Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 284

obtained from coastal regions in Japan. Because the sediment samples were obtained from
various depths in the total sediment layer, the concentration levels were not uniform, and
some of the shallower samples were contaminated. The background concentrations can be
obtained using a normalizing factor. The procedure adopted for the zinc concentrations
shown in Figure 8.10 was to use the ines content as the normalizing factor. The ines con-
tent refers to the ine particle sizes in the sediment, generally clay and silt, and is deined
as the content of clay and silt fractions <0.075 mm. The line representing the approximate
lower limit shown in Figure 8.10 can be deined as the background zinc concentrations for
the sediments. The detailed theoretical approach to obtain the background line has been
reported by Fukue et al. (2006).
Similar relationships with lead (Pb) and copper (Cu) have been obtained, as shown in
Figures 8.11 and 8.12. Fukue et al. (2006) have used relationships between calculated spe-
ciic surface area and ine content and also limitation of sorption of ine particles under a
relatively low equilibrium concentration. This is due to the limited concentrations of the
substance in nature. The background values for Zn, Pb, and Cu shown in the igures are
lower than the values presented as the ISQGs in Table 8.2. When the background concen-
tration B G is known, the degree of contamination, P d will be obtained as

P d = ( C − B G )/ B G , (8.1)

where C is the current concentration of speciic substance or element (Fukue et al., 1999).

100

Estimated B G

80

Pb = 20 mg/kg

60

40

20

0

0 20 40 60 80 100

Fines content (%)

FIGURE 8.11
Deviation of lead (Pb) concentration in various sediments.