Francesco De Simone

Development and application of a regional-scale atmospheric mercury model based on WRF/Chem: a Mediterranean area investigation

The emission, transport, deposition and eventual fate of mercury (Hg) in the Mediterranean area has been studied using a modified version of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem). This model version has been developed specifically with the aim to simulate the atmospheric processes determining atmospheric Hg emissions, concentrations and deposition online at high spatial resolution. For this purpose, the gas phase chemistry of Hg and a parametrised representation of atmospheric Hg aqueous chemistry have been added to the regional acid deposition model version 2 chemical mechanism in WRF/Chem. Anthropogenic mercury emissions from the Arctic Monitoring and Assessment Programme included in the emissions preprocessor, mercury evasion from the sea surface and Hg released from biomass burning have also been included. Dry and wet deposition processes for Hg have been implemented. The model has been tested for the whole of 2009 using measurements of total gaseous mercury from the European Monitoring and Evaluation Programme monitoring network. Speciated measurement data of atmospheric elemental Hg, gaseous oxidised Hg and Hg associated with particulate matter, from a Mediterranean oceanographic campaign (June 2009), has permitted the model’s ability to simulate the atmospheric redox chemistry of Hg to be assessed. The model results highlight the importance of both the boundary conditions employed and the accuracy of the mercury speciation in the emission database. The model has permitted the reevaluation of the deposition to, and the emission from, the Mediterranean Sea. In light of the well-known high concentrations of methylmercury in a number of Mediterranean fish species, this information is important in establishing the mass balance of Hg for the Mediterranean Sea. The model results support the idea that the Mediterranean Sea is a net source of Hg to the atmosphere and suggest that the net flux is ≈30 Mg year−1 of elemental Hg.

Model study of global mercury deposition from biomass burning

Mercury emissions from biomass burning are not well characterized and can differ significantly from year to year. This study utilizes three recent biomass burning inventories (FINNv1.0, GFEDv3.1, and GFASv1.0) and the global Hg chemistry model, ECHMERIT, to investigate the annual variation of Hg emissions, and the geographical distribution and magnitude of the resulting Hg deposition fluxes. The roles of the Hg/CO enhancement ratio, the emission plume injection height, the Hg(g)0 oxidation mechanism and lifetime, the inventory chosen, and the uncertainties with each were considered. The greatest uncertainties in the total Hg deposition were found to be associated with the Hg/CO enhancement ratio and the emission inventory employed. Deposition flux distributions proved to be more sensitive to the emission inventory and the oxidation mechanism chosen, than all the other model parametrizations. Over 75% of Hg emitted from biomass burning is deposited to the world’s oceans, with the highest fluxes predicted i...

A Modeling Comparison of Mercury Deposition from Current Anthropogenic Mercury Emission Inventories

Human activities have altered the biogeochemical cycle of mercury (Hg) since precolonial times, and anthropogenic activities will continue to perturb the natural cycle of Hg. Current estimates suggest the atmospheric burden is three to five times greater than precolonial times. Hg in the upper ocean is estimated to have doubled over the same period. The Minamata convention seeks to reduce the impact human activities have on Hg releases to the environment. A number of the Articles in the Convention concern the development of detailed inventories for Hg emissions and releases. Using the global Hg chemical transport model, ECHMERIT, the influence of the anthropogenic emission inventory (AMAP/UNEP, EDGAR, STREETS) on global Hg deposition patterns has been investigated. The results suggest that anthropogenic Hg emissions contribute 20-25% to present-day Hg deposition, and roughly two-thirds of primary anthropogenic Hg is deposited to the worlds oceans. Anthropogenic Hg deposition is significant in the North Pacific, Mediterranean and Arctic. The results indicate immediate reductions in Hg emissions would produce benefits in the short term, as well as in the long term. The most impacted regions would be suitable to assess changes in Hg deposition resulting from implementation of the Minamata convention.

