خيارات البحث
النتائج 151 - 160 من 446
PM10, O₃, CO Concentrations and Elemental Analysis of Airborne Particles in a School Building
2008
Triantafyllou, A. G | Zoras, S | Evagelopoulos, V | Garas, S
Measurements of indoor and outdoor PM10, as well as indoor O₃ and CO concentrations were conducted and are presented here. These measurements were carried out at an institute building, located in a suburban industrial area in Greece. Both indoor and outdoor PM10 samples were also collected and their elemental composition was identified by ED-XRF analysis. Twenty seven major, minor and trace elements were identified. The measurements took place generally in different periods of institute operation, from June 2004 to February 2005. The indoor PM10 concentrations which were measured during the normal operation period of the institute were found to be many times higher than the respective outdoor PM10 concentrations of the same periods. On the contrary, the indoor PM10 concentrations which were measured during the holiday period were found to be lower than their corresponding outdoor values. Indoor O₃ and CO concentrations were found to be in low level. Indoor PM10 concentrations were found to be in a relative good correlation with O₃ (r = 0.45) and in high correlation (r = 0.98) with CO concentrations. On average, total elements concentrations were much higher indoors relative to outdoors. Based on above findings we attempted to determine the pollution sources of the indoor environment and to investigate some parameters or chemical processes that affect indoor pollutants' levels.
اظهر المزيد [+] اقل [-]Sediment Quality Assessment of Road Runoff Detention Systems in Sweden and the Potential Contribution of Tire Wear
2008
Wik, Anna | Lycken, Jenny | Dave, Göran
Sediments from 18 different road runoff detention systems, located on the Swedish West Coast, were assessed for their ecological hazard potential. Thirteen of the sites were detention ponds, three were manholes within the same sedimentation construction, and two were detention basins handling wash water from road tunnels. Sediments from all sites were analysed for a range of physico-chemical parameters and contaminants, and screened for acute toxicity using Hyalella azteca (sediment), Daphnia magna (elutriate), and Ceriodaphnia dubia (elutriate) as the test organisms, and for chronic toxicity using C. dubia as the test organism. The benthic fauna of the thirteen detention ponds was also studied. Sediment quality guidelines probable effect levels were exceeded for one or several contaminants at half of the sites, and one third revealed toxicity in some of the bioassays. Most of the detention ponds were dominated by tolerant taxa indicating low biological quality. Relationships between contaminant concentrations, toxicity in bioassays, and benthic fauna were, however, found to be weak. Extractable organic Zn, which was used as a tire wear marker, correlated with Zn, Cu, presumably from brake linings, and W, a common component of tire studs. The highest concentration, which was found in the manholes (14 mg kg⁻¹ ds), corresponds to a tire wear concentration of 11 g kg⁻¹ ds. The results of the present study have shown that traffic related contaminants accumulate in the studied runoff treatment systems, and, therefore, the maintenance of them is crucial in order to prevent contamination of surrounding waters.
اظهر المزيد [+] اقل [-]Atmospheric Impacts due to Anthropogenic Activities in Remote Areas: The Case Study of Admiralty Bay/King George Island/Antarctic Peninsula
2008
The aim of the present work is to characterize the local atmospheric emissions levels and compare them to the component derived from global pollution in a remote site at South Hemisphere (Admiralty Bay located at King George Island in Antarctic Peninsula). Airborne particles, snow and soil/sediments samples were analyzed. Local-produced atmospheric aerosol dispersion was estimated for metals originated by fossil fuel burning from the permanent scientific stations using a simplified Gaussian model. Validation of atmospheric dispersion was established by in situ measurements. Soluble and insoluble particles deposited in freshly snow and airborne particles were analyzed by PIXE (Particle Induced X-Ray Emission) for the determination of the elemental mass concentration and to obtain the Mass Median Aerodynamic Diameter (MMAD). The results showed significant correlation between the concentration of atmospheric aerosol and the freshly deposited particles in the snow, and permitted an estimate of the atmospheric snow deposition factor for K, Cu, Zn, Fe, Pb, and Ti. Results of long-term aerosol data compilation suggest that besides the local aerosol sources, the continental atmospheric transport of airborne particles is not significantly affected by the airborne particles produced by local human impacts at King George Island.
