones, benthic foraminifera were characterised by the highest percentages of deformed individuals.     

Influence of large-spectrum environmental contamination on the micro–meiobenthic assemblages in harbour sediments of the ligurian sea (W Mediterranean)

The concentration of a large spectrum of environmental contaminants (PCBs, PAHs, pesticides and metals) was assessed in surface sediments of two Ligurian harbours (Sanremo and Alassio, NW Mediterranean Sea, Italy) and their relative impact on micro–meiobenthic assemblages was analysed. Concentration, distribution and relative importance of the different contaminants varied considerably between harbours in relation to the different anthropic activities and contamination sources. Results from Principal Component Analysis indicated that high levels of contaminants were typically correlated with low micro–meiobenthic abundance in the sediment. Heavy metals and the organic enrichment were the main factors affecting the distribution and abundance of the bacterial and meiofaunal assemblages in Alassio harbour, whereas hydrocarbons and pesticides played a major role in Sanremo sediments. Neither the bacteria density nor the meiofauna abundance were dependent on sediment grain size, suggesting that micro–meiobenthic parameters may be under the influence of other variables. Our results suggest that high concentrations of contaminants independently from their source or typology are responsible for the impact observed on micro–meiobenthic assemblages in these harbours.