Particulate-phase mercury emissions from biomass burning and impact on resulting deposition: a modelling assessment

Mercury (Hg) emissions from biomass burning (BB) are an important source of atmospheric Hg and a major factor driving the interannual variation of Hg concentrations in the troposphere. The greatest fraction of Hg from BB is released in the form of elemental Hg(Hg(g)0). However, little is known about the fraction of Hg bound to particulate matter (HgP) released from BB, and the factors controlling this fraction are also uncertain. In light of the aims of the Minamata Convention to reduce intentional Hg use and emissions from anthropogenic activities, the relative importance of Hg emissions from BB will have an increasing impact on Hg deposition fluxes. Hg speciation is one of the most important factors determining the redistribution of Hg in the atmosphere and the geographical distribution of Hg deposition. Using the latest version of the Global Fire Emissions Database (GFEDv4.1s) and the global Hg chemistry transport model, ECHMERIT, the impact of Hg speciation in BB emissions, and the factors which influence speciation, on Hg deposition have been investigated for the year 2013. The role of other uncertainties related to physical and chemical atmospheric processes involving Hg and the influence of model parametrisations were also investigated, since their interactions with Hg speciation are complex. The comparison with atmospheric HgP concentrations observed at two remote sites, Amsterdam Island (AMD) and Manaus (MAN), in the Amazon showed a significant improvement when considering a fraction of HgP from BB. The set of sensitivity runs also showed how the quantity and geographical distribution of HgP emitted from BB has a limited impact on a global scale, although the inclusion of increasing fractions HgP does limit Hg(g)0 availability to the global atmospheric pool. This reduces the fraction of Hg from BB which deposits to the world’s oceans from 71 to 62 %. The impact locally is, however, significant on northern boreal and tropical forests, where fires are frequent, uncontrolled and lead to notable Hg inputs to local ecosystems. In the light of ongoing climatic changes this effect could be potentially be exacerbated in the future.

Short-term stock price prediction using MLP in moving simulation mode

The features of a short-term prediction of a stock price using a multi-layer perceptron in a moving simulation application mode are considered in this paper. The input data for the short-term prediction mode are analyzed. The architecture of the predicting model is developed. The simulation modeling results show a high accuracy of the prediction on the historical stock prices of Fiat company.

Hedging Market and Credit Risk in Corporate Bond Portfolios

The European market for corporate bonds has grown significantly over the last two decades to become a preferable financing channel for large corporations in the local and Eurobond markets. The 2008 credit crisis has, however, dramatically changed corporations funding opportunities with similar effects on borrowing policies of sovereigns as well. Accordingly institutional and individual investors have progressively reduced the share of credit risky instruments in their portfolios. This chapter investigates the potential of multistage stochastic programming to provide the desired market and credit risk control for such portfolios over the recent, unprecedented financial turmoil. We consider a Eurobond portfolio, traded in the secondary market, subject to interest and credit risk and analyse whether a jump-to-default risk model and a dynamic control policy would have reduced the impact of severe market shocks on the portfolios during the crisis, to limit the systemic impact of investment strategies. The methodology is shown to provide an effective alternative to popular hedging techniques based on credit derivatives at a time in which such markets became extremely illiquid during the Fall of 2008.

Diagnostic Evalutation of Bromine Reactions on Mercury Chemistry

This model study about the influence of chemical reactants on the transport of mercury is part of an international mercury model inter-comparison (MMTF) coordinated by the EU-FP7 Research Project GMOS (Global Mercury Observation System). GMOS focuses on the improvement and validation of mercury models to assist establishing a global monitoring network and to support the implementation of the Minamata Convention. For the model inter-comparison, several global and regional Chemistry Transport Models (CTM) were used to simulate the influence of reactants on mercury oxidation. For this, gas and aqueous phase reactions of mercury with bromine were implemented into the models. As reactants, precalculated bromine concentrations were taken from the global bromine models P-TOMCAT and GEOS-CHEM. The modelled concentrations of oxidized mercury were compared to observations from GMOS measurement stations, and air craft campaigns. It was found that, even outside of polar regions, bromine plays an important role in the oxidation of mercury. Moreover, the chosen reactant influenced the vertical distribution of mercury in the atmosphere. While little difference was found for GOM concentrations at the surface level, the bromine reaction was able to explain the elevated concentration of GOM observed in the free troposphere.