اظهر المزيد [+] اقل [-]Urban Rivers as Pollutant Sinks and Sources: a Public Health Concern for Recreational River Users?
2008
Scholes, Lian | Faulkner, Hazel | Tapsell, Sue | Downward, Stuart
Although the area of urban river sediment quality has received increasing attention over the last 10 years, the presence of contaminated sediments in urban rivers and the potential risk to public health it poses has yet to be rigorously addressed within the urban river restoration context. This is an issue of particular concern at the current time, as the opening-up of urban rivers is being strongly promoted by many legislative and non-legislative bodies as a multi-benefit approach to tackling a range of urban challenges; from decreasing the risk of flooding to increasing the quality-of-life in urbanised areas. This paper brings together these two contrasting concepts; urban rivers as pollutant sinks and sources (presentation of data on urban river sediment quality) and urban rivers as sites of flood alleviation, amenity, recreation and wildlife value (review of the drivers and initiatives behind the increasing implementation of urban river rehabilitation schemes). In light of this combined assessment, the urgent need for a risk assessment of restored urban river sites to establish whether the presence of contaminated sediments poses a risk to public health is strongly recommended. Should such a risk be demonstrated, a tiered approach to supporting the identification and pro-active management of these risks is proposed as a way to inform and enable, rather than to prevent, the safe and appropriate use of the increasing number of urban river restoration schemes being implemented.
اظهر المزيد [+] اقل [-]Contamination of Urban Soils in an Area of Northern France Polluted by Dust Emissions of Two Smelters
2008
The contamination of 27 urban topsoils has been assessed around two lead and zinc smelters (Metaleurop Nord and Umicore) in the North of France. Eighteen trace elements have been analysed (Ag, As, Bi, Cd, Co, Cr, Cu, Hg, In, Ni, Pb, Sb, Se, Sn, Tl, Th, U and Zn). The investigation included the study of the vertical distribution of Cd, Pb and Zn as indicators of pollution. It was shown that Cd, In, Pb, Sb and Zn were major pollutants followed in lesser quantities by Ag, Bi, Cu and Hg. In addition, As, Ni, Se, Sn and Tl were present at levels slightly higher than regional agricultural values. The other elements (Co, Cr, Th and U) were at endogenous levels. The observations have highlighted the strong heterogeneity of the physico-chemical parameters of urban soils and the existence of heavy contamination of the under layers by Cd, Pb and Zn. A potential transfer of metals from the topsoil to the deeper layers and especially Cd and Zn, is not excluded. Indeed the soil rework is not the only factor explaining contamination level of the deeper layers of the studied soils. The comparison of the studied element concentrations in urban soils with nearby local agricultural values shows that the dust emission originating from the Metaleurop and Umicore smelters were not the only source of contamination. Thus a large contamination of the studied urban soils by Sb and In could be explained by domestic combustion of coal for heating.
