Source and selectivity in the accumulation of mercury and other metals by the plants of Mt. Etna

The air Hg content at and near the summit of Mt. Etna is approximately 500- to 2000-fold lower than it is in the atmospheres around Antarctic, Hawaiian and Icelandic volcanoes. In contrast, the soils and plants on Mt. Etna show only 10- to 30-fold reductions in Hg content; in other words, there is at least a ten-fold enrichment relative to air. This disparity called into question the source of Hg in the vegetation and upper soil layers. Soils and a variety of plant species were analyzed for Hg, Fe, Cu, and Mn content at a number of stations on Mt. Etna including several also sampled for air Hg, and compared with the data for plants and soils from other volcanic and non-volcanic locations, especially Hawaii, Africa and Iceland. Etna vascular plants do not accumulate Hg, and lichens do so only to a moderate extent. Relative to their Fe content, however, all the Etna soils are enriched in Hg, but the reverse is true for Cu relative to Hg. The plants, on the other hand, when compared with their soils, are enriched in Hg relative to Cu. By comparing Fe/Hg atomic ratios for plants and soil, we calculated an Enrichment Factor (EF) for Hg. This value ranged from 19 to 102 for Etna, and 19 to 184 for all subtropical plants discussed here. The Hg EF for Icelandic samples was ca. 823, reflecting other environmental/geochemical determinants. No net surface deposition of Hg takes place on Etna from plant or atmospheric sources, and the relative Hg contents of soils and plants do not show a consistent relation to air Hg concenctration. Nevertheless, the plant/soil Cu and Hg ratios (CR) vary similarly as do the atomic ratio (AR) values for Fe and Hg. We conclude from these relationships that the atmosphere is not a major source of plant (or soil) Hg and that the likely alternatives are: release at some relatively remote point in time, but not to any significant degree since; release into the atmosphere as Hg = species other than Hg⁰; or movement from very deep subsurface compartments. These alternatives are not mutually exclusive. It is highly improbable that summit emissions constitute a significant source of Hg in the Mediterrean Basin.     

Accumulation of mercury and other metals by the lichen,Parmelia sulcata,at an italian minesite and a volcanic area

Young thallus tissue of the epiphytic lichen, Parmelia sulcata, and surface soil associated with its host trees were collected on Mt. Amiata for analysis of metal content including Al, Fe, Mn, Cu, Zn and Hg. The purpose of this study was to achieve a better understanding of plant-soil Hg relationships by comparisons of the Mt. Amiata minesite with the summit of an active volcano — Mt. Etna — and thereby to gain more insight into metal source and eco-physiology as factors in plant-Hg distribution. Although an Hg source-plant distance relationship clearly exists on Mt. Amiata, its precise nature is still in doubt, as it was impossible to distinguish statistically at p<0.01 among linear, log-linear, exponential, and third order polynomial regressions, even with N=47. Nevertheless, the distance-from-source relationship for Hg was clearly unique. No significant pattern could be assigned to the other metals studied, nor was there evidence of a regular relationship between soil content and plant content except in the case of Hg. Parmelia from Mt. Amiata accumulates Hg from soil degassing which was not at all the case for its mercury source on Mt. Etna. The data also suggests that high Zn values in the lichen of Mt. Amiata may be based on long range atmospheric transport. The Zn content of Parmelia was not analyzed on Mt. Etna. Element atomic ratios, Fe/Al for example, provide good evidence for accumulation of surface soil particulates, other than cinnabar by the thallus. Finally, we conclude that widely separated populations of the same species can display biogeochemical differences that are best explained on an eco-physiological basis.     

Assessment of mercury dispersal in an abandoned mining area by soil and lichen analysis

The total Hg content in soil and in the epiphytic lichen Parmelia sulcata was determined in a former cinnabar mining area on Mt. Amiata. Metal concentrations in soil and in lichen are significantly related and decrease at increasing distances from the zone most affected by minespoil and by air which is still vented from mine shafts. On the basis of these results and of Al analysis, it seems likely that anomalous Hg content in Mt. Amiata lichens is mainly due to the out-gassing of volatile Hg from soil, from vegetation and, in the most heavily polluted zone, to the air from mine shafts.     

