A Schumpeterian Growth Model with Heterogenous Firms

A common assumption in the Schumpeterian growth literature is that the innovation size is constant and identical across industries. This is in contrast with the empirical evidence which shows that: (i) the innovation size is far from being identical across industries; and (ii) the size distribution of profit returns from innovation is highly skewed toward the low value side, with a long tail on the high value side. In the present paper, we develop a Schumpeterian growth model that is consistent with this evidence. In particular, we assume that when a firm innovates, the size of its quality improvement is the result of a random draw from a Pareto distribution. This enables us to extend the class of quality-ladder growth models to encompass firm heterogeneity. We study the policy implications of this new set-up numerically and find that it is optimal to heavily subsidize R&D for plausible parameter values. Although it is optimal to tax R&D for some parameter values, this case only occurs when the steady-state rate of economic growth is very low.Schumpeterian Growth, R&D, optimal policy

Geochemistry and mineralogy of travertine deposits of the SW flank of Mt. Etna (Italy): Relationships with past volcanic and degassing activity

Travertine deposits outcropping in the lower SW flank of Mt. Etna were studied for their mapping, as well as for their chemical, mineralogical and isotopic compositions. These deposits are dated to about 24 to 5 ka in the Adrano area, located at the western limit of the study area. In this area travertines show high Mg contents and are composed mostly of dolomite, thus apparently ruling out any primary deposition in favour of a diagenetic origin. Travertines outcropping near Paternò, in the east part of the study area, should be younger than 18 ka. Those located to the SSW of Paternò (Paternò–Diga) show high Sr contents and aragonite as dominant mineralogical phase, thus suggesting primary deposition. Those located to the Wof Paternò (Paternò Simeto–Stazione) are instead poor both in Mg and in Sr and show calcite as dominant phase. Carbon isotope composition of travertines indicates a magmatic origin of CO2 that formed them. Based on the estimated volume of travertines, between 10 and 20 Gg/a of CO2 were involved in their formation. The time-span of travertine formation coincided with the eruptive cycles of Ellittico and the first part of Mongibello, which were probably characterised by a greater amount of CO2 transported through groundwater circulation. Widespread travertine deposition probably ceased after the opening of the Valle del Bove depression that modified the volcanologic and hydrologic conditions in the summit crater area

Rain-ash interaction during paroxysmal events as potential input of toxic trace element in the environment: example from Mt. Etna Volcano

Volcanic emissions represent one of the most relevant natural sources of trace elements to the troposphere, both during and between eruptions. Due to their potential toxicity they may have important environmental impacts from the local to the global scale. Mount Etna, the largest European volcano and one of the most active volcano in the world, covers an area of about 1250 km2 and reaches an altitude of about 3340 m. It has been persistently active during historical time, with frequent paroxysmal episodes separated by passive degassing periods. Atmospheric precipitation was collected approximately every two weeks, from April 2006 to December 2007, using a network of five rain gauges, located at various altitudes on the upper flanks around the summit craters of Etna Volcano. The collected samples were analysed for major (Ca, Mg, K, Na, F, SO4, Cl, NO3) and a large suite of trace elements (Ag, Al, As, Au, B, Ba, Be, Bi, Cd, Co, Cr, Cs, Cu, Fe, Hg, La, Li, Mn, Mo, Ni, Pb, Rb, Si, Sb, Sc, Se, Sr, Th, Ti, Tl, U, V, Zn) by using different techniques (IC, SPEC, ICP-MS and CV-AFS). The monitoring of atmospheric deposition gave the opportunity to occasionally sample volcanic fresh ashes emitted by the volcano during the paroxysmal events. This was possible because the network of five rain gauges were equipped with a filter-system to block the coarse material. In this way, more than twenty events of ashfall were collected. Unfortunately, only half of these samples were suitable for a complete chemical analysis, because of the small amount of sample. In order to obtain elemental chemical composition of ashes, powdered samples were analysed by a combination of methods, including X-ray Fluorescence Spectroscopy (XRF), total digestion followed by Inductively Coupled Plasma Emission Mass Spectrometry (ICP-MS), Instrumental Neutron Activation Analysis (INAA), and infrared detection (IR). The chemistry of rainwater reveals that most of the investigated elements have higher concentrations close to the emission vent of the volcano, confirming the prevailing volcanic contribution. Rainwater composition clearly reflects the volcanic plume input. Ash-normalised rainwater composition indicates a contrasting behaviour between volatile elements, which are highly-enriched in rainwater, and refractory elements, which have low rainwater/ash concentration ratios. The degree of interaction between collected ash and rainwater was variable, depending on several factors: (i) the length of the period in which tephra was present in the sampler (the ash fall may have occurred any day from the first to the last day of the rain collecting period); (ii) the amount of rainwater fallen on the collectors after the ash-fall event, and its acidity; (iii) the granulometry of the ash samples that was widely variable (from few centimetres to micrometric particles) increasing the interaction with decreasing dimensions of the grains; (iv) the distance of collector with respect to the craters. In order to investigate the role of volcanic ash on the evolution of the rainwater chemistry, absolute concentrations of rain and ash were plotted in binary plot diagrams (Figure 1). Each diagram corresponds to a single event, and pH and TDS of the solution collected is reported. The diagonal bars in the diagrams represent the rain/ash ratios (1:1 and 1:10000). The results confirm that sulphate and halide salt aerosols are adsorbed onto ash particles, and their rate of dissolution in rainwater depends on solubility. Moreover, rapid chemical weathering of the silicate glass by volcanic acid (SO2, HCl and HF) can also explain the enrichment of several refractory elements (Na, K, Ca, Mg, Si, Al, Fe, Ti, Sc). Our observations highlight how explosive activity can increase enormously the deposition rate of several chemical elements, up to several km away from the emission vents

