Compositions and greenhouse gas emission factors of flared and vented gas in the Western Canadian Sedimentary Basin

A significant obstacle in evaluating mitigation strategies for flaring and venting in the upstream oil and gas industry is the lack of publicly available data on the chemical composition of the gas. This information is required to determine the economic value of the gas, infrastructure and processing requirements, and potential emissions or emissions credits, all of which have significant impact on the economics of such strategies. This paper describes a method for estimating the composition of solution gas being flared and vented at individual facilities, and presents results derived for Alberta, Canada, which sits at the heart of the Western Canadian Sedimentary Basin. Using large amounts of raw data obtained through the Alberta Energy Resources Conservation Board, a relational database was created and specialized queries were developed to link production stream data, raw gas samples, and geography to create production-linked gas composition profiles for approximately half of the currently active facilities. These were used to create composition maps for the entire region, to which the remaining facilities with unknown compositions were geographically linked. The derived data were used to compute a range of solution gas composition profiles and greenhouse gas emission factors, providing new insight into flaring and venting in the region and enabling informed analysis of future management and mitigation strategies.

Implications: Accurate and transparent determination of environmental impacts of flaring and venting of gas associated with oil production, and potential benefits of mitigation, is severely hampered by the lack of publicly available gas composition data. In jurisdictions within the Western Canadian Sedimentary Basin, frameworks exist for regulating and trading carbon offset credits but current potential for mitigation is limited by a lack of standardized methods for calculating CO₂ equivalent emissions. The composition and emission factor data derived in this paper will be useful to industry, regulators, policy researchers, and entrepreneurs seeking statistically significant and openly available data necessary to manage and mitigate upstream flaring and venting activity and estimate greenhouse gas impacts.     

Inhomogeneity of methane emissions from a dairy waste lagoon

Methane (CH₄) is the dominant greenhouse gas emitted by animal agriculture manure. Since the gas is relatively insoluble in water, it is concentrated in discrete bubbles that rise through waste lagoons and burst at the surface. This results in lagoon emissions that are inhomogeneous in both space and time. Emissions from a midwestern dairy waste lagoon were measured over 2 weeks to evaluate the spatial homogeneity of the source emissions and to compare two methods for measuring this inhomogeneous emission. Emissions were determined using an inverse dispersion model based on CH₄ concentrations measured both by a single scanning tunable diode laser (TDL) aimed at a series of reflectors and by flame ionization detection (FID) gas chromatography on line-sampled air. Emissions were best estimated using scanned TDL concentrations over relatively short optical paths that collectively span the entire cross-wind width of the source, so as to provide both the best capture of discrete plumes from the bursting bubbles on the lagoon surface and the best detection of CH₄ background concentrations. The lagoon emissions during the study were spatially inhomogeneous at hourly time scales. Partitioning the inhomogeneous source into two source regions reduced the estimated emissions of the overall lagoon by 57% but increased the variability. Consequently, it is important to assess the homogeneity of a source prior to measurements and final emissions calculation.

Implications: Plans for measuring methane emissions from waste lagoons must take into account the spatial inhomogeneity of the source strength. The assumption of emission source homogeneity for a low-solubility gas such as CH₄ emitted from an animal waste lagoon can result in significant emission overestimates. The entire breadth and length of the area source must be measured, preferably with multiple optical paths, for the detection of discrete plumes from the different emitting regions and for determining the background concentration. Other gases with similarly poor solubility in water may also require partitioning of the lagoon source area.     

