A preliminary study into the use of tree-ring and foliar geochemistry as bio-indicators for vehicular NOx pollution in Malta

Duncan V. Mifsud is the grateful recipient of an Endeavour Scholarship (Republic of Malta). The Endeavour Scholarship Scheme is part-financed by the European Union – European Social Fund (ESF): Operational Programme II – Cohesion Policy 2014-20.Emissions from traffic over the past few decades have become a significant source of air pollution. Among the pollutants emitted are nitrogen oxides (NOx), exposure to which can be detrimental to public health. Recent studies have shown that nitrogen (N) stable isotope ratios in tree-rings and foliage express a fingerprint of their major N source, making them appropriate for bio-monitoring purposes. In this study, we have applied this proxy to Aleppo pines (Pinus halepensis) at three distances from one of the busiest roads in Malta, a country known to suffer from intense traffic pollution. Our results showed that N and organic carbon (C) stable isotope ratios in tree-rings do not vary over the period 1980–2018 at any of the investigated sites; however, statistically significant spatial trends were apparent in both tree-rings and foliage. The roadside and transitional sites exhibited more positive δ15N and more negative δ13C values compared to those at a rural control site. This is likely due to the incorporation of 15N-enriched NOx and 13C-depleted CO2 from traffic pollution. Sampled top-soil also exhibited the δ15N trend. Our results constitute the first known application of dendrogeochemistry to atmospheric pollution monitoring in Malta.PostprintPeer reviewe

Batoid abundances, spatial distribution, and life history traits in the strait of sicily (Central mediterranean sea): Bridging a knowledge gap through three decades of survey

Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas of the Central Mediterranean (South of Sicily and Malta Island), in a timeframe ranging from 1990 to 2018. Excluding some batoids, the abundance trends were stable or increasing. Only R. clavata, R. miraletus, and D. oxyrinchus showed occurrence and abundance indexes notable enough to carry out more detailed analysis. In particular, spatial distribution analysis of these species highlighted the presence of two main hotspots in Sicilian waters whereas they seem more widespread in Malta. The lengths at first maturity (L50) were 695 and 860, 635 and 574, and 364 and 349 mm total length (TL), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The asymptotic lengths (L∞) and the curvature coefficients (K) were 1365 and 1240 (K = 0.11 and 0.26), 1260 and 1100 (K = 0.16 and 0.26), and 840 and 800 mm TL (K = 0.36 and 0.41), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The lack of detailed quantitative historical information on batoids of Sicily and Malta does not allow to analytically judge the current status of the stocks, although the higher abundance of some species within Malta raises some concern for the Sicilian counterpart. In conclusion, suitable actions to protect batoids in the investigated area are recommended

Assessment of goods and services, vulnerability, and conservation status of European seabed biotopes: a stepping stone towards ecosystem-based marine spatial management

The goal of ecosystem-based marine spatial management is to maintain marine ecosystems in a healthy, productive and resilient condition; hence, they can sustainably provide the needed goods and services for human welfare. However, the increasing pressures upon the marine realm threaten marine ecosystems, especially seabed biotopes, and thus a well-planned approach of managing use of marine space is essential to achieve sustainability. The relative value of seabed biotopes, evaluated on the basis of goods and services, is an important starting point for the spatial management of marine areas. Herein, 56 types of European seabed biotopes and their related goods, services, sensitivity issues, and conservation status were compiled, the latter referring to management and protection tools which currently apply for these biotopes at European or international level. Fishing activities, especially by benthic trawls, and marine pollution are the main threats to European seabed biotopes. Increased seawater turbidity, dredged sediment disposal, coastal constructions, biological invasions, mining, extraction of raw materials, shipping-related activities, tourism, hydrocarbon exploration, and even some practices of scientific research, also exert substantial pressure. Although some first steps have been taken to protect the European sea beds through international agreements and European and national legislation, a finer scale of classification and assessment of marine biotopes is considered crucial in shaping sound priorities and management guidelines towards the effective conservation and sustainability of European marine resources

Bombardment of CO ice by cosmic rays: I. Experimental insights into the microphysics of molecule destruction and sputtering