A Schumpeterian Growth Model with Heterogenous Firms

A common assumption in the Schumpeterian growth literature is that the innovation size is constant and identical across industries. This is in contrast with the empirical evidence which shows that: (i) the innovation size is far from being identical across industries; a (ii) the size distribution of profit returns from innovation is highly skewed toward the low value side, with a long tail on the high value side. In the present paper, we develop a Schumpeterian growth model that is consistent with this evidence. In particular, we assume that when a firm innovates, the size of its quality improvement is the result of a random draw from a Pareto distribution. This enables us to extend the class of quality-ladder growth models to encompass firm heterogeneity. We study the policy implications of this new set-up numerically and find that it is optimal to heavily subsidize R&D for plausible parameter values. Although it is optimal to tax R&D for some parameter values,this case only occurs when the steady-state rate of economic growth is very low

Mount Etna the major point source of metals in the Mediterranean basin: impact on atmospheric precipitation

Mount Etna is a huge volcano in the Mediterranean basin and is located in the eastern part of Sicily. It is considered to be, on the long-term average, the major atmospheric point source of many environmental harmful compounds. Their emission occurs either through continuous passive degassing from open-conduit activity or through sporadic paroxysmal eruptive activity, in the form of gases, aerosols or particulate. Volcanic volatiles and aerosol emitted into the atmosphere fall on the Earth’s surface as wet or dry deposition, and can influence the environment both at local and regional scale. To estimate the environmental impact of magma-derived trace metals and their depositions processes, bulk deposition samples have been collected approximately fortnightly, using a network of 5 rain gauges located at various altitudes on the upper flanks close to the summit craters, from April 2006 to December 2007. Samples were analyzed for the main chemicalphysical parameters (electric conductivity and pH) and for major and trace elements concentrations. The data obtained clearly show that the volcanic contribution is always prevailing in the sampling site closest to the summit craters (∼1.5 km). In the distal sites (5.5-10 km from the summit) and downwind of the summit craters, the volcanic contribution is also detectable but often overwhelmed by anthropogenic or other natural (seawater spray, geogenic dust) contributions. Volcanogenic contribution may derive from both dry and wet deposition of gases and aerosols from the volcanic plume, but sometimes also from leaching of freshly emitted volcanic ashes. In fact, in our background site (7.5 km in the upwind direction), after an ash deposition event high concentration of lithophiles elements (Si, Al, Fe, Ti) have been measured. Sulphur, Chlorine and Fluorine, represent the main constituents that characterize the volcanic contribution in the bulk deposition on Mt. Etna, although high concentrations of many trace elements (Si, Al, Fe, Ti, Cu, As, Rb, Pb, Tl, Cd, Cr, U and Ag) display, in the site most exposed to the volcanic emissions, average concentrations of about two orders of magnitude higher than those measured in the background site (Mount Intraleo)

