Bromine, iodine and sodium along the EAIIST traverse: Bulk and surface snow latitudinal variability.

During the East Antarctic International Ice Sheet Traverse (Eaiist, december 2019), in an unexplored part of the East Antarctic Plateau, snow samples were collected to expand our knowledge of the latitudinal variability of iodine, bromine and sodium as well as their relation in connection with emission processes and photochemical activation in this unexplored area. A total of 32 surface (0-5 cm) and 32 bulk (average of 1 m depth) samples were taken and analysed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our results show that there is no relevant latitudinal trend for bromine and sodium. For bromine they also show that it has no significant post-depositional mechanisms while its inland surface snow concentration is influenced by spring coastal bromine explosions. Iodine concentrations are several orders of magnitude lower than bromine and sodium and they show a decreasing trend in the surface samples concentration moving southward. This suggests that other processes affect its accumulation in surface snow, probably related to the radial reduction in the ozone layer moving towards central Antarctica. Even though all iodine, bromine and sodium present similar long-range transport from the dominant coastal Antarctic sources, the annual seasonal cycle of the ozone hole over Antarctica increases the amount of UV radiation (in the 280-320 nm range) reaching the surface, thereby affecting the surface snow photoactivation of iodine. A comparison between the bulk and surface samples supports the conclusion that iodine undergoes spring and summer snow recycling that increases its atmospheric lifetime, while it tends to accumulate during the winter months when photochemistry ceases.

Author Correction: 2600-years of stratospheric volcanism through sulfate isotopes.

The authors became aware of a mistake in the data and axis labeling in Fig. 2 in the original version of the Article. Specifically, the authors mistakenly copied and pasted a formula for background correction instead of the actual values. As a result of this, Fig. 3 was updated to replace the incorrect label 'sulfate flux (kg km-2)' with the correct 'sulfate concentrations (ng g-1)' on the far-left y-axes in both panels, and to add the correct data for Δ33S, as given by the red dotted lines. The correct version of Fig. 3 is shown below as Fig. 1, which replaced the previous incorrect version, shown below as Fig. 2. This has been corrected in both the PDF and the HTML versions of the Article. The findings and interpretations in the original Article are based on the correct dataset, and this error does not affect the original discussion or conclusions of the Article. The authors apologize for the confusion caused by this mistake.

2600-years of stratospheric volcanism through sulfate isotopes.

High quality records of stratospheric volcanic eruptions, required to model past climate variability, have been constructed by identifying synchronous (bipolar) volcanic sulfate horizons in Greenland and Antarctic ice cores. Here we present a new 2600-year chronology of stratospheric volcanic events using an independent approach that relies on isotopic signatures (Δ33S and in some cases Δ17O) of ice core sulfate from five closely-located ice cores from Dome C, Antarctica. The Dome C stratospheric reconstruction provides independent validation of prior reconstructions. The isotopic approach documents several high-latitude stratospheric events that are not bipolar, but climatically-relevant, and diverges deeper in the record revealing tropospheric signals for some previously assigned bipolar events. Our record also displays a collapse of the Δ17O anomaly of sulfate for the largest volcanic eruptions, showing a further change in atmospheric chemistry induced by large emissions. Thus, the refinement added by considering both isotopic and bipolar correlation methods provides additional levels of insight for climate-volcano connections and improves ice core volcanic reconstructions.

Microorganisms in dry polar snow are involved in the exchanges of reactive nitrogen species with the atmosphere.

The snowpack is a complex photochemical reactor that emits a wide variety of reactive molecules to the atmosphere. In particular, the photolysis of nitrate ions, NO(3)(-), produces NO, NO(2), and HONO, which affects the oxidative capacity of the atmosphere. We report measurements in the European High Arctic where we observed for the first time emissions of NO, NO(2), and HONO by the seasonal snowpack in winter, in the complete or near-complete absence of sunlight and in the absence of melting. We also detected unusually high concentrations of nitrite ions, NO(2)(-), in the snow. These results suggest that microbial activity in the snowpack is responsible for the observed emissions. Isotopic analysis of NO(2)(-) and NO(3)(-) in the snow confirm that these ions, at least in part, do not have an atmospheric origin and are most likely produced by the microbial oxidation of NH(4)(+) coming from clay minerals into NO(2)(-) and NO(3)(-). These metabolic pathways also produce NO. Subsequent dark abiotic reactions lead to NO(2) and HONO production. The snow cover is therefore not only an active photochemical reactor but also a biogeochemical reactor active in the cycling of nitrogen and it can affect atmospheric composition all year round.

