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251.
Supercritical fluid extraction of polycyclic aromatic hydrocarbons from marine sediments and soil samples 总被引:4,自引:0,他引:4
Supercritical fluid extraction (SFE) was used to extract polycyclic aromatic hydrocarbons (PAH) from a certified sample of marine sediment. This sample contains a great number of organic pollutants that are present in low concentrations. The extractions were carried out at 50 and 80 degrees C, at a pressure varying from 230 to 600 bar and using CO2 in the supercritical phase and the effect of three organic modifiers (methanol, n-hexane and toluene), added at 5%/vol, at the same temperature and pressure conditions, were then considered. PAHs were characterized by GC-MS and the recover yield was estimated for 6 PAHs that were representative of those present in the sample, according to their molecular weight and to the number of condensed rings. The analytical conditions giving the best recovery efficiency were used on an unpolluted soil sample spiked with 11 PAHs of environmental importance at a concentration similar to that certified for the sediment sample. An increase in the yield of recovered PAHs, using methanol as co-solvent, was observed while higher temperatures caused a negative effect on the quantity of recovered pollutants. The recovery yield for PAHs from the spiked soil sample was measured and found to be greater than 90%. Better recoveries were obtained for those compounds with higher molecular weight. 相似文献
252.
A promising alternative to conventional single phase processing, the use of sequential anaerobic-aerobic digestion, was extensively investigated on municipal sewage sludge from a full scale wastewater treatment plant. The objective of the work was to evaluate sequential digestion performance by testing the characteristics of the digested sludge in terms of volatile solids (VS), Chemical Oxygen Demand (COD) and nitrogen reduction, biogas production, dewaterability and the content of proteins and polysaccharides. VS removal efficiencies of 32% in the anaerobic phase and 17% in the aerobic one were obtained, and similar COD removal efficiencies (29% anaerobic and 21% aerobic) were also observed. The aerobic stage was also efficient in nitrogen removal providing a decrease of the nitrogen content in the supernatant attributable to nitrification and simultaneous denitrification. Moreover, in the aerobic phase an additional marked removal of proteins and polysaccharides produced in the anaerobic phase was achieved. The sludge dewaterability was evaluated by determining the Optimal Polymer Dose (OPD) and the Capillary Suction Time (CST) and a significant positive effect due to the aerobic stage was observed. Biogas production was close to the upper limit of the range of values reported in the literature in spite of the low anaerobic sludge retention time of 15 days. From a preliminary analysis it was found that the energy demand of the aerobic phase was significantly lower than the recovered energy in the anaerobic phase and the associated additional cost was negligible in comparison to the saving derived from the reduced amount of sludge to be disposed. 相似文献
253.
De Luca E Novelli C Barbato F Menegoni P Iannetta M Nascetti G 《Environmental monitoring and assessment》2011,183(1-4):437-450
This study describes the conservation status of dune systems in relation to disturbance factors in the coastal stretch of the Viterbo province, Latium Region, Italy. Particular emphasis was given to the bioindication value of plant communities and their sequence. Each plant community was considered as a "habitat" in accordance with Annex I of the Directive 92/43/EU. Stress factors, such as sand dynamic and erosion, and anthropogenic pressures, such as trampling and bathing settlements, influence the sequence of habitats and weaken the system of relations that makes these coenoses to occur in extreme conditions. The choice to carry out surveys along wide transects, recording different data, allowed to explore the use of habitats as bioindicators. Comparing sites characterized by the same extension in a homogeneous area, it was possible to expand the use of canonical correspondence analysis (CCA) as a tool to correlate habitat composition and disturbance factors. The application of CCA showed a high correlation of degradation and habitat loss with coastal erosion, trampling and presence of waste. Furthermore, floristic surveys allowed the application of different biodiversity indices to quantify species richness of sampled areas. The conservation status of the sites investigated was found to be diverse, from the total disappearance of the mobile dune habitats to their complete sequence. The proposed methodology has been useful to fulfill the objective of the work and is applicable to other case studies in the Mediterranean. 相似文献
254.
Giuseppe Curcurù Giacomo Maria Galante Concetta Manuela La Fata 《Journal of Loss Prevention in the Process Industries》2013,26(6):1285-1292
The paper proposes an imprecise Fault Tree Analysis in order to characterize systems affected by the lack of reliability data. Differently from other research works, the paper introduces a classification of basic events into two categories, namely Initiators and Enablers. Actually, in real industrial systems some events refer to component failures or process parameter deviations from normal operating conditions (Initiators), whereas others refer to the functioning of safety barriers to be activated on demand (Enablers). As a consequence, the output parameter of interest is not the classical probability of occurrence of the top event, but its Rate of OCcurrence (ROCOF) over a stated period of time. In order to characterize the basic events, interval-valued information supplied by experts are properly aggregated and propagated to the top. To this purpose, the Dempster–Shafer Theory of evidence is proposed as a more appropriate mathematical framework than the classical probabilistic one. The proposed methodology, applied to a real industrial scenario, can be considered a helpful tool to support risk managers working in industrial plants. 相似文献
255.
