1982; Fossing and Jorgensen 1990; Elsgaard and Jorgensen 1992, Lee and Fisher
1992). The disadvantage of this method is the unknown relationship between the
experiments and the reality in nature. In addition, it does not provide relationships
between the sediments and the porewater.
The second is the use of sediment traps (flux chambers), which are pushed some
centimeters into sediments or above sediments. This method allows to study the role
of suspended particles depositing on sediments. It gives a direct and real in situ
measurement for the recycling of nutrients and heavy metals from sediments. Since
the chambers are inserted on site, this method does not substantially alter the studied
natural system, whereas a disturbance generally occurs with the core incubation
method. The disadvantage of this method is that it does not provide information on
the changes in different sediment layer and the distributions of elements between
sediments and porewater (Aller 1980a,b; Davison et al. 1982; Hamilton-Taylor et al.
1984; Sakata 1985; Sigg 1986; Westerlund et al. 1986; Sigg et al. 1987; Barbanti et
al. 1992a,b)
The third method consists of the analysis of porewaters and sediments. Since any
change in the diagenetic processes should be reflected by concentration gradients
with depth, this study gives a relationship between sediments and porewater.
Assuming a steady state, a diagenetie model can be used to evaluate the
decomposition rate of organic matter and the role of different oxidants. The diffuse
flux from (into) the sediments can be calculated by Fick's First Law based on the
concentration gradients. The disadvantage of this method is that it does not offer any
information about the reactions occurring directly on the sediment surface and the
role of freshly depositing particles. In addition, porewater sampling requires more
equipment to prevent the oxidation of samples during sample collection,
Recently, porewater sampling by in situ dialysis has been widely used (Kuivila and
Murray 1984; Car~gnan and Nriagu 1985; Carignan 1985; Kuivila et al. 1989;
Vuynovich 1989; Carignan and Lean 1991; Dahmke et al. 1991). Compared to the
conventional squeezing or centrifuging methods, the use of dialysis samplers
('Peeper') requires less equipment and does not disturb the primary conditions in the
porewater.
1992). The disadvantage of this method is the unknown relationship between the
experiments and the reality in nature. In addition, it does not provide relationships
between the sediments and the porewater.
The second is the use of sediment traps (flux chambers), which are pushed some
centimeters into sediments or above sediments. This method allows to study the role
of suspended particles depositing on sediments. It gives a direct and real in situ
measurement for the recycling of nutrients and heavy metals from sediments. Since
the chambers are inserted on site, this method does not substantially alter the studied
natural system, whereas a disturbance generally occurs with the core incubation
method. The disadvantage of this method is that it does not provide information on
the changes in different sediment layer and the distributions of elements between
sediments and porewater (Aller 1980a,b; Davison et al. 1982; Hamilton-Taylor et al.
1984; Sakata 1985; Sigg 1986; Westerlund et al. 1986; Sigg et al. 1987; Barbanti et
al. 1992a,b)
The third method consists of the analysis of porewaters and sediments. Since any
change in the diagenetic processes should be reflected by concentration gradients
with depth, this study gives a relationship between sediments and porewater.
Assuming a steady state, a diagenetie model can be used to evaluate the
decomposition rate of organic matter and the role of different oxidants. The diffuse
flux from (into) the sediments can be calculated by Fick's First Law based on the
concentration gradients. The disadvantage of this method is that it does not offer any
information about the reactions occurring directly on the sediment surface and the
role of freshly depositing particles. In addition, porewater sampling requires more
equipment to prevent the oxidation of samples during sample collection,
Recently, porewater sampling by in situ dialysis has been widely used (Kuivila and
Murray 1984; Car~gnan and Nriagu 1985; Carignan 1985; Kuivila et al. 1989;
Vuynovich 1989; Carignan and Lean 1991; Dahmke et al. 1991). Compared to the
conventional squeezing or centrifuging methods, the use of dialysis samplers
('Peeper') requires less equipment and does not disturb the primary conditions in the
porewater.