scholarly journals Study of size-segregated particle (PM1, PM2,5, PM10) concentrations over Greece

2013 ◽  
Vol 10 (2) ◽  
pp. 132-139 ◽  
Keyword(s):  
Regional Scale ◽  
Monitoring Network ◽  
Quality Standard ◽  
Anthropogenic Source ◽  
Data Sets ◽  
Limit Values ◽  
Back Trajectories ◽  
Dust Transport ◽  
Limit Value

This study reports particulate matter levels of various size fractions (PM10, PM2.5, and PM1) and identify their controlling factors, in various locations over Greece. It combines long-term data sets involving particle concentrations as measured in the island of Crete in the Eastern Mediterranean and the Greater Area of Athens. Measurements were carried out in various sites at urban (Central Athens and Heraklion, Crete), suburban (Lykovrissi, Athens) and natural background (Finokalia, Crete) locations, for a time period extending from 2004 to 2006. Size-segregated mass measurements of 3 sizes (PM10, PM2.5 and PM1) are reported. The EU annual limit value of 40 μg m-3 for PM10 was exceeded on a yearly basis at both of measurement sites in Athens, while frequent exceedances of the 24-h limit value of 50 μg m-3 were recorded. Concentration levels of PM2.5 and PM1 were also found elevated, when regarded in perspective to either existing limit values (for PM2.5) or levels reported for other large metropolitan areas (for PM1). In addition even at the background station of Finokalia in Crete, average PM10 concentrations exceeded 30 μg m-3. Moreover, at the same station, average concentrations of PM2.5, notably exceed 15 μg m-3 (a characteristic value, relative to the USEPA PM2.5 air quality standard). At all sites coarse particles have been found to comprise a noteworthy portion of total PM10 particles (with PM2.5/PM10 ratios ranging between 45-60%), while fine particle mass concentrations heavily relied on those of particles in the submicron range (PM1/PM2.5 ratios spanning between 55-75%). The short and long-term temporal variability of each fraction were examined and spatial associations were statistically analyzed, in an attempt to identify possible affinities in particle level profiles, effective over a larger regional scale. It has been observed that at several instances, severe particle episodes recorded in the region of Crete have largely affected the Greek mainland and have triggered a response to the monitoring network in Athens. Special focus has been given to events of dust transport from N. Africa, which is found to be more frequent during spring and fall, and during which the PM10 limit value of 50 μg m-3 is violated and concentrations of even finer particle fractions are affected. Air mass back trajectories were studied, for episode days during dust transport events. Data of particle chemical composition were utilized, contributing to an initial identification and characterization of major natural and anthropogenic source types, which determine particle concentrations.

scholarly journals GUV long-term measurements of total ozone column and effective cloud transmittance at three Norwegian sites

2021 ◽  
Vol 21 (10) ◽  
pp. 7881-7899
Author(s):  
Tove M. Svendby ◽  
Bjørn Johnsen ◽  
Arve Kylling ◽  
Arne Dahlback ◽  
Germar H. Bernhard ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Total Ozone ◽  
Monitoring Network ◽  
High Time Resolution ◽  
Data Sets ◽  
Total Ozone Column ◽  
Ice Melt ◽  
Arctic Ice ◽  
Ozone Column

Abstract. Measurements of total ozone column and effective cloud transmittance have been performed since 1995 at the three Norwegian sites Oslo/Kjeller, Andøya/Tromsø, and in Ny-Ålesund (Svalbard). These sites are a subset of nine stations included in the Norwegian UV monitoring network, which uses ground-based ultraviolet (GUV) multi-filter instruments and is operated by the Norwegian Radiation and Nuclear Safety Authority (DSA) and the Norwegian Institute for Air Research (NILU). The network includes unique data sets of high-time-resolution measurements that can be used for a broad range of atmospheric and biological exposure studies. Comparison of the 25-year records of GUV (global sky) total ozone measurements with Brewer direct sun (DS) measurements shows that the GUV instruments provide valuable supplements to the more standardized ground-based instruments. The GUV instruments can fill in missing data and extend the measuring season at sites with reduced staff and/or characterized by harsh environmental conditions, such as Ny-Ålesund. Also, a harmonized GUV can easily be moved to more remote/unmanned locations and provide independent total ozone column data sets. The GUV instrument in Ny-Ålesund captured well the exceptionally large Arctic ozone depletion in March/April 2020, whereas the GUV instrument in Oslo recorded a mini ozone hole in December 2019 with total ozone values below 200 DU. For all the three Norwegian stations there is a slight increase in total ozone from 1995 until today. Measurements of GUV effective cloud transmittance in Ny-Ålesund indicate that there has been a significant change in albedo during the past 25 years, most likely resulting from increased temperatures and Arctic ice melt in the area surrounding Svalbard.