The NO+O3 reaction: a triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly.

Atmospheric nitrate shows a large oxygen isotope anomaly (Delta 17 O), characterized by an excess enrichment of 17 O over 18 O, similar to the ozone molecule. Modeling and observations assign this specific isotopic composition mainly to the photochemical steady state that exists in the atmosphere between ozone and nitrate precursors, namely, the nitrogen oxides (NOx=NO+NO2). However, this transfer is poorly quantified and is built on unverified assumptions about which oxygen atoms of ozone are transferred to NO(x), greatly weakening any interpretation of the nitrate oxygen isotopic composition in terms of chemical reaction pathways and the oxidation state of the atmosphere. With the aim to improve our understanding and quantify how nitrate inherits this unusual isotopic composition, we have carried out a triple isotope study of the reaction NO+O3. Using ozone intramolecular isotope distributions available in the literature, we have found that the central atom of the ozone is abstracted by NO with a probability of (8+/-5)%(+/-2 sigma) at room temperature. This result is at least qualitatively supported by dynamical reaction experiments, the non-Arrhenius behavior of the kinetic rate of this reaction, and the kinetic isotope fractionation factor. Finally, we have established the transfer function of the isotope anomaly of O3 to NO2, which is described by the linear relationship Delta 17 O(NO2)=A x Delta 17 O(O3)+B, with A=1.18+/-0.07(+/-1 sigma) and B=(6.6+/-1.5)[per thousand](+/-1 sigma). Such a relationship can be easily incorporated into models dealing with the propagation of the ozone isotope anomaly among oxygen-bearing species in the atmosphere and should help to better interpret the oxygen isotope anomaly of atmospheric nitrate in terms of its formation reaction pathways.

Sulfur and oxygen isotope analysis of sulfate at micromole levels using a pyrolysis technique in a continuous flow system.

The discovery of a mass-independent isotopic composition (delta17O = (delta17O - 0.512 * delta18O) no equal to 0) in aerosol sulfate and the identification of its origin (aqueous-phase oxidation by 03 and H2O2) have renewed interest in measuring the oxygen isotopic content of sulfate. In this paper, we present a new method to measure both delta17O and delta18O in SO4, with the possibility of sulfur isotope analysis on the same sample. The technique takes advantage of the easy pyrolysis of Ag2SO4 to SO2, O2, and Ag metal in a continuous flow system. Because the technique is not quantitative in oxygen (yield approximately 45% for O2), a calibration is needed. Correction factors of +0.87 and +0.44% were obtained for delta18O and delta17O, respectively. A technique to convert micromole levels of sulfate in any form to silver sulfate is described. To reach this goal, a solid electrolyte (Nafion membrane) is used in an electrolysis apparatus. Reproducibilities for micromole sample sizes are (1sigma) 0.5, 0.3, and 0.1% for delta18O, delta17O, and delta17O, respectively. No memory effects or isotopic exchange during the treatment of the sample is observed. The main advantages of this new method over the existing ones are no fluorinating agent is needed, both oxygen and sulfur isotopes can be measured on the same sample, only very small amounts of sulfate are needed (down to 100 microg (1 micromol)), it is relatively fast and inexpensive, and the possibility exists to couple this technique to an on-line analysis.

Mass-independent isotopic compositions in terrestrial and extraterrestrial solids and their applications.

In 1983, Thiemens and Heidenreich reported the first chemically produced mass-independent isotope effect. This work has been shown to have a wide range of applications, including atmospheric chemistry, solar system evolution, and chemical physics. This work has recently been reviewed (Weston, R. E. Chem. Rev. 1999, 99, 2115-2136; Thiemens, M. H. Science 1999, 283, 341-345). In this Account, observations of mass-independent isotopic compositions in terrestrial and Martian solids are reviewed. A wide range of applications, including formation and transport of aerosols in the present atmosphere, chemistry of ancient atmospheres and oceans, history and coupling of the atmosphere-surface in the Antarctic dry valleys, origin and evolution of oxygen in the Earth's earliest environment, and the chemistry of the atmosphere and surface of Mars, are discussed.

Use of a clinical event monitor to prevent and detect medication errors.

Errors in health care facilities are common and often unrecognized. We have used our clinical event monitor to prevent and detect medication errors by scrutinizing electronic messages sent to it when any medication order is written in our facility. A growing collection of medication safety rules covering dose limit errors, laboratory monitoring, and other topics may be applied to each medication order message to provide an additional layer of protection beyond existing order checks, reminders, and alerts available within our computer-based record system. During a typical day the event monitor receives 4802 messages, of which 4719 pertain to medication orders. We have found the clinical event monitor to be a valuable tool for clinicians and quality management groups charged with improving medication safety.

