Methyl bromide: Ocean sources, ocean sinks, and climate sensitivity

The oceans play an important role in the geochemical cycle of methyl bromide (CH_3Br), the major carrier of O_3-destroying bromine to the stratosphere. The quantity of CH_3Br produced annually in seawater is comparable to the amount entering the atmosphere each year from natural and anthropogenic sources. The production mechanism is unknown but may be biological. Most of this CH_3Br is consumed in situ by hydrolysis or reaction with chloride. The size of the fraction which escapes to the atmosphere is poorly constrained; measurements in seawater and the atmosphere have been used to justify both a large oceanic CH_3Br flux to the atmosphere and a small net ocean sink. Since the consumption reactions are extremely temperature-sensitive, small temperature variations have large effects on the CH_3Br concentration in seawater, and therefore on the exchange between the atmosphere and the ocean. The net CH_3Br flux is also sensitive to variations in the rate of CH_3Br production. We have quantified these effects using a simple steady state mass balance model. When CH_3Br production rates are linearly scaled with seawater chlorophyll content, this model reproduces the latitudinal variations in marine CH_3Br concentrations observed in the east Pacific Ocean by Singh et al. [1983] and by Lobert et al. [1995]. The apparent correlation of CH_3Br production with primary production explains the discrepancies between the two observational studies, strengthening recent suggestions that the open ocean is a small net sink for atmospheric CH_3Br, rather than a large net source. The Southern Ocean is implicated as a possible large net source of CH_3Br to the atmosphere. Since our model indicates that both the direction and magnitude of CH_3Br exchange between the atmosphere and ocean are extremely sensitive to temperature and marine productivity, and since the rate of CH_3Br production in the oceans is comparable to the rate at which this compound is introduced to the atmosphere, even small perturbations to temperature or productivity can modify atmospheric CH_3Br. Therefore atmospheric CH_3Br should be sensitive to climate conditions. Our modeling indicates that climate-induced CH_3Br variations can be larger than those resulting from small (±25%) changes in the anthropogenic source, assuming that this source comprises less than half of all inputs. Future measurements of marine CH_3Br, temperature, and primary production should be combined with such models to determine the relationship between marine biological activity and CH_3Br production. Better understanding of the biological term is especially important to assess the importance of non anthropogenic sources to stratospheric ozone loss and the sensitivity of these sources to global climate change

Adsorption of HO_x on Aerosol Surfaces: Implications for the Atmosphere of Mars

The potential impact of heterogeneous chemistry on the abundance and distribution of HO_x in the atmosphere of Mars has been assessed by combining observational data of dust and ice aerosol distributions with an updated photochemical model. Critical parameters include the altitude distributions of aerosols, and the surface loss coefficients (γ) of HO_2 on dust and ice in the lower atmosphere, and H on ice above 40 km. We find that adsorption of HO_2 on dust (γHO_2 ≥ 0.01), or ice near 30 km (γHO_2 ≥ 0.1), can deplete OH abundances in the lower atmosphere by 10% or more. Such depletions approach those obtained by lowering the water vapor abundance by an order of magnitude below the global average observed by Viking (≈ 25%). Since the oxidation of CO is catalyzed by HO_x in the lower atmosphere via the reaction CO + OH → CO_2 + H, loss of OH due to adsorption of HO_2 on dust or ice at low altitudes could have a significant effect on the ratio CO : CO_2. The adsorption of H on ice at 50 km (γ_H ≥ 0.01) can result in even larger OH depletions. However, this effect is localized to altitudes > 40 km, where CO oxidation is relatively unimportant. Laboratory data suggest that γHO_2 ≈ 0.01 is a reasonable estimate for adsorption on dust. Larger values are plausible, but are not strongly supported by experimental evidence. The reactivity of HO_2 on ice is unknown, while γH on ice appears to be < 0.001. There is a need for measurements of HO_x adsorption on surfaces representative of Martian aerosols at temperatures < 220 K