scholarly journals Using crop analysis in the precision nutrient supply system of maize

2012 ◽  
pp. 183-186
Author(s):  
Zoltán Izsáki
Keyword(s):  
Grain Yield ◽  
Nutrient Supply ◽  
Limit Values ◽  
Leaf Analysis ◽  
Yield Level ◽  
Limit Value ◽  
P Concentration ◽  
Maize Leaves ◽  
K Concentration

The effect of the N, P and K supplies of soil on the grain yield and N, P and K status of maize was studied in a long-term mineral fertilisation experiment between 2001 and 2008 and nutrient supply limit values were determined to plant analysis. Based on the interaction between the N concentrtion of maize leaves measured at the beginnig of tasseling and grain yield, the satisfactory limit value of N supply to reach 10–14 t ha-1 yield was between 2.0–4.0%. Leaf analysis at the beginning of tasselling indicated that better P and K supplies were associated with a higher P and K concentration in the maize leaves. Correlation analysis on the P concentration of the maize leaves and the grain yield showed that at a grain yield level of 10–14 t ha-1 a P concentration of 0.20–0.37% represented a satisfactory P supply level. The satisfactory K supply limit value to reach 10–14t ha-1 grain yield was 1.5–2.6%.

scholarly journals The role of long-range transport and domestic emissions in determining atmospheric secondary inorganic particle concentrations across the UK

2013 ◽  
Vol 13 (12) ◽  
pp. 33433-33462
Author(s):  
M. Vieno ◽  
M. R. Heal ◽  
S. Hallsworth ◽  
D. Famulari ◽  
R. M. Doherty ◽  
...  
Keyword(s):  
Long Range ◽  
Regional Scale ◽  
Long Range Transport ◽  
Substantial Part ◽  
Limit Values ◽  
Substantial Impact ◽  
Inorganic Particle ◽  
Range Transport ◽  
The Uk

Abstract. Surface concentrations of secondary inorganic particle components over the UK have been analysed for 2001–2010 using the EMEP4UK regional atmospheric chemistry transport model. In early 2003 an episode of substantially elevated surface concentrations of ammonium nitrate was measured across the UK by the AGANET network. The EMEP4UK model was able accurately to represent both the long-term decadal surface concentrations and the episode in 2003. The latter was identified as consisting of three separate episodes, each of less than 1 month duration, in February, March and April. The primary cause of the elevated nitrate levels across the UK was meteorological, a persistent high pressure system, but whose varying location impacted the relative importance of transboundary vs. domestic emissions. Whilst long-range transport dominated the elevated nitrate in February, in contrast it was domestic emissions that mainly contributed to the March episode, and for the April episode both domestic emissions and long-range transport contributed. A prolonged episode such as the one in early 2003 can have substantial impact on annual average concentrations. The episode led to annual concentration differences at the regional scale of similar magnitude to those driven by long-term changes in precursor emissions over the full decade investigated here. The results demonstrate that a substantial part of the UK, particularly the south and south-east, may be close to or actually exceeding annual mean limit values because of import of inorganic aerosol components from continental Europe under specific conditions. The results reinforce the importance of employing multiple year simulations in the assessment of emissions reduction scenarios on PM concentrations and the need for international agreements to address the transboundary component of air pollution.

Estimated nitrogen concentrations in humus based on initial nitrogen concentrations in foliar litter: a synthesis. XII. Long-term decomposition in a Scots pine forest

2000 ◽  
Vol 77 (12) ◽  
pp. 1712-1722
Author(s):  
Björn Berg ◽  
Ryszard Laskowski ◽  
Amalia Virzo Santo
Keyword(s):  
Linear Relationship ◽  
Limit Values ◽  
Significant Linear Relationship ◽  
Limit Value ◽  
N Concentration ◽  
Linear Relationships ◽  
Significant Difference ◽  
Nitrogen Concentrations ◽  
Scots Pine Forest

The final (limit) values for litter decomposition were estimated and, by extrapolating a linear relationship between accumulated litter mass loss and litter N concentration, the N concentration at the limit value (Nlimit) was estimated. The values for Nlimit were compared with those of the A01 layer (Nhumus) and of newly shed litter (Ninit). No difference was found between the A01 and A02 layers when their N concentrations were compared with the values for Nlimit. There was a highly significant linear relationship between Nlimit and Ninit (R2 = 0.769 and p < 0.001). Likewise, there was a highly significant linear relationship between Nhumus and Ninit. When these two linear relationships were compared, there was no significant difference in slope, while there was a significant difference in the intercepts of 6.76 and 7.25 mg·g-1 for Nhumus and Ninit, respectively. Thus, for a given site in our investigation, the estimated value for N concentration in humus would be 6.8% lower than the measured one.

