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Distribution of hydrocarbon concentrations from urban runoff
The Science of the Total Environment, 93 (1990) 465-480 Elsevier
465
D I S T R I B U T I O N OF H Y D R O C A R B O N C O N C E N T R A T I O N S
FROM URBAN RUNOFF
M. T. Bomboi, A. Hern~ndez, F. M a r i ~ o and E. H o n t o r i a Dept. of H e a l t h and E n v i r o n m e t a l E n g i n e e r i n g A d v a n c e d Civil Engineers' School U n i v e r s i t y City. 28040 Madrid. SUMMARY H y d r o c a r b o n r u n o f f d a t a from M a d r i d h a v e b e e n a n a l y s e d in order to d e t e r m i n e the e f f e c t of time, area c h a r a c t e r i s t i c s and w a t e r flow on the r u n o f f c o n c e n t r a t i o n f r e q u e n c y d i s t r i b u t i o n . In this study, a l i p h a t i c and a r o m a t i c h y d r o c a r b o n c o n c e n t r a t i o n s o b t a i n e d from r u n o f f s a m p l i n g from d i f f e r e n t areas of M a d r i d at d i f f e r e n t times of the year were used. The cumulative frequency d i s t r i b u t i o n s of a n u m b e r of the h y d r o c a r b o n s are c h a r a c t e r i z e d as m o d a l l o g n o r m a l d i s t r i b u t i o n s . The close c o r r e l a t i o n found b e t w e e n a l i p h a t i c and a r o m a t i c h y d r o c a r b o n c o n c e n t r a t i o n s can be e x p r e s s e d by a r e g r e s s i o n line.
INTRODUCTION A
sampling
during
the
determine
programme
period the
from
organic
was May
carried 1985
pollution
to
load
out
in the c i t y
of M a d r i d
April
1986
in
present
in
urban
order
to
runoff.
This i n v o l v e d the a n a l y s i s of a r o m a t i c and a l i p h a t i c h y d r o c a r b o n s which
are
heating health
emitted
systems and the
surfaces
estimated
large
have
their
compounds
environment
receiving
and
by
vehicles
harmful
may
be
removed the
by
urban
emission
and
effects
After being deposited
concentrations,
and p r e v e n t i v e
the
amounts
noxious
environment.
these
assessing
protect
and
in
central on
human
on the street runoff levels
and may
by be
and c o r r e c t i v e m e a s u r e s m a y be t a k e n to
water
courses,
treatment
plants
and
the
in general.
In t h i s study, m a n y and v e r y d i f f e r e n t d a t a are o b t a i n e d for e a c h one the a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s analysed.
0048-9697/90/$03.50
© 1990 Elsevier Science Publishers B.V.
~6
The
aim of this w o r k
is to k n o w h o w d a t a are g r o u p e d and its
behaviour.
Statistical
and
frequency
data
lines
calculated
analyses
have
histograms
as
been
well
carried
as
out
regression
in o r d e r to be able to relate a l i p h a t i c w i t h
aromatic hydrocarbons. Data
frequency
histograms
statistical
analyses
distribution
when
reasonable
to
variability thereof
it
group
distribution,
in
the
order
has
them
carried
find
each
different
in
and
which
the
most
and
Thus
the
out
it
the
data
is
form of
exist,
characteristic
from o b s e r v i n g the histogram,
in
variable's
values
into a d j a c e n t values.
them
can be found
usually
to
many
frequency
between
are
the
values
for to assess
n o r m a l i t y and to d e t e r m i n e the m o m e n t s of the d i s t r i b u t i o n . Histograms and
aromatic
this of
work,
each
of
the
frequency
hydrocarbon
with
the
individual
distributions
concentrations
purpose compound
of
of the
have
finding the
been
aliphatic derived
in
form of d i s t r i b u t i o n
and
finding how and where the v a l u e s
the
statistical
are c o n c e n t r a t e d . The and
results
mode,
deviation an
aid
and
have used
dispersion:
, (refs. in
i,
finding
how
near
distribution
(ref.
carried
out
to
order
or
correlation
variance
far the
3).
know
The
the
a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s Pearson
coefficient
data
and
were
correlation
relationship
was
calculated, and
determined
expression
obtain a
mathematical
a l i p h a t i c to a r o m a t i c h y d r o c a r b o n s
median
standard
indices w e r e to
or
from
analysis
existing
in road runoff.
the r e l a t i o n b e t w e e n t h e s e v a r i a b l e s ; to
mean,
2). The s k e w n e s s and k u r t o s i s
normal
in
range,
terms:
was
between
For this,
which
a
the
measures
a r e g r e s s i o n line was
in u r b a n runoff.
which
relates
467
MATERIAL AND METHODS S a m p l i n g and A n a l y t i c a l P r o c e d u r e s The areas
samples
of
used
Madrid.
in
this
Sampling
were
and
analytical
4),
so
pertinent
i n f o r m a t i o n will be p r e s e n t e d here.
