Chapter 21
Solid Speciation and Selective Extraction Procedures:
Trace Metal Distribution and Speciation in
Coastal Sediments of the Adriatic Sea
C. Ianni· N. Ruggieri
21.1
Introduction
Studies on distribution and speciation of heavy metals in sediments can not only provide information on the degree of pollution, but also on the effective environmental
impact, metal bioavailability, and their origin. Sediments, in fact, are important sinks
for various substances including heavy metals, but they can also be a metal source.
The extension of the phenomena depends on the association of the metals with the
different phases of the sediments, defined as "solid speciation;' which is usually determined by utilizing selective sequential extraction procedures.
In this work, some case studies concerning determination of metal speciation in
coastal sediments of Adriatic Sea will be shown, in order to better explain the importance of solid speciation in environmental studies better. The data presented are part
of different projects: the former is a quasi-synoptic research project for the safeguard
of the Adriatic Sea (PRISMA 2), in particular of the sector "Physical, chemical and biological oceanography;' undertaken in 1996-98. The latter is an INTERREG II project
involving Italy and Greece for the monitoring of the southern Adriatic and Ionic Sea,
undertaken in 1999 and still in progress.
21.2
Role of Marine Sediments in the Environment
Marine sediments are caused by unconsolidated accumulations of particles brought
to the ocean by rivers, glaciers and winds, mixed with shells and skeletons of marine
organisms (Yen and Tang 1977). They are the final destination of trace metals, as a result of adsorption, desorption, precipitation, diffusion, chemical reactions, biological
activity and a combination of those phenomena. When some physical disturbance
occurs, or because of diagenesis and/or changes in pH or redox potential, sediments
can act as a source of metals, releasing them in the overlying water column. This phenomenon can occur even long after the end of direct discharge (Jones and Turki 1997),
and its extension depends on the metal association with the different mineralogical
fractions of the sediment. Therefore, metal behaviour and availability strictly depends
on their chemical form and thus on their speciation. Determination of solid speciation, defined as the identification and quantification of the different species, forms or
phases present in a sediment, has become increasingly important. The measurement
of total content, in fact, is not sufficient to get information on the potential availability of metals (whether toxic or essential) to biota under various environmental conditions (Davidson et al. 1994).
Solid Speciation and Selective Extraction Procedures:
Trace Metal Distribution and Speciation in
Coastal Sediments of the Adriatic Sea
C. Ianni· N. Ruggieri
21.1
Introduction
Studies on distribution and speciation of heavy metals in sediments can not only provide information on the degree of pollution, but also on the effective environmental
impact, metal bioavailability, and their origin. Sediments, in fact, are important sinks
for various substances including heavy metals, but they can also be a metal source.
The extension of the phenomena depends on the association of the metals with the
different phases of the sediments, defined as "solid speciation;' which is usually determined by utilizing selective sequential extraction procedures.
In this work, some case studies concerning determination of metal speciation in
coastal sediments of Adriatic Sea will be shown, in order to better explain the importance of solid speciation in environmental studies better. The data presented are part
of different projects: the former is a quasi-synoptic research project for the safeguard
of the Adriatic Sea (PRISMA 2), in particular of the sector "Physical, chemical and biological oceanography;' undertaken in 1996-98. The latter is an INTERREG II project
involving Italy and Greece for the monitoring of the southern Adriatic and Ionic Sea,
undertaken in 1999 and still in progress.
21.2
Role of Marine Sediments in the Environment
Marine sediments are caused by unconsolidated accumulations of particles brought
to the ocean by rivers, glaciers and winds, mixed with shells and skeletons of marine
organisms (Yen and Tang 1977). They are the final destination of trace metals, as a result of adsorption, desorption, precipitation, diffusion, chemical reactions, biological
activity and a combination of those phenomena. When some physical disturbance
occurs, or because of diagenesis and/or changes in pH or redox potential, sediments
can act as a source of metals, releasing them in the overlying water column. This phenomenon can occur even long after the end of direct discharge (Jones and Turki 1997),
and its extension depends on the metal association with the different mineralogical
fractions of the sediment. Therefore, metal behaviour and availability strictly depends
on their chemical form and thus on their speciation. Determination of solid speciation, defined as the identification and quantification of the different species, forms or
phases present in a sediment, has become increasingly important. The measurement
of total content, in fact, is not sufficient to get information on the potential availability of metals (whether toxic or essential) to biota under various environmental conditions (Davidson et al. 1994).