Environmental controls on methane (CH4) emission from lakes are poorly understood at subdaily time scales due to a lack of continuous data, especially for ebullition. We used a novel technique to ...partition eddy covariance CH4 flux observed in the littoral zone of a midlatitude shallow lake in Japan and examined the environmental controls on diffusion and ebullitive CH4 flux separately at a subdaily time scale in different seasons. Using the high‐frequency data, we investigated how CH4 accumulation in the water and sediment layers alters the dynamics and environmental controls of fluxes. The contribution of ebullitive flux to total flux was 57% on average. Environmental controls of diffusive and ebullitive fluxes known in the literature were confirmed. We further found that the environmental controls were different in different seasons and suggested that additional consideration of CH4 accumulation could explain the variability. The transfer of accumulated dissolved CH4 from the bottom water layer to the surface in summer and the accumulation of dissolved CH4 under surface ice in winter were suggested to be important for explaining the variability of diffusive flux. In summer, a higher ebullitive flux tended to occur following triggers such as a decrease in hydrostatic pressure. In winter, the impact of triggers was not obvious, and a higher ebullitive flux tended to occur in the morning. We suggested that the low CH4 production rate in winter slowed the replenishment of bubbles in the sediment, negating the effect of triggers on ebullition.
Plain Language Summary
Lakes are one of the main natural sources of methane (CH4). Methane is emitted from lake sediments to the atmosphere via diffusion through the water column and episodic emission of bubbles (ebullition). Currently, environmental controls at subdaily time scales are poorly understood due to a lack of continuous data, especially for ebullition. We applied a new technique to partition continuous CH4 flux data obtained with the eddy covariance technique in a midlatitude shallow lake into diffusive and ebullitive fluxes and examined their environmental controls separately. We confirmed that the diffusive flux increased with increasing wind speed and increasing dissolved CH4 concentrations in the surface water as known in the literature. We further suggested that for this shallow lake, the transfer of accumulated dissolved CH4 from the bottom water layer to the surface under thermally stratified conditions was important for explaining the variability in diffusive flux. In summer, a higher ebullitive flux tended to occur following a decrease in hydrostatic pressure. In winter, however, the impact of triggers was not obvious. We suggested that, in winter, the low CH4 production rate slowed the replenishment of bubbles in the sediment, negating the effect of triggers on ebullition.
Key Points
Partitioned diffusive and ebullitive methane fluxes from a shallow lake were examined for their subdaily environmental controls
The subdaily environmental controls of diffusive and ebullitive fluxes were different in different seasons
The accumulations of methane in the water and sediment were suggested to alter the environmental controls of fluxes between seasons
ABSTRACT
Objectives Coronary artery disease and osteoporosis increase in women after menopause. Computed tomography (CT) scans of the heart used to evaluate coronary arterial calcification include ...images of the thoracic vertebrae. The utility of using these images to assess bone health in women remains to be defined. Analyses of thoracic spine volumetric bone mineral density (vBMD) from CT scans of the heart were performed to determine how specific calibration affects the ability to assess vBMD in recently menopausal women and to evaluate how vBMD relates to areal bone mineral density (aBMD) using dual-energy X-ray absorptiometry (DEXA).
Methods Women (n = 111) enrolled in the Kronos Early Estrogen Prevention Study (KEEPS) at Mayo Clinic underwent a CT scan of the heart that included calibration phantoms and a DEXA of the lumbar spine. The Spine Cancer Assessment program was used to determine vBMD of thoracic vertebrae with and without the calibration correction.
Results Trabecular bone vBMD at T8 averaged 163.57±28.58 and 157.94±27.55 mg/cc (mean±standard deviation, SD) for calibrated and uncalibrated values, respectively. The relationship between calibrated and uncalibrated measures approached unity (R = 0.98). Lumbar spine (L2-4) aBMD was 1.19±0.16 g/cm2 (mean±SD). Both calibrated and uncalibrated thoracic vBMD correlated positively and significantly with lumbar aBMD, but the relationship was less than unity (R = 0.63).
Conclusion Uncalibrated measures of thoracic spine vBMD obtained from CT scans of the heart may provide clinically relevant information about bone health and osteoporosis/osteopenia risk in recently menopausal women.