The contribution of mercury from thermal springs to the environmental contamination of Mt. Amiata

Historically Mt. Amiata has served as an important source of Hg in the Mediterranean basin. In spite of more than a decade without mining or smelting operations, the area remains heavily contaminated. Many old mine sites as well as geothermal plumes still exist. A common belief is, however, that the many thermal springs which carry their contents over the mountainous area, constitute a significant source of Hg. A 1987–88 study of the Hg distribution in air, soil and vegetation at the Bagno Vignoni and Bagni S. Filippo thermal springs, and at the mining town of Abbadia S. Salvatore has demonstrated that Hg content around the springs was comparable to reported values in areas of little or no contamination, whereas those values found at Abbadia S. Salvatore compare well with high levels reported in the mining community of Fort St. James, British Columbia.     

A contribution to the environmental biology of mercury accumulation in plants

Samples of six common plant species collected in the old mining areas near Prince George, British Columbia (Canada) and Mount Amiata, Tuscany (Italy) show remarkable similarities in the variation of plant/soil Hg concentration ratio with soil Hg content irrespective of species or other biological differences. In contrast, plants sampled in the geothermally active areas of New Zealand, Hawaii and around Mount St. Helens exhibit more individuality in the concentration ratio to soil Hg relationship, but the relationships are distinctly different from the mine site specimens. This distinction is particularly evident when the same species of Equisetum and Plantago taken from these two different areas are compared. These and other data support the hypothesis that specific local environmental factors strongly influence the accumulation of Hg in plants even when the immediate soil concentrations are the same. Our findings show that some plants contain concentrations of total Hg as high as 5500 to 14000 μg kg^?1 (dw).     

A comparative study of mercury distribution on the aeolian volcanoes,vulcano and stromboli

Total Hg content was determined in the vegetation, soil and atmosphere of two mediterranean volcanic islands, Vulcano and Stromboli. The metal contents of vegetation, lichens and soil were generally low. By contrast, atmospheric gaseous Hg measured at various stations was as high as levels found elsewhere in proximity to geochemical anomalies such as cinnabar deposits. Comparisons with Mt. Etna and Mt. Amiata were also made in the hope of reaching a better understanding of the role of volcanoes as a source of the metal in the mediterranean basin as a whole.     

Preliminary results on the role of rivers in total Hg concentrations in marine sediments and benthic organisms of a coastal area of Italy

The paper reports the results of mercury (Hg) concentrations in the <20 μm grain-size fraction of shallow sediments of the northern Tyrrhenian sea, collected near the mouths of rivers flowing down from the Monte Amiata area (central Italy), which is characterized by cinnabar mineralization which was developped as mercury mine in the past. A few species of benthic marine organisms collected in the sediment sampling area were also analyzed. From the results, it emerged that the rivers contribute to the Hg concentration in the marine sediments which already contain high natural Hg background levels. The benthic organisms, which reflect sediment contamination, showed high Hg concentrations as well.     

Size Related Mercury Accumulations in Edible Marine Species from an Area of the Northern Tyrrhenian Sea

Mercury concentrations were studied in important edible species from an area of the northern Tyrrhenian Sea, near Mt. Amiata (Tuscany, Italy), affected by mercury contamination. The studied species were: Nephrops norvegicus (Norway lobster), Parapenaeus longirostris (pink shrimp), Merluccius merluccius(hake) and Eledone cirrhosa (horned octopus). From the results it was found that in N. norvegicus and M. merluccius the accumulation was exponential, while in the other two species it was linear. In females ofN. norvegicus, a sharper increase of Hg concentration beyond three centimetres of carapace length was observed and explained by the reduction in growth rate after sexual maturity. In M. merluccius, the metal concentration increased sharply after 40 cm of length, probably due to a reduction in growth rate over this size. In P. longirostris no statistically significant difference between the slope of the linear regressions of males and that of females was found. In Eledone cirrhosa nomercury accumulation difference between the two sexeswas found. The metal concentration was generally highin all the studied species, with a maximum of 4.2 μg g^-1 of fresh weight in N. norvegicus.