Secondary Organic Carbon Estimations with Hourly Monitoring Data and the OC/EC Primary Ratio Method

2013 ◽  
Vol 295-298 ◽  
pp. 849-853
Author(s):  
Mei Fang Lu ◽  
Mei Chuan Huang ◽  
Chiau Yi Wen ◽  
Yi Hui Wu ◽  
Jim Jui Min Lin
Keyword(s):  
Organic Carbon ◽  
Pollution Source ◽  
Photochemical Reactions ◽  
Monitoring Data ◽  
Ratio Method ◽  
High Temporal Resolution ◽  
Data Set ◽  
Daily Data ◽  
Hourly Data ◽  
Secondary Organic Carbon

This study examined the hourly monitoring data from 2006 to 2009 collected by the Aerosol Supersite of the Environmental Protection Administration of Taiwan. The OC/EC primary ratio method has been applied to estimate the content of secondary organic carbon (SOC). Results of this study indicated that the monthly concentrations of PM2.5, OC, and EC all remained low in summer but went up in winter. Possible factors were climate-related and influences from continental high pressure systems. The content (24–36%) of SOC in summer was significantly higher than in other seasons, indicating that a great formation of organic carbon in summer. When considering the hourly trend, apparent peaks can be consistently observed in the morning, which may be due to an increase of mobile pollution source and photochemical reactions. (OC/EC)min ratio values were calculated based on both hourly and daily concentrations of OC and EC, then annual values (2006~2009) were 0.20~1.11 and 0.68~2.72 for hourly and daily data base respectively. Content of SOC in PM2.5 and OC were estimated to be 16~23 % and 75~93 % based on (OC/EC)min ratio from hourly data set, and were 11~18 % and 42~77 % based on (OC/EC)min ratio from daily data set. Results from this study, as well as those from other studies, demonstrated that the OC/EC ratio is dependent upon the sampling method as well as the method of analysis. Furthermore, the daily OC/EC ratio may change, and significant variations may be found even within 24 hours. Taken together, when conducting estimation of SOC, it is important to eliminate the consideration on background concentrations but to take a good advantage of the high temporal resolution of hourly monitoring data in order to estimate SOC using a corrective approach.

scholarly journals Application of positive matrix factorization in estimating aerosol secondary organic carbon in Hong Kong and insights into the formation mechanisms

2005 ◽  
Vol 5 (4) ◽  
pp. 5299-5324 ◽  
Author(s):  
Z. B. Yuan ◽  
J. Z. Yu ◽  
A. K. H. Lau ◽  
P. K. K. Louie ◽  
J. C. H. Fung
Keyword(s):  
Hong Kong ◽  
Organic Carbon ◽  
Matrix Factorization ◽  
Large Data ◽  
Positive Matrix Factorization ◽  
Carbonaceous Aerosol ◽  
Formation Mechanisms ◽  
Positive Matrix ◽  
Data Set ◽  
Secondary Organic Carbon

Abstract. Secondary organic carbon (SOC) is often a significant portion of organic carbon (OC) in ambient particulate matter (PM). The levels and seasonal patterns of SOC in Hong Kong were examined using more than 2000 PM10 measurements made over a 4.5-year period (1998–2002) in a network of ten air quality monitoring stations. The positive matrix factorization (PMF) model was used to analyze this large data set for source identification and apportioning. SOC was subsequently estimated to be the sum of OC present in the secondary sources, i.e., secondary sulfate, secondary nitrate, and secondary organic aerosol. The annual average SOC as estimated by the PMF method was 4.25 µg C/m3 while the summer average was 1.66 µg C/m3 and the winter average was 7.05 µg C/m3. In comparison, the method that uses EC as a tracer for primary carbonaceous aerosol sources to derive SOC overestimated SOC by 70–212% for the summer samples and by 4–43% for the winter samples. The overestimation by the EC tracer method resulted from the inability of obtaining a single OC/EC ratio that represented a mixture of primary sources varying in time and space. We found that SOC and secondary sulfate had synchronous seasonal variation and were correlated in individual seasons, suggesting common factors that control their formation. Considering the well-established fact that both gas phase oxidation and in-cloud processing are important formation pathways for sulfate, the synchronicity of SOC and sulfate suggests that in-cloud pathways are also important for SOC formation. Additionally, the presence of SOC was found to be enhanced more than that of secondary sulfate in the winter. We postulate this to be a combined result of favorable partitioning of semivolatile SOC species in the particle phase and more abundant SOC precursors in the winter.

