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Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in Havana were quantified and analyzed in relation to possible emission sources to assess metropolitan soil contaminations in a highly dynamic, urban environment. The results of this study will serve Cuban legislators as a basis to develop environmental quality standards for organic pollutants in soils.
Materials and methodsPossible emission sources as, e.g., the vicinity to roads or industrial plants and the influence of the land use were related to the organic contaminants concentrations. Therefore, 28 topsoils in the Havana urban and semi-urban area were sampled at agricultural (n?=?12), organoponic (urban gardens in the capital, n?=?8), public park (n?=?7), and remediation (on-site bioremediation of an oil refinery, n?=?1) sites. Their PAH and PCB concentrations were measured with gas chromatography mass spectroscopy and the total organic carbon (TOC) and black carbon (BC) concentrations with the chemo-thermal oxidation.
Results and discussionThe sum of the 16 PAH concentrations ranged from 0.04 mg/kg in agricultural and organoponic soils to up to 72 mg/kg in a public park at about 1.5 km distance from an oil refinery. The lowest sum of the seven PCB congener concentrations was also measured in organoponic soils (0.002 mg/kg) and the highest in an arable patch of land between the rail roads and a main road (0.1 mg/kg). Both, PAH as well as PCB soil concentrations in Havana were almost up to two orders of magnitudes higher compared to a soil monitoring in the neighboring province of Mayabeque, but overall in the typical range of urban soils reported by other studies. The pollutants showed no relationship between TOC and BC except for PAHs with BC. For PAHs, combustion was the main source.
ConclusionsA comparison of the pollutant concentrations with regulatory guidance values (RGV) of other countries revealed PCB concentrations in Havana soils far below these RGV. In contrast, some concentrations of benzo[a]pyrene, the most carcinogenic PAH, in agricultural and park soils in Havana exceeded some RGV. Thus, some public parks pose a risk according to the Canadian quality guidelines when people have direct contact with these soils but not if they were consuming products thereof.
相似文献Objective
To determine the accuracy and precision of flowmeters used for oxygen therapy in a veterinary teaching hospital.Study design
An observational study.Methods
A total of 50 flowmeters used for oxygen therapy were evaluated using Defender 530 gas flow analyzers to measure flow. For each flowmeter, a minimum of seven flow settings were tested in random order and in triplicate. Flow measured at ambient conditions was converted to standardized flow specifications (21.1 °C and 760 mmHg) and analyzed using general linear mixed models. Flowmeters were considered accurate at a given flow setting when the targeted mean flow was within the corresponding 95% confidence interval. Precision of flow was characterized based on the magnitude of variance component estimates.Results
Flowmeters of 1.0, 3.5 and 8.0 L minute?1 were considered accurate across flow settings corresponding to their capacity range. Flowmeters of 7.0 and 15.0 L minute?1 were accurate at flow settings ≤2.0 L minute?1. For flow settings ≥3.0 L minute?1, average oxygen flow was consistently below reference values. Precision varied with the capacity of the flowmeter, ranked by decreasing precision as 1.0 > 3.5 > 8.0 > 7.0 > 15.0 L minute?1.Conclusions and clinical relevance
A flowmeter of the smallest maximum capacity within the desired flow range is more appropriate for smaller patients where accurate, precise flow delivery is needed. Although 15.0 L minute?1 flowmeters were accurate at flow settings ≤2.0 L minute?1, the graduated increments do not allow exact flow settings <0.5 L minute?1. Flowmeters of 15 L minute?1 capacity should be useful for high-flow oxygen delivery for which accuracy and precision are not critical. 相似文献![点击此处可从《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)