خيارات البحث
النتائج 291 - 300 من 456
Assessment of the Impact Produced by the Traffic Source on VOC Level in the Urban Area of Canosa di Puglia (Italy) النص الكامل
2008
Bruno, Paolo | Caselli, Maurizio | de Gennaro, Gianluigi | Scolletta, Lucia | Trizio, Livia | Tutino, Maria
Volatile organic compounds (VOC) have been monitored in 12 sites of Canosa di Puglia, a city located in the Southern of Italy, in order to identify the main VOC source--vehicular traffic or industrial--and to evaluate the critical situations in the city. Monitoring, carried out by using Radiello® diffusive samplers, has been planned taking into account the traffic density and the architecture of the city. From the study of the data it has been emerged that, among all considered VOC, benzene, toluene, ethylbenzene and xylenes (BTEX) are the pollutants at higher concentration. However no critical situation has appared from the present monitoring. Maps of daily benzene and toluene concentrations have shown that the most significant pollution phenomena happens in the center of the urban area which is in a valley with narrow roads and high buildings that do not allow an efficient dispersion of pollutants. The study of the diagnostic ratios between the toluene and benzene concentrations in the several areas (average T/B = 3.4) and the high Pearson's coefficient among the pollutants, and in particular between benzene and toluene concentrations (r = 0.9505), have suggested that in urban area these pollutants are emitted from the same source: the vehicular traffic.
اظهر المزيد [+] اقل [-]Pollution Detection by Magnetic Susceptibility Measurements Aided by the Stemflow Effect النص الكامل
2008
Klučiarová, Denisa | Márton, Péter | Pichler, Viliam | Márton, Emő | Túnyi, Igor
The applicability of magnetic susceptibility measurements was tested for the detection of industrial pollution by fly ash in topsoil in a beech stand in the vicinity of a steel factory at Široka near Oravskyỳ Podzámok (Slovakia). The first trial measurements already showed that there is at least one spot near the trunk of each tree in which the susceptibility is significantly higher than anywhere else beneath the crown of the same tree. Detailed measurements showed that the susceptibility anomaly is associated with stemflow, and extends to some distance on the slope side of the trunk. Elsewhere beneath the crowns, at spots unaffected by stemflow, the variation of susceptibility is moderate. Samples were collected systematically from the topsoil around five trees in the beech stand, and another one elsewhere exposed to direct flow of fly ash from Široka. The results of measurements of low and high frequency susceptibility allow to conclude that in the beech stand where the ground is effectively shielded by the canopy from direct precipitation of pollution particles, all susceptibility values unaffected by stemflow are dominated by fine-grained magnetic particulates having formed by biogenic processes during pedogenesis, while those pertaining to the stemflow zone are dominated by larger multidomain particles conveyed to the ground in the stemflow. So, in this particular environment, it is the stemflow and its effect that makes magnetic pollution detectable by using susceptibility parameters. The case of the site exposed to direct precipitation of pollution particles is different in that that every susceptibility value irrespective of being small or large is dominated by large multidomain pollution particles. The heavy metal concentration of the soils investigated is elevated with respect to background levels of the Geochemical atlas of Slovakia, and have strong positive relationship, basically established by the effect of stemflow, with magnetic susceptibility. Without the stemflow effect the variation either in susceptibility or heavy metal concentration would not be sufficient to recognise existing relationships between them in the topsoil of the beech stand selected for the present study.