Short-term secondary organic carbon estimations with a modified OC/EC primary ratio method at a suburban site in Madrid (Spain)

2011 ◽  
Vol 45 (15) ◽  
pp. 2496-2506 ◽  
Author(s):  
Javier Plaza ◽  
Begoña Artíñano ◽  
Pedro Salvador ◽  
Francisco J. Gómez-Moreno ◽  
Manuel Pujadas ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Ratio Method ◽  
Short Term ◽  
Secondary Organic Carbon ◽  
Suburban Site

scholarly journals Seasonal variation of PM<sub>10</sub> main constituents in two valleys of the French Alps. I: EC/OC fractions

2007 ◽  
Vol 7 (3) ◽  
pp. 661-675 ◽  
Author(s):  
G. Aymoz ◽  
J. L. Jaffrezo ◽  
D. Chapuis ◽  
J. Cozic ◽  
W. Maenhaut
Keyword(s):  
Organic Carbon ◽  
Ratio Method ◽  
French Alps ◽  
Residential Heating ◽  
Secondary Organic Carbon ◽  
Urban Sites ◽  
Pm10 Mass ◽  
Daily Pm10 ◽  
Very High ◽  
High Range

Abstract. Daily PM10 samples were collected at two urban sites within two valleys in the French Alps (Chamonix and St Jean de Maurienne) during a period of two and a half years. The carbonaceous species EC (elemental carbon) and OC (organic carbon) were analysed to investigate the possible sources of EC and OC, and their seasonal variations. Mean OC concentrations are in the very high range of concentrations measured for other European sites, and represent at least one third of the PM10 mass on each site. On the basis of the comparison between EC and OC concentrations with several tracers, we were able to show that their main sources are local primary combustion sources. Biomass burning emissions (residential heating) have a significant impact on OC concentrations while heavy duty traffic emissions have an impact only on EC concentrations. Finally, we estimated the contribution of SOA (secondary organic carbon) to OC, using the EC-to-OC primary ratio method (Castro et al., 1999) and demonstrated that the calculation of SOA mass with this method is highly uncertain, if the hypothesis of a constant primary EC-to-OC ratio is not very closely examined.

scholarly journals Seasonal variation of PM<sub>10</sub> main constituents in two valleys of the French Alps. I: EC/OC fractions

2006 ◽  
Vol 6 (4) ◽  
pp. 6211-6254 ◽  
Author(s):  
G. Aymoz ◽  
J.-L. Jaffrezo ◽  
D. Chapuis ◽  
J. Cozic ◽  
W. Maenhaut
Keyword(s):  
Organic Carbon ◽  
Ratio Method ◽  
French Alps ◽  
Residential Heating ◽  
Secondary Organic Carbon ◽  
Urban Sites ◽  
Pm10 Mass ◽  
Daily Pm10 ◽  
Very High ◽  
High Range

Abstract. Daily PM10 samples were collected at two urban sites within two valleys in the French Alps (Chamonix and St Jean de Maurienne) during a period of two and a half years. The carbonaceous species EC (elemental carbon) and OC (organic carbon) were analysed to investigate the possible sources of EC and OC, and their seasonal variations. Mean OC concentrations are in the very high range of concentrations measured for other European sites, and represent at least one third of the PM10 mass on each site. On the basis of the comparison between EC and OC concentrations with several tracers, we were able to show that their main sources are local primary combustion sources. Biomass burning emissions (residential heating) have a significant impact on OC concentrations while heavy duty traffic emissions have an impact only on EC concentrations. Finally, we estimated the contribution of SOA (secondary organic carbon) to OC, using the EC-to-OC primary ratio method (Castro et al., 1999) and demonstrated that the calculation of SOA mass with this method is highly uncertain, if the hypothesis of a constant primary EC-to-OC ratio is not very closely examined.

scholarly journals Evaluation of four years continuous δ<sup>13</sup>C(CO<sub>2</sub>) data using a running Keeling approach

2016 ◽  
Author(s):  
Sanam Noreen Vardag ◽  
Samuel Hammer ◽  
Ingeborg Levin
Keyword(s):  
Fossil Fuel ◽  
Co2 Concentration ◽  
High Temporal Resolution ◽  
Data Set ◽  
Additional Information ◽  
Hourly Data ◽  
The Mean ◽  
Carbon Dioxide Co2 ◽  
End Members ◽  
Different Sources

Abstract. As different carbon dioxide (CO2) emitters have different carbon isotope ratios, measurements of atmospheric δ13C(CO2) and CO2 concentration contain information on the CO2 source mix in the catchment area of an atmospheric measurement site. Often, this information is illustratively presented as mean isotopic source signature. Recently an increasing number of continuous measurements of δ13C(CO2) and CO2 have become available, opening the door to quantification of CO2 shares from different sources at high temporal resolution. Here, we present a method to compute the CO2 source signature (δS) continuously without introducing biases and evaluate our result using model data. We find that biases in δS are smaller than 0.2 ‰ with uncertainties of about 1.2 ‰ for hourly data. Applying the method to a four year data set of CO2 and δ13C(CO2) measured in Heidelberg, Germany, yields a distinct seasonal cycle of δS. Disentangling this seasonal source signature into its source components is, however, only possible if the isotopic end members of these sources, i.e., the biosphere, δbio, and the fuel mix, δF, are known. From the mean source signature record in 2012, δbio could be reliably estimated only for summer to (−25 ± 1) ‰ and δF only for winter to (−32.5 ± 2.5) ‰. As the isotopic end members δbio and δF were shown to change over the season, no year-round estimation of the fossil fuel or biosphere share is possible from the measured mean source signature record without additional information from emission inventories or other tracer measurements, such as Δ14C(CO2).

