Monitored Natural Attenuation of Manufactured Gas Plant Tar Mono- and Polycyclic Aromatic Hydrocarbons in Ground Water: A 14-Year Field Study

Site 24 was the subject of a 14-year (5110-day) study of a ground water plume created by the disposal of manufactured gas plant (MGP) tar into a shallow sandy aquifer approximately 25 years prior to the study. The ground water plume in 1988 extended from a well-defined source area to a distance of approximately 400 m down gradient. A system of monitoring wells was installed along six transects that ran perpendicular to the longitudinal axis of the plume centerline. The MGP tar source was removed from the site in 1991 and a 14-year ground water monitored natural attenuation (MNA) study commenced. The program measured the dissolved mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs) periodically over time, which decreased significantly over the 14-year period. Naphthalene decreased to less than 99% of the original dissolved mass, with mass degradation rates of 0.30 per year (half-life 2.3 years). Bulk attenuation rate constants for plume centerline concentrations over time ranged from 0.33 ± 0.09 per year (half-life 2.3 ± 0.8 years) for toluene and 0.45 ± 0.06 per year (half-life 1.6 ± 0.2 years) for naphthalene. The hydrogeologic setting at Site 24, having a sandy aquifer, shallow water table, clay confining layer, and aerobic conditions, was ideal for demonstrating MNA. However, these results demonstrate that MNA is a viable remedial strategy for ground water at sites impacted by MAHs and PAHs after the original source is removed, stabilized, or contained.     

Solar activity and life: a review

During the early stages of the study of the origin of life, not enough attention was paid to the question of the correlation of chemical evolution on Earth and the all-important evolution of the still-to-be understood early Sun. Today, due to the advent of a significant fleet of space missions and the possibility of performing experiments in the International Space Station (ISS), a meaningful study begins to be possible concerning factors that led to an early onset of life on Earth. We wish to review and update recent work concerning the frontier between Space Weather (SpW) and Astrobiology. We argue that the present robust programs of various space agencies reinforce our hope for a better understanding of the bases of Astrobiology. Eventually, with a more realistic model of the Sun, more reliable discussions of all the factors influencing the origin of life on Earth, and hence Astrobiology, will be possible.     

The Afragola settlement near Vesuvius,Italy: The destruction and abandonment of a Bronze Age village revealed by archaeology,volcanology and rock-magnetism

Public works in progress in the Campanian plain north of Somma-Vesuvius recently encountered the remains of a prehistoric settlement close to the town of Afragola. Rescue excavations brought to light a Bronze Age village partially destroyed and buried by pyroclastic density currents (PDCs) of the Vesuvian Pomici di Avellino eruption (3.8 ¹⁴C ka BP) and subsequently sealed by alluvial deposits. Volcanological and rock-magnetic investigations supplemented the excavations.Careful comparison between volcanological and archaeological stratigraphies led to an understanding of the timing of the damage the buildings suffered when they were struck by a series of PDCs. The first engulfed the village, located some 14 km to the north of the inferred vent, and penetrated into the dwellings without causing major damage. The buildings were able to withstand the weak dynamic pressure of the currents and deviate their path, as shown by the magnetic fabric analyses. Some later collapsed under the load of the deposits piled up by successive currents. Stepwise demagnetization of the thermal remanent magnetization (TRM) carried by potsherds embedded in the deposits yields deposition temperatures in the order of 260–320 °C, fully consistent with those derived from pottery and lithic fragments from other distal and proximal sites. The fairly uniform temperature of the deposits is here ascribed to the lack of pervasive air entrainment into the currents. This, in turn, resulted from the lack of major topographical obstacles along the flat plain.The coupling of structural damage and sedimentological analyses indicates that the currents were not destructive in the Afragola area, but TRM data indicate they were still hot enough to cause death or severe injury to humans and animals. The successful escape of the entire population is apparent from the lack of human remains and from thousands of human footprints on the surface of the deposits left by the first PDCs. People were thus able to walk barefoot across the already emplaced deposits and escape the subsequent PDCs. The rapid cooling of the deposits was probably due to both their thinness and heat dissipation due to condensation of water vapour released in the mixture by magma–water interaction.     