اظهر المزيد [+] اقل [-]Precipitation Chemistry as an Indicator of Urban Air Quality in Mersin, North-Eastern Mediterranean Region النص الكامل
2008
Özsoy, Türkan | Türker, Pelin | Örnektekin, Sermin
The chemical composition of precipitation in the city of Mersin on the Mediterranean coast of Turkey has been studied. Spatial and temporal variability of rainwater constituents have been determined from samples collected at two central and two suburban stations for the December 2003-May 2005 period. A total of 246 samples covering all precipitation events were analyzed to determine pH, conductivity, as well as major anion (Cl-, [graphic removed] , [graphic removed] ); major cation (H⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, [graphic removed] ) and formaldehyde (HCHO) concentrations. The pH varied within a range of 4.8-8.5, with only 8 out of 246 samples being acidic (pH < 5.6), and the remaining highly alkaline samples being neutralized by either [graphic removed] in rainwater, or by CaCO₃ resulting from wet deposition of atmospheric dust. The volume weighted mean ΣAnion/ΣCation ratio was 0.49. The equivalent concentration of major ionic species followed the order: [graphic removed] . Formaldehyde concentrations varied in the range of 0.01-17.9 μM, and was found to be dependent on precipitation volume. Relatively higher [graphic removed] , [graphic removed] , [graphic removed] and HCHO concentrations, mainly of anthropogenic origin, measured near the city center suggest increased pollution from local anthropogenic sources, e.g., residential heating, industrial and/or traffic emissions. In general, the results of this study suggest local precipitation chemistry is more strongly influenced by natural (mineral dust and marine) sources compared to anthropogenic ones.
اظهر المزيد [+] اقل [-]Are Pseudokirchneriella subcapitata and Chlorella vulgaris Affected by Environmental Samples from a Rice Field النص الكامل
2008
Marques, Catarina R. | Abrantes, Nelson | de Figueiredo, Daniela R. | Pereira, Mário J. | Gonçalves, Fernando
Rice fields represent important production rates in Portugal. However, the intensive soil management and the exploitation of agrochemicals may pose a threat to nontarget organisms. Hence, the present work regards the toxicity screening of surface waters and sediment elutriates collected during the drainage of fields in the vicinity of a rice paddy (Quinta do Seminário, Soure, Portugal): 1. in River Pranto (RP), the river from which the field irrigation water is canalized; 2. inside the rice paddy, from the main drainage channel - Vala de Enxugo (VE). For that purpose, it was used a combination of physico-chemical analyses and bioassays with two green algae species - Pseudokirchneriella subcapitata and Chlorella vulgaris. The chemical screening showed an apparent absence of xenobiotics in sediment samples, while no pesticides were found within the chemical contaminants detected in water samples. The nutrient load reflected low levels of inorganic contamination. Bioassays revealed that P. subcapitata was more sensitive to the overall physico-chemical conditions in natural samples than C. vulgaris, being its growth inhibited under water samples from both sites. On a whole, water samples, mainly those from the main irrigation/drainage channel of the rice fields (VE), were more deleterious to microalgae than those from RP or any of the elutriates.
اظهر المزيد [+] اقل [-]Bacterial Transport from Agricultural Lands Fertilized with Animal Manure النص الكامل
2008
Mishra, Anurag | Benham, Brian L. | Mostaghimi, Saied
A plot scale study was conducted to determine bacterial transport in runoff from cropland treated with poultry litter and dairy manure applied at phosphorus (P) agronomic rates. Treatments included surface application of dairy manure, surface application of poultry litter, incorporation of dairy manure and control. A rainfall simulator was used to induce runoff 1 and 2 days after manure application. Runoff was analyzed to determine the concentration of indicator bacteria-fecal coliform, Escherichia coli, and Enterococcus. Observed edge-of-field bacterial concentrations were 10² to 10⁵ times higher than Virginia's in-stream bacteria criteria for primary contact recreation waters. No significant treatment effects were observed on edge-of-field bacteria concentration or yield. Results suggest that the manure application based on agronomic P rates may yield significant bacterial loading to downstream waterbodies if rainfall occurs soon after manure application. This research underscores the need for BMPs that reduce runoff volumes and filter pollutants associated with animal manures.
