Microbial-derived pirite as evidence of early diagenetic processes on a Late Holocene shoreface deposits (Sulcis Iglesiente, West Sardinia, Italy)

Since Roman time, SW Sardinia was a mine district and its fluorishing industrial activity lasted few decades ago. Mine activity in the district resulted in enhanced amount of sediments transported by rivers to the coast and, one of the major concern is elucidating the mineralogical background before and after industrial activity along the present-day coasts. A 3-m long core was collected in the shoreface zone, at -13–m depth below sea level and ca. 500 m far from the coastal area located on the southern-western of Sardinia (west Mediterranean, Italy). A multidisciplinary approach was followed to study the core and two samples were collected for dating purpose. 14C analysis revealed a Late Holocene age comprises between 4320 ± 30 BP (base) and 1420 ± 30 yeas BP (close to the top). Preliminary sedimentological data show that the core is composed of medium-fine grained sand, with the presence of aligned pebbles and/or shells at the base of the strata. These strata can be interpreted as the results of major storms occurred in a shoreface setting. Pervasive early diagenetic processes and sub-oxic conditions are observed as well. The preliminary geochemical results can be summarized as follows: 1) residual metal sulphides are not detected; 2) Zn and Pb carbonates can be found in samples collected close to the beaches, 3) barite and other minerals are often concentrated in the fine fraction (<63 microns). Moreover, the microscopic analysis reveals the presence of secondary pyrite that is interpreted to be of microbial origin. Thus the microbial activity most likely plays a fundamental tool in the pervasive early digenesis of the studied core. Bacterial activity and its effect on biominerals processes and sedimentological features are actually under investigation

Microbial borings in benthic foraminifera from an heavy metal polluted coastal area (Portovesme, southwestern Sardinia)

A monitoring survey from coastal environments facing the industrial area of Portoscuso-Portovesme (South-Western Sardinia, Italy) has revealed intense bioerosional processes in tests of benthic foraminifera collected in water less than 2m deep. Electron Microscopic investigation show that 1) microbial communities extensively infest foraminifera, 2) heavy metals fluxes (Zn, Pb, Cd) and carbonate dissolution are correlated and this correspond to decrease in foraminifera richness, low population density, biodiversity and to marked increase in abnormality and pyritisation of the tests. In addition, carbonate dissolution induced by euendoliths is selective depending on Mg content and morpho-structural types of foraminiferal taxa. The bioerosional process on foraminiferal tests was analyzed via SEM (ESEM QUANTA 200, FEI, Hillsboro, Oregon, and partly with EVOLS15, ZEISS) at Cagliari University (Italy). The epoxy resin-casts of foraminifera were made at Erlangen University (Germany) in collaboration with M. Wisshak. To estimate quantitatively the impact of the microbial borings on the foraminifera and the selective bioerosion on high-Mg and low-Mg foraminiferal tests, 300 individuals were picked randomly from each sample on the fraction >63 μm and were observed with scanning electron microscope. A total of 1200 foraminifera was examined. As well as the bioerosional features on several morpho-structural taxa have been quantitatively calculated. The percentages of calcareous dissolution in foraminifera, distinguish between high-Mg and low-Mg tests, have been compared with heavy metals values, ph-pore waters and richness of specimens. Scanning Electron Microscope images of the test surfaces and of epoxy resin-casts of foraminifera provide the recognition of microboring traces and cavities produced by phototrophic (cyanobacteria, chlorophyta) and heterotrophic (fungi) organisms. Comparing foraminiferal hosts belonging to diversified morpho-structural types with the bioerosional features, our data point out that the increase in heavy metal fluxes is clearly marked by an increase of microbial infestation, reaching a peak at the more polluted sites. Consistent carbonate dissolution differences occur between porcelanaceous imperforate and hyaline perforate groups. When comparing hyaline with porcelanaceous specimens for each sampling site, it was observed that the percentage of bioerosion in hyaline specimens increases from 19.9% to 59.7%, whereas in porcelanaceous tests bioerosion increases from 35.1% to 80.3%. An opposite behavior show the benthic foraminifera assemblages, which abruptly decrease increasing the heavy metal fluxes, while the percentage of the teratological increases (until 11%) in accordance with the increase of the pollutants. Our multiproxy analyses show that the affects of the biochemical dissolution are controlled, as well, by the chemical composition and ultramicrostructure of the foraminifera substrates and by the bioavailability of organic matter in their skeleton texture

Biomineralization processes in heavily metal-polluted environments

Intense industrial activity in SW Sardinia has resulted in heavy metal dispersion processes over a large area. In this study biomineralization processes are shown to be useful for environmental monitoring, in agreement with existing literature. Investigations of benthic foraminifera sampled in shallow water from a metal-contaminated environment (Portoscuso, SW Sardinia) reveal intense micro-boring processes by cyanobacteria, chlorophycean, and fungi. A positive correlation between heavy metal impurity content (Pb and Zn, in particular) and bioerosional processes is found. This result indicates that in the investigated area, the amount of heavy metals discharged cannot be diluted or taken up via water-rock interaction, and are therefore released to the biosphere

Aortic root dilatation in hypertensive patients: a multicenter survey in echocardiographic practice.

Aortic root dilatation (ARD) is a cardiovascular phenotype of adverse prognostic value; its prevalence has been mostly investigated in population-based samples and selected hypertensive cohorts. Data from clinical practice are rather scant. Thus, we examined the prevalence and correlates of ARD in a large sample of hypertensive patients referred by general practitioners for a routine echocardiographic examination.A total of 2229 untreated and treated hypertensive subjects (mean age 62 years) referred to 17 outpatient echocardiographic laboratories across Italy for detection of hypertensive subclinical cardiac damage were included in the study. ARD was defined by aortic diameter exceeding 3.7 cm in women and 3.9 cm in men.ARD was found in 263 patients, with an overall prevalence of 11.8\% (16.9\% in men and 6.2\% in women, p < 0.05). In multivariate regression analyses, body surface area (BSA), left ventricular (LV) mass and age were in ranking order the most important correlates of aortic root size in the whole population study as well as in men. In women, LV mass and its derivative indexes were the most important independent variables associated to aortic root size.This multicenter nationwide survey indicates that ARD is a frequent cardiovascular phenotype in hypertensives referred to echo-labs for detection of hypertensive organ damage. BSA, LV mass and age are the most important correlates of this phenotype. The hierarchical order of these factors differs between genders, LV mass being the strongest independent variable in women