On the variability of simulated source-receptor relationships for sulfur deposition

The use of Lagrangian models to estimate source-receptor relationships for ambient SO 4 = concentrations and S deposition has become fairly widespread over the past several years. This paper addresses the sensitivity of long-term simulations of a Lagrangian S transport and deposition model to actual variations in SO 2 emissions and meteorological conditions. The variations of predicted source-receptor relationships due to (1) the inclusion of day to day variations in emissions strength as opposed to the use of the annual average daily emission rate and (2) year-to-year variations in meteorological conditions were studied to identify causes of uncertainty in a Lagrangian model. The results suggested that adding information on day to day emission variations for a specific point source resulted in variations in estimated S wet deposition of the order of only 20% within 500 km of the source.Year-to-year variations in meteorological conditions, on the other hand, resulted in variations in predicted S wet deposition of the order of 50% for some receptors. The variation in estimated source-receptor relationships for a given source/receptor combination was found to range as high as 70% over a 5-yr modeling period.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43900/1/11270_2004_Article_BF00303346.pd

Use of cluster analysis to define periods of similar meteorology and precipitation chemistry in eastern North America.

An aggregation approach is needed to overcome the prohibitive expense involved in exercising the Regional Acid Deposition Model to determine annual deposition loads in eastern North America. A necessary first step in this process is to identify those events which are representative of annual meteorology and to determine their frequencies and pollutant loadings. In this dissertation the statistical technique of cluster analysis is applied to transport vectors and precipitation chemistry data to identify and define representative periods for use in aggregation schemes. Transport vectors representing the travel of air masses in the twelve hours preceding their daily arrival at chemistry sampling sites were calculated for 1979, 1981 and 1983 from mixed-layer back trajectories, arranged in a three-day moving format, and subjected to cluster analysis. The mean transport vectors at twenty-two sites were plotted for each resulting cluster to examine their flow patterns. The associated precipitation and analyte deposition fields were also studied. The sensitivity of the clustering process to differing methods, different sites or number of sites and other factors was assessed. The resulting clusters represent groups whose mean air-mass transport fields are different from one another and correspond to weather situations seen on daily weather maps. The distributions of the transport variables are, in most cases, statistically significantly different from each other. The clusters were relatively insensitive to changes in number of sites or years used; however, different clustering methods yielded different results. The transport clusters were successful in defining wet, dry, polluted and non-polluted clusters in a median sense and in terms of significantly different distributions. The chemistry fields are a plausible result of the transport and persistence characteristics of each cluster. There was a large amount of overlap among the chemistry distributions and large variation within most of the clusters. Cluster analysis has been shown to he useful in the computer-assisted classification of spatial patterns of weather and pollution data and should be considered for use along with more widely used synoptic climatological tools such as principal component analysis and correlation analysis.Ph.D.Physics, Atmospheric ScienceUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161915/1/8821570.pd

A Critical Review of Four Types of Air Quality Models Pertinent to MMS Regulatory and Environmental Assessment Missions

This is a report covering the Minerals Management Service (MMS) is responsibility on leasing offshore lands for oil and gas exploration and development. The reports looks to expand air quality models

Escherichia coli sequence type 131 (ST131) subclone h30 as an emergent multidrug-resistant pathogen among US Veterans

Background. Escherichia coli sequence type 131 (ST131), typically fluoroquinolone-resistant (FQ-R) and/or extended-spectrum -lactamase (ESBL)-producing, has emerged globally. We assessed its prevalence and characteristics among US veterans.Methods. In 2011, 595 de-identified E. coli clinical isolates were collected systematically within 3 resistance groups (FQ-susceptible [FQ-S], FQ-R, and ESBL-producing) from 24 nationally distributed Veterans Affairs Medical Centers (VAMCs). ST131 and its H30 subclone were detected by polymerase chain reaction and compared with other E. coli for molecular traits, source, and resistance profiles.Results. ST131 accounted for 78% (184/236) of FQ-R and 64.2% (79/123) of ESBL-producing isolates, but only 7.2% (17/236) of FQ-S isolates (P \u3c. 001). The H30 subclone accounted for ≥95% of FQ-R and ESBL-producing, but only 12.5% of FQ-S, ST131 isolates (P \u3c. 001). By back-calculation, 28% of VAMC E. coli isolates nationally represented ST131. Overall, ST131 varied minimally in prevalence by specimen type, inpatient/outpatient source, or locale; was the most prevalent ST, followed distantly by ST95 and ST12 (13% each); and accounted for ≥40% (-lactams), \u3e50% (trimethoprim-sulfamethoxazole, multidrug), or \u3e70% (ciprofloxacin, gentamicin) of total antimicrobial resistance. FQ-R and ESBL-producing ST131 isolates had higher virulence scores than corresponding non-ST131 isolates. ST131 pulsotypes overlapped extensively among VAMCs.Conclusions. Among US veterans, ST131, primarily its H30 subclone, accounts for most antimicrobial-resistant E. coli and is the dominant E. coli strain overall. Possible contributors include multidrug resistance, extensive virulence gene content, and ongoing transmission. Focused attention to ST131, especially its H30 subclone, could reduce infection-related morbidity, mortality, and costs among veterans. © 2013 Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2013. This work is written by (a) US Government employee(s) and is in the public domain in the US

Escherichia coli Sequence Type 131 (ST131) Subclone H30 as an Emergent Multidrug-Resistant Pathogen Among US Veterans

Background. Escherichia coli sequence type 131 (ST131), typically fluoroquinolone-resistant (FQ-R) and/or extended-spectrum β-lactamase (ESBL)–producing, has emerged globally. We assessed its prevalence and characteristics among US veterans. Methods. In 2011, 595 de-identified E. coli clinical isolates were collected systematically within 3 resistance groups (FQ-susceptible [FQ-S], FQ-R, and ESBL-producing) from 24 nationally distributed Veterans Affairs Medical Centers (VAMCs). ST131 and its H30 subclone were detected by polymerase chain reaction and compared with other E. coli for molecular traits, source, and resistance profiles. Results. ST131 accounted for 78% (184/236) of FQ-R and 64.2% (79/123) of ESBL-producing isolates, but only 7.2% (17/236) of FQ-S isolates (P < .001). The H30 subclone accounted for ≥95% of FQ-R and ESBL-producing, but only 12.5% of FQ-S, ST131 isolates (P < .001). By back-calculation, 28% of VAMC E. coli isolates nationally represented ST131. Overall, ST131 varied minimally in prevalence by specimen type, inpatient/outpatient source, or locale; was the most prevalent ST, followed distantly by ST95 and ST12 (13% each); and accounted for ≥40% (β-lactams), >50% (trimethoprim-sulfamethoxazole , multidrug), or >70% (ciprofloxacin, gentamicin) of total antimicrobial resistance. FQ-R and ESBL-producing ST131 isolates had higher virulence scores than corresponding non-ST131 isolates. ST131 pulsotypes overlapped extensively among VAMCs. Conclusions. Among US veterans, ST131, primarily its H30 subclone, accounts for most antimicrobial-resistant E. coli and is the dominant E. coli strain overall. Possible contributors include multidrug resistance, extensive virulence gene content, and ongoing transmission. Focused attention to ST131, especially its H30 subclone, could reduce infection-related morbidity, mortality, and costs among veterans