Serrani Dominique Ajmone-Marsan Franco Corti Giuseppe Cocco Stefania Cardelli Valeria Adamo Paola 《Environmental geochemistry and health》2022,44(10):3425-3449
Environmental Geochemistry and Health - Urban soils are often mixed with extraneous materials and show a high spatial variability that determine great differences from their agricultural or natural... 相似文献
256.
Water Security in Uzbekistan: Implication of Return Waters on the Amu Darya Water Quality 总被引:1,自引:0,他引:1
Crosa G Stefani F Bianchi C Fumagalli A 《Environmental science and pollution research international》2006,13(1):37-42
- DOI: http://dx.doi.org/10.1065/espr2006.01.007
Goal, Scope and Background Amu Darya river, one of the main water resources of Uzbekistan, shows a relevant longitudinal enrichment of soluble contents
which strongly limits the human uses of its waters. Because of the low natural run-off processes, salts and pollutants are
mainly driven to the river by the return waters used for washing and irrigating the surrounding lands. The influence of return
waters on stream quality is dramatically relevant in the lower reaches of the river where almost all the flowing waters have
been previously used for the agriculture practises. To provide analytical evidence on the potential effects of return waters
on the quality of the Amu Darya river, the paper reports and comments data on salinity and metals contents of the waters flowing
in the artificial channel network of Bukhara and in the Amu Darya river, from Bukhara up to the dam forming the Tuyamuyn Hydro
Complex (THC).
Methods A total of 15 sampling sites were selected for the analytical survey: Two sites were located on the Amu Darya river downstream
from the inflow of the return waters from Bukhara, two in the river entering in the THC, and three downstream from the dam
forming the reservoir complex. The waters entering and leaving the Bukhara agricultural area were sampled in two main collectors,
while the waters flowing in the channel system were sampled in six distinct collectors. The following parameters were considered
in the survey: pH, Oxygen, Hardness, Salinity, Conductivity, P-PO4 3–, P tot, N tot, N-NO3 2–, N-NO2 –, COD, Ca2+, Mg2+, Fe,
Mn, Zn, Cr, Cu, Ni, Cd, Pb.
Results and Discussion Salt concentrations below 1000 mg/l were measured in the Amu Darya waters upstream to Bukhara. In the drainage system, salinity
exceeds the palatability limit and reaches the maximum peak of 3200 mg/l in the outflow collector. Due to dilution effects,
salinity returns to lower values (400–700 mg/l) along the Amu Darya river downstream from Bukhara; calcium and magnesium resulted
the major constituents of the overall salinity. No serious metal contaminations were detected in the waters entering and leaving
the examined channel system. Differently, the Amu Darya waters upstream to the THC showed a relevant metal contamination,
with Cr, Ni, Fe concentrations exceeding the limits for human consumption. In the downstream sites, located in the Tuyamuyn
Hydro Complex and in the Amu Darya river flowing out from this reservoir, excluding Fe, all the examined metals showed lover
concentrations and values below the normative limits.
Conclusion The direct human consumption of the lower Amu Darya waters is strongly limited by salinity and by metal contamination. Although
the salinity of the return waters from the Bukhara drainage system results in above normal limits, no corresponding increases
were measured in the Amu Darya river downstream from the return water inflow at the time of the survey. As for the metal contamination
of the Amu Darya river, the survey revealed the presence of relevant sources of metal contamination downstream from Bukhara
external to the agricultural drainage system. This contamination resulted in reduced sedimentation processes taking place
in the limnetic zones of the Amu Darya river upstream to the dam forming the Tuyamuyn Hydro Complex.
Recommendation and Outlook To fully understand the longitudinal increase of Amu Darya salinity, an evaluation of the cumulative effects of the loads
from the main agricultural areas is required, also by using mass-balance models. As for the metals, an investigation should
be addressed to identify the anthropogenic sources of contaminations present in the lower Amu Darya region and the metal loads
should be diverted. 相似文献
257.
D’Amico Sebastiano Comite Valeria Paladini Giuseppe Ricca Michela Colica Emanuele Galone Luciano Guido Sante Mantella Giuseppe Crupi Vincenza Majolino Domenico Fermo Paola La Russa Mauro Francesco Randazzo Luciana Venuti Valentina 《Environmental science and pollution research international》2022,29(20):29478-29497
Environmental Science and Pollution Research - In this study, a multimethodological analysis involving optical and physical/chemical diagnostic techniques and 3D photogrammetric survey was... 相似文献
258.
Picone Marco Distefano Gabriele Giuseppe Marchetto Davide Russo Martina Volpi Ghirardini Annamaria 《Environmental science and pollution research international》2022,29(21):31002-31024
Environmental Science and Pollution Research - Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects... 相似文献