Maximum decomposition limits of forest litter types: a synthesis

1996 ◽  
Vol 74 (5) ◽  
pp. 659-672 ◽  
Author(s):  
Björn Berg ◽  
Maj-Britt Johansson ◽  
Gunnar Ekbohm ◽  
Charles McClaugherty ◽  
Flora Rutigliano ◽  
...  
Keyword(s):  
Litter Decomposition ◽  
Forest Litter ◽  
Limit Values ◽  
Limit Value ◽  
Needle Litter ◽  
Linear Relationships ◽  
Asymptotic Function ◽  
Linear Regressions ◽  
Negative Linear Relationship

We used long-term litter decomposition data to estimate final decomposition levels using an asymptotic function. The estimated final limit values for decomposition were compared with available chemical data for the different litter types. A total of 41 limit values were estimated from as many different decomposition studies, and 20 different litter types were incubated in eight different forest systems. The limit values estimated varied with litter type. They ranged from about 35 to about 100% decomposition and were linearly related to the initial litter concentrations of N, Mn, and Ca in the newly shed litter. For these three nutrients, there are causal relationships to lignin degradation and to the lignin-degrading microbial community. Using all available data, we made simple and multiple linear regressions and obtained a negative linear relationship between limit value and initial N concentration ([Formula: see text]; n = 41; p < 0.001). For needle litter alone, we obtained a better relationship ([Formula: see text]; n = 23; p < 0.001). Manganese concentrations in litter gave a positive relationship ([Formula: see text]; n = 25; p < 0.001), with a clear improvement when needle litter was tested for alone ([Formula: see text]; n = 16; p < 0.001). Calcium alone gave a barely significant relationship. When combining nutrients in multiple linear relationships we obtained high R2 values, indicating that the models were good. Thus for all sites and litter types, N, Mn, and Ca combined gave an [Formula: see text] value of 0.640 with n = 25 (p < 0.001). All needle litters combined gave an [Formula: see text] of 0.745 (n = 16; p < 0.001). The significance of this finding is discussed. Keywords: litter decomposition, limit values, maximum decomposition, nitrogen, manganese, calcium.

Asian Americans and Pacific Islanders: Employment Issues in the United States

2011 ◽  
Vol 9 (1-2) ◽  
pp. 58-69
Author(s):  
Marlene Kim
Keyword(s):  
United States ◽  
Asian Americans ◽  
The United States ◽  
Current Data ◽  
Pacific Islanders ◽  
Native Hawaiians ◽  
Data Sets ◽  
High Poverty ◽  
Unemployment Rates

Asian Americans and Pacific Islanders (AAPIs) in the United States face problems of discrimination, the glass ceiling, and very high long-term unemployment rates. As a diverse population, although some Asian Americans are more successful than average, others, like those from Southeast Asia and Native Hawaiians and Pacific Islanders (NHPIs), work in low-paying jobs and suffer from high poverty rates, high unemployment rates, and low earnings. Collecting more detailed and additional data from employers, oversampling AAPIs in current data sets, making administrative data available to researchers, providing more resources for research on AAPIs, and enforcing nondiscrimination laws and affirmative action mandates would assist this population.

Epidemiological Evidence that Maternal Influenza Contributes to the Aetiology of Schizophrenia

1993 ◽  
Vol 163 (4) ◽  
pp. 522-534 ◽  
Author(s):  
W. Adams ◽  
R. E. Kendell ◽  
E. H. Hare ◽  
P. Munk-Jørgensen
Keyword(s):  
Data Sets ◽  
Time Lags ◽  
Epidemiological Evidence ◽  
Intrauterine Development ◽  
Increased Risk ◽  
Schizophrenic Patients ◽  
The Relationship ◽  
Monthly Incidence ◽  
Maternal Influenza

The epidemiological evidence that the offspring of women exposed to influenza in pregnancy are at increased risk of schizophrenia is conflicting. In an attempt to clarify the issue we explored the relationship between the monthly incidence of influenza (and measles) in the general population and the distribution of birth dates of three large series of schizophrenic patients - 16 960 Scottish patients born in 1932–60; 22 021 English patients born in 1921–60; and 18 723 Danish patients born in 1911–65. Exposure to the 1957 epidemic of A2 influenza in midpregnancy was associated with an increased incidence of schizophrenia, at least in females, in all three data sets. We also confirmed the previous report of a statistically significant long-term relationship between patients' birth dates and outbreaks of influenza in the English series, with time lags of - 2 and - 3 months (the sixth and seventh months of pregnancy). Despite several other negative studies by ourselves and others we conclude that these relationships are probably both genuine and causal; and that maternal influenza during the middle third of intrauterine development, or something closely associated with it, is implicated in the aetiology of some cases of schizophrenia.

