Found 9884 publications. Showing page 98 of 396:
2023
2006
2013
2017
In this paper, the effect of the lockdown measures on nitrogen dioxide (NO2) in Europe is analysed by a statistical model approach based on a generalised additive model (GAM). The GAM is designed to find relationships between various meteorological parameters and temporal metrics (day of week, season, etc.) on the one hand and the level of pollutants on the other. The model is first trained on measurement data from almost 2000 monitoring stations during 2015–2019 and then applied to the same stations in 2020, providing predictions of expected concentrations in the absence of a lockdown. The difference between the modelled levels and the actual measurements from 2020 is used to calculate the impact of the lockdown measures adjusted for confounding effects, such as meteorology and temporal trends. The study is focused on April 2020, the month with the strongest reductions in NO2, as well as on the gradual recovery until the end of July. Significant differences between the countries are identified, with the largest NO2 reductions in Spain, France, Italy, Great Britain and Portugal and the smallest in eastern countries (Poland and Hungary). The model is found to perform best for urban and suburban sites. A comparison between the found relative changes in urban surface NO2 data during the lockdown and the corresponding changes in tropospheric vertical NO2 column density as observed by the TROPOMI instrument on Sentinel-5P revealed good agreement despite substantial differences in the observing method.
MDPI
2021
2021
2016
2024
2016
2023
2014
2016
2016
2007
2007
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2005
2003
Microplastic (MP) is of growing concern to environmentaland humanhealth. Thisstudy investigated three analytical approachesto measure MPin tissues of salmonids. The studyaimed to 1) determine and demonstrate the sensitivity of current analytical methods for MP in salmon tissues for the three different quantitative methods, 2) compare the utility of the different methods in terms of cost, time and sensitivity 3) quantify MP in a relevant selection of tissues of farmedand wildsalmon in order to establish likely indicator organs for future documentation purposes. We here present the results, compare themethodsand discuss uncertainties and needs for further method development.
NORCE Norwegian Research Centre
2020
2018
Quantitative chemical analysis of airborne particulate matter (PM) is vital for the understanding of health effects in indoor and outdoor environments, as well as for enforcing EU air quality regulations. Typically, airborne particles are sampled over long time periods on filters, followed by lab-based analysis, e.g., with inductively coupled plasma mass spectrometry (ICP-MS). During the EURAMET EMPIR AEROMET project, cascade impactor aerosol sampling is combined for the first time with on-site total reflection X-ray fluorescence (TXRF) spectroscopy to develop a tool for quantifying particle element compositions within short time intervals and even on-site. This makes variations of aerosol chemistry observable with time resolution only a few hours and with good size resolution in the PM10 range. The study investigates the proof of principles of this methodological approach. Acrylic discs and silicon wafers are shown to be suitable impactor carriers with sufficiently smooth and clean surfaces, and a non-destructive elemental mass concentration measurement with a lower limit of detection around 10 pg/m3 could be achieved. We demonstrate the traceability of field TXRF measurements to a radiometrically calibrated TXRF reference, and the results from both analytical methods correspond satisfactorily.
MDPI
2021
Quantification Approaches in Non-Target LC/ESI/HRMS Analysis: An Interlaboratory Comparison
Nontargeted screening (NTS) utilizing liquid chromatography electrospray ionization high-resolution mass spectrometry (LC/ESI/HRMS) is increasingly used to identify environmental contaminants. Major differences in the ionization efficiency of compounds in ESI/HRMS result in widely varying responses and complicate quantitative analysis. Despite an increasing number of methods for quantification without authentic standards in NTS, the approaches are evaluated on limited and diverse data sets with varying chemical coverage collected on different instruments, complicating an unbiased comparison. In this interlaboratory comparison, organized by the NORMAN Network, we evaluated the accuracy and performance variability of five quantification approaches across 41 NTS methods from 37 laboratories. Three approaches are based on surrogate standard quantification (parent-transformation product, structurally similar or close eluting) and two on predicted ionization efficiencies (RandFor-IE and MLR-IE). Shortly, HPLC grade water, tap water, and surface water spiked with 45 compounds at 2 concentration levels were analyzed together with 41 calibrants at 6 known concentrations by the laboratories using in-house NTS workflows. The accuracy of the approaches was evaluated by comparing the estimated and spiked concentrations across quantification approaches, instrumentation, and laboratories. The RandFor-IE approach performed best with a reported mean prediction error of 15× and over 83% of compounds quantified within 10× error. Despite different instrumentation and workflows, the performance was stable across laboratories and did not depend on the complexity of water matrices.
American Chemical Society (ACS)
2024
2002