A robust X-ray fluorescence technique for multielemental analysis of solid samples

X-ray fluorescence (XRF) quantitation software programs are widely used for analyzing environmental samples due to their versatility but at the expense of accuracy. In this work, we propose an accurate, robust, and versatile technique for multielemental X-ray fluorescence analytical applications, by spiking solid matrices with standard solutions. National Institute of Standards and Technology (NIST)-certified soil standards were spiked with standard solutions, mixed well, desiccated, and analyzed by an energy dispersive XRF. Homogenous targets were produced and low error calibration curves, for the added and not added, neighboring, elements, were obtained. With the addition of few elements, the technique provides reliable multielemental analysis, even for concentrations of the order of milligram per kilogram (ppm). When results were compared to the ones obtained from XRF commercial quantitation software programs, which are widely used in environmental monitoring and assessment applications, they were found to fit certified values better. Moreover, in all examined cases, results were reliable. Hence, this technique can also be used to overcome difficulties associated with interlaboratory consistency and for cross-validating results. The technique was applied to samples with an environmental interest, collected from a ship/boat repainting area. Increased copper, zinc, and lead loads were observed (284, 270, and 688 mg/kg maximum concentrations in soil, respectively), due to vessels being paint stripped and repainted

Global Oil Market and the U.S. Stock Returns

This paper provides an analysis of the link between the oil market and the U.S. stock market returns at the aggregate as well as industry levels. We empirically model oil price changes as driven by speculative demand shocks along with consumption demand and supply shocks in the oil market. We also take into account in our model all the factors that affect stock market price movements over and above the oil market, in order to quantify the pure effect of oil price shocks on returns. The results show that stock returns respond to oil price shocks differently, depending on the causes behind the shocks. Impulse response analysis suggests that consumption demand shocks are the most relevant drivers of the stock market return, relative to other oil market driven shocks. Industry level analysis is performed to control for the heterogeneity of the responses of returns to oil price changes. The results show that both cost side and demand side effects of oil price shocks matter for the responses of industries to oil price shocks. However, the main driver of the variation in industries’ returns is the shock to aggregate stock market