CHAPTER 55
The Link between Continental and Marine Geochemistry
as shown by Mercury and Arsenic Anomalies in Sediments
from Southern Tuscany and Tyrrhenian Sea
M. naIl' Agliol, O. Ferretti 2 , F. Manfredi Frattarelli 2 , and I. Niccolai 2
ABSTRACT
Presenting and discussing new data stressing the link between marine and continental trace
element geochemistry is the aim of this paper.
1. Among the maps from geochemical exploration surveys, applied to environmental issues, it
is worth mentioning the one that shows the distribution of Hg in the stream sediments from
Tuscany, where 1,000 samples were examined from an area of 20,000 km 2 (1966). Fifteen
years later huge Hg anomalies were picked up in marine sediments from Tyrrhenian sea and
20 years later Hg contents in local fisheries were frequently found to be higher than the
allowed Maximum Admissible Concentration (MAC) values.
2. Data on the anomalous As contents, in both continental and marine environments, are presented.ln particular, the new maps of As distribution in the stream sediments of southern
Tuscany, as well as in marine sediments from the Piombino channel, show huge and wide
anomalies. These last data are impressive, because the average value of all the 57 samples is
as high as 66 mg/kg (vs an average value for the Earth's crust of about 2 mg/kg) and the samples collected around Elba Island have an average value as high as 252 mg/kg, with peaks of
over 400 mg/kg. The isoconcentration curves clearly identify the origin of the dispersion
aureole on the eastern coast of the Island. With reference to As distribution, two very extensive and distinct aureoles can be distinguished: one originating from the mining sector of
eastern Elba Island (high arsenopyrite content in sulfide deposits) and the other located in
mainland Tuscany and represented by multiple dispersion sources.
The need for urgently initiating research in two related complementary areas to get more information on the As aureoles and on their effects on the biota is also discussed.
Introduction
Studying geochemical anomalies of toxic trace
elements in dispersion media related to the biosphere. taking into account continental and marine
environments as a whole, is the best way to evaluate the environmental and health effects caused
by geochemical anomalies.
The abundance and the bioavailability of
chemical elements have. in fact, always had a
strong influence on the survival and development of the biosphere. affecting either the different ecosystems in general or individual living
species in particular.
The distribution of essential, critical and toxic
elements corresponds, to a fIrst approximation, to
standards of uniformity within the different geochemical spheres. The anomalous distribution of
these elements, especially within geochemical
spheres which mostly interact with the biosphere,
may have direct effects on the health of animals,
in general, and of man, in particular. The scientific community - moreover - has just recently realized that the appearance of life on and the subsequent biological evolution of our planet are closely related to and dependent on the geochemical
evolution that occurred at the Earth's surface in
geological times (Dall' Aglio 1995).
I Dipartimento eli Scienze della Terra, Universitil "La Sapienza", Roma, Italy
2 Centro Ricerche Ambiete Marino, ENEA St. Teresa. Pozzuolo eli !.eric 316, 19100 La Spezia. Italy
F.M. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag Italia 200 1
The Link between Continental and Marine Geochemistry
as shown by Mercury and Arsenic Anomalies in Sediments
from Southern Tuscany and Tyrrhenian Sea
M. naIl' Agliol, O. Ferretti 2 , F. Manfredi Frattarelli 2 , and I. Niccolai 2
ABSTRACT
Presenting and discussing new data stressing the link between marine and continental trace
element geochemistry is the aim of this paper.
1. Among the maps from geochemical exploration surveys, applied to environmental issues, it
is worth mentioning the one that shows the distribution of Hg in the stream sediments from
Tuscany, where 1,000 samples were examined from an area of 20,000 km 2 (1966). Fifteen
years later huge Hg anomalies were picked up in marine sediments from Tyrrhenian sea and
20 years later Hg contents in local fisheries were frequently found to be higher than the
allowed Maximum Admissible Concentration (MAC) values.
2. Data on the anomalous As contents, in both continental and marine environments, are presented.ln particular, the new maps of As distribution in the stream sediments of southern
Tuscany, as well as in marine sediments from the Piombino channel, show huge and wide
anomalies. These last data are impressive, because the average value of all the 57 samples is
as high as 66 mg/kg (vs an average value for the Earth's crust of about 2 mg/kg) and the samples collected around Elba Island have an average value as high as 252 mg/kg, with peaks of
over 400 mg/kg. The isoconcentration curves clearly identify the origin of the dispersion
aureole on the eastern coast of the Island. With reference to As distribution, two very extensive and distinct aureoles can be distinguished: one originating from the mining sector of
eastern Elba Island (high arsenopyrite content in sulfide deposits) and the other located in
mainland Tuscany and represented by multiple dispersion sources.
The need for urgently initiating research in two related complementary areas to get more information on the As aureoles and on their effects on the biota is also discussed.
Introduction
Studying geochemical anomalies of toxic trace
elements in dispersion media related to the biosphere. taking into account continental and marine
environments as a whole, is the best way to evaluate the environmental and health effects caused
by geochemical anomalies.
The abundance and the bioavailability of
chemical elements have. in fact, always had a
strong influence on the survival and development of the biosphere. affecting either the different ecosystems in general or individual living
species in particular.
The distribution of essential, critical and toxic
elements corresponds, to a fIrst approximation, to
standards of uniformity within the different geochemical spheres. The anomalous distribution of
these elements, especially within geochemical
spheres which mostly interact with the biosphere,
may have direct effects on the health of animals,
in general, and of man, in particular. The scientific community - moreover - has just recently realized that the appearance of life on and the subsequent biological evolution of our planet are closely related to and dependent on the geochemical
evolution that occurred at the Earth's surface in
geological times (Dall' Aglio 1995).
I Dipartimento eli Scienze della Terra, Universitil "La Sapienza", Roma, Italy
2 Centro Ricerche Ambiete Marino, ENEA St. Teresa. Pozzuolo eli !.eric 316, 19100 La Spezia. Italy
F.M. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag Italia 200 1