اظهر المزيد [+] اقل [-]Transport and Attenuation of Microbial Tracers and Effluent Microorganisms in Saturated Pumice Sand Aquifer Material
2008
Land disposal of treated human and animal effluent through pumice sand soils is a common practice around Rotorua, in the central North Island of New Zealand. There is increasing concern about the possibility of contamination of shallow pumice sand aquifers associated with this practice. In this study, we investigated the transport and attenuation of F-RNA bacteriophages and Escherichia coli in saturated pumice sand aquifer media using a field tracing experiment, and laboratory batch and column studies. The influence of dissolved organic carbon on microbial transport was also investigated by conditioning the 18 cm-long column with ultrafiltered sewage. The CXTFIT curve-fitting program was used to model the experimental data and to determine transport and attenuation parameters. Batch studies showed more than 90% adsorption of both microbial indicators onto pumice sand. High mass removal of microbial indicators was shown in the field (>99% for phage MS2 and E. coli at 2 m down gradient of the injection well; not detected at 6 m) and in the 'clean sand' column (65% for phage MS2 and 90% or E. coli). These results suggest that uncontaminated pumice is an effective sorbent capable of retaining microbial contaminants due to high surface area and porosity. However, in the column, with additional dissolved organic carbon, phages showed a progressive reduction in mass removal and retardation between experiments (93%, 75%, and 63% removal; retardation factor: 3.5, 2.5 and 1.2). This suggests that the organic matter competed with phages for the sorption sites, thus promoting phage transport. As a result, viral transport rates may be significantly greater in contaminated compared with uncontaminated pumice sand aquifers.
اظهر المزيد [+] اقل [-]A Comparison of Tree Rings and Peat Deposit Geochemical Archives in the Vicinity of a Lead Smelter
2008
Mihaljevič, Martin | Zuna, Milan | Ettler, Vojtéch | Chrastný, Vladislav | Šebek, Ondřej | Strnad, Ladislav | Kyncl, Tomáš
The content of Pb, Cd, Mn, K, Ca, Mg and ²⁰⁶Pb/²⁰⁷Pb isotope ratios in spruce tree rings (Picea abies) and peat cores from the Brdy Hills area (10 km W of the Pb smelter) were compared with those in spruce tree rings in the vicinity of the Pb smelter. Maximum Pb content in tree rings (up to 60 mg kg-¹ Pb) corresponds to a peak of metallurgical production in the mid 1970s and highest smelter emissions in the early 1970s. The Pb concentration curves obtained from peat deposit profiles closely correlate with the Pb concentrations in tree rings at both sampling sites. The small differences between the individual tree cores, with the identical general trend, may be attributed to the difference in distance from the smelter and the altitude of each sampling site. Similar behaviour to Pb can be observed for Cd and Ca. Lead isotope composition in tree rings (²⁰⁶Pb/²⁰⁷Pb ~1.143-1.174) is controlled mainly by the smelter emissions (²⁰⁶Pb/²⁰⁷Pb ~1.16-1.17), with the exception of the youngest segments from the more distant locality from the smelter, which yield isotopic signatures corresponding to car-emission Pb (²⁰⁶Pb/²⁰⁷Pb ~1.143-1.150). Higher content of Mn, Mg and Ca in tree rings corresponding to the 1970s and 1980s may be related to soil chemistry changes caused by acid deposition. In addition, an increase in K, Mg (and in some cases also Mn) in the youngest part of wood cores corresponds to the physiological processes in sapwood, and may be influenced by a decrease in Pb in organic soil horizons, which limited the cycling of basic inorganic nutrients.
اظهر المزيد [+] اقل [-]Lead Bioaccessibility in Soil and Mine Wastes After Immobilization with Phosphate
2008
Bosso, Sérgio T. | Enzweiler, Jacinta | Angélica, Rômulo S.
The immobilization of lead by the reaction with phosphate bearing materials is a promising remediation method for contaminated soils. Low soluble neo-formed lead-phosphate phases similar to chloropyromorphite [Pb₅(PO₄)₃Cl], can control availability and mobility of lead in the environment, and consequently reduce human exposure, if soils are the main contamination pathway. We used three phosphate source materials [NaH₂(PO₄)₃, commercial superphosphate and phosphate rock] to study lead immobilization in soil and mining waste samples. Products were examined after 1, 3 and 6 months of contact. The samples are from a contaminated area by former Pb mining and smelting activities, in southeastern Brazil, where epidemiological studies showed high lead blood levels in local population. The PBET (physiological based extraction test) bioaccessibility test was used to measure changes in the amount of soluble lead after sample treatment. Results show that the most efficient phosphate source was NaH₂(PO₄)₃, which reduced lead solubility to 92% in acidic gastric conditions after the first month of contact. Superphosphate and phosphate rock also diminished Pb solubility, but the effect was more time dependent. None specific Pb-phosphate phases could be identified by XRD in whole treated samples, but the Pb-Ca-P elemental associations, observed on SEM images and EDS spectra of portions of the samples, combined with the reduced solubility, indicate that more insoluble lead phases were formed after the treatment. Based in these results, the in site phosphate application on soils to induce lead immobilization should be considered as a possible alternative to reduce human exposure at the area.