We found that aquatic crustaceans, decapoda; atyidae (
Caridina multidentata,
Neocaridina denticulate, and
Paratya compressa), metabolize pyrene to a new conjugation product. The results of ...deconjugation treatments indicated that glucose and sulfate combined with 1-hydroxypyrene. Further analysis by LC/ESI-MS/MS showed that the molecular weight of the product was 460 (
m/
z 459; deprotonated ion), and that it has a glucose–sulfate moiety (
m/
z 241; fragment ion). These results indicated that the new metabolite was the glucose–sulfate conjugate of 1-hydroxypyrene. The glucose–sulfate conjugate is a phase II product that has not been reported previously from any organism. Several studies have demonstrated that sulfation is an important pathway for metabolism of xenobiotics in aquatic invertebrates. Thus, glucose–sulfate conjugates may add an important signal for excretion or sequestration of xenobiotics for aquatic invertebrates.
To elucidate the historical changes in polychlorinated dibenzo-
p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), coplanar polychlorinated biphenyl (co-PCB), and polycyclic aromatic hydrocarbon ...(PAH) inflows in Lake Suwa, their concentrations in the sediment core were analyzed in 5
cm interval. The maximum concentrations (depth cm) of PCDDs/DFs, co-PCBs, and PAHs were 25.2
ng/g dry (30–35
cm), 19.0
ng/g dry (30–35
cm), and 738, 795
ng/g dry (50–55
cm, 30–35
cm), respectively. Age and sedimentation rate of the sediment were estimated from the vertical changes in apparent density. Deposition rate of dioxins and PAHs were calculated from the concentration and sedimentation rate of the sediment. The results indicate that large amounts of dioxins and PAHs flowed into the lake in flood stage compared to normal stage.
Large amounts of dioxins and PAHs flowed into a lake in flood events.
Effects of gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thyroid function of offspring were investigated in the rat. Pregnant Holtzman rats, TCDD-sensitive ...strain, were given a single oral dose of 200 ng or 800 ng TCDD/kg on gestational day 15. Parameters related to the thyroid functions were examined on postnatal days (PNDs) 21 and 49. Serum T4 levels in offspring decreased significantly on PND21 in the two TCDD-exposed groups but increased on PND 49 only in the high-dose group. A dose of 800 ng TCDD/kg exerted a more than 2-fold increase in serum TSH level in male offspring on PNDs 21 and 49. A significant induction of uridine diphosphate-glucuronosyltransferase-1 gene by TCDD was observed on PND 21 but returned to basal levels on PND 49. Gene expression of cytochrome P4501A1 was markedly induced in the liver treated with TCDD. Even a single oral perinatal exposure to 800 ng TCDD/kg resulted in hyperplasia of the thyroid gland of offspring on PND 49. Proliferating cell nuclear antigen immunocytochemistry also supported this finding. Thus, gestational and lactational exposure to TCDD was found to disrupt thyroid hormone homeostasis, which results in a sustained excessive secretion of TSH, followed by the hyperplasia of thyroid follicular cells.
Objectives Cardiovascular disease and osteoporosis increase in women after menopause. While aortic calcification is associated with bone loss in women, a similar relationship for coronary arterial ...calcification (CAC), a risk factor for coronary artery disease in women, is less clear. This study was designed to examine the relationship between CAC and volumetric bone mineral density (vBMD) in women (n = 137) who were within a median of 18 months past their last menses at screening for the Kronos Early Estrogen Prevention Study (KEEPS).
Methods CAC was measured using 64-slice computed tomography; vBMD was measured from these images using the Spine Cancer Assessment program. Concentrations of osteocalcin, bone alkaline phosphatase, tartrate-resident acid phosphatase-5b and osteopontin as bone matrix protein in serum and plasma were evaluated by ELISA.
Results CAC scores ranged from 0 to 327.6 Agatston Units (AU); 113 women had a score of 0 AU, 20 had a CAC score between 0 and 50 AU, and four had a CAC score > 50 AU. Although not statistically significant, there was a trend toward decreasing central density of thoracic T9 with increasing CAC. On average, levels of markers of bone turnover were within the normal range but did not correlate with age or with months past menopause.