November
1985
artificially
a
samples were collected
and
March
simulate
1986.
runoff,
A
brief
in M a y
hose
producing
a
minutes,
after having
e i g h t minutes.
the
catchment
been
throughly
had
been
washed
several
have
summary
1985,
July
was
water
curtain
hosed
five
the
1985,
used
to
which
S a m p l i n g was
down
days
been
of
pipe
s w e p t the c a t c h m e n t b e c a u s e M a d r i d has low rainfall. performed
in
procedures
elsewhere
runoff
only
collected
described
Urban
(ref.
study
for
two
beforehand
for
R u n o f f was c o l l e c t e d in m e t a l traps s e c u r e d to the
g r o o v e d streets. Samples methylene
were
chloride
centrifuged and
the
chloride/methanol.
Extracts
column.
was
The
aliphatic
column
hydrocarbons
and
water
particulate were
eluted and
the
matter
hexane
extracted with
fractionated
with
with
was
in
in
hexane/methylene
methylene
a
order
with
florisil to
chloride
obtain which
r e s u l t e d in the c o l l e c t i o n of a r o m a t i c h y d r o c a r b o n s . The
hydrocarbons
resolution detector.
gas
were
analysed
with a
Dani
6800
chromatograph
equipped
with
flame
ionization
Thirty metre
e i t h e r S£-30 or S£-54
a
high
fused silica c a p i l l a r y c o l u m n s c o a t e d w i t h (0.25 mm i.d, J & W Scientific)
a l i p h a t i c and a r o m a t i c analyses,
w e r e u s e d for
respectively.
STUDY DESIGN Samples including
a
were
collected
landscaped
area,
from a
several
residential
areas area,
of a
Madrid
commercial
468
area w i t h m a n y
shops
and
large p a r k i n g
area,
an area
in the old
q u a r t e r w i t h c l o s e d in, c o m p a c t b u i l d i n g s and an i n d u s t r i a l area. Two
sampling
contrasting and
the
points daily
were
chosen
traffic
other with
flows;
in each
of the
one w i t h
< i0,000 v e h i c l e s / d a y
five
> i0,000
were
determine
taken
the
at
variation
different in
the
with
vehicles/day
in o r d e r to assess
i n f l u e n c e of the t r a f f i c to the r e s u l t s obtained. samples
areas
washing
polluting
At some points,
times
load
the
in
with
order
the
to
washing
stage.
Data A n a l y s i s and S t a t i s t i c a l
Procedures
Data was r e c o r d e r for s t a t i s t i c a l plus
(+)
programme's
computer
analysis
backup.
on the DBase III
Statistical
analyses
p e r f o r m e d w i t h the S t a t i s t i c a l P a c k a g e for Social S c i e n c e s (ref.
5),
with
the
information
being
processed
on
a
were
(SPSS)
IBM
3270
computer.
RESULTS FreQuency Distribution The
results
determined
aromatic
hydrocarbon
frequency
histograms.
were the
taken
as v a r i a b l e s
individual
probability within a The
of
this
study
concentrations
were
The
in
resulting
aliphatic
used
to
and
produce
frequencies
in o r d e r to o b s e r v e the d i s t r i b u t i o n
averages~ thus an
of
individual
enabling
the
measurement,
calculation
taken
randomly,
of
of the
being
s p e c i f i c range. histograms
hydrocarbons
are
obtained
similar
in
for shape
each and
of
the
represent
aliphatic non-normal
d i s t r i b u t i o n s w i t h p e a k s t o w a r d s the lowest c o n c e n t r a t i o n values. Distribution
values
for C27
and C 2 9 , w h i c h
are
s i m i l a r to those
469
of the o t h e r a l i p h a t i c h y d r o c a r b o n s , C27
has
5.5
ug/L
44.77%
of
and
83.6%
between
2.5
and
60.62,
indicate
concentrations. distributed
are g i v e n in t h i s paper.
its c o n c e n t r a t i o n s of
8.5
all
the
values
ug/L.
The
range,
that It
is
towards
around
there not
a
the
right
exist
normal
2.5 ug/L,
determined 44.4, a
the
i)
positive
at are
variance
variability
distribution,
with
(Fig.
and
high
26.85%
rather
in
it
kurtosis
is and
skewness.
Count
Midpoint
30
1
18
4
8
7
3 2
1('~ 13 16
!