Bacterial response to seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea

Bacterial abundance, biomass and cell size were studied in the oligotrophic sediments of the Cretan Sea (Eastern Mediterranean), in order to investigate their response to the seasonal varying organic matter (OM) inputs. Sediment samples were collected on a seasonal basis along a transect of seven stations (ranging from 40 to 1570 m depth) using a multiple-corer. Bacterial parameters were related to changes in chloroplastic pigment equivalents (CPE), the biochemical composition (proteins, lipids, carbohydrates) of the sedimentary organic matter and the OM flux measured at a fixed station over the deep basin (1570 m depth). The sediments of the Cretan Sea represent a nutrient depleted ecosystem characterised by a poor quality organic matter. All sedimentary organic compounds were found to vary seasonally, and changes were more evident on the continental shelf than in deeper sediments. Bacterial abundance and biomass in the sediments of the Cretan Sea (ranging from 1.02 to 4.59 × 10⁸ cells g⁻¹ equivalent to 8.7 and 38.7 μgC g⁻¹) were quite high and their distribution appeared to be closely related to the input of fresh organic material. Bacterial abundance and biomass were sensitive to changes in nutrient availability, which also controls the average cell size and the frequency of dividing cells. Bacterial abundance increased up to 3-fold between August '94 and February '95 in response to the increased amount of sedimentary proteins and CPE, indicating that benthic bacteria were constrained more by changes in quality rather than the quantity of the sedimentary organic material. Bacterial responses to the food inputs were clearly detectable down to 10 cm depth. The distribution of labile organic compounds in the sediments appeared to influence the vertical patterns of bacterial abundance and biomass. Cell size decreased significantly with water depth. Bacterial abundance and biomass were characterised by clear seasonal changes in response to seasonal OM pulses. The strong coupling between protein flux and bacterial biomass together with the strong bacterial dominance over the total biomass suggest that the major part of the carbon flow was channelled through the bacteria and the benthic microbial loop.     

Internal rotation of the Sun as inferred from GONG observations

Helioseismology is a direct and most informative method of studying the structure and dynamics of the Sun. Determining the internal differential rotation of the Sun requires that the frequencies of its eigentones be estimated with a high accuracy, which is possible only on the basis of continuous long-term observations. The longest quasi-continuous series of data have been obtained by the Global Oscillation Network Group (GONG). The parameters of each individual mode of solar acoustic oscillations with low spherical degrees l=0, 1, 2, 3, 4, 5, 6 are determined by using 1260-day-long series of GONG observations. The mean frequency splitting by rotation for the modes of each radial order n is calculated by using all possible combinations between the eigenfrequencies in multiplets. As a result, it has become possible to statistically estimate the splitting and its measurement errors for the modes of each radial order. The mean splitting for each given degree l=1–6 is presented under the assumption of its independence of oscillation frequency, which holds for the achieved accuracy. The frequencies and splittings for the modes with low spherical degrees l, together with the MDI group results for higher degrees l, are used to invert the radial profile of solar angular velocity. Using the SOLA method to solve the inverse problem of restoring the rotation profile has yielded solutions sensitive to the deepest stellar interiors. Our results indicate that the solar core rotates faster than the surface, and there may be a local minimum in angular velocity at its boundary.     

Gully head modelling: A Mediterranean badland case study

Predicting the location of gully heads in various environments is an important step towards predicting gully erosion rates. So far, field data collection and modelling of topographic thresholds for gully head development has mainly focused on gullies that formed in forested areas, rangelands, pastures and cropland. Such information for gullies in badlands however is very scarce. Therefore, this paper aims to extend the database on gully head topographical thresholds through data collection in a badland area and to improve the prediction of gully heads forming at sites with a very low erosion resistance value. For this, we chose a badland site located in central Italy that is characterized by biancana forms and both active and dormant gullies. The definition of the conditions under which present‐day gully heads developed allowed a better modelling of the gully head threshold equation, with modification of a previous model and the exemplification of how to use the updated model. The model shows that the resistance to gully head retreat depends on slope gradient and drainage area at gully heads, land use at the moment of gully development (as numerically expressed using parameters derived from the Runoff Curve Number method), surface rock fragment cover, presence of joints, pipes, and factors/processes affecting detachment rate. This study attempted to better understand environmental conditions that control the development of gully heads in badlands through a combination of field data collection of gully heads, an analysis of land use changes over 10 centuries, focusing on the period 1820–2005, and land use management through repeat photography and a critical examination of historical documents. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

