Black carbon particulate matter emission factors for buoyancy-driven associated gas flares

Flaring is a technique used extensively in the oil and gas industry to burn unwanted flammable gases. Oxidation of the gas can preclude emissions of methane (a potent greenhouse gas); however, flaring creates other pollutant emissions such as particulate matter (PM) in the form of soot or black carbon (BC). Currently available PM emissionfactors for flares were reviewed and found to be questionably accurate, or based on measurements not directly relevant to open-atmosphere flares. In addition, most previous studies of soot emissions from turbulent diffusion flames considered alkene or alkyne based gaseous fuels, and few considered mixed fuels in detail and/or lower sooting propensity fuels such as methane, which is the predominant constituent of gas flared in the upstream oil and gas industry. Quantitative emission measurements were performed on laboratory-scale flares for a range of burner diameters, exit velocities, and fuel compositions. Drawing from established standards, a sampling protocol was developed that employed both gravimetric analysis of filter samples and real-time measurements of soot volume fraction using a laser-induced incandescence (LII) system. For the full range of conditions tested (burner inner diameter [ID] of 12.7-76.2 mm, exit velocity 0.1-2.2 m/sec, 4- and 6-component methane-based fuel mixtures representative of associated gas in the upstream oil industry), measured soot emission factors were less than 0.84 kg soot/10(3) m3 fuel. A simple empirical relationship is presented to estimate the PM emission factor as a function of the fuel heating value for a range of conditions, which, although still limited, is an improvement over currently available emission factors.     

Defining core outcomes of reproductive genetic carrier screening: A Delphi survey of Australian and New Zealand stakeholders

Objective

Understanding the value, benefits and harms of health interventions is needed to inform best practice and ensure responsible implementation of new approaches to patient care. Such value is demonstrated through the assessment of outcomes; however, which outcomes are assessed is often highly varied across studies and can hinder the ability to draw robust conclusions. The Core Outcome Development for Carrier Screening study aims to understand the outcomes that can meaningfully capture the value of reproductive genetic carrier screening (RGCS).

Method

The authors report an iterative, two-round online Delphi survey of Australian and New Zealand stakeholders to determine the degree of consensus regarding the core outcomes of RGCS. Panellists ranked 83 outcomes according to their perceived importance on a nine-point Likert scale. Using the distribution of rankings, outcomes were grouped into tiers representative of their perceived level of importance and agreement between groups.

Results

The top tier outcomes represent those agreed to be critically important for all future studies of RGCS to assess and were used to define a preliminary core outcome set encompassing the domains (1) primary laboratory outcomes, (2) pregnancy outcomes, (3) resource use and, (4) perceived utility of RGCS.

Conclusion

These findings can guide the selection of meaningful outcomes in studies aiming to demonstrate the value of RGCS. A future international consensus process will expand on these findings and guide the inclusion of diverse perspectives across the range of settings in which RGCS is offered.     

Changes in Tundra Pond Limnology: Re-sampling Alaskan Ponds After 40 Years

The arctic tundra ponds at the International Biological Program (IBP) site in Barrow, AK, were studied extensively in the 1970s; however, very little aquatic research has been conducted there for over three decades. Due to the rapid climate changes already occurring in northern Alaska, identifying any changes in the ponds’ structure and function over the past 30–40 years can help identify any potential climate-related impacts. Current research on the IBP ponds has revealed significant changes in the physical, chemical, and biological characteristics of these ponds over time. These changes include increased water temperatures, increased water column nutrient concentrations, the presence of at least one new chironomid species, and increased macrophyte cover. However, we have also observed significant annual variation in many measured variables and caution that this variation must be taken into account when attempting to make statements about longer-term change. The Barrow IBP tundra ponds represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure and function. Continued monitoring and protection of these invaluable sites is required to help understand the implications of climate change on freshwater ecosystems in the Arctic.     

Role of protein, amino acids, and enzyme activity on odor production from anaerobically digested and dewatered biosolids.

The main objective of this research was to test the hypothesis that bioavailable protein and, more specifically, the sulfur-containing amino acids within the protein, can be degraded by proteolytic enzymes to produce odor-causing compounds--mainly volatile sulfur compounds (VSCs)--during biosolids storage. To achieve these objectives, samples of digester effluent and cake solids were collected at 11 different wastewater treatment plants in North America, and the samples were analyzed for protein and amino acid content and general protein-degrading enzyme activity. At the same time, cake samples were stored using headspace bottles, the concentration of VSCs were measured using gas chromatography, and olfactometry measurements were made by a trained odor panel. The results showed that the bound cake protein content and methionine content was well-correlated with VSC production and the detection threshold measured by the odor panel.     

Organophosphate Residues in Grasshoppers from Sprayed Rangelands

Grasshoppers (Orthoptera) were collected in pastures that had been sprayed with malathion and acephate to estimate the secondary exposure of insectivorous birds to those pesticides. Residues of malathion were below 3 ppm at 30 and 54 hours after spraying and no malaoxon was detected. In contrast, acephate was found at 8 and 9 ppm 4 hours after spray; 3-5 ppm of the toxic metabolite methamidophos were also detected at that time. By 53 hours postspray, acephate levels declined to 2 ppm and methamidophos to less than 1 ppm. These results suggest that although malathion may not be a hazard to insectivorous species, acephate may be hazardous through metabolic transformation to methamidophos.     

An analysis of the Canadian Research and Development System for Agriculture/Food

The report entitled An Analysis of the Canadian Research and Development System for Agriculture/Food which was presented to the Science Council of Canada in July, 1991 contains many far-reaching recommendations for revisions of the research and educational components of the Agriculture/Food System in Canada. The report calls for research of holistic and interdisciplinary nature. It calls for determination of research priorities by broadly constituted committees which would include reporesentaitves heretofore not included in the process of decisionmaking regarding scientific research. In addition, it calls for restructuring of the agricultural education system. The Co-editors of this Journal, believe that these recommendations should be wildely discussed and, therefore, requested publication of the Executive Summary of this Report.