Implications of Organic Mass to Carbon Ratios Increasing Over Time in the Rural United States

The thermal evolution procedure used by most monitoring programs in the United States to determine carbonaceous aerosol concentrations is referred to as the thermal‐optical reflectance method, where an aerosol sample that has been collected on a quartz filter is heated and evolved carbon is characterized as either organic (OC) or light absorbing carbon (LAC). Evolved carbon assigned to OC is multiplied by a factor, Roc, to achieve an estimate of organic mass. Over the last 10–15 years, Roc, estimated through multiple linear regression analysis of data collected in the Interagency Monitoring of Protected Visual Environments (IMPROVE) program, has increased at about a rate of about 0.02 per year, reaching values above 2.0 in many regions of the United States. Analysis of evolved carbon concentration temporal trends suggests that thermal‐optical reflectance analysis, on the average, inaccurately bifurcates particulate carbon into the OC and LAC fractions with some LAC being inadvertently and wrongly assigned to the OC fraction. It is shown that misapportioned LAC assigned to OC is decreasing faster than true OC, resulting in a compensating increase in the Roc assigned to reported OC over time. A first‐order model is proposed to correct for the misapportioned carbon

Interactions between Simulant Vitrified Nuclear Wastes and high pH solutions: A Natural Analogue Approach

This study details the characterization of a glass sample exposed to hyperalkaline water and calcium-rich sediment for an extended time period (estimated as 2-70 years) at a lime (CaO) waste site in the UK. We introduce this site, known as Peak Dale, in reference to its use as a natural analogue for nuclear waste glass dissolution in the high pH environment of a cementitious engineered barrier of a geological disposal facility. In particular, a preliminary assessment of alteration layer chemistry and morphology is described and the initiation of a long-term durability assessment is outlined

Magmatism and metamorphism at ca. 1.45 Ga in the northern Gawler Craton: the Australian record of rifting within Nuna (Columbia)

U–Pb monazite and zircon geochronology and calculated metamorphic phase diagrams from drill holes in the northern Gawler Craton, southern Australia, reveal the presence of ca. 1.45 Ga magmatism and metamorphism. Magmatism and granulite facies metamorphism of this age has not previously been recognised in the Gawler Craton. The magmatic rocks have steep LREE-enriched patterns and high Ga/Al values, suggesting they are A-type granites. Calculated metamorphic forward models suggest that this event was associated with high apparent thermal gradients and reached pressures of 3.2–5.4 kbar and temperatures of 775–815 °C. The high apparent thermal gradients may reflect pluton-enhanced metamorphism, consistent with the presence of A-type granites. The recognition of ca. 1.45 Ga tectonism in the northern Gawler Craton is added to a compilation of ca. 1.50–1.40 Ga magmatism, shear zone reactivation, rift basin development and isotope resetting throughout the South and North Australian Cratons that shows that this event was widespread in eastern Proterozoic Australia. This event is stylistically similar to ca. 1.45 Ga A-type magmatism and high thermal gradient metamorphism in Laurentia in this interval and provides further support for a connection between Australia and Laurentia during the Mesoproterozoic. The tectonic setting of the 1.50–1.40 Ga event is unclear but may record rifting within the Nuna (or Columbia) supercontinent, or a period of intracontinental extension within a long-lived convergent setting.Laura J. Morrissey, Karin M. Barovich, Martin Hand, Katherine E. Howard, Justin L. Payn

Experiments in Bayesian Recommendation

The performance of collaborative filtering recommender systems can suffer when data is sparse, for example in distributed situations. In addition popular algorithms such as memory-based collaborative filtering are rather ad-hoc, making principled improvements difficult. In this paper we focus on a simple recommender based on naïve Bayesian techniques, and explore two different methods of modelling probabilities. We find that a Gaussian model for rating behaviour works well, and with the addition of a Gaussian-Gamma prior it maintains good performance even when data is sparse

Citizen Science 2.0 : Data Management Principles to Harness the Power of the Crowd

Citizen science refers to voluntary participation by the general public in scientific endeavors. Although citizen science has a long tradition, the rise of online communities and user-generated web content has the potential to greatly expand its scope and contributions. Citizens spread across a large area will collect more information than an individual researcher can. Because citizen scientists tend to make observations about areas they know well, data are likely to be very detailed. Although the potential for engaging citizen scientists is extensive, there are challenges as well. In this paper we consider one such challenge – creating an environment in which non-experts in a scientific domain can provide appropriate and accurate data regarding their observations. We describe the problem in the context of a research project that includes the development of a website to collect citizen-generated data on the distribution of plants and animals in a geographic region. We propose an approach that can improve the quantity and quality of data collected in such projects by organizing data using instance-based data structures. Potential implications of this approach are discussed and plans for future research to validate the design are described

Implications of Organic Mass to Carbon Ratios Increasing Over Time in the Rural United States

The thermal evolution procedure used by most monitoring programs in the United States to determine carbonaceous aerosol concentrations is referred to as the thermal‐optical reflectance method, where an aerosol sample that has been collected on a quartz filter is heated and evolved carbon is characterized as either organic (OC) or light absorbing carbon (LAC). Evolved carbon assigned to OC is multiplied by a factor, Roc, to achieve an estimate of organic mass. Over the last 10–15 years, Roc, estimated through multiple linear regression analysis of data collected in the Interagency Monitoring of Protected Visual Environments (IMPROVE) program, has increased at about a rate of about 0.02 per year, reaching values above 2.0 in many regions of the United States. Analysis of evolved carbon concentration temporal trends suggests that thermal‐optical reflectance analysis, on the average, inaccurately bifurcates particulate carbon into the OC and LAC fractions with some LAC being inadvertently and wrongly assigned to the OC fraction. It is shown that misapportioned LAC assigned to OC is decreasing faster than true OC, resulting in a compensating increase in the Roc assigned to reported OC over time. A first‐order model is proposed to correct for the misapportioned carbon