Aircraft-based measurements of methane (CH4) and other air pollutants in the Athabasca Oil Sands Region (AOSR) were made during a summer intensive field campaign between 13 August and 7 September 2013 in support of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring. Chemical signatures were used to identify CH4 sources from tailings ponds (BTEX VOCs), open pit surface mines (NOy and r BC) and elevated plumes from bitumen upgrading facilities (SO2 and NOy). Emission rates of CH4 were determined for the five primary surface mining facilities in the region using two mass-balance methods. Emission rates from source categories within each facility were estimated when plumes from the sources were spatially separable. Tailings ponds accounted for 45% of total CH4 emissions measured from the major surface mining facilities in the region, while emissions from operations in the open pit mines accounted for +/- 50 %. The average open pit surface mining emission rates ranged from 1.2 to 2.8 t of CH4 h(-1) for different facilities in the AOSR. Amongst the 19 tailings ponds, Mildred Lake Settling Basin, the oldest pond in the region, was found to be responsible for the majority of tailings ponds emissions of CH4 (> 70 %). The sum of measured emission rates of CH4 from the five major facilities, 19.2 +/- 1.1 tCH(4) h(-1), was similar to a single mass-balance determination of CH4 from all major sources in the AOSR determined from a single flight downwind of the facilities, 23.7 +/- 3.7 tCH(4) h(-1). The measured hourly CH4 emission rate from all facilities in the AOSR is 48 +/- 8% higher than that extracted for 2013 from the Canadian Greenhouse Gas Reporting Program, a legislated facility-reported emissions inventory, converted to hourly units. The measured emissions correspond to an emissions rate of 0.17 +/- 0.01 TgCH(4) yr(-1) if the emissions are assumed as temporally constant, which is an uncertain assumption. The emission rates reported here are relevant for the summer season. In the future, effort should be devoted to measurements in different seasons to further our understanding of the seasonal parameters impacting fugitive emissions of CH4 and to allow for better estimates of annual emissions and year-to-year variability.
We study the effects of infrared radiation on a two-dimensional Bardeen–Cooper–Schrieffer superconductor coupled with a normal metal substrate through a tunneling barrier. The phase transition is analyzed by inspecting the stability of the system against perturbations of pairing potentials. We find an oscillating gap phase with a frequency not directly related to the radiation frequency, but instead resulting from the asymmetry of electron density of states of the system as well as the tunneling amplitude. When such a superconductor is in contact with another superconductor, gives rise to an unusual alternating Josephson current .
The North China Plain has been identified as a significant hotspot of ammonia (NH3) due to extensive agricultural activities. Satellite observations suggest a significant increase of about 30% in tropospheric gas-phase NH3 concentrations in this area during 2008-2016. However, the estimated NH3 emissions decreased slightly by 7% because of changes in Chinese agricultural practices, i.e., the transition in fertilizer types from ammonium carbonate fertilizer to urea, and in the livestock rearing system from free-range to intensive farming. We note that the emissions of sulfur dioxide (SO2) have rapidly declined by about 60% over the recent few years. By integrating measurements from ground and satellite, a long-term anthropogenic NH3 emission inventory, and chemical transport model simulations, we find that this large SO2 emission reduction is responsible for the NH3 increase over the North China Plain. The simulations for the period 2008-2016 demonstrate that the annual average sulfate concentrations decreased by about 50 %, which significantly weakens the formation of ammonium sulfate and in- creases the average proportions of gas-phase NH3 within the total NH3 column concentrations from 26% (2008) to 37% (2016). By fixing SO2 emissions of 2008 in those multi-year simulations, the increasing trend of the tropospheric NH3 concentrations is not observed. Both the decreases in sulfate and increases in NH3 concentrations show highest values in summer, possibly because the formation of sulfate aerosols is more sensitive to SO2 emission reductions in summer than in other seasons. Besides, the changes in NOx emissions and meteorological conditions both decreased the NH3 column concentrations by about 3% in the study period. Our simulations suggest that the moderate reduction in NOx emissions (16 %) favors the formation of particulate nitrate by elevating ozone concentrations in the lower troposphere.
Economic, policy, and climate changes have profoundly influenced pastoral social-ecological systems on the Tibetan Plateau. Climate change is believed to be leading to increasing extreme weather conditions such as snow disasters and droughts, putting a strain on the rangeland resources herders must have to increase income. Market-based economic reforms and interrelated development policies such as the Rangeland Household Contract Policy, the Ecological Construction Project, and herder settlement Initiatives have increased integration of pastoral regions into modern markets with promotion of tourism, expanded livestock markets, and marketing opportunities for rangeland resources. Although allocating common rangelands to households is the foundation of current rangeland management strategies to achieve these goals, it removes important technologies for coping with high variability in rangeland forage production from the traditional rangeland management portfolio on the Tibetan Plateau. These include shared risk, shared labor, seasonal and yearly herd mobility, and access to diverse areas of rangelands and multiple water sources. Field study of two villages in Guinan County of Qinghai Province, and Ruoergai County of Sichuan Province from 2011 to 2014 found that the villages responded to externally driven policy, economic, and climate changes with an innovative locally adapted quota-based grazing management system that preserves valuable management technologies, conserves rangeland resources, and provides individual opportunities for financial gain. In this way the village social-ecological system has exhibited considerable resiliency, maintaining a form of community governance that functions to manage the rangelands, improve well-being as indicated by livestock productivity, and, according to local perceptions, maintain rangeland condition. The community-based grazing quota system devised by the villages occupies a middle ground between common and individual models for resource use because it focuses more on how to equitably distribute services and utilities from rangelands, instead of how to distribute rangelands.
Background: Oxidative stress is involved in thoracic diseases and health responses to air pollution. Malondialdehyde (MDA) is a well-established marker of oxidative stress, but it may be present in unconjugated and conjugated forms. To our knowledge, no studies have conducted a systemic evaluation of both free MDA (unconjugated MDA) and total MDA (the sum of both unconjugated and conjugated MDA) across various types of human biospecimens.Methods: Free MDA and total MDA were simultaneously measured in a range of human biospecimens, including nasal fluid (N=158), saliva (N=158), exhaled breath condensate (N=40), serum (N=232), and urine (N=429). All samples were analyzed using an HPLC-fluorescence method with high sensitivity and specificity. Due to the right skewed distribution of free MDA and total MDA, we performed natural-log transformation before subsequent statistical analyses. The relationship between the natural log of free and total MDA was evaluated by R-2 of simple linear regression. T test was used for comparisons of means between two groups. One-way analysis of variance was used in combination with Tukey's test to compare the natural log of the ratio of free MDA to total MDA across various types of biospecimens.Results: For exhaled breath condensate, serum, urine, nasal fluid and saliva samples, the R-2 between free and total MDA were 0.61, 0.22, 0.59, 0.47 and 0.06, respectively; the medians of the free MDA to total MDA ratio were 48.1%, 17.4%, 9.8%, 5.1% and 3.0%, respectively; the free MDA to total MDA ratio in EBC > serum > urine > nasal fluid > saliva (P < 0.001 for pairwise comparisons).Conclusions: For exhaled breath condensate and urine samples, using either free or total MDA can provide information regarding the level of oxidative stress; however, that is not the case for serum, nasal fluid, and saliva given the low correlations between free and total MDA.