0
c
19
2
~
~
I
~=
0
28
1 0
34
ii m m i m i
31
I
37 40 43 46
0
0 0 1
l ....
+....I
0
....
+ ....
I ....
+ ....
I ....
+ ....
6 12 18 Histogram Frequency
I ....
+ ....
24
I
30
Fig i. H i s t o g r a m of C27 c o n c e n t r a t i o n d i s t r i b u t i o n s in road runoff.
The
C29
frequency
concentrations with range
are
near
81% of the v a l u e s 99.4
to
1.25
The
dispersion.
(Fig. ug/L,
occuring between
and the v a r i a n c e
results.
kurtosis,
histogram
standard
347.3
2)
shows
32.5%
2.98.
31% of the
to
8.75
16.25 ug/L.
c o n f i r m the v a r i a b i l i t y
deviation,
and skewness,
close
1.25 and
18.86,
T h i s is a non normal d i s t r i b u t i o n ,
i0.i,
that
also
shows
ug/L The
of the this
also with positive
470
Count 0 21 22 12 3 3 3 0
Midpoint -10.0 -2.5 5.0 12.5 20.0 27.5 35.0 42.5 c 50.0 ~D -~ 57.5 65.0 72.5 80.0 87.5 95.0 102.5 110.0
1 1
0 0 0 1
0 1
0
m m m m m
m m
.... + .... I .... + .... I .... + .... I .... + .... I .... + .... I 0
Figure
5 10 15 Histogram Frequency
2. H i s t o g r a m o f C 2 9 in r o a d r u n o f f .
Representation and
C29
on
of
probability
obtained
(Fig.
compounds,
therefore,
type the
of
3),
distribution
log-normality From
the
frequency
paper which show
of
histograms
in this
study,
in urban
surface
water
is shown, t w o are
a
almost
similar
obtained those
will
and benzo(a)pyrene.
for
data
straight
obtained
for
lines
parallel.
C27
being
These
two
far
as
the
is c o n c e r n e d
and
variability
distributions
25
distributions
distribution
concentrations
of these
analysed
pyrene
the
concentration
20
as
is c o n f i r m e d . the
aromatic
hydrocarbons
for compounds
with
a high
be highlighted,
such
as
incidence
fluoranthene,
471
Y
~
gg,llO-
C27
~
c29
90.
5O
L
I
I
. . . .
110¢ M+
Figure
The
3. Cumulative frequency distribution in urban runoff.
histogram
fluorantheneis
obtained
for
the
frequency
for C27 and C29
distributions
of
given in Fig. 4 and it can be seen that the values
are widely distributed over the different frequencies. The
variance,
6.6,
and
2.5,indicate that the variability high, and
with 3.1
ug/L.
approached seen which
the majority
of the
Distribution
more
closely
than
by the median values, are
fairly
close
is
the between
standard
deviation,
the results
is not very
concentrations not
for
symmetric, the
other.
although
aliphatic
2.0, the mean,
to each
being between
0.i
this
is
hydrocarbons,as
2.8 and the mode 3.2,
There
is a peak
and bias
towards the high values, with positive kurtosis and skewness
.
472
Count
Mi d p o i ryI2
':}
- 1.00
4
-.25
14 9
.50 1.25
1 ()
2. ()0
3
2.75
8
•~2 , .
2 5 1
I
~
| ,
!
I
I
I
!
I
~
I
I
"
I
~
I
~ {.)
4.2~5
C ~
5. < x ] 5.75
3
1
6.50 7, 25
3 0
8 ~ 75 9 ,, 5
I"
I IL~I|
10.25 i.
0
1
.... + .... I .... + .... I .... + .... I .... + .... I .... + .... I 4 8 12 16 20 Histogram Frequency
0
Figure
4. H i s t o g r a m distributions
Pyrene towards
the
variability deviation between ~cDurl t
!
P'.e.9~ /
(Fig.5) right is
0.45
shows and
not
2.0,
a
non
positive
very
with
and
of fluoranthene in road runoff.
the
2.45
normal
kurtosis
high,
with
majority
concentration
distribution, and
skewness
variance of
4.1,
concentration
with
bias
values.
Data
and
standard
values
being
ug/L.
i'l:t(:![]Oi riC
J7 3 J3 7 8 1 3
,,;2 .7
1.2 1.7 2.2 2,,7
~ t l i l l ~ . l
l
l
~
i
l
m
t
~
3.2
0
~
3. 7
3
~.
4.:~
1 4 ! 1 1 0 0
4.7 5.2 5.7 6.2 6.7
2
8.2
m I
m
7.2
7.7 ....
0
Figure
5.
+ ....
I ....
+ ....