We present a dedicated experimental study of microscopic mechanisms controlling radiolysis and sputtering of astrophysical ices due to their bombardment by cosmic ray ions. Such ions are slowed down due to inelastic collisions with bound electrons, resulting in ionization and excitation of ice molecules. In experiments on CO ice irradiation, we show that the relative contribution of these two mechanisms of energy loss to molecule destruction and sputtering can be probed by selecting ion energies near the peak of the electronic stopping power. We have observed a significant asymmetry, both in the destruction cross section and the sputtering yield, for pairs of ion energies corresponding to same values of the stopping power on either side of the peak. This implies that the stopping power does not solely control these processes, as usually assumed in the literature. Our results suggest that electronic excitations represent a significantly more efficient channel for radiolysis and, possibly, also for sputtering of CO ice. We also show that the charge state of incident ions as well as the rate for CO$^+$ production in the ice have negligible effect on these processes.Comment: Accepted for publication in Ap

Molecular-rotation-induced splitting of the binary ridge in the velocity map of sub-eV H+ ions ejected from H2 molecules by ion impact

In studies of ion-induced molecular fragmentation, the challenging measurement of the velocity distribution of fragments emitted below 1-eV kinetic energy is rarely achieved, although most fragments have an energy below this value. Here, we study H+ fragment emission in collisions of 10-keV O+ ions with H2 molecules using a field-free time-of-flight technique developed specifically to detect sub-eV fragments. We find that, in the velocity map, the binary ridge due to direct H+ knockout is split into two parts arising from the rotational motion of the H2 molecule, and that this split scales with rotational velocity. The velocity distribution of the nuclei in the original molecule is determined and the thermally populated J = 1 rotational level is found to be the dominant contributor, although asymmetry in the split indicates projectile-induced rotational transitions between M sub-levels. These rotation effects influence fragment emission probabilities, thus carrying important consequences for the radiation-induced hydrogen loss and H2 dissociation in the atmospheres or exospheres of planets and moons

Proton and electron irradiations of CH4:H2O mixed ices

The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH4:H2O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K.We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C2H6, C3H8, C2H2, CH3OH, CO, CO2, and probably also H2CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects.Comment: Published as an open access article in the MDPI journal Atom