Conclusions Clinically significant CAC and spine vBMD are quantifiable from the same scans within the first 3 years of menopause. Additional work is needed to determine how these measurements change with increasing age or with estrogenic treatments.
To elucidate whether immunoglobulin (Ig) E or IgG are involved in the murine asthma model, we compared the pathogenic features of mice that were high IgG responders (C3H/He) with mice that were high ...IgE responders (BALB/c) after intratracheal instillation of diesel exhaust particles (DEP) and ovalbumin sensitization. Both mouse strains received DEP intratracheally once a week for 5 weeks. After the second injection of DEP, ovalbumin and aluminium hydroxide were injected intraperitoneally. After the last DEP administration, the mice were challenged by exposure to an aerosol of ovalbumin. DEP caused increased IgG1 production and airway hyperresponsiveness after ovalbumin sensitization in C3H/He mice, although IgE production did not change in either strain. Furthermore, in C3H/He mice, the number of eosinophils and goblet cells in the bronchial epithelium, and the expression of interleukin-5 and interleukin-2 were increased by DEP and ovalbumin treatments. In contrast, the pathogenic changes in BALB/c mice were weak, even though the same protocol was used. In conclusion, murine strain differences in response to air pollutants and allergens seem to be related to antigen-specific immunoglobulin G1 production and cytokine expression in the lungs.
This article reports the organ distribution and bioaccumulation of hepatotoxic microcystins (MCs) in freshwater fishes at different trophic levels from the large, shallow, eutrophic Lake Chaohu in ...September 2003, when there were heavy surface blooms of toxic cyanobacteria. Among all fish, intestines and blood had the highest average content of MC-RR + MC-LR (22.0 and 14.5 microgram g(-1) DW, respectively), followed by liver, bile, and kidney (7.77, 6.32, and 5.81 microgram g(-1) DW, respectively), whereas muscle had the least (1.81 microgram g(-1) DW). MC content in muscle was highest in carnivorous fish (Culter ilishaeformis, 2.22 microgram g(-1) DW) and omnivorous fish (Carassius auratus, 1.96 microgram g(-1) DW) and was lowest in phytoplanktivorous fish (Hypophthalmichthys molitrix, 1.65 microgram g(-1) DW) and herbivorous fish (Parabramis pekinensis 0.660 microgram g(-1) DW). However, the amount of MC in the gut of H. molitrix (137 microgram g(-1) DW) was more than 20 times that in the other fish (<6.50 microgram g(-1) DW). The MCs showed a tendency to accumulate up the food chain, and piscivorous fish at the top of the food chain were at high risk of exposure to MCs in Lake Chaohu. Our study is the first to report MC concentrations in the bile and blood of wild fish. One hundred grams of fish muscle would contain 2.64-49.7 microgram of MC-LR equivalent, or about 1.3-25 times the recommended tolerable daily intake of MC-LR by humans, indicating that fish are already severely contaminated by MCs and that the local authorities should warn the public of the risk of poisoning by eating the contaminated fish.
Previous experimental studies have suggested that nasal instillation of diesel exhaust particles (DEP) can enhance nasal IgE response and cytokine production. However, there is no experimental ...evidence for the relation of DEP to allergic asthma. We investigated the effects of DEP inoculated intratracheally on antigen-induced airway inflammation, local expression of cytokine proteins, and antigen-specific immunoglobulin production in mice. DEP aggravated ovalbumin-induced airway inflammation characterized by infiltration of eosinophils and lymphocytes and an increase in goblet cells in bronchial epithelium. DEP with antigen markedly increased interleukin-5 (IL-5) protein levels in lung tissue and bronchoalveolar lavage supernatants compared with either antigen or DEP alone. The combination of DEP and antigen induced significant increases in local expression of IL-4, granulocyte macrophage-colony stimulating factor (GM-CSF), and IL-2, whereas expression of interferon-gamma was not affected. In addition, DEP exhibited adjuvant activity for the antigen-specific production of IgG and IgE. These results provide the first experimental evidence that DEP can enhance the manifestations of allergic asthma. The enhancement may be mediated mainly by the increased local expression of IL-5, and also by the modulated expression of IL-4, GM-CSF, and IL-2.
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