Evidence of atmospheric sulphur in the martian regolith from sulphur isotopes in meteorites.

Sulphur is abundant at the martian surface, yet its origin and evolution over time remain poorly constrained. This sulphur is likely to have originated in atmospheric chemical reactions, and so should provide records of the evolution of the martian atmosphere, the cycling of sulphur between the atmosphere and crust, and the mobility of sulphur in the martian regolith. Moreover, the atmospheric deposition of oxidized sulphur species could establish chemical potential gradients in the martian near-surface environment, and so provide a potential energy source for chemolithoautotrophic organisms. Here we present measurements of sulphur isotopes in oxidized and reduced phases from the SNC meteorites--the group of related achondrite meteorites believed to have originated on Mars--together with the results of laboratory photolysis studies of two important martian atmospheric sulphur species (SO2 and H2S). The photolysis experiments can account for the observed sulphur-isotope compositions in the SNC meteorites, and so identify a mechanism for producing large abiogenic 34S fractionations in the surface sulphur reservoirs. We conclude that the sulphur data from the SNC meteorites reflects deposition of oxidized sulphur species produced by atmospheric chemical reactions, followed by incorporation, reaction and mobilization of the sulphur within the regolith.

Predicting hospitalization and functional decline in older health plan enrollees: are administrative data as accurate as self-report?

OBJECTIVE: To compare the predictive accuracy of two validated indices, one that uses self-reported variables and a second that uses variables derived from administrative data sources, to predict future hospitalization. To compare the predictive accuracy of these same two indices for predicting future functional decline. DESIGN: A longitudinal cohort study with 4 years of follow-up. SETTING: A large staff model HMO in western Washington State. PARTICIPANTS: HMO Enrollees 65 years and older (n = 2174) selected at random to participate in a health promotion trial and who completed a baseline questionnaire. MEASUREMENT: Predicted probabilities from the two indices were determined for study participants for each of two outcomes: hospitalization two or more times in 4 years and functional decline in 4 years, measured by Restricted Activity Days. The two indices included similar demographic characteristics, diagnoses, and utilization predictors. The probabilities from each index were entered into a Receiver Operating Characteristic (ROC) curve program to obtain the Area Under the Curve (AUC) for comparison of predictive accuracy. RESULTS: For hospitalization, the AUC of the self-report and administrative indices were .696 and .694, respectively (difference between curves, P = .828). For functional decline, the AUC of the two indices were .714 and .691, respectively (difference between curves, P = .144). CONCLUSIONS: Compared with a self-report index, the administrative index affords wider population coverage, freedom from nonresponse bias, lower cost, and similar predictive accuracy. A screening strategy utilizing administrative data sources may thus prove more valuable for identifying high risk older health plan enrollees for population-based interventions designed to improve their health status.

Development of a clinical event monitor for use with the Veterans Affairs Computerized Patient Record System and other data sources.

We are developing an event monitor to operate with the Veterans Affairs Computerized Patient Record System (CPRS). The event monitor is designed to receive messages when important patient events such as posting of new results, patient movement, and orders occur. Our design separates the event monitor from CPRS itself, using communication via a network connection to receive HL7 messages, to access other data needed to run rules, and to communicate with providers by message display, electronic mail and other mechanisms. Results from operation of the event monitor using patient data in our test account show that a wide variety of data can be accessed by the event monitor with acceptable response times.

The association between the purchase of a handgun and homicide or suicide.

OBJECTIVES: The purpose of this study was to determine whether purchase of a handgun from a licensed dealer is associated with the risk of homicide or suicide and whether any association varies in relation to time since purchase. METHODS: A case-control study was done among the members of a large health maintenance organization. Case subjects were the 353 suicide victims and 117 homicide victims among the members from 1980 through 1992. Five control subjects were matched to each case subject on age, sex, and zip code of residence. Handgun purchase information was obtained from the Department of Licensing. RESULTS: The adjusted relative risk of suicide was 1.9 (95% confidence interval [CI] = 1.4, 2.5) for persons with a history of family handgun purchase from a registered dealer. The adjusted relative risk for homicide, given a history of family handgun purchase, was 2.2 (95% CI = 1.3, 3.7). For both suicide and homicide, the elevated relative risks persisted for more than 5 years after the purchase. CONCLUSIONS: Legal purchase of a handgun appears to be associated with a long-lasting increased risk of violent death.

Conflicting national recommendations and the use of screening mammography: does the physician's recommendation matter?