4 Histogram
Histogram of pyrene in road runoff.
I ....
+ ....
8 Frequency
I ....
12
concentration
+ ....
I ....
+ ....
16
distributions
I
20
473 The
benzo(a)pyrene
that
it is n o t
being
between
in the data, The for
a symmetrical 0.25
with
and
accumulated the
but
establish
because main
pyrene
the
and gives
are
data three
(Fig.
with is
paper
to
obtained,
of
3
very
variability
of
2.1.
results
their
(Fig.
fluoranthene it
is
7), and
impossible
log-normality
separated
obtained
against lines
distribution its
indicates
of the values
much
benzo(a)pyrene rise
6)
deviation
of distributions
points
92%
not
and standard
benzo(a)pyrene
with
there
There
probability
log-normality
for
ug/L. 4.7,
on
frequencies
confirming
to
3.25
representation
histogram
distribution,
variance,
fluoranthene,
pyrene;
frequency
clearly,
in r e l a t i o n
to
the
line.
COLII7"I
[' 1
"1 ~C'I~ n "
0
- 3.5
0
....2 . 0 -.5
14 36 1) 4 0 0 0
•
1. ( 2.5 4.0 ~ I1~ ~
0
'
o
m
5.5 7.0
8.5 1().C 11.5
0 0 0 0 1 0
14.5 16.0 17.5 19.0
0
2(:). 5
13.0
III .... + .... I .... + .... I .... + .... I .... +....i .... + .... I 8 16 24 32 40 Histogram Frequency
Figure
6. H i s t o g r a m o f b e n z o ( a ) p y r e n e , distributions in road runoff.
concentration
474
% benz o (a)pyrene pyrene .
sg.
~
,~fluoranthene
s0-1 ~ ....
I0-1 5
5
lo
Figure
lt£
X
7. C u m u l a t i v e f r e q u e n c y d i s t r i b u t i o n , b e n z o ( a ) p y r e n e , p y r e n e and f l u o r a n t h e n e in u r b a n runoff.
ReGression AnalYsis W i t h the p u r p o s e of d e t e r m i n i n g at all times the h y d r o c a r b o n levels
in
urban
calculated
expressing
existing
between
obtained
in this
and
total
surface
study.
aromatic
from C12 chosen
as
compounds
sum
of
to C34 total with
in
variables
the a r e a s studied, The
runoff,
The
a
a
straight
simple easy
total
hydrocarbons
fashion
to
the
calculate
linear
were
regression
chosen
was
relationship
from
aliphatic
line
the
data
hydrocarbons
as v a r i a b l e s
in all
since t h e s e c o m p o u n d s are a l w a y s present.
the
individual
and of the linear
isoalkanes,
aliphatic
molecular
benzo(g,h,i)perylene
concentrations
were
chosen
pristane
hydrocarbons.
weights to
of
the
n-alkanes
and p h y t a n e The
between represent
was
sum of those
naphthalene the
and
aromatic
475
hydrocarbon
fraction.
data
two
of
the
The
variables
correlation
coefficient
is
=
high,
r
0.725,
between
p
<
0.01
the
which
c o n f i r m s the r e l a t i o n s h i p e x i s t i n g b e t w e e n them. The squares
straight method;
dependent
line
equation
taking
total
variable
and
independent variable.
was
determined
by
the
minimum
aliphatic
hydrocarbons
as
the
aromatic
hydrocarbons
as
the
of
the
total
The f o l l o w i n g e q u a t i o n was obtained:
u g / L t o t a l a l i p h a t i c = -12.99 + 4.24 u g / L total a r o m a t i c hydrocarbons hydrocarbons
The straight
statistical
values
regression
line
obtained
which
relates
regression
equation,
other, can be
generalized
enable
for
the
correctness
to
be
the
two
a population
checked variables
greater
and
this
to
each
in size
than
ours w e r e d e t e r m i n e d .
X var constant
Standard which
are
B
SE-B
4.244 -12.992
.344 13.221
slope
estimates
and
constant
a
linear
population. obtaining which
Sig.T
12.333 -.983
errors
of the p o p u l a t i o n ' s
the s l o p e had a zero value, exist
T
.0000 .3300
appear standard
in
column
SE-B
deviation.
If
it w o u l d i n d i c a t e t h a t t h e r e d o e s not
relationship
between
the
To c h e c k t h a t this will not occur,
variables
in
the
the p r o b a b i l i t y of
a zero v a l u e was c a l c u l a t e d a c c o r d i n g to the s t a t i s t i c is
the
relation
between
the
slope's
value
plus
the
476
constant's
value
and the s t a n d a r d
Significance indicates observed
that when
this v a l u e
levels
postulating
statistical
model
fixed
value
of the c o e f f i c i e n t is
predicted value
to the
also
the
by
regression
indicates
total
variance.