Atmospheric impact of volcanic volatiles: trace elements in snow and bulk deposition samples at Mount Etna (Italy)

Volcanoes represent an important natural source of several trace elements to the atmosphere. For some species (e.g., As, Cd, Pb and Se) they may be the main natural source and thereby strongly influencing geochemical cycles from the local to the global scale. Mount Etna is one of the most actively degassing volcanoes in the world, and it is considered to be, on the long-term average, the major atmospheric point source of many environmental harmful compounds. Their emission occurs either through continuous passive degassing from open-conduit activity or through sporadic paroxysmal eruptive activity, in the form of gases, aerosols or particulate. To estimate the environmental impact of magma-derived trace metals and their depositions processes, rainwater and snow samples were collected at Mount Etna area. Five bulk collectors have been deployed at various altitudes on the upper flanks around the summit craters of the volcano; samples were collected every two week for a period of one year and analyzed for the main chemical-physical parameters (electric conductivity and pH) and for major and trace elements concentrations. Chemical analysis of rainwater clearly shows that the volcanic contribution is always prevailing in the sampling site closest to the summit crater (about 1.5 km). In the distal sites (5.5-10 km from the summit) and downwind of the summit craters, the volcanic contribution is also detectable but often overwhelmed by anthropogenic or other natural (seawater spray, geogenic dust) contributions. Volcanic contribution may derive from both dry and wet deposition of gases and aerosols from the volcanic plume, but sometimes also from leaching of freshly emitted volcanic ashes. In fact, in our background site (7.5 km in the upwind direction) volcanic contribution has been detected only following an ash deposition event. About 30 samples of fresh snow were collected in the upper part of the volcano, during the winters 2006 and 2007 to estimate deposition processes at high altitude during cold periods. Some of the samples were collected immediately after a major explosive event from the summit craters to understand the interaction between snow and fresh erupted ash. Sulphur, Chlorine and Fluorine, are the major elements that prevailingly characterize the volcanic contribution in atmospheric precipitation on Mount Etna, but high concentrations of many trace elements are also detected in the studied samples. In particular, bulk deposition samples display high concentration of Al, Fe, Ti, Cu, As, Rb, Pb, Tl, Cd, Cr, U and Ag, in the site most exposed to the volcanic emissions: median concentration values are about two orders of magnitude higher than those measured in our background site. Also in the snow samples the volcanic signature is clearly detectable and decreases with distance from the summit craters. Some of the analysed elements display very high enrichment values with respect to the average crust and, in the closest site to the summit craters, also deposition values higher than those measured in polluted urban or industrial sites

CHEMICAL COMPOSITION OF ATMOSPHERIC BULK DEPOSITION AT THE INDUSTRIAL AREA OF GELA (SICILY, ITALY)

Bulk deposition has been collected at six sampling sites in area of Gela plain (Italy) in the period from February 2008 to May 2009. Samples collected each two weeks were analysed for the major ion and trace elements content. Preliminary results allow identifying three different sources that control the abundance of the elements in atmospheric deposition: (1) sea spray, (2) geogenic dust, and (3) anthropogenic pollution. Due to the closeness of the coast, clear evidence of sea spray input is detectable for most of the samples. The high excess of non sea-salt sulphate (50 - 90% of the total) is prevailingly ascribable to the abundant SO2 emissions of the refinery. The pH values of the collected samples range from 4.2 to 8.6, with 80% of them above pH 6.5, indicating an extensive neutralization. This is due to NH3 coming from widespread agricultural activities in the plain of Gela, and geogenic CaCO3 either from local or from regional (desert dust) sources. Elevated levels of trace metals (Zn, V, Sb, Ni, Cr, Ni and Cu) can be observed in the samples collected close to the industrial area. All these elements can be identified as “anthropogenic” and attributed to the human activities, mainly to the industrial emissions, but a contribution could also derive from the intensive vehicular traffic

Chemical and mineralogical characterization of Etnean volcanic emissions using active biomonitoring technique (moss-bags)