Chemical speciation of PM2.5 and PM10 in south Phoenix, AZ, USA

Phoenix, AZ, experiences high particulate matter (PM) episodes, especially in the wintertime. The spatial variation of the PM concentrations and resulting differences in exposure is of particular concern. In this study, PM2.s (PM with aerodynamic diameter <2.5 microm) and PM10 (PM with aerodynamic diameter <10 microm) samples were collected simultaneously from the east and west sides of South Phoenix and at a control site in Tempe and analyzed for trace elements and bulk elemental and organic carbon. Measurements showed that although PM2.5 concentrations had similar trends in temporal scale across all sites, concentrations of PM10 did not. The difference in PM10 concentrations and fluctuation across the three sites suggest effects of a local soil source as evidenced by high concentrations of Al, Ca, and Fe in PM10. K and anthropogenic elements (e.g., Cu, Pb, and Zn) in PM2.5 samples on January 1 were strikingly high, suggesting the influence of New Year's fireworks. Concentrations of toxic elements (e.g., Pb) in the study presented here are not different from similar studies in other U.S. cities. Application of principal component analysis indicated two broad categories of emission sources--soil and combustion--together accounting for 80 and 90% of variance, respectively, in PM2.5 and PM10. The soil and combustion components explained approximately 60 and 30% of the variance in PM10, respectively, whereas combustion sources dominated PM2.5 (>50% variance). Many elements associated with anthropogenic sources were highly enriched, with enrichment factors in PM2.5 an order of magnitude higher than in PM10 relative to surface soil composition in the study area.     

Vascular function and short-term exposure to fine particulate air pollution

Exposure to fine particulate air pollution has been implicated as a risk factor for cardiopulmonary disease and mortality. Proposed biological pathways imply that particle-induced pulmonary and systemic inflammation play a role in activating the vascular endothelium and altering vascular function. Potential effects of fine particulate pollution on vascular function are explored using controlled chamber exposure and uncontrolled ambient exposure. Research subjects included four panels with a total of 26 healthy nonsmoking young adults. On two study visits, at least 7 days apart, subjects spent 3 hr in a controlled-exposure chamber exposed to 150-200 microg/m3 of fine particles generated from coal or wood combustion and 3 hr in a clean room, with exposure and nonexposure periods alternated between visits. Baseline, postexposure, and post-clean room reactive hyperemia-peripheral arterial tonometry (RH-PAT) was conducted. A microvascular responsiveness index, defined as the log of the RH-PAT ratio, was calculated. There was no contemporaneous vascular response to the few hours of controlled exposure. Declines in vascular response were associated with elevated ambient exposures for the previous 2 days, especially for female subjects. Cumulative exposure to real-life fine particulate pollution may affect vascular function. More research is needed to determine the roles of age and gender, the effect of pollution sources, the importance of cumulative exposure over a few days versus a few hours, and the lag time between exposure and response.     

An analysis of flaring and venting activity in the Alberta upstream oil and gas industry

Alberta, Canada, is an important global producer of petroleum resources. In association with this production, large amounts of gas (1.14 billion m3 in 2008) are flared or vented. Although the amount of flaring and venting has been measurably reduced since 2002, data from 2005 reveal sharp increases in venting, which have important implications in terms of resource conservation and greenhouse gas emissions (which exceeded 8 million tonnes of carbon dioxide equivalent in 2008). With use of extensive monthly production data for 18,203 active batteries spanning the years 2002-2008 obtained in close cooperation with the Alberta Energy Resources Conservation Board, a detailed analysis has been completed to examine activity patterns of flaring and venting and reasons behind these trends in the Alberta upstream oil and gas industry. In any given year, approximately 6000 batteries reported flaring and/or venting, but the distribution of volumes flared and vented at individual sites was highly skewed, such that small numbers of sites handled large fractions of the total gas flaring and venting in the Province. Examination of month-to-month volume variability at individual sites, cast in terms of a nominal turndown ratio that would be required for a compressor to capture that gas and direct it into a pipeline, further revealed that volumes at a majority of sites were reasonably stable and there was no evidence that larger or more stable sites had been preferentially reduced, leaving potential barriers to future mitigation. Through linking of geospatial data with production data coupled with additional statistical analysis, the 31.2% increase in venting volumes since 2005 was revealed to be predominantly associated with increased production of heavier oils and bitumen in the Lloydminster region of the Province. Overall, the data suggest that quite significant reductions in flaring and venting could be realized by seeking mitigation solutions for only the largest batteries in the Province.     