Analysis
line
for
model
which
data
the
model
value
column
slope is
however,
being
of
matches the
is
the
0.8549
of
correctness
which
that with
is the
The
between
absolute
the
values
observed.
confirms
R square
regression
of the
the two v a r i a b l e s
which
that
value
explains
=
73%
The the 0.73
of
the
is correct,
the
Mean Squares
760546.19 280009.18
In o r d e r to see w h e t h e r proportion
of
can
be
calculated.
the
total
explained
Thus
squares
760546.19 5000.16
Signif
F=152.1
mean
than
of V a r i a n c e
Regression Residual
the
0.0000
0.00005,
and the v a l u e s
Sum of S q u a r e s
that
the
between
results.
line
less
than
correlation
of r e g r e s s i o n
T:
0.3300.
is the R multiple, of c o r r e l a t i o n
Siq.
being
less
describing
R multiple
that
in
of the
coefficient
the
obtained
shown
the p r o b a b i l i t y
for the constant,
Another
and
are
error.
the of
the
statistic the
obtained
of F = 152.1
confirms
that
there
the r e g r e s s i o n
variability by
F
exists
a level a
of
model
the
dependent
independent
variable
expresses
regression
with
F= 0.0000
and
the
the
residual.
relation
is
relation
of s i g n i f i c a n c e
linear
variable
The
below
between
also
between value 0.00005 the
two
477 variables to
the
which
mean
is
square
residual's
to
calculated.
The
difference
between
dependent
t h e data,
whether
the
the
the
residuals
the
as r e s i d u a l
PRED. PRED.Z RESID.Z
PRED.:
Value
such
Z in the
observed
that
bigger
line
of
residual
line
of
than
those
line
the
regression
values
regression
and
if the
according
were
is
the
calculated
adapts
for
perfectly
to
are zero. been
its
are
standardized
standard
large
following
Minimum
Maximum
i0.000 -180.42 0.97 2.55
532.89 212.46 3.72 3.00
predicted
a
much
the
several
in
estimated
being
matching
values
by
residuals
Difference
RESID.:
of
have
-
RESID.
regression
residual
value
variability
results,
variable
each
the
aim
all r e s i d u a l s
The dividing
to
of the
With
determined
the
due
in
deviation
or small,
and
in they
this
study,
order are
to
find
expressed
table:
Mean
Std.
103.10 0.000 0.000 0.000
Dev.
Cases
115,51 70.08 1.00 0.99
58 58 58 58
from the l i n e a r model.
between
the
value
observed
and
that
calculated. PRED.Z.: RESID.Z.:
Prediction Residual
There were 6.5%
value divided
4 samples
of t h e v a l u e s The
v a l u e d i v i d e d b y the s t a n d a r d
with a RESID.Z
error.
o v e r 2, w h i c h m e a n s
only
studied.
histogram
standardized
by the s t a n d a r d
error.
residuals
obtained (Fig.
for 8)
shows
the that
frequencies the
for
distribution
the of
478
residuals
is
normally
also
normal,
distributed
independent
to
observed
the
of
on
the
straight
coefficient
were
NExD
i,
N
.09 5. ()0 .2:3 2.67 *
dependent for
variable
each
value
is
of
the
0
.52
1.Oh
2..3:7: ":~.( )
0
1.9~
I.([~7
4 4.68 1 3.18
regression
would
to
occur
the
a graph if
X
axis
and
very
the
similar
correlation
I Ca~es,
:
= Normal
Curve)
.
"',~
:~;~i~,~
-I.L)(.! : ~ : ~ . -1.33 * .
.04
may
rise
on
9).
1.33 1.0(~ *** . .67 ~*~*:~ .~:':3 * ~ . ().0 ~ $ ~ -.~;?5 * ~ $ *
0 1.~'4-1.07 2 1.Oh -2.00 0 .52 -2.3:5 1 .2.3-2.67 0 .09 -3.00
Figure
give
values
0u t
2
7 6.16
expected
which
~:t =
l I
6 7.27 7.68 4 7.27
because
the
population
Y axis
(Fig.
.0~
U
the
the
line
0
0 3.18 3 4.68
It
over
that
variable.
Representation those
i.e.,
:* .
Out
8. H i s t o g r a m
be
said
equation
of standarized
from
the
established
residuals.
previous for
these
discussion variables
that is
the
correct
of:
-
the
statistical
-
the
small
Z value.
number
values
confirming
of standardized
it residual
values
exceeding
the
479
-
The m e a n
of
103.1 ug/L,
95.4
concentration
of total
linear aliphatic hydrocarbons
o b t a i n e d by the equation,
ug/L being determined
w i t h the annual m e a n of
from the r e s u l t s of this study,
which
m e a n s a d i f f e r e n c e of only 7.5%.