Biomonitoring may be defined as the use of organisms and biomaterials (biomonitors) to obtain informations on certain characteristics of a particular medium (atmosphere, hydrosphere etc.). In particular, mosses accumulate large amounts of trace metals, making them good bioaccumulators to estimate atmospheric pollution. The moss-bags technique, introduced in the early 1970’, has become very popular. Such active biomonitoring technique is particularly useful in highly polluted areas and has been extensively used in industrial and/or urban areas to examine deposition patterns and to recognize point sources of pollution. The main objective of this study, which represents the first application of the moss-bags technique in an active volcanic area, was to test its efficacy in such environment. Complementary objectives were: to determine the different behaviour and the areal dispersion of volcanogenic elements emitted from Mt. Etna; to characterize the morphology and mineralogy of particles transported in the plume-system, basing on microscopy investigation. A mixture of Sphagnum species was picked in a clean area, treated in laboratory (rinsed, dried and packed) and exposed in field for 1 month. Sites were chosen considering the prevailing wind at Mt. Etna’s summit. Milled samples were analyses for major and trace elements concentrations, after microwave digestion (HNO3 + H2O2), by ICP-MS and ICP-OES techniques. Morphology and mineralogy of volcanic particulate were investigated by using a SEM with EDS. Analyses clearly showed the efficacy of the moss-bags technique also in this peculiar environment. Several elements were strongly enriched in the mosses exposed to the volcanic emissions. The highest enrichment was measured close to the summit crater, but evidences of metals bioaccumulation were also found in down wind sites, at several km from the volcanic source. The accumulation factor (exposed/unexposed moss) allowed us to distinguish a group of elements (Tl, Bi, Se, Cu, As, Cd, S), which are highly mobile in the high temperature volcanic environment. Also alkali metals showed a significant increase in their concentrations, probably because of their affinity for the halide species carried by the volcanic plume. Microscopic observations evidenced sulphate and halide crystals on particles trapped by the mosses. Mosses exposed at sites directly fumigated by the volcanic plume showed crystal growth also directly on the moss surface

Application of the moss bag miomonitoring technique in an active volcanic environment (Mt. Etna, Italy)

This paper presents the preliminary results of a biomonitoring study based on the use of moss bags exposed at 24 sites on Etna volcano. Sphagnum mosses were used to study bioaccumulation originating from atmospheric deposition, by measuring the tissue contents of major and a large suite of trace elements. Elements, such as Tl, Bi, As, Se, Cu and Cd, display high concentrations in the exposed samples close to the active vents. This study confirms the effectiveness of the moss bags technique also in active volcanic areas

The use of moss-bags technique for volcanic aerosols investigation on Mt. Etna (Italy)

Explosive eruptions and volcanic passive degassing inject large quantities of gas and particles into the atmosphere that are ultimately deposited at the Earth’s surface through wet or dry deposition processes, affecting the atmosphere, the hydrosphere and the biosphere. Mount Etna (Italy) is one of the most prodigious and persistent sources of gases and particles to the troposphere. Volcanic emissions were studied at Etna volcano by using moss-bags technique. Mosses (Sphagnum species) were exposed around the volcano at different distances from the active vents to evaluate the impact of its emissions into the atmosphere and in the local surrounding. The results confirmed the huge amount of silicates, sulfates and halides compounds emitted into the atmosphere from Mount Etna. X-ray microanalysis showed that chemical composition of the particles is mostly defined by silicate (from pure silica to metal-rich silicate composition) and sulfate/halide compounds. The contents of major and trace elements in the Sphagnum moss-bags significantly increased after their exposure to volcanic emissions, confirming mosses as efficient accumulators. Metals uptake rate rapidly decreases with the distance from the volcanic emission vents. The elements that showed the greatest accumulation after exposition were S, Na, Fe, Al, Cu, V, As, Cd, Li, Se, Sc, Th, Bi and Tl. This study confirmed the marked environmental impact of volcanic emissions in the eastern sector of Etna, leading to an intense “geochemical anomaly” of volatile major and trace elements due to the fumigation by the volcanic plume, in agreement with passive biomonitoring studies reported by previous authors. Finally, moss-bags techniques provide a cheap and efficient method to investigate quantitatively in space and time the environmental impact of volcanogenic atmospheric deposition