1,720,972 research outputs found
Spatial-temporal variations of summertime ozone concentrations across a metropolitan area using a network of low-cost monitors to develop 24 hourly land-use regression models
No full textTen relatively-low-cost ozone monitors (Aeroqual Series 500 with OZL ozone sensor) were deployed to assess the spatial and temporal variability of ambient ozone concentrations across residential areas in the Monroe County, New York from June to October 2017. The monitors were calibrated in the laboratory and then deployed to a local air quality monitoring site where they were compared to the federal equivalent method values. These correlations were used to correct the measured ozone concentrations. The values were also used to develop hourly land use regression models (LUR) based on the deletion/substitution/addition (D/S/A) algorithm that can be used to predict the spatial and temporal concentrations of ozone at any hour of a summertime day and given location in Monroe County. Adjusted R2 values were high (average 0.83) with the highest adjusted R2 for the model between 8 and 9 AM (i.e. 1–2 h after the peak of primary emissions during the morning rush hours). Spatial predictors with the highest positive effects on ozone estimates were high intensity developed areas, low and medium intensity developed areas, forests + shrubs, average elevation, Interstate + highways, and the annual average vehicular daily traffic counts. These predictors are associated with potential emissions of anthropogenic and biogenic precursors. Maps developed from the models exhibited reasonable spatial and temporal patterns, with low ozone concentrations overnight and the highest concentrations between 11 AM and 5 PM. The adjusted R2 between the model predictions and the measured values varied between 0.79 and 0.87 (mean = 0.83). The combined use of the network of low-cost monitors and LUR modeling provide useful estimates of intraurban ozone variability and exposure estimates that will be used in future epidemiological studies
Evaluation and Field Calibration of a Low-cost Ozone Monitor at a Regulatory Urban Monitoring Station
Get PDFThe performance of a low cost ozone monitor (Aeroqual Series 500 portable gas monitors coupled with a metal oxide sensor for ozone; model OZL) was assessed under field conditions. Ten ozone monitors were initially calibrated in clean-air laboratory conditions and tested at controlled ozone concentrations of 5 to 100 ppb. Results showed good linearity and fast response with respect to a conventional research-grade ozone monitor. One monitor was then co-located at a regulatory air quality monitoring station that uses a U.S. federal equivalent method (FEM) ozone analyzer. Raw data from the Aeroqual monitor collected over 4 months (June–October) at a 10-minute time-resolution, showed good agreement (r2 = 0.83) with the FEM values but with an overestimation of ~12%. Data were averaged to different time resolutions; 1 h time averaged concentrations showed the best fit with the FEM results (r2 = 0.87). An analysis of the ratio of FEM/monitor concentrations against chemical and meteorological variables suggested the potential of interferences due to temperature, relative humidity, nitrogen oxides, and volatile organic compounds. Three correction models using temperature, humidity, and nitrogen dioxide (NO2) were then tested to better relate the monitor concentrations to the FEM values. Temperature and humidity are two variables commonly available (or easily measurable) at sampling sites. The model (#3) that added NO2 did not provide a substantial improvement in the fit. Thus, the proposed models with only temperature and humidity can be easily adopted and adapted by any user. The corrected data explained up to 91% of the variance and showed statistically significant improvement of the goodness of fits as well as decreased influence of the interfering variables on the diurnal and weekly patterns. The correction models were also able to lower the effect of seasonal temperature changes, allowing the use of the monitors over long-term sampling campaigns. This study demonstrated that the Aeroqual ozone monitors can return “FEM-like” concentrations after appropriate corrections. Therefore, data provided by a network of monitors could determine the intra-urban spatial variations in ozone concentrations. These results suggest that these monitors could provide more accurate human exposure assessments and thereby reduce exposure misclassification and its resulting bias in epidemiological studies
Estimating hourly exposure to residential wood combustion for human health
No full textDuring the last decade, there has been a substantial rise in the use of wood for space and water heating in North America, in addition to recreational burning. While there are national, state and regional programs to improve efficiency and reduce emissions from wood burning appliances, wood combustion remains a major source of airborne particulate matter (PM) and related pollutants during the heating season. While current regulatory air monitoring for PM2.5 provides daily measurements, with one monitoring site representing a relatively large area, health outcomes may be triggered by hourly pollutant exposures. For example, acute myocardial infarctions (MI), were found to be triggered within hours of short term increases in ambient PM2.5 concentrations (Gardner et al., 2014). Thus, more temporally and spatially resolved estimates of wood smoke exposure are needed to assess whether health outcomes may be impacted by this source specific PM a few hours after exposure, rather than after a few days or weeks.
For this study, continuous 1-minute indoor and outdoor PM and indoor carbon monoxide (CO) concentrations were measured from November through April of 2015/16 and 2016/17 at 50 residences across Monroe County, near Rochester, New York (25 residences per season). Inclusion criteria for the study were that homes had wood burning appliances or were located in ‘high wood smoke’ areas of Monroe County. Although wood combustion in most Monroe County residences is recreational only, we found that wood smoke can represent up to 30% of the winter-time PM2.5 concentrations there (Wang et al., 2012a,b).