Standaralzed 8~si~ual 1.0
"I
$$$$$ $$$ $$ $ $$8
• 75
. .
• .
$$$
0 b e
I
.
.5
$
V e
$$
d • 25
Expected
F i g u r e 9. The r e l a t i o n s h i p between e x p e c t e d and o b s e r v e d v a l u e s for a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s .
CONCLUSIONS The
statistical
study
aliphatic
and a r o m a t i c
sampling
programme
expression, and
which
hydrocarbons
during relates
anthropogenic
carried
the
out
origins a with
data
o b t a i n e d for
in u r b a n r u n o f f of M a d r i d in a
year,
aliphatic
on
indicates
hydrocarbons, aromatic
a from
linear natural
hydrocarbons
from
a n t h r o p o g e n i c origin. B a s i c a l l y t h o s e are in this u r b a n r u n o f f and have
noxious
environment. hydrocarbons
and On
harmful considering
of
the
effects in
areas
on
this of
human work,
Madrid
health
and
concentrations with
the of
different
480
characteristics, linear
distinct
expression
compounds
is
whenever
traffic
very
level
useful
qualities
of
in
along
order
the
city
all to
are
seasons,
determine the
same
this these
as
in
t h i s study. Although
values
hydrocarbon, aromatic, each
in
are
one
of
positive
vary
general,
grouped them
as
kurtosis data
too
it has
obtained
from
of
normal
distributions
between
hydrocarbon
toward
and
much
lower
as
values
demostrated
skewness these
data,
them both
of
those
found
Frequency
compound
showed
that
it
possible
the
aliphatic
by h i s t o g r a m
values.
was
for
shapes
and for and
histograms
they to
same
are
non
check
in
r e p r e s e n t a t i o n s on p r o b a b i l i s t i c paper.
REFERENCES 1 2 3 4 5
A.G. Barbancho. E s t a d i s t i c a e l e m e n t a l moderna, N a t i o n a l Public A d m i n i s t r a t i o n School (ed.) Madrid, 1967. R°E. Parker. E s t a d i s t i c a para biologos, O m e g a S.A. (ed.), Barcelona, 1981. F. Moller. M a n u a l of m e t h o d s in a q u a t i c e n v i r o n m e n t research. Part 5. S t a t i s t i c a l Test. F.A.O. F i s h e r i e s T e c h n i c a l p a p e r no. 182, F.A.O., Rome, 1979. M.T. B o m b c i and A. Hernandez. H y d r o c a r b o n s in u r b a n runoff: T h e i r c o n t r i b u t i o n to w a s t e water, Madrid, 1989. In press. N.H. Nie, C.H. Hull, J e n k i n s J. G., K. S t e i n b r e n n e r and D.H. Bent, S t a t i s t i c a l p a c k a g e for the social sciences, 2nd. edition, M c G r a w Hill Company, N e w York, 1975, pp320-365.
465
D I S T R I B U T I O N OF H Y D R O C A R B O N C O N C E N T R A T I O N S
FROM URBAN RUNOFF
M. T. Bomboi, A. Hern~ndez, F. M a r i ~ o and E. H o n t o r i a Dept. of H e a l t h and E n v i r o n m e t a l E n g i n e e r i n g A d v a n c e d Civil Engineers' School U n i v e r s i t y City. 28040 Madrid. SUMMARY H y d r o c a r b o n r u n o f f d a t a from M a d r i d h a v e b e e n a n a l y s e d in order to d e t e r m i n e the e f f e c t of time, area c h a r a c t e r i s t i c s and w a t e r flow on the r u n o f f c o n c e n t r a t i o n f r e q u e n c y d i s t r i b u t i o n . In this study, a l i p h a t i c and a r o m a t i c h y d r o c a r b o n c o n c e n t r a t i o n s o b t a i n e d from r u n o f f s a m p l i n g from d i f f e r e n t areas of M a d r i d at d i f f e r e n t times of the year were used. The cumulative frequency d i s t r i b u t i o n s of a n u m b e r of the h y d r o c a r b o n s are c h a r a c t e r i z e d as m o d a l l o g n o r m a l d i s t r i b u t i o n s . The close c o r r e l a t i o n found b e t w e e n a l i p h a t i c and a r o m a t i c h y d r o c a r b o n c o n c e n t r a t i o n s can be e x p r e s s e d by a r e g r e s s i o n line.
