Constraining predictions of the carbon cycle using data

We use a carbon-cycle data assimilation system to estimate the terrestrial biospheric CO(2) flux until 2090. The terrestrial sink increases rapidly and the increase is stronger in the presence of climate change. Using a linearized model, we calculate the uncertainty in the flux owing to uncertainty in model parameters. The uncertainty is large and is dominated by the impact of soil moisture on heterotrophic respiration. We show that this uncertainty can be greatly reduced by constraining the model parameters with two decades of atmospheric measurements.     

Reverse Oxidation Zoning in Mine Tailings Generating Arsenic-rich Acidic Waters (Carnoulès,France)

The Carnoulès Pb mine closed 40 years ago, leaving tailings (pyrite-rich silts) exposed. In 1982, the tailings were gathered and placed behind a concrete dam, above a drainage pipe, and then covered with a clay layer. The As-rich pyrite in the tailings has oxidized; acidic water with high As concentrations (100–350 mg/L As) now emerges from the base of the dam. Strikingly, there is no oxidation zone at the surface of the tailings. The clay cover and the low hydraulic conductivity of most of the tailings (10⁻⁷ m/s) strongly limit rainwater infiltration. Water table variations, water balance calculations, and flow modelling indicate subsurface water input and water flow along the bedrock within a more permeable sandy horizon. This lower horizon is strongly oxidized due to this flow pattern. The As-rich water is mainly produced in the northern part of the tailings area, where seasonal variations in the water table (a succession of aerobic/anaerobic periods) are important. This water flows through a drainage pipe to an acidic spring. The disposal of tailings can release acidic and toxic waters into the environment. Monitoring and modelling of such tailings allow one to define the potential impact and propose remedies.     

Layer double hydroxides for enhanced poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) crystallization

Enabling the widespread utilization of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) is strongly associated with enhancing its crystallization kinetics. In this article, we utilize a highly surface active (one reactive group per nanometer square) anion exchanged layered‐double hydroxide (LDH) functionalized by stearic acid to probe the crystallization kinetics of PHBV. Our prior work has shown that the addition of LDH decreases the cold crystallization and induces a melt recrystallization peak in PHBV. Since the melt‐recrystallization temperature shifted to higher temperature and its corresponding enthalpy increased with increasing LDH loading, this article is focused on understanding the effect of LDH on kinetics and energetics of PHBV crystallization. Both Avrami and Lauritzen–Hoffman modeling are utilized to develop a comprehensive understanding of thermal history effects through differential scanning calorimetry and polarized optical microscopy measurements. Five concentrations by weight of LDH are used: 1, 3, 5, and 7%. The results show that the addition of LDH promoted both primary and secondary nucleation at low concentrations but additional LDH resulted in primary nucleation alone. The crystallization rate and activation energy show a significant increase, which is accompanied by a decrease in the nucleation constant, the surface energy and the work of chain folding for PHBV crystallization. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2013     

A Fitted L-Multi-Point Flux Approximation Method for Pricing Options

Computational Economics - In this paper, we introduce a special kind of finite volume method called Multi-Point Flux Approximation method (MPFA) to price European and American options in two...     

Contribution to the development of a method of maple sap soft drink stabilization by electro-activation technology

Electro-activation (EA) of a maple sap/syrup beverage was studied. The purpose of the study was to assess the product parameters, such as pH, ORP, transmittance and degree Brix, while minimizing energy consumption. The experiments were conducted using three different configurations of the reactor that differed by the position of the anion (AEM) and cation (CEM) exchange membrane relative to the electrodes as well as the nature of the electrolyte (NaCl vs. Na₂CO₃) in the central cell of the reactor. The results showed that the type of configuration, the electric current and the temperature influenced the parameters of the electro-activated beverage. At 23 °C, the beverage was acidified to pH 3.89 with a Redox potential (ORP) of 417.33 mV. At 55 °C and 150 mA, the minimum pH of 3.78 and an ORP of 329.67 mV were obtained. The electric resistance of the electro-activation reactor (EAR) decreased during electro-activation, indicating a gain of energy efficiency corresponding to an electric resistance of 266.76 Ω. Moreover, the reactor configuration and electric current affected the presence or absence of a fouling of the ion exchange membrane at the anodic side. The beverages' transmittance increased slightly during EA without any effect on the degree Brix.     

High-throughput trace analysis of explosives in water by laser diode thermal desorption/atmospheric pressure chemical ionization-tandem mass spectrometry

Harmful explosives can accumulate in natural waters in the long term during their testing, usage, storage, and dumping and can pose a health risk to humans and the environment. For the first time, attachment of small anions to neutral molecules in laser diode thermal desorption/atmospheric pressure chemical ionization was systematically investigated for the direct determination of trace nitroaromatics, nitrate esters, and nitramine explosives in water. Using ammonium chloride as an additive improved the instrument response for all the explosives tested and promoted the formation of several characteristic adduct ions. The method performs well achieving good linearity over at least 2 orders of magnitude, with coefficients of determination greater than 0.995. The resulting limits of detection are in the range of 0.009-0.092 μg/L. River water samples were successfully analyzed by the proposed method with accuracy in the range of 96-98% and a response time of 15 s, without any further pretreatment or chromatographic separation.     

Assessment of the bacteriological quality and nitrate pollution risk of Quaternary groundwater in the southern part of Abidjan District (Côte d’Ivoire)

In this study, total coliforms, thermotolerant coliforms, Escherichia coli and groundwater nitrate concentration were monitored at 127 groundwater sampling points (only 62 water points for bacteriological parameters) located in the southern part of Abidjan District. Each water sampling location was sampled in March and July 2007, representing respectively the long dry season and the long wet season. Geostatistical methods were used to analyze the spatial variability of nitrates and the groundwater nitrate pollution risk. The maximum seasonal content of total coliforms and thermotolerant coliforms ranged from 400 to 1000 CFU/100 mL and from 200 to 500 CFU/100 mL respectively. Moreover, 94% of these locations presented traces of bacteriological contamination. This contamination was mainly recorded during the rainy period. The degree of correlation between bacterial abundance and chemical parameters is variable. Nitrites, ammonium and potassium favoured coliform abundance. In the 127 water points, groundwater nitrate concentrations ranged from 4 to 198 mg L^?1 and were log-normally distributed in the study area. The groundwater contamination risk map indicated that the strongly urbanized west side of the site presented a high probability of exceeding the WHO drinking water standard (50 mg L^?1NO₃^?).