Results from the first heating season validate the importance of including indoor exposure to combustion appliance emissions when assessing cumulative inhalation exposure to wood smoke. A regular daily cycle of PM was observed at all homes, with peaks associated with human activity, cooking, and wood burning appliance use. Indoor/outdoor PM concentration ratios were significantly higher when the carbon monoxide measurement indicated the presence of a combustion source. Most of the sites showed clear diurnal patterns with higher PM concentrations and indoor/outdoor PM concentration ratios in the late afternoon and evening hours.
Monitoring data were used as input for a land use regression model to predict hourly ambient PM2.5 concentrations across the region. Raster surfaces (spatial resolution 10 x 10 m) were developed for a series of predictors, including the number of bedrooms, fireplaces, and kitchens, as well as the property value, year the property was built, nearby road type and road traffic densities, railways, elevation, and density of various land cover data features. In general, the relationships between PM concentrations and the predictors were moderate and results were similar to a previous study predicting 24-h concentrations (Su et al., 2015).
References:
Gardner B, Ling F, Hopke PK, Frampton MW, Utell MJ, Zareba W, Cameron SJ, Chalupa D, Kane C, Ku-landhaisamy S, Topf M, Rich DQ. 2014. Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST-elevation myocardial infarction. Particle & Fibre Toxicology, 11, pp. 1.
Su JG, Hopke PK, Tian Y, Baldwin N, Thurston SW, Evans K and Rich DQ. 2015. Modeling particulate matter concentrations measured through mobile monitoring in a deletion/substitution/addition approach. Atmospheric Environment, 122, pp.477-483.
Wang Y, Hopke PK, Rattigan OV, Chalupa DC and Utell MJ. (2012a) Multiple-year black carbon measurements and source apportionment using delta-C in Rochester, New York. J Air Waste Manag Assoc. 62:880-887.
Wang Y, Hopke PK, Xia X, Rattigan OV, Chalupa DC and Utell MJ. (2012b) Source apportionment of airborne particulate matter using inorganic and organic species as tracers. Atmospheric Environment. 55:525-532.
Acknowledgements:
This work was supported by the New York State Energy Research and Development Authority (NYSERDA) under agreement 63040
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Characterizing indoor-outdoor PM relationships using low cost monitors during two heating seasons in Rochester, New York
No full textSUMMARY
The overall goal of this project is to obtain a better understanding of community-wide indi-vidual exposures to residential wood smoke such that the impacts of wood combustion emis-sions on human health and the environment can be more accurately assessed. The study confirmed that low cost PM sensors can be utilized to provide spatially and temporally re-solved PM data. The results showed increases in PM associated with indoor combustion sources as well as daily and weekly patterns of occupancy and typical activity patterns.
1 INTRODUCTION
During the last decade, there has been a substantial rise in the use of wood for space and water heating in North America. Wood combustion is a major source of airborne PM and related pollutants during the heating season in Rochester, NY (Wang et al., 2012). Since health outcomes may be triggered by hourly PM exposures (e.g., Gardner et al., 2014), tem-porally and spatially resolved estimates of wood smoke exposure are needed to assess whether health outcomes may be impacted by this source specific PM a few hours after ex-posure.
2 METHODS
Continuous 1-minute indoor and outdoor PM and indoor CO concentrations were measured from November through April of 2015/16 and 2016/17 at 50 residences across Monroe County, near Rochester, New York (25 residences per season). Inclusion criteria for the study were homes that had wood burning appliances or homes for which the residents smelled wood smoke in the vicinity of their homes. Low cost Speck monitors (Airviz Inc., Carnegie Mellon University, Pittsburgh, PA), which use an infra-red LED-based Samyoung (South Korea) DSM501A dust sensor (size range 0.5 to 3 μm), were deployed for PM moni-toring. CO was measured using data loggers with electrochemical sensors (EL-USB-CO, Lascar Electronics, Erie, PA). During the second season, a thermocouple with a datalogger was attached to the wood burning appliance to record when the appliance was in use.
3 RESULTS AND DISCUSSION
The results of this study confirmed that wood-burning appliances increased indoor expo-sures to airborne particles in homes. Increases in wood-burning appliance temperature and indoor CO concentrations were associated with significant increases in indoor PM2.5 concen-trations. Other indoor PM sources include other combustion sources (e.g., gas stoves, can-dles) as well as non-combustions sources (e.g., cleaning). The mean indoor/outdoor (I/O) PM ratio was 1.7 for all homes, which increased to 2.5 when a combustion source was pre-sent (Figure 1).
The link between human activity patterns and PM concentrations can be seen in the daily and weekly concentration cycles (Figure 2), with higher concentrations recorded during the weekends when people are expected to be home more. The daily pattern showed clear morn-ing and evening peaks. Hourly patterns on Saturdays and Sundays showed a peak that coin-cided with expected increased human activities in the home. Because concentrations meas-ured during the study were often lower than the nominal detection limit of the Speck PM monitors, and many combustion particles are in the size range below the nominal 0.5 μm sensor lower limit of detection, the estimated PM concentrations produced by wood combus-tion sources are likely to have been underestimated in this study.
5 CONCLUSIONS
The outcome of the study provides improved estimated exposures at any given time during the heating season for these individuals. Future studies may use this approach for exposure assessment in combination with health outcomes
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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