INTRODUCTION A
sampling
during
the
determine
programme
period the
from
organic
was May
carried 1985
pollution
to
load
out
in the c i t y
of M a d r i d
April
1986
in
present
in
urban
order
to
runoff.
This i n v o l v e d the a n a l y s i s of a r o m a t i c and a l i p h a t i c h y d r o c a r b o n s which
are
heating health
emitted
systems and the
surfaces
estimated
large
have
their
compounds
environment
receiving
and
by
vehicles
harmful
may
be
removed the
by
urban
emission
and
effects
After being deposited
concentrations,
and p r e v e n t i v e
the
amounts
noxious
environment.
these
assessing
protect
and
in
central on
human
on the street runoff levels
and may
by be
and c o r r e c t i v e m e a s u r e s m a y be t a k e n to
water
courses,
treatment
plants
and
the
in general.
In t h i s study, m a n y and v e r y d i f f e r e n t d a t a are o b t a i n e d for e a c h one the a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s analysed.
0048-9697/90/$03.50
© 1990 Elsevier Science Publishers B.V.
~6
The
aim of this w o r k
is to k n o w h o w d a t a are g r o u p e d and its
behaviour.
Statistical
and
frequency
data
lines
calculated
analyses
have
histograms
as
been
well
carried
as
out
regression
in o r d e r to be able to relate a l i p h a t i c w i t h
aromatic hydrocarbons. Data
frequency
histograms
statistical
analyses
distribution
when
reasonable
to
variability thereof
it
group
distribution,
in
the
order
has
them
carried
find
each
different
in
and
which
the
most
and
Thus
the
out
it
the
data
is
form of
exist,
characteristic
from o b s e r v i n g the histogram,
in
variable's
values
into a d j a c e n t values.
them
can be found
usually
to
many
frequency
between
are
the
values
for to assess
n o r m a l i t y and to d e t e r m i n e the m o m e n t s of the d i s t r i b u t i o n . Histograms and
aromatic
this of
work,
each
of
the
frequency
hydrocarbon
with
the
individual
distributions
concentrations
purpose compound
of
of the
have
finding the
been
aliphatic derived
in
form of d i s t r i b u t i o n
and
finding how and where the v a l u e s
the
statistical
are c o n c e n t r a t e d . The and
results
mode,
deviation an
aid
and
have used
dispersion:
, (refs. in
i,
finding
how
near
distribution
(ref.
carried
out
to
order
or
correlation
variance
far the
3).
know
The
the
a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s Pearson
coefficient
data
and
were
correlation
relationship
was
calculated, and
determined
expression
obtain a
mathematical
a l i p h a t i c to a r o m a t i c h y d r o c a r b o n s
median
standard
indices w e r e to
or
from
analysis
existing
in road runoff.
the r e l a t i o n b e t w e e n t h e s e v a r i a b l e s ; to
mean,
2). The s k e w n e s s and k u r t o s i s
normal
in
range,
terms:
was
between
For this,
which
a
the
measures
a r e g r e s s i o n line was
in u r b a n runoff.
which
relates
467
MATERIAL AND METHODS S a m p l i n g and A n a l y t i c a l P r o c e d u r e s The areas
samples
of
used
Madrid.
in
this
Sampling
were
and
analytical
4),
so
pertinent
i n f o r m a t i o n will be p r e s e n t e d here.
November
1985
artificially
a
samples were collected
and
March
simulate
1986.
runoff,
A
brief
in M a y
hose
producing
a
minutes,
after having
e i g h t minutes.
the
catchment
been
throughly
had
been
washed
several
have
summary
1985,
July
was
water
curtain
hosed
five
the
1985,
used
to
which
S a m p l i n g was
down
days
been
of
pipe
s w e p t the c a t c h m e n t b e c a u s e M a d r i d has low rainfall. performed
in
procedures
elsewhere
runoff
only
collected
described
Urban
(ref.
study
for
two
beforehand
for
R u n o f f was c o l l e c t e d in m e t a l traps s e c u r e d to the
g r o o v e d streets. Samples methylene
were
chloride
centrifuged and
the
chloride/methanol.
Extracts
column.
was
The
aliphatic
column
hydrocarbons
and
water
particulate were
eluted and
the
matter
hexane
extracted with
fractionated
with
with
was
in
in
hexane/methylene
methylene
a
order
with
florisil to
chloride
obtain which
r e s u l t e d in the c o l l e c t i o n of a r o m a t i c h y d r o c a r b o n s . The
hydrocarbons
resolution detector.
gas
were
analysed
with a
Dani
6800
chromatograph
equipped
with
flame
ionization
Thirty metre
e i t h e r S£-30 or S£-54
a
high
fused silica c a p i l l a r y c o l u m n s c o a t e d w i t h (0.25 mm i.d, J & W Scientific)
a l i p h a t i c and a r o m a t i c analyses,
w e r e u s e d for
respectively.