Climatic change and the Mediterranean

The temperature and precipitation scenarios for the Malta region developed by the Climate Research Unit of the University of East Anglia suggest that annual temperature will increase by 0.8 to 0.9°C per degree Celsius of global change and that there will be little if any change in the annual rainfall amounts around Malta. A statistical analysis of past meteorological data for Malta indicates an existing trend towards increasing extremes of temperature; namely an increase in the maximum and a decrease in the minimum temperatures. The mean annual temperature is also apparently increasing. These data also suggest a trend towards lower total annual rainfall; an increase in the atmospheric pressure; an increase in the number of days with thunderstorms; and decreases in cloud cover and the number of hours of bright sunshine. These trends suggest that a process of desertification is already occurring in Malta, and that there is an increase in the suspended particle concentration including pollutants, in the atmosphere over the island. The hydrological cycle will be significantly affected by global warming. In Malta, natural sources of freshwater account for about 37% of all potable water in the public supply and for 84% of all irrigation water. Global warming will affect the freshwater supply through changes to relative sea level, and through changes in rainfall and evapotranspiration. A eustatic rise in sea level of around 65 ± 35 cm by the year 2100 would adversely affect the existing extraction rates from Malta's principal aquifer and make it more vulnerable to sea water intrusion. In contrast, the direct climatic effect will be less pronounced, since only a small change in local precipitation is predicted to accompany global warming. Climate is a fundamental factor influencing the nature of the soils of Malta. Since an increase in temperature with little change in the total rainfall is anticipated, evapotranspiration will increase, leading to an increase in aridity, and to soil degradation mainly due to salinization and alkalinization. The anticipated increase in temperature; a shift in precipitation patterns; a decrease in soil water availability; and a rise in sea level, will have negative impacts on agriculture, natural vegetation and associated fauna, favouring an increase in xerophilic, thermophilic and halophilic species. Such species are likely to be introduced ones, thriving at the expense of native species. It is predicted that the character of the vegetation will change from that typical of Mediterranean coastal lowlands, to associations more typical of deserts. This shift in vegetation pattern would be enhanced by soil erosion and increased soil salinity. Remedial action at a local level could include measures to prevent soil erosion by gradually changing to crops and trees that stabilize soils and which tolerate the new climatic conditions. A change in temperature could possibly lead to an increase in agricultural pests, whilst sea level rise may cause inundation of low-lying agricultural land such as that at Pwales and of groves such as those at Salina Bay. The impacts on fisheries may be less dramatic but changes in migration patterns of important fish such as lampuki might happen; and the potentially adverse effects which competitive thermophilic seaweeds may have on the important Posidonia meadows may be of concern in the future. The effects on aquaculture are difficult to assess but may include an increase in pathogens. The control of pollutants and protection of the Posidonia meadows are recommended, together with development of more sustainable use of fisheries resources. The present coastal, near-shore and freshwater ecosystems are threatened by a number of anthropogenic, non-climatic changes. Any additional impacts on these ecosystems resulting from climatic changes will have to be assessed in the light of such nonclimatic effects, if the overall projections of future changes are to be accurate. Increased eutrophic conditions and increased water stratification are likely to occur under conditions of global change in certain localities already influenced by other non-climatic human activities. Non-linear biological responses to climatic changes are discussed and may prove to be quite significant but difficult to predict with the present state of knowledge. Coastal sandy beaches, sand dunes and saline marsh habitats are considered to be sensitive to predicted climate change impacts, through increased erosion, enhanced shoreline recession and increased environmental fluctuations. The extent of impacts on such habitats, under less severe climatic change scenarios, will depend largely on present and future land-use management practices. Given the coastal topography, present drainage patterns and negligible tectonic movements in Malta, the predicted rise in sea level will have coast and especially those in the main drainage basins will become more susceptible to periodic rainfall-induced flooding and anticipatory action will be needed to address the consequential economic and social disruption. Impacts on coastal settlements are expected as a result of tidal and storm surges rather than from permanent inundation. A rise in sea level may cause sewage systems to flood, and new systems may have to be developed to reduce public health risks from such a hazard, including the increased risk of epidemics of enteric disorders such as typhoid fever. Salt water intrusion into aquifers will reduce the quantity and quality of potable water resources. Temperature rise and an increased frequency of extreme high temperatures, especially when combined with high humidity, will put some population groups such as the elderly and infants at risk from heat stress. Diseases presently confined to the tropics may spread to higher latitudes, and tropical and sub-tropical vector borne diseases may become more widespread, partly because vector survival will increase and partly because the parasites may be able to complete their life cycle more easily. Malaria may reappear in Europe, whilst Leishmaniasis, which has been under control in the recent past, already seems to be on the increase, possibly as a result of recent increases in temperature and humidity. Increased exposure to the sun when combined with possible ozone layer depletion may result in a further rise in the incidence of both melanomas and non-melanotic skin cancers. Exposure to increased ultraviolet (UV) radiation is expected to cause damage to the cornea and lens and an increased incidence of cataracts. The effect of UVB radiation on the human immune system is far less well understood, but it is a well accepted fact however, that UV, possibly acting through DNA damage, is an important precipitating factor of the auto-immune condition, systemic lupus erythematosus. The tourist industry has, for many years, been one of the Islands' most important economic activities, employing 5.8% of the total working population. If the climate conditions of the Maltese Islands change, the tourist industry could suffer, causing disruption to the Maltese economy and hardship to the population. Sea level rise will certainly have an impact on this site-dependent and coastal industry, which would be adversely affected by the loss of sandy beaches and the reduction in potable water supply. The tourist industry, is by its very nature, fragile and susceptible to political, economic and social changes. Climate change will add another element of uncertainty to this sector. Transport in Malta depends entirely on roads, whilst a ferry service connects the islands of Malta, Gozo and Comino and is also used around the Grand Harbour area. Road traffic would suffer in the event of flooding of the main traffic arteries as a result of severe rain storms, which will probably increase along with the anticipated increase in autumn precipitation. Changes in climate are expected to have an effect on the patterns of energy demand to heat and cool buildings. Electricity generation, which accounts for almost two thirds of primary energy consumption, has grown on average by about 8.5% per year in recent years. The predicted average temperature increases would, theoretically, reduce the need to provide heating, thereby saving energy. Given the low thermal performance of Maltese buildings, an increase in ambient temperature may merely result in a more thermally comfortable interior, rather than a saving of energy. · In the commercial and industrial sectors, the interhal heat generated by the use of machinery is high and an increase in ambient temperature, may result in a need for cooling through increased ventilation and possibly an extension of the air conditioning season. The introduction of thermal insulation to the building envelope, would reduce both the heating demand in winter as well as the cooling demand in summer. The displacement of fossil fuels by renewable energy sources particularly biomass and hydro power would reduce carbon dioxide emissions. In Malta there is good potential for development of solar energy, although land availability is a major obstacle. There is less possibility of harnessing wind energy on a large scale although wind energy is already widely used for water pumping in agriculture.peer-reviewe