اظهر المزيد [+] اقل [-]Partitioning of Hg Between Solid and Dissolved Organic Matter in the Humus Layer of Boreal Forests النص الكامل
2008
Åkerblom, Staffan | Meili, Markus | Bringmark, Lage | Johansson, Kjell | Kleja, Dan Berggren | Bergkvist, Bo
The mobility of mercury (Hg) deposited on soils controls the concentration and toxicity of Hg within soils and in nearby streams and lakes, but has rarely been quantified under field conditions. We studied the in situ partitioning of Hg in the organic top layer (mor) of podsols at two boreal forest sites differing in Hg deposition and climatic regime (S. and N. Sweden, with pollution declining to the north). Soil solution leaching from the mor layer was repeatedly sampled using zero-tension lysimeters over 2 years, partly in parallel with tension lysimeters. Concentrations of Hg and dissolved organic carbon (DOC) were higher while pH was lower at the southern site (means ± SD: Hg = 44 ± 15 ng L-¹, DOC = 63.0 ± 31.3 mg L-¹, pH = 4.05 ± 0.53) than at the northern site (Hg = 22 ± 6 ng L-¹, DOC = 41.8 ± 12.1 mg L-¹, pH = 4.28 ± 0.43). There was a positive correlation over time between dissolved Hg and DOC at both sites, even though the DOC concentration peaked during autumn at both sites, while the Hg concentration remained more constant. This correlation is consistent with the expected strong association of Hg with organic matter and supports the use of Hg/C ratios in assessments of Hg mobility. In the solid phase of the overlying Of layer, both Hg concentrations and Hg/C ratios were higher at the southern site (means ± SD: 0.34 ± 0.06 μg g-¹ dw and 0.76 ± 0.14 μg g-¹ C, respectively) than at the northern site (0.31 ± 0.05 μg g-¹ dw and 0.70 ± 0.12 μg g-¹ C, respectively). However, concentrations in the solid phase differed less than might be expected from the difference in current atmospheric input, suggesting that the fraction of natural Hg is still substantial. At both sites, Hg/C ratios in the upper half of the mor layer were only about two thirds of those in the lower half, suggesting that the recent decrease in anthropogenic Hg deposition onto the soil is offset by a natural downward enrichment of Hg due to soil decomposition or other processes. Most interestingly, comparison with soil leachate showed that the average Hg/C ratios in the dissolved phase of the mor layers at both sites did not differ from the average Hg/C ratios in the overlying solid organic matter. These results indicate a simple mobilisation with negligible fractionation, despite differences in Hg deposition patterns, soil chemistry and climatic regimes. Such a straight-forward linkage between Hg and organic matter greatly facilitates the parameterisation of watershed models for assessing the biogeochemical fate, toxic effect and critical level of atmospheric Hg input to forest soils.
اظهر المزيد [+] اقل [-]Effect of Microorganisms on the Sorption of Lanthanides by Quartz and Goethite at the Different pH Values النص الكامل
2008
Perelomov, L. V. | Yoshida, S.
The effect of Rhodopseudomonas pallustris bacterium on the sorption of 16 isotopes of lanthanides by quartz and goethite at different pHs values was studied. pH of sorption solution and affinity of elements to surface seems to be most important parameters in the interactions between metal ions and surfaces of biological and mineral sorbents. At acidic (pH°4) and neutral (pH°7) conditions these interactions was affected by electrostatic forces; at alkaline conditions (pH°9) the mechanism of lanthanides precipitation was dominant. Microorganisms sufficiently affected on lanthanides sorption by quartz at acidic and neutral conditions, but largest one was at pH°7. They increased sorption of all elements by goethite at pH°4. There was negligible effect of bacteria on the sorption of lanthanides at pH°7 and 9 by goethite that demonstrates greater affinity of the elements to goethite surface. Microorganisms increased concentration of lanthanides in the nonexchangeable states on the surfaces of quartz at pH°7 and 9, and on the surface of goethite at pH°7 in comparison to the minerals alone. It may be attributed to formation of low-soluble complexes of lanthanides with organic substances, produced by bacterium.
