Found 9889 publications. Showing page 184 of 396:
2015
Low cost sensor systems for air quality assessment. Possibilities and challenges.
Air quality is enjoying popular interest in the last years, with numerous projects initiated by civil society or individuals that aim to assess the quality of air locally, aided by new, low-cost monitoring technologies that can be used by “everyone”. Such initiatives are very welcome, but in this highly technical and (in the western world) thoroughly regulated area, the professional community seems to struggle with communication with these initiatives, trying to reconcile the often highly technical aspects with the social ones. The technical issues include subjects such as monitoring techniques, air quality assessment methods, or quality control of measurements, and disciplines such as metrology, atmospheric science or informatics.
In this report, we would like to provide the reader with a practically oriented overview indicating the position of these new technologies in the ecosystem of air quality monitoring and measurement activities. Sensing techniques are rapidly evolving. This ‘ever’ improving capability implies among other, that there is currently no traceable method of evaluation of data quality. Despite the efforts of numerous groups, including within the European standardization system, a certification system will take some time to develop. This has important implications for example, when comparing measurements taken in time, by different devices (or different versions of the same sensor system device). Fitness for purpose – why are we measuring or monitoring and how do we intend to use the information we obtain – should always be the main criterion for the technological choice.
The report starts with an overview of elements of a monitoring system and proceed to describe the new technologies. Then, we give examples of how low-cost sensor technologies are being used by citizens. These examples are followed by reflections upon providing actionable information. Having learned from practical applications of sensor systems, we also discuss how the data from citizen activities can be used to develop new information, and provide some reflections on developing sensor systems monitoring on a larger scale.
We feel that the new technologies, while a disruptive change, provide many exciting opportunities, and we hope that this report will contribute to promote their use alongside with other assessment methods. We believe that increased understanding of technical issues we discuss will ultimately lead to better communication on air quality, and in its consequence, will enable further improvements in this domain.
ETC/ACM
2019
2008
Low concentrations of persistent organic pollutants (POPs) in air at Cape Verde
Ambient air is a core medium for monitoring of persistent organic pollutants (POPs) under the Stockholm Convention
and is used in studies of global transports of POPs and their atmospheric sources and source regions. Still,
data based on active air sampling remain scarce in many regions. The primary objectives of this study were to
(i) monitor concentrations of selected POPs in air outside West Africa, and (ii) to evaluate potential atmospheric
processes and source regions affecting measured concentrations. For this purpose, an active high-volume air
sampler was installed on the Cape Verde Atmospheric Observatory at Cape Verde outside the coast of West
Africa. Sampling commenced in May 2012 and 43 samples (24 h sampling) were collected until June 2013. The samples were analyzed for selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB) and chlordanes. The concentrations of these POPs at Cape Verde were generally low and comparable to remote sites in the Arctic for several compounds. Seasonal trends varied between compounds and concentrations exhibited strong temperature dependence for chlordanes. Our results indicate
net volatilization fromthe Atlantic Ocean north of Cape Verde as sources of these POPs. Air mass back trajectories
demonstrated that air masses measured at Cape Verdewere generally transported fromthe Atlantic Ocean or the North African continent. Overall, the low concentrations in air at Cape Verde were likely explained by absence of major emissions in areas from which the air masses originated combined with depletion during long-range atmospheric
transport due to enhanced degradation under tropical conditions (high temperatures and concentrations of hydroxyl radicals).
Elsevier
2018
2022
2006
2004
Long-term trends of short-lived pollutants in the Arctic, their source regions and emissions. NILU F
2010
2014
2010
Long-term trends of air pollutants at national level 2005-2019
Trend calculations of air pollutants for the periods 2005-2019 have been applied. Sulphur dioxide shows the largest decrease of all pollutants with a reduction of the order of 60-70 %. The agreement between reported emission data and measured concentrations are quite good. For NO2, a mismatch between the trend in air concentrations and NOx emissions is found. While the overall NOx emissions are reported to be reduced by 45 %, the measured NO2 data indicate a decline of the order of 30 % although marked differences between the countries are found. This mismatch could not be explained by changes in meteorology as this is accounted for. Possible reasons for the mismatch could be the NO2/NOx ratio of the emissions, changes in baseline hemispheric ozone concentration and natural emissions. For PM data (PM10 and PM2.5) we find an opposite mismatch, meaning that the PM concentrations show stronger downward trends than the reported emissions. This is likely an effect of the importance of secondary aerosols which are mitigated by other activities than the direct PM emissions. An overall reduction in PM10 of the order of 30-38 % is found during 2005-2019 while the direct emissions give a reduction that is 5-10 percentage units smaller. Similar results are found for PM2.5, but these findings are uncertain due to the less amount of long-term data. For O3, our findings are in line with earlier studies noting that the annual mean ozone concentration has increased while the high peaks have been reduced. But the reduction of the peaks is now within only a few percent and non-significant, while for the 2000-2017 period it was significant and about 10%.
ETC/ATNI
2021
2008
2014
The UK Toxic Organic Micro Pollutants (TOMPs) Network, which has operated since 1991, collects ambient air samples at six urban, rural, and semi-rural sites across England and Scotland, using high-volume active air samplers [1]. Furthermore, in 1994, a latitudinal sampling transect from the south of England to the north of Norway was established with eleven sampling sites, mainly in remote locations, using Semi-Permeable Membrane Devices (SPMDs) as passive air samplers [2]. Both networks provide continuous, long-term ambient air trend data for a range of Persistent Organic Pollutants (POPs), including PCBs and PBDEs, and have helped demonstrating a decline in POPs air concentrations over the last three decades. However, in recent years no further significant declines have been observed. SumPCB and SumPBDE levels in the UK are lowest at the rural sites and highest for the urban sites (TOMPs), and they generally decrease from the south of England to the north of Norway (UK/Norway) in line with expectations. Higher values at less remote sites and sites downwind from population centres show that POPs concentrations may still mainly be influenced by primary emissions. Concentrations at semi-rural sites lie between rural and urban sites; however, they can exceed the latter in some years. This can probably be attributed to short-term local effects. The data from the TOMPs network shows that concentrations of PCBs are higher in warmer than in colder months, while the seasonal patterns are less uniform for PBDEs.
2018
2017
2022
2016