Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 273

8.4.1 Standards and Guidelines
8.4.1.1 Guidelines
Guidelines have been established in some countries for the purpose of evaluating sedi-
ments contaminated with toxic chemicals. The aim of these guidelines is to limit the con-
centration of toxic chemicals using various criteria—such as those shown in Table 8.1. As
with all criteria based on observed effects on human health, differences exist between the
guidelines used by the various countries. To a large extent, this is because of the different
means for determination of the effective levels, and also in the perception of what consti-
tutes an acceptable risk. For example, since apparent effects threshold (AET) values are
essentially determined by a single result (i.e., the highest nontoxic sample) as opposed to
the entire distribution of results (e.g., as with threshold effect levels TEL or probable effects
level PEL), the inal AET values used by the regulatory agency may vary substantially
depending on the outcome of their analyses. A considerable amount of work remains to
be done in this area. The use of interim values as preliminary values at the present time
recognizes the fact that additional technical work on individual AET values together with
reliability analyses and discussions with other involved agencies are required.
8.4.1.2 Chemicals
The guidelines issued by the various countries and agencies for environmental quality for
sediments include trace and heavy metals and different types of organic chemical com-
pounds. There is no deinitive common listing of elements and chemicals between the
agencies and countries, and no common agreement as to criteria used to evaluate and
target the listed elements and chemicals. An example of sediment quality guidelines can
be seen in the interim sediment quality guidelines (ISQG) and probable effect level (PEL)
values given in the 2003 Canadian Environmental Quality guidelines (Table 8.2). The U.S.
National Oceanic and Atmospheric Administration (NOAA), meanwhile, has established
sediment quality guidelines that contain 9 trace metals, 13 individual polycyclic aromatic
hydrocarbons (PAHs), 3 classes of PAHs, and 3 classes of chlorinated organic hydrocar-
bons. As an example, for lead the ERL (effects: range—low) is 46.7 ppm dry weight, ERM
(effects: range—medium) is 218 ppm dry weight, and the incidence of effects is 90.2% when
the concentration is higher than the ERM. When concentration exceeded the ERM values,
the incidence of adverse effects increased from 60% to 90% for most trace metals and 80%
to 100% for most organics. However, the reliability of the ERMs for nickel, mercury, DDE,
total DDTs, and total PCBs are much lower than those for other substances.
8.4.2 Background and Bioconcentration
8.4.2.1 Background Concentration
As discussed in Section 2.3 in Chapter 2, the elements shown in Table 8.3 are known
to exist naturally in the environment, generally in the form of compounds and miner-
als such as sodium chloride, copper carbonate (azurite Cu 3 (CO 3 ) 2 (OH) 2 , and malachite
Cu 2 CO 3 (OH) 2 ), magnesite (for magnesium), and in food sources such as spinach and
nuts (for magnesium). Not all the elements shown are toxic or totally harmful to human
health. In the listing shown in Table 8.3, both lead (Pb) and cadmium (Cd) are known
as toxic elements and can be safely identiied as contaminants. There are no acceptable
daily intake values for these. The rest of the elements shown in Table 8.3 are known