Molybdenum evidence for expansive sulfidic water masses in ~750Ma oceans

The Ediacaran appearance of large animals, including motile bilaterians, is commonly hypothesized to reflect a physiologically enabling increase in atmospheric and oceanic oxygen abundances (pO2). To date, direct evidence for low oxygen in pre-Ediacaran oceans has focused on chemical signatures in the rock record that reflect conditions in local basins, but this approach is both biased to constrain only shallower basins and statistically limited when we seek to follow the evolution of mean ocean chemical state through time. Because the abundance and isotopic composition of molybdenum (Mo) in organic-rich euxinic sediments can vary in response to changes in global redox conditions, Mo geochemistry provides independent constraints on the global evolution of well-oxygenated environments. Here, we establish a theoretical framework to access global marine Mo cycle in the past from the abundance and isotope composition of ancient seawater. Further, we investigate the ~ 750 Ma Walcott Member of the Chuar Group, Grand Canyon, which accumulated in a rift basin with open connection to the ocean. Iron speciation data from upper Walcott shales indicate that local bottom waters were anoxic and sulfidic, consistent with their high organic content (up to 20 wt.%). Similar facies in Phanerozoic successions contain high concentrations of redox-sensitive metals, but in the Walcott Member, abundances of Mo and U, as well as Mo/TOC (~ 0.5 ppm/wt.%) are low. δ98Mo values also fall well below modern equivalents (0.99 ± 0.13‰ versus ~ 2.35‰ today). These signatures are consistent with model predictions where sulfidic waters cover ~ 1–4% of the global seafloor, corresponding to a ~ 20–80 fold increase compared to the modern ocean. Therefore, our results suggest globally expansive sulfidic water masses in mid-Neoproterozoic oceans, bridging a nearly 700 million-year gap in previous Mo data. We propose that anoxic and sulfidic (euxinic) conditions governed Mo cycling in the oceans even as ferruginous subsurface waters re-appeared 800–750 Ma, and we interpret this anoxic ocean state to reflect a markedly lower atmospheric and oceanic O2 level, consistent with the hypothesis that pO2 acted as an evolutionary barrier to the emergence of large motile bilaterian animals prior to the Ediacaran Period.Organismic and Evolutionary Biolog

Using Natural Stable Calcium Isotopes to Rapidly Assess Changes in Bone Mineral Balance Using a Bed Rest Model to Induce Bone Loss

Metabolic bone diseases like osteoporosis result from the disruption of normal bone mineral balance (BMB) resulting in bone loss. During spaceflight astronauts lose substantial bone. Bed rest provides an analog to simulate some of the effects of spaceflight; including bone and calcium loss and provides the opportunity to evaluate new methods to monitor BMB in healthy individuals undergoing environmentally induced-bone loss. Previous research showed that natural variations in the Ca isotope ratio occur because bone formation depletes soft tissue of light Ca isotopes while bone resorption releases that isotopically light Ca back into soft tissue (Skulan et al, 2007). Using a bed rest model, we demonstrate that the Ca isotope ratio of urine shifts in a direction consistent with bone loss after just 7 days of bed rest, long before detectable changes in bone mineral density (BMD) occur. The Ca isotope variations tracks changes observed in urinary N-teleopeptide, a bone resorption biomarker. Bone specific alkaline phosphatase, a bone formation biomarker, is unchanged. The established relationship between Ca isotopes and BMB can be used to quantitatively translate the changes in the Ca isotope ratio to changes in BMD using a simple mathematical model. This model predicts that subjects lost 0.25 0.07% ( SD) of their bone mass from day 7 to day 30 of bed rest. Given the rapid signal observed using Ca isotope measurements and the potential to quantitatively assess bone loss; this technique is well suited to study the short-term dynamics of bone metabolism

Childhood habit cough treated with consultation by telephone: a case report

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Childhood habit cough has been treated successfully by making suggestions that it can be stopped, desensitization techniques, use of distractors, provision of rewards, and selfhypnosis. All of these techniques have involved personal contact between a health care provider and a patient. Case presentation: A 5-year-old with cystic fibrosis was diagnosed with habit cough following evaluation by a pediatric pulmonologist and otolaryngologist. An expert in the treatment of habit cough provided instruction by telephone to the patient&apos;s mother regarding use of hypnotic techniques in this setting, which was associated with resolution of the cough within a week. Conclusion: As this report describes a single patient, it is possible that his improvement was unrelated to the given advice. Therefore, it remains to be seen whether therapy by telephone for habit cough is applicable widely. Background Childhood habit cough has been treated successfully b

Identification of children who may benefit from self-hypnosis at a pediatric pulmonary center