scholarly journals Application of positive matrix factorization in estimating aerosol secondary organic carbon in Hong Kong and its relationship with secondary sulfate

2006 ◽  
Vol 6 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Z. B. Yuan ◽  
J. Z. Yu ◽  
A. K. H. Lau ◽  
P. K. K. Louie ◽  
J. C. H. Fung
Keyword(s):  
Hong Kong ◽  
Organic Carbon ◽  
Matrix Factorization ◽  
Large Data ◽  
Positive Matrix Factorization ◽  
Carbonaceous Aerosol ◽  
Positive Matrix ◽  
Data Set ◽  
Secondary Sources ◽  
Secondary Organic Carbon

Abstract. Secondary organic carbon (SOC) is often a significant portion of organic carbon (OC) in ambient particulate matter (PM). The levels and seasonal patterns of SOC in Hong Kong were examined using more than 2000 PM10 measurements made over a 4.5-year period (1998–2002) in a network of ten air quality monitoring stations. The positive matrix factorization (PMF) model was used to analyze this large data set for source identification and apportioning. SOC was subsequently estimated to be the sum of OC present in the secondary sources, i.e., secondary sulfate, secondary nitrate, and secondary organic aerosol. The annual average SOC as estimated by the PMF method was 4.25 μg C/m3 while the summer average was 1.66 μg C/m3 and the winter average was 7.05 μg C/m3. In comparison, the method that uses EC as a tracer for primary carbonaceous aerosol sources to derive SOC overestimated SOC by 70–212% for the summer samples and by 4–43% for the winter samples. The overestimation by the EC tracer method resulted from the inability of obtaining a single OC/EC ratio that represented a mixture of primary sources varying in time and space. We found that SOC and secondary sulfate had synchronous seasonal variation and were correlated in individual seasons, suggesting common factors that control their formation. Additionally, the presence of SOC was found to be enhanced more than that of secondary sulfate in the winter. We postulate this to be a combined result of favorable partitioning of semivolatile SOC species in the particle phase and more abundant SOC precursors in the winter.

scholarly journals Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and major and trace ions in the Fraser River, Canada

2015 ◽  
Vol 12 (19) ◽  
pp. 5597-5618 ◽  
Author(s):  
B. M. Voss ◽  
B. Peucker-Ehrenbrink ◽  
T. I. Eglinton ◽  
R. G. M. Spencer ◽  
E. Bulygina ◽  
...  
Keyword(s):  
Time Series ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Fraser River ◽  
Data Set ◽  
Inorganic Species ◽  
Rapid Changes ◽  
Spring Freshet ◽  
Daily Sampling ◽  
Dom Composition

Abstract. Rapid changes in the volume and sources of discharge during the spring freshet lead to pronounced variations in biogeochemical properties in snowmelt-dominated river basins. We used daily sampling during the onset of the freshet in the Fraser River (southwestern Canada) in 2013 to identify rapid changes in the flux and composition of dissolved material, with a focus on dissolved organic matter (DOM). Previous time series sampling (at twice monthly frequency) of dissolved inorganic species in the Fraser River has revealed smooth seasonal transitions in concentrations of major ions and tracers of water and dissolved load sources between freshet and base flow periods. In contrast, daily sampling reveals a significant increase in dissolved organic carbon (DOC) concentration (200 to 550 μmol L−1) occurring over a matter of days, accompanied by a shift in DOM optical properties, indicating a transition towards higher molecular weight, more aromatic DOM composition. Comparable changes in DOM composition, but not concentration, occur at other times of year, underscoring the role of seasonal climatology in DOM cycling. A smaller data set of total and dissolved Hg concentrations also showed variability during the spring freshet period, although dissolved Hg dynamics appear to be driven by factors beyond DOM as characterized here. The time series records of DOC and particulate organic carbon (POC) concentrations indicate that the Fraser River exports 0.25–0.35 % of its annual basin net primary productivity. The snowmelt-dominated hydrology, forested land cover, and minimal reservoir impoundment of the Fraser River may influence the DOC yield of the basin, which is high relative to the nearby Columbia River and of similar magnitude to that of the Yukon River to the north. Anticipated warming and decreased snowfall due to climate changes in the region may cause an overall decrease in DOM flux from the Fraser River to the coastal ocean in coming decades

scholarly journals Broadband waveforms and site effects at a borehole seismometer in the Po alluvial basin (Italy)

