The chemistry of plutonium partitioning to an acidic, sandy sediment

Knowledge of the chemistry controlling the partitioning of actinides to soils and sediments in natural systems is essential for modeling their environmental fate and developing safe and cost-effective strategies for remediation. Plutonium (Pu) is known to cycle between sediments and the water column in warm, monomictic reservoirs. The geochemical processes that influence Pu mobility in such systems remain elusive; however, the mechanisms of sorption and release are controlled by the chemistry of the interaction between Pu and specific components of the sediment. Sequential extraction methods were used to elucidate Pu partitioning in a sediment matrix. Two sequential extraction methods were employed, and the methods provided similar results. The majority of the Pu was extracted from the bulk sediment by the treatment intended to target oxidizable components such as natural organic matter. Filter pore size was varied to study the effects of colloidal and suspended material. A fraction of the Pu in this sediment is colloidal, and that material is refractory rather than oxidizable. Finally, studies of Pu distributions in various particle size fractions of the sediment indicate isotopic fractionation with larger fractions of 238Pu being associated with smaller particles than 239+240Pu. When the amount of organic matter associated with each size fraction is considered, these studies suggest that the partitioning of 239+240Pu is more influenced by organic matter than the 238Pu. Based on these results the feasibility of ex-situ remediation technologies such as supercritical fluid extraction (SFE) is considered. Ligand assisted SFE was applied to this sediment, and changes in the partitioning of actinides and other metals was determined. This work suggests that under suitable chemical conditions, SFE can be used to extract many metal cations, including actinides, from the sediment while minimizing the generation of secondary waste streams

Gains and structural effects of exploiting scale-economies in Norwegian dairy production

In this paper, we present calculations of the economic gains in terms of reduced costs by exploiting scale-economies in dairy production in Norway, and the effect this would have had on the number of farms. We also explore whether or not optimal scale and unexploited scale-economies change over time due to scale-augmenting technical change. The analysis is based on homothetic cost functions estimated by means of data for individual dairy farms for the period 1972-1996. For 1972, we find that, by full exploitation of scale-economies, the costs could have been reduced by almost 40%, while the number of farms would have been reduced by more than 85%. The number of small farms has been substantially reduced in the period considered. This fact, combined with small scale-augmenting technical change, implies that the gains and structural effects of exploiting scale-economies have decreased over time. In 1996, costs could have been reduced by close to 30% by full exploitation of scale-economies, while the number of farms would have been reduced by slightly more than 70%. Thus, both gains and structural effects are substantially less than in 1972. Nevertheless, the calculated gains for 1996 make almost 5 billion NOK. This corresponds almost exactly to the total public support to the dairy farms in 1996. The unexploited scale-economies are largely due to the agricultural policy. Thus, a substantial share of the same can be considered as part of the 'price' the Norwegian society has to pay for this policy. In addition, there are likely to be large hidden costs of this policy due in particular to the quota system and other direct production regulations. They imply that technical innovations and other efficiency-improving investments requiring increased production to be profitable are not carried out. This is the more likely explanation for the extremely poor efficiency development in Norwegian dairy production in the period studied. © 2001 Elsevier Science B.V. All rights reserved

An empirical investigation of CPA firm attributes and professional liability coverage

The purpose of this study is to determine what variables are significant in predicting the type of professional liability insurance, if any, an accounting firm would have. The three dependent variables are firms that: purchased commercial liability insurance, are members of a captive company or risk retention group, and have no commercial liability insurance coverage. Independent variables include characteristics of the firm (form of the business, size of the firm) and of the client (recently merged clients, clients that are financial institutions). The study uses the multinomial logit model with maximum likelihood. The Hausman-McFadden test is used to test for independence of irrelevant alternatives. Various methods are used to detect multicollinearity, the most sophisticated of which is the Belsley, Kuh, and Welsch test. Correlation tables and stepwise backward elimination are also used. The seven significant variables identified by the model as useful for predictors are: (1) Is the firm a sole practitioner? (2) What is the size of the firm? (3) What is the firm\u27s review and compilation revenue as a percent of total revenue? (4) Does the firm audit, review, or compile for companies recently merged? (5) Does the firm perform a cold review of audits? (6) Does the firm evaluate new clients, and (7) Does the firm use engagement letters

Chemical extractions to determine metal partitioning to sediments and soils

Previously, we have reported on methods for sequential extractions to determine the partitioning of contaminants and stable elements within soils and sediments. Recently, we have explored single step extractions to obtain similar information. Using a well characterized pond sediment, we have applied single step extractions to remove stable metals partitioned as exchangeable metals, those metals associated with iron oxides, and those metals associated with natural organic matter. The results obtained using single extractions will be compared to observations made when a sequential extraction method is employed with the same sediment