scholarly journals A Novel LSTM Model with Interaction Dual Attention for Radar Echo Extrapolation

2021 ◽  
Vol 13 (2) ◽  
pp. 164
Author(s):  
Chuyao Luo ◽  
Xutao Li ◽  
Yongliang Wen ◽  
Yunming Ye ◽  
Xiaofeng Zhang
Keyword(s):  
Short Term Memory ◽  
Weather Forecast ◽  
Vital Role ◽  
Data Sets ◽  
Short Term ◽  
Learning Techniques ◽  
Radar Echo ◽  
Hidden States ◽  
Better Than

The task of precipitation nowcasting is significant in the operational weather forecast. The radar echo map extrapolation plays a vital role in this task. Recently, deep learning techniques such as Convolutional Recurrent Neural Network (ConvRNN) models have been designed to solve the task. These models, albeit performing much better than conventional optical flow based approaches, suffer from a common problem of underestimating the high echo value parts. The drawback is fatal to precipitation nowcasting, as the parts often lead to heavy rains that may cause natural disasters. In this paper, we propose a novel interaction dual attention long short-term memory (IDA-LSTM) model to address the drawback. In the method, an interaction framework is developed for the ConvRNN unit to fully exploit the short-term context information by constructing a serial of coupled convolutions on the input and hidden states. Moreover, a dual attention mechanism on channels and positions is developed to recall the forgotten information in the long term. Comprehensive experiments have been conducted on CIKM AnalytiCup 2017 data sets, and the results show the effectiveness of the IDA-LSTM in addressing the underestimation drawback. The extrapolation performance of IDA-LSTM is superior to that of the state-of-the-art methods.

scholarly journals Pan-Arctic aerosol number size distributions: seasonality and transport patterns

2017 ◽  
Vol 17 (13) ◽  
pp. 8101-8128 ◽  
Author(s):  
Eyal Freud ◽  
Radovan Krejci ◽  
Peter Tunved ◽  
Richard Leaitch ◽  
Quynh T. Nguyen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Regional Scale ◽  
Arctic Region ◽  
The Arctic ◽  
Research Station ◽  
Size Distributions ◽  
Back Trajectories ◽  
Accumulation Mode ◽  
Source Regions ◽  
The Arctic Ocean

Abstract. The Arctic environment has an amplified response to global climatic change. It is sensitive to human activities that mostly take place elsewhere. For this study, a multi-year set of observed aerosol number size distributions in the diameter range of 10 to 500 nm from five sites around the Arctic Ocean (Alert, Villum Research Station – Station Nord, Zeppelin, Tiksi and Barrow) was assembled and analysed.A cluster analysis of the aerosol number size distributions revealed four distinct distributions. Together with Lagrangian air parcel back-trajectories, they were used to link the observed aerosol number size distributions with a variety of transport regimes. This analysis yields insight into aerosol dynamics, transport and removal processes, on both an intra- and an inter-monthly scale. For instance, the relative occurrence of aerosol number size distributions that indicate new particle formation (NPF) event is near zero during the dark months, increases gradually to  ∼ 40 % from spring to summer, and then collapses in autumn. Also, the likelihood of Arctic haze aerosols is minimal in summer and peaks in April at all sites.The residence time of accumulation-mode particles in the Arctic troposphere is typically long enough to allow tracking them back to their source regions. Air flow that passes at low altitude over central Siberia and western Russia is associated with relatively high concentrations of accumulation-mode particles (Nacc) at all five sites – often above 150 cm−3. There are also indications of air descending into the Arctic boundary layer after transport from lower latitudes.The analysis of the back-trajectories together with the meteorological fields along them indicates that the main driver of the Arctic annual cycle of Nacc, on the larger scale, is when atmospheric transport covers the source regions for these particles in the 10-day period preceding the observations in the Arctic. The scavenging of these particles by precipitation is shown to be important on a regional scale and it is most active in summer. Cloud processing is an additional factor that enhances the Nacc annual cycle.There are some consistent differences between the sites that are beyond the year-to-year variability. They are the result of differences in the proximity to the aerosol source regions and to the Arctic Ocean sea-ice edge, as well as in the exposure to free-tropospheric air and in precipitation patterns – to mention a few. Hence, for most purposes, aerosol observations from a single Arctic site cannot represent the entire Arctic region. Therefore, the results presented here are a powerful observational benchmark for evaluation of detailed climate and air chemistry modelling studies of aerosols throughout the vast Arctic region.

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