Tetracycline photolysis in natural waters: loss of antibacterial activity

Previous work has shown that tetracycline undergoes direct photolysis in the presence of sunlight, with the decomposition rate highly dependent on conditions such as water hardness and pH. The purpose of this study was to examine the potential long-term significance of photoproducts formed when tetracycline undergoes photodegradation under a range of environmentally relevant conditions. Tetracycline was photolyzed in nine different natural and artificial water samples using simulated sunlight. The pH values of the samples ranged from 5 to 9. Total hardness values (combined Ca²⁺ and Mg²⁺ concentrations) varied from 30 to 450 ppm. Assays based on growth inhibition of two bacterial strains, Escherichia coli DH5α and Vibrio fischeri, were used to determine the antibacterial activity of tetracycline’s photoproducts in these water samples. In all tested conditions, it was determined that the photoproducts retain no significant antibacterial activity; all observed growth inhibition was attributable to residual tetracycline. This suggests that tetracycline photoproducts formed under a wide range of pH and water hardness conditions will not contribute to the selection of antibiotic-resistant bacteria in environmental systems.     

Management Implications of the Response of Two Tilapiine Cichlids to Long-Term Changes in Lake Level,Allodiversity and Exploitation in an Equatorial Lake

The tilapiine cichlids Oreochromis leucostictus and Tilapia zillii were introduced into Lake Naivasha, Kenya, in 1956. Previous studies on data collected to 1987 revealed they were persistent following establishment, despite environmental variability and exploitation. Recent data, however, suggest this persistence is under threat as data indicate some significant declines in aspects of their abundance since 1999. The influence of changes in lake level, allodiversity and fishing effort on this decline was tested and showed that a decline in lake level was a significant causal factor. The recent change in allodiversity, with the establishment and dominance of Cyprinus carpio in the fishery, was not significant on the catch per unit effort of O. leucostictus but was on T. zillii. Since 1999, catches of tilapiines in the fishery have been independent of fishing effort, contrary to between 1975 and 1987, suggesting their management through application of fishery models may no longer be applicable. As it was anthropogenic-mediated lake level changes that were mainly responsible for their decline, then lake management should focus on sustainable water utilization that maximizes lake levels in accordance with the basin-wide water balance.     

Knowledge coproduction on the impact of decisions for waterbird habitat in a changing climate

Scientists, resource managers, and decision makers increasingly use knowledge coproduction to guide the stewardship of future landscapes under climate change. This process was applied in the California Central Valley (USA) to solve complex conservation problems, where managed wetlands and croplands are flooded between fall and spring to support some of the largest concentrations of shorebirds and waterfowl in the world. We coproduced scenario narratives, spatially explicit flooded waterbird habitat models, data products, and new knowledge about climate adaptation potential. We documented our coproduction process, and using the coproduced models, we determined when and where management actions make a difference and when climate overrides these actions. The outcomes of this process provide lessons learned on how to cocreate usable information and how to increase climate adaptive capacity in a highly managed landscape. Actions to restore wetlands and prioritize their water supply created habitat outcomes resilient to climate change impacts particularly in March, when habitat was most limited; land protection combined with management can increase the ecosystem's resilience to climate change; and uptake and use of this information was influenced by the roles of different stakeholders, rapidly changing water policies, discrepancies in decision-making time frames, and immediate crises of extreme drought. Although a broad stakeholder group contributed knowledge to scenario narratives and model development, to coproduce usable information, data products were tailored to a small set of decision contexts, leading to fewer stakeholder participants over time. A boundary organization convened stakeholders across a large landscape, and early adopters helped build legitimacy. Yet, broadscale use of climate adaptation knowledge depends on state and local policies, engagement with decision makers that have legislative and budgetary authority, and the capacity to fit data products to specific decision needs.     

超高效液相色谱/电喷雾串联质谱(UPLC/MS/MS)分析全氟代化合物(PFCs)

近年来,在全球范围内的环境和人体血液中检测到全氟代化合物(PFCs)增长的趋势,引起了研究者和有关当局的关注.PFCs同时具有亲水性和疏水性,经常用于地毯、纤维、皮革的处理、纸张和食品包装物等,也是塑料生产、灭火剂、抛光剂和杀虫剂的功能化学品.