The Italian guidelines for seismic risk classification of constructions: technical principles and validation

The Italian “Guidelines for the seismic risk classification of constructions” approved in February 2017 define the technical principles for exploiting tax deductions with respect to seismic strengthening interventions on existing buildings (Sismabonus). Tax deductions represent a unique opportunity to improve the seismic safety of the existing Italian building stock. The guidelines are very simple and allow practitioners to deal with the sophisticated concepts behind modern seismic design, such as expected annual losses (EAL) and repair costs (expressed as a fraction of the Reconstruction Cost: %RC). The seismic risk classes of buildings and the class upgrade due to strengthening interventions can be assessed using the principles included in the guidelines. The seismic risk class is the minimum between the class defined by the building safety index at the ultimate limit state and the one related to the EAL. The latter class depends on the area under the curve of the expected losses, which is easily obtained by computing the safety index converted in the return period (annual frequency) at different limit states and the relevant %RC. This paper illustrates the technical principles at the base of the guidelines and the procedure used to calibrate the repair costs associated with the different limit states using the actual repair costs monitored in the reconstruction process following recent Italian earthquakes. Finally, simple tools to estimate the cost of the strengthening interventions to improve the seismic capacity at the life-safety limit states are provided.     

Runoff-generated debris flows: Observation of initiation conditions and erosion–deposition dynamics along the channel at Cancia (eastern Italian Alps)

In the Dolomitic region, abundant coarse hillslope sediment is commonly found at the toe of rocky cliffs. Ephemeral channels originate where lower permeability bedrock surfaces concentrate surface runoff. Debris flows initiate along such channels following intense rainfall and determine the progressive erosion and deepening of the channels. Sediment recharge mechanisms include rock fall, dry ravel processes and channel-bank failures. Here we document debris flow activity that took place in an active debris flow basin during the year 2015. The Cancia basin is located on the southwestern slope of Mount Antelao (3264 m a.s.l.) in the dolomitic region of the eastern Italian Alps. The 2.5 km² basin is incised in dolomitic limestone rocks. The data consist of repeated topographic surveys, distributed rainfall measurements, time-lapse (2 s) videos of two events and pore pressure measurements in the channel bed. During July and August 2015, two debris flow events occurred, following similarly intense rainstorms. We compared rainfall data to existing rainfall triggering thresholds and simulated the hydrological response of the headwater catchment with a distributed model in order to estimate the total and peak water discharge. Our data clearly illustrate how debris entrainment along the channel is the main contributor to the overall mobilized volume and that erosion is dominant when the channel slope exceeds 16°. Further downstream, sediment accumulation and depletion occurred alternately for the two successive events, indicating that sediment availability along the channel also influences the flow behaviour along the prevailing-transport reach. The comparison between monitoring data, topographical analysis and hydrological simulation allows the estimation of the average solid concentration of the two events and suggests that debris availability has a significant influence on the debris flow volume. © 2020 John Wiley & Sons, Ltd.     

The Balance Between Capturing Phosphorus from Manure and Wastewater and the Demand for Crop Fertilizer in Italy

Phosphorus (P) is an essential nutrient required for plant growth and at the same time a costly pollutant, which can cause eutrophication of water bodies. Modern agriculture relies heavily on mineral fertilisers, which contain phosphorus derived from phosphate rock, because, without regular applications, crop yields would be limited. Since phosphate rock is a non-renewable resource, there are growing concerns regarding future phosphorus scarcity and the sustainability of modern agriculture. For many farmers, animal manure was once a means of maintaining soil fertility, but now it presents a major operational problem. This study evaluated the possibility of recycling phosphorus on a national and regional scale in Italy, using major sources of manure and wastewater. These results were successively compared with an estimate of the agricultural demand for phosphorus. Considering the quantity of phosphorus fertilizer that was applied to the soil–plant system, for the years 2001–2010, the annual phosphorus requirement of Italian crops was about 101,000 t of P. Therefore, the phosphorus source comprising animal manure and civil/industrial waste (117,500 t of P and 40,000 t of P, respectively) could potentially satisfy the average annual agronomic phosphorus demand. Regarding the geographical distribution of phosphorus supply and demand on a regional scale, areas with a large deficit of phosphorus included Calabria, Puglia and Marche. However, when only livestock waste was considered, Sicily, Umbria and Friuli could also be considered to be regions experiencing a phosphorus deficit.