اظهر المزيد [+] اقل [-]Measurement of Infiltration in Small Field Plots by a Portable Rainfall Simulator: Application to Trace-Element Mobility
2008
Fernández-Gálvez, J. | Barahona, E. | Mingorance, M. D.
Elevated concentrations of trace metals in soil can increase the risk of pollution to ecosystems and human health. This cannot be predicted solely from the total and/or extracted concentration of metals from soil samples, as movement of trace elements to the groundwater is also a result of the flow solution through the vadose zone. The rate at which trace elements move are not usually directly measurable, and thus it must be estimated taking into account water transport through the soil. Therefore, a field portable drop-former rainfall simulator has been designed and used to study trace-element mobility in small field plots. The rainfall simulator permits a wide range of variation in rainfall intensities and provides a homogeneous distribution of the simulated rain in a 0.25 m² plot with low cost per data collected and short time. Performance of the rainfall simulator has been evaluated and a preliminary assessment of the amount of pollutants present in the soil (As, Cu and Zn) that can reach groundwater via soil drainage is made by combining rainfall-simulation experiments with infiltration estimates based on a stochastic model of the local climate. The study was conducted in soils affected by the Aznalcóllar toxic spill in the Guadiamar river basin (Spain). Infiltration experiments reveal that the trace elements could be classified according to their mobility as As < Cu < Zn. The presence of high gravel content below this depth increased the amount of drainage and therefore the risk of groundwater pollution, especially with Zn, which was found below 50 cm depth.
اظهر المزيد [+] اقل [-]Nitrogen Removal, N2O Emission, and NH3 Volatilization Under Different Water Levels in a Vertical Flow Treatment System
2008
Zhou, Sheng | Hou, Hong | Hosomi, Masaaki
Two series of laboratory-scale vertical flow systems (flooded and nonflooded columns) were designed to compare nitrogen removal performance, nitrous oxide emission, and ammonia volatilization under different water levels upon treating diluted digested livestock liquid. In these systems, influent was supplied at three hydraulic loading rates (HLRs of 1.25, 2.5, and 5 cm day⁻¹) during stage 1 and the rates were doubled during stage 2 when the water levels of nonflooded columns were elevated from zero to half the height of the soil column. After hydraulic loading rates doubled, the average removal rates of total nitrogen in flooded columns varied from 1.27 to 2.94 g⁻² day⁻¹ and those in nonflooded columns ranged from 1.23 to 3.88 g⁻² day⁻¹. The T-N removal at an HLR of 10 cm day⁻¹ in the nonflooded column with an elevated water table level had higher efficiency than that in the flooded column, suggesting T-N removal is enhanced in the nonflooded column probably due to the improved coupled nitrification–denitrification process under the elevated water table level condition. On the other hand, there was a significant correlation (r ² = 0.532, p < 0.001) between the N₂O flux and redox potential that mainly corresponded to water levels and HLRs, suggesting anoxic or aerobic conditions stimulate N₂O emission by enhancing the nitrification (nitrification–denitrification) process. In contrast, NH₃ volatilization had a high flux in the anaerobic condition mainly because of flooding. Based on the experimental results, it is hypothesized a nonflooded condition with higher water table level (Eh range of −160 to +260 mV) would be suitable to reduce N₂O emission and NH₃ volatilization peak value by at least half while maintaining relatively efficient nitrogen removal performance.
اظهر المزيد [+] اقل [-]