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Figure 1. sampling points on a regular-mesh
grid
This procedure is articulated in the following
phases:
1.
calculation of the mean concentration
2.
calculation of the error
3.
determination of Student's t value
4.
calculation of UCL95 of the mean
1)
Using the data measured during a char-
acterization campaign it is possible to
represent the punctual concentration
values on the nodes of a regular-mesh
grid (Figure 1) and their corresponding
errors. The C
m
value is given by the
relation (Dacquino, 2004):
n
m
n
m
å
å
å
å
Cb
C
ij
ij
ij
i
=
1
j
=
1
i
=
1
j
=
1
C
=
=
3)
In the Student table (Gilbert, 1987) the t value
is found, univocally determined once known
the level of approximation, that is 0.05 and
n×m-1, where n×m is the number of cells.
In the table, for n×m-1≥ 120, tn×m-1,0.95
= N0.95, where N is the normal distribution
of the data.
m
B
nm
´
(18)
In which C
ij
represents the concentration cal-
culated by means of the application of kriging in
correspondence of node ij (row i, column j), n
and m are respectively the rows and the columns
of the grid, b
ij
is the area of the mesh ij (Figure
1) and, being the grid regular:
In this way the Source Representative Concen-
tration can be obtained from the formulation:
B
nm
b
ij
==
´
cos
t
(19)
C
=
CL
= +
Ct
´ =+ ´
e
CN
e
R
95
m
nm
´-
1095
,.
m
095
.
(21)
2)
From the (18) it is possible to obtain the error
value by means of the relation (Dacquino,
2004):
geostatistics for characterization
and Monitoring
n
m
n
m
n
m
å
å
å
å
å
å
2
e
22
b
e
2
e
By means of the application of geostatistical
techniques it is possible to get to the definition
of a model able to describe the spatial variability
of parameters, in order to make operations of
inference in localizations where no information
is available, estimating also the associated error.
The knowledge of the structure of the variability
and of the variance of the estimation permits to im-
ij
ij
ij
ij
i
=
1
nnm
j
=
1
i
=
1
j
=
1
i
=
1
j
=
1
e
=
=
( )
=
2
2
´
B
nm
(20)
In which ε
ij
represents the smallest possible
error, calculated through application of kriging
at node ij.
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