اظهر المزيد [+] اقل [-]Transformation of Petroleum Saturated Hydrocarbons during Soil Bioremediation Experiments النص الكامل
2008
Jovančićević, Branimir | Antić, Mališa | Pavlović, Ivona | Vrvić, Miroslav | Beškoski, Vladimir | Kronimus, Alexander | Schwarzbauer, Jan
This paper presents transformations of saturated hydrocarbons of petroleum type pollutants during ex situ bioremediation of soil on the pilot heap (halde), during a period of 6 months, within the grounds of Petroleum Refinery Pančevo (Serbia). Samples for analysis were taken in time intervals of 2 weeks (P₁-P₁₂ samples). Organic substance was extracted by Soxhlet's method and quantified. Isoprenoid aliphatics, in particular pristane and phytane, and polycyclic aliphatics of sterane and triterpane types in saturated hydrocarbon fractions were analysed by GC-MS (SIM method). Significant amounts of n-alkanes have not been detected. The MS-chromatogram revealed only marginal amounts of pristane and phytane in sample P₁. Pristane and phytane occurred in sample P₈, and in even higher quantities in the final sample P₁₂. The proceeding bioremediation process was accompanied by the decrease of the relative amounts of pentacyclic terpanes of hopane type, compared to tri- and tetracyclic terpanes. In the initial sample P₁ the distribution of steranes and hopanes follows a pattern, which is characteristic for crude oils. However, their identification by SIM method was not possible in samples P₈ and P₁₂ because of the reduced concentration. The observed changes in the alkane fractions' compositions may be considered as atypical, referring to the fact that during oil biodegradation under natural conditions, decomposition of isoprenoids occurs much easier and faster than decomposition of polycyclic alkanes of tri-, tetra- and pentacyclic terpane, sterane and diasterane types, after the decomposition of n-alkanes has been almost completed.
اظهر المزيد [+] اقل [-]Characterization of Indoor and Outdoor Aerosols in a Suburban Area of Prague النص الكامل
2008
Smolík, J | Dohányosová, P | Schwarz, J | Ždímal, V | Lazaridis, M
The mass, ionic and elemental size distributions of particulate matter (PM) measured indoors and outdoors in an apartment situated in a north-westward suburb of Prague are presented. The PM samples were collected by two Berner type low pressure impactors separating particles into 10 size fractions from 26 nm to 10 μm and were further analyzed by ion chromatography (IC) and proton induced X-ray emission (PIXE). Temperature, pressure and relative humidity were measured both indoors and outdoors parallel to PM sampling. The indoor and outdoor PM dynamics were recorded by two scanning mobility particle sizers (SMPS) and an aerodynamic particle sizer (APS). Finally, the ventilation rate was determined by a radon technique. Ion chromatography showed that the major inorganic components of the fine particle mode are sulfate, nitrate, and ammonium with very low indoor nitrate concentration. Crustal elements (Al, Si, Ca, Ti, Mn, and Fe) were associated with the coarse aerosol mode. The presence of people increased the mass concentration of coarse particles, whereas cooking, smoking, and burning of incense and candles contributed predominantly to the fine particle mode. Smoking and the burning of incense also increased the concentration of potassium, bromine and chlorine content in fine particles.
اظهر المزيد [+] اقل [-]Spatially Explicit Integrated Risk Assessment of Present Soil Concentrations of Cadmium, Lead, Copper and Zinc in The Netherlands النص الكامل
2008
de Vries, W. | Römkens, P. F. A. M. | Bonten, L. T. C.
Historic and current agricultural and industrial activities have resulted in accumulation of Cd, Cu, Pb and Zn in soil. To estimate potential risks for ecosystems, agriculture and water quality, an integrated risk assessment was performed for The Netherlands. Risks of metal contamination were assessed on a national scale by comparing present soil concentrations of Cd, Pb, Cu and Zn with critical concentrations of those metals in view of agricultural impacts, ecological impacts and impacts on the quality of groundwater and surface waters. Results show that present soil metal concentrations cause few risks for agriculture or ecosystems; for less than 2% of the surface area present metal levels exceed critical limits. Critical limits for groundwater are only significantly exceeded for Pb (17% of the area), but critical limits for surface water are exceeded throughout the country for Cu and Zn. Taking critical limits used in The Netherlands, the area where exceedances take place is nearly negligible for Cd and low for Pb (less than 3%), but much larger (between 40% and 50%) for both Cu and Zn. Results from this study suggest that accumulation of heavy metals in Dutch soils at present primarily affects the quality of surface waters. This stresses the need for harmonization of soil and water policy. Measures to reduce the load in surface waters to meet target levels, under conditions like those prevailing in The Netherlands, are bound to have an impact on land management.
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