BACKGROUND: This study evaluated whether women's perceptions of the conflicting recommendations for breast cancer screening were associated with decreased use of mammography. METHODS: We conducted a random-digit-dial telephone survey of 1024 women in four communities of western Washington State. In addition to collecting data for demographics, beliefs about mammography, and insurance coverage, we inquired whether the respondents were aware of any conflicting recommendations about when to begin or how frequently to perform screening mammography, whether their physicians had recommended a mammogram, and whether they were likely to do what their physicians recommended. After grouping women according to whether they perceived conflicting recommendations, we used chi-square statistics to compare the distribution of proportions of women by age, race, household income, education, and insurance coverage. To estimate the odds of their having a mammogram in the previous 2 years (yes or no), we used multivariate logistic regression and included the above variables as covariates. RESULTS: Sixty-two percent of eligible women completed the survey, and 49 percent (479 of 985) perceived conflicting recommendations. The association between perceiving conflict and mammography use was not significant. Eighty-three percent of women who perceived conflicting recommendations reported being more comfortable using their own judgment about getting the procedure. After controlling for whether women perceived conflicting recommendations and all other factors, women who said they followed their physician's advice but did not recall their physician recommending mammography were 71 percent less likely to have received a recent mammogram than were women who reported their physician did recommend it (odds ratio 0.29, confidence interval 0.16-0.51). CONCLUSIONS: The conflicting recommendations surrounding breast cancer screening are not influencing women's choices about mammography. The physician recommendation and women's self-reported likeliness to follow it are the most important factors associated with mammography use.

Practicing population-based care in an HMO: evaluation after 18 months.

OBJECTIVE: To determine whether population-based care in a primary care practice results in improvement in compliance with patient care guidelines. DESIGN: Time series analysis. SETTING: One primary care practice in Group Health Cooperative of Puget Sound (GHC). PARTICIPANTS: Approximately 1500 enrollees cared for by the practice. INTERVENTIONS: An ongoing approach to aid clinical planning at the level of the primary care team--population-based care--that depends on clinical guidelines, a computing system to provide epidemiologic data on guideline performance in the practice and reminders, and a process whereby the practice team analyzed and designs interventions for specific clinical problems. MAIN OUTCOME MEASURES: We compared compliance with practice guidelines for preventive care and chronic illness management at baseline and after 18 months in the intervention population with other patients in the same clinic and with patients in GHC as a whole. RESULTS: Compliance with breast cancer screening and colorectal cancer screening guidelines in the intervention population increased from baseline 32% and 18% respectively. These increases were significantly greater than in the remainder of the clinic or in GHC as a whole. CONCLUSIONS: The availability of practice-based data, clinical guidelines and a local intervention design process resulted in significant improvements in compliance with patient care guidelines.

Factors influencing the duration of work-related disability: a population-based study of Washington State workers' compensation.

OBJECTIVES: The purpose of this study was to examine factors predictive of duration of work-related disability. METHODS: Multivariate survival analysis techniques were used to conduct a population-based, retrospective cohort study on a random sample of 28,473 workers' compensation claims from Washington State filed for injuries occurring in 1987 to 1989. The principal outcome measure was length of time for which compensation for lost wages was paid, used as a surrogate for duration of temporary total disability. RESULTS: The findings suggest that, even after adjusting for severity of injury, older age, female gender, and a diagnosis of carpal tunnel syndrome or back/neck sprain significantly predict longer duration of disability. Other predictors that were stable and significant, but involved lower magnitudes of effect included divorced marital status, firm size of fewer than 50 employees, higher country unemployment rates, and construction and agricultural work. CONCLUSIONS: Greater disability prevention efforts targeting these higher risk subgroups could have significant economic and public health effects. The greatest impact may be on claimants who remain disabled at 6 months after an injury that did not require hospitalization.

Cost of VA adult day health care programs and their effect on utilization and cost of care.

The VA-ADHC Evaluation included a detailed assessment of the cost of the VA-ADHC programs and an evaluation of their effect on patients' utilization and costs of other health care services. Although each VA-ADHC program had little variation in its program costs over the 3 years of the study, there were large variations between the programs in total costs, their costs per patient day, and in some cost components. The 3 most important factors in determining the level of program costs were: the way patients were transported to and from ADHC, the availability of space to house the program, and the staff-to-patient ratio. The total cost of health care for patients randomly assigned to VA-ADHC was significantly (15.5%) higher than those assigned to customary care. Although ADHC care did substitute for certain other forms of care (i.e., home care and clinic visits), there was not enough of a substitution effect to offset the additional costs of ADHC services.