BACKGROUND: Emotional difficulties can trigger respiratory symptoms. Thus, children presenting with respiratory complaints may benefit from a psychological intervention. The purpose of this study was to define the proportion of patients referred to a Pediatric Pulmonary Center who may benefit from instruction in self-hypnosis, as a psychological intervention. METHODS: A retrospective chart review was conducted for all newly referred patients to the SUNY Upstate Medical University Pediatric Pulmonary Center during an 18 month period beginning January 1, 2000. Patients were offered hypnosis if they presented with symptoms or signs suggestive of psychological difficulties. Hypnosis was taught in one or two 15–45 minute sessions by a pediatric pulmonologist. RESULTS: Of 725 new referrals, 424 were 0–5 years old, 193 were 6–11 years old, and 108 were 12–18 years old. Diagnoses of anxiety, habit cough, or vocal cord dysfunction accounted for 1% of the 0–5 year olds, 20% of the 6–11 year olds, and 31% of the 12–18 year olds. Hypnotherapy was offered to 1% of 0–5 year olds, 36% of 6–11 year olds, and 55% of 12–18 year olds. Of 81 patients who received instruction in self-hypnosis for anxiety, cough, chest pain, dyspnea, or inspiratory difficulties, 75% returned for follow-up, and among the returning patients 95% reported improvement or resolution of their symptoms. CONCLUSION: A large number of patients referred to a Pediatric Pulmonary Center appeared to benefit from instruction in self-hypnosis, which can be taught easily as a psychological intervention

Hypnosis-associated blue-tinted vision: a case report

BACKGROUND: Self-hypnosis has been taught routinely at the SUNY Upstate Medical University for treatment of pulmonary symptoms thought to be amenable to psychological therapy. While using hypnosis for relaxation, four individuals, including a patient with cystic fibrosis, reported development of blue-tinted vision. Based on a search of the literature, we believe this is the first published report of hypnosis-associated blue-tinted vision. CASE PRESENTATION: The patient reported blue-tinted vision when he used hypnosis on an almost daily basis for seven years. The visual change typically occurred when he was relaxed. Moreover, a concurrent erection in the absence of sexual thoughts usually was present. The other three individuals reported blue-tinted vision after learning how to use hypnosis for relaxation as part of a group hypnosis instruction. CONCLUSION: The blue-tinted vision experienced by the individuals in this report may be the result of an hypnosis-induced primary change in cognitive processing. Additionally, as the relaxing effect of hypnosis can be associated with a reduction in blood pressure and increased blood flow, hypnosis-associated blue-tinted vision also may be related to retinal vasodilation

Rapidly Assessing Changes in Bone Mineral Balance Using Natural Stable Calcium Isotopes

We demonstrate that variations in the Ca isotope ratios in urine rapidly and quantitatively reflect changes in bone mineral balance. This variation occurs because bone formation depletes soft tissue of light Ca isotopes, while bone resorption releases that isotopically light Ca back into soft tissue. In a study of 12 individuals confined to bed rest, a condition known to induce bone resorption, we show that Ca isotope ratios shift in a direction consistent with net bone loss after just 7 days, long before detectible changes in bone density occur. Consistent with this interpretation, the Ca isotope variations track changes observed in N-teleopeptide, a bone resorption biomarker, while bone-specific alkaline phosphatase, a bone formation biomarker, is unchanged. Ca isotopes can in principle be used to quantify net changes in bone mass. Ca isotopes indicate an average loss of 0.62 +/- 0.16 % in bone mass over the course of this 30-day study. The Ca isotope technique should accelerate the pace of discovery of new treatments for bone disease and provide novel insights into the dynamics of bone metabolism

An Archean Biosphere Initiative

The search for life on extrasolar planets will necessarily focus on the imprints of biolgy on the composition of planetary atmospheres. The most notable biological imprint on the modern terrestrial atmosphere is the presence of 21 % O2, However, during most of the past 4 billion years, life and the surface environments on Earth were profoundly different than they are today. It is therefore a major goal of the astrobiology community to ascertain how the O2 content of the atmosphere has varied with time. and to understand the causes of these variations. The NAI and NASA Exobiology program have played critical roles in developing our current understanding of the ancient Earth's atmosphere, supporting diverse observational, analytical, and computational research in geoscience, life science, and related fields. In the present incarnation of the NAI, ongoing work is investigating (i) variations in atmospheric O2 in the Archean to the Cambrian, (ii) characterization of the redox state of the oceans shortly before, during and after the Great Oxidation Event (GOE), and (iii) unraveling the complex connections between environmental oxygenation, global climate, and the evolution of life