2001 ◽  
Vol 44 (1) ◽  
Author(s):  
M. Cocco ◽  
F. Ardizzoni ◽  
R. M. Azzara ◽  
L. Dall'Olio ◽  
A. Delladio ◽  
...  
Keyword(s):  
Site Effects ◽  
Velocity Structure ◽  
Dynamic Range ◽  
Site Response ◽  
Seismic Exploration ◽  
Ratio Method ◽  
Data Set ◽  
Broadband Seismometer ◽  
Local Earthquakes ◽  
Teleseismic Events

Broadband seismograms recorded at a borehole three-component (high dynamic range) seismic station in the Po Valley (Northern Italy) were analyzed to study the velocity structure of the shallow sedimentary layers as well as the local site effects in soft sediments. The broadband borehole seismometer was installed at a depth of 135 m just below the quaternary basement, while a second digital broadband seismometer was installed in the same site at the Earth surface. The velocity structure in the shallower layers was determined both by means of cross-hole and up-hole measurements and by inverting seismic data recorded during a seismic exploration experiment.Velocity discontinuities are quite well related to the stratigraphy of the site. We are interested to record local earthquakes as well as regional and teleseismic events. The analyzed data set includes local, regional and teleseismic events, most of which were recorded during the seismic sequence that started on October 15, 1996, near Reggio Emilia 80 km away from the borehole site. The orientation of the borehole sensor is determined using the recordings of a teleseismic event and of some local earthquakes. The noise reduction for the borehole sensor is 2 decades in power spectral density at frequencies larger than 1.0 Hz. We studied the site amplification of the shallow alluvial layers by applying the spectral ratio method. We analyzed the spectral ratios of noise recorded by the surface and borehole seismometers as well as those from local earthquakes. We compared these observations with a theoretical model for the site response computed by the Haskell-Thomson method.

scholarly journals Sensitivity Of Differential Item Functioning Detection Methods On National Mathematics Examination In North Sumatera Province, Indonesia

2019 ◽  
Vol 8 (5C) ◽  
pp. 1538-1549
Keyword(s):  
Differential Item Functioning ◽  
Likelihood Ratio ◽  
Classical Test Theory ◽  
Test Theory ◽  
Detection Methods ◽  
Ratio Method ◽  
Suitable Model ◽  
Data Set ◽  
Item Functioning ◽  
Mathematics Examination

The purpose of this study was to examine the differences in sensitivity of three methods: IRT-Likelihood Ratio (IRT-LR), Mantel-Haenszel (MH) and Logistics Regression (LR), in detecting gender differential item functioning (DIF) on National Mathematics Examination (Ujian Nasional: UN) for 2014/2015 academic year in North Sumatera Province of Indonesia. DIF item shows the unfairness. It advantages the test takers of certain groups and disadvantages other group test takers, in the case they have the same ability. The presence of DIF was reviewed in grouping by gender: men as reference groups (R) and women as focus groups (F). This study used the experimental method, 3x1 design, with one factor (i.e. method) with three treatments, in the form of 3 different DIF detection methods. There are 5 types of UN Mathematics Year 2015 packages (codes: 1107, 2207, 3307, 4407 and 5507). The 2207 package code was taken as the sample data, consisting of 5000 participants (3067 women, 1933 men; for 40 UN items). Item selection was carried out based on the classical test theory (CTT) on 40 UN items, producing 32 items that fulfilled, and item response theory selection (IRT) produced 18 items that fulfilled. With program R 3.333 and IRTLRDIF 2.0, it was found 5 items were detected as DIF by the IRT-Likelihood Ratio-method (IRTLR), 4 items were detected as DIF by the Logistic Regression method (LR), and 3 items were detected as DIF by the MantelHaenszel method (MH). To test the sensitivity of the three methods, it is not enough with just one time DIF detection, but formed six groups of data analysis: (4400,40),(4400,32), (4400,18), (3000,40), (3000,32), (3000,18), and generate 40 random data sets (without repetitions) in each group, and conduct detecting DIF on the items in each data set. Although the data lacks model fit, the 3 parameter logistic model (3PL) is chosen as the most suitable model. With the Tukey's HSD post hoc test, the IRT-LR method is known to be more sensitive than the MH and LR methods in the group (4400,40) and (3000,40). The IRT-LR method is not longer more sensitive than LR in the group (4400,32) and (3000,32), but still more sensitive than MH. In the groups (4400,18) and (3000,18) the IRT-LR method is more sensitive than LR, but not significantly more sensitive than MH. The LR method is consistently tested to be more sensitive than the MH method in the entire analysis groups.

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