Environmental Engineering Reference
In-Depth Information
•
soil: barium (Ba), cadmium (Cd), cobalt (Co), cupper (Cu), mercury (Hg), lead
(Pb), nickel (Ni), selenium (Se), vanadium (V), zinc (Zn), chloride (Cl), min-
eral oil, sum of EOX (Extractable Organic Halogens) and the sum of PAHs
(10 specified representatives);
•
and groundwater: cadmium (Cd), cobalt (Co), cupper (Cu), mercury (Hg), lead
(Pb), nickel (Ni), selenium (Se), vanadium (V), zinc (Zn), chloride (Cl) , min-
eral oil, naphthalene, some specified volatile aromatic hydrocarbons (including
BTEX), and some specified volatile halogenated hydrocarbons.
Since sampling and laboratory analysis are relatively expensive, generally there
is lack of data. Multivariate and geostatistical tools can support the characterisation
of a site, e.g., Carlon et al. (
2000
) who extracted additional PAH concentrations by
Kriging interpolation of spatial data and Principle Component Analyses (PCA), at
an industrial site close to Parma, Italy.
Generally, two important decisions need to be taken, which require a com-
bination of science and pragmatism. First, the number of samples needs to be
determined. Often, the number of samples that results from a pure statistical anal-
ysis is too costly. Therefore, statistics need to be combined with pragmatism. In
Lamé (
Chapter 3
of this topic) the procedure for sampling has been described, pri-
marily from a practical perspective. In Brus (
Chapter 4
of this topic), this procedure
is approached from a statistical perspective.
Second, a decision needs to be taken about the construction of
composite soil
samples
; these are lumped samples through mixing of separate samples. Obviously,
a chemical analysis of composite samples is factors cheaper than a sampling of the
separate samples. In case the composite samples do not provide enough information
for a well-founded risk appraisal, appropriate separate samples could be analysed
at a later stage. The decisions pertaining to the number of individual samples and
composite samples depend on the degree of heterogeneity of the contaminant (and
of some important soil characteristics such as pH, organic matter content) in the soil
and groundwater.
Also the (statistical) interpretation of the measured concentrations is important.
Altfelder et al. (
2002
), for example, showed that part of the area that may be
declared safe based on merely kriged estimates can actually exceed the German limit
values by a probability of up to 50%. Millis et al. (
2004
) showed for lettuce (vari-
ety Crispino) that variation in plant-scale heterogeneity of cadmium in soil affects
bioavailability and hence the concentration factors plant-soil by a factor of two.
1.5 Risk Assessment
1.5.1 Principles
A measured concentration in soil or groundwater is a rather vague criterion with
regard to determine possible associated problems. The simple purpose of Risk
Assessment is to transfer this measured concentration into a more manageable
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