STUDY DESIGN Samples including
a
were
collected
landscaped
area,
from a
several
residential
areas area,
of a
Madrid
commercial
468
area w i t h m a n y
shops
and
large p a r k i n g
area,
an area
in the old
q u a r t e r w i t h c l o s e d in, c o m p a c t b u i l d i n g s and an i n d u s t r i a l area. Two
sampling
contrasting and
the
points daily
were
chosen
traffic
other with
flows;
in each
of the
one w i t h
< i0,000 v e h i c l e s / d a y
five
> i0,000
were
determine
taken
the
at
variation
different in
the
with
vehicles/day
in o r d e r to assess
i n f l u e n c e of the t r a f f i c to the r e s u l t s obtained. samples
areas
washing
polluting
At some points,
times
load
the
in
with
order
the
to
washing
stage.
Data A n a l y s i s and S t a t i s t i c a l
Procedures
Data was r e c o r d e r for s t a t i s t i c a l plus
(+)
programme's
computer
analysis
backup.
on the DBase III
Statistical
analyses
p e r f o r m e d w i t h the S t a t i s t i c a l P a c k a g e for Social S c i e n c e s (ref.
5),
with
the
information
being
processed
on
a
were
(SPSS)
IBM
3270
computer.
RESULTS FreQuency Distribution The
results
determined
aromatic
hydrocarbon
frequency
histograms.
were the
taken
as v a r i a b l e s
individual
probability within a The
of
this
study
concentrations
were
The
in
resulting
aliphatic
used
to
and
produce
frequencies
in o r d e r to o b s e r v e the d i s t r i b u t i o n
averages~ thus an
of
individual
enabling
the
measurement,
calculation
taken
randomly,
of
of the
being
s p e c i f i c range. histograms
hydrocarbons
are
obtained
similar
in
for shape
each and
of
the
represent
aliphatic non-normal
d i s t r i b u t i o n s w i t h p e a k s t o w a r d s the lowest c o n c e n t r a t i o n values. Distribution
values
for C27
and C 2 9 , w h i c h
are
s i m i l a r to those
469
of the o t h e r a l i p h a t i c h y d r o c a r b o n s , C27
has
5.5
ug/L
44.77%
of
and
83.6%
between
2.5
and
60.62,
indicate
concentrations. distributed
are g i v e n in t h i s paper.
its c o n c e n t r a t i o n s of
8.5
all
the
values
ug/L.
The
range,
that It
is
towards
around
there not
a
the
right
exist
normal
2.5 ug/L,
determined 44.4, a
the
i)
positive
at are
variance
variability
distribution,
with
(Fig.
and
high
26.85%
rather
in
it
kurtosis
is and
skewness.
Count
Midpoint
30
1
18
4
8
7
3 2
1('~ 13 16
!
0
c
19
2
~
~
I
~=
0
28
1 0
34
ii m m i m i
31
I
37 40 43 46
0
0 0 1
l ....
+....I
0
....
+ ....
I ....
+ ....
I ....
+ ....
6 12 18 Histogram Frequency
I ....
+ ....
24
I
30
Fig i. H i s t o g r a m of C27 c o n c e n t r a t i o n d i s t r i b u t i o n s in road runoff.
The
C29
frequency
concentrations with range
are
near
81% of the v a l u e s 99.4
to
1.25
The
dispersion.
(Fig. ug/L,
occuring between
and the v a r i a n c e
results.
kurtosis,
histogram
standard
347.3
2)
shows
32.5%
2.98.
31% of the
to
8.75
16.25 ug/L.
c o n f i r m the v a r i a b i l i t y
deviation,
and skewness,
close
1.25 and
18.86,
T h i s is a non normal d i s t r i b u t i o n ,
i0.i,
that
also
shows
ug/L The
of the this
also with positive
470
Count 0 21 22 12 3 3 3 0
Midpoint -10.0 -2.5 5.0 12.5 20.0 27.5 35.0 42.5 c 50.0 ~D -~ 57.5 65.0 72.5 80.0 87.5 95.0 102.5 110.0
1 1
0 0 0 1
0 1
0
m m m m m
m m
.... + .... I .... + .... I .... + .... I .... + .... I .... + .... I 0
Figure
5 10 15 Histogram Frequency
2. H i s t o g r a m o f C 2 9 in r o a d r u n o f f .
Representation and
C29
on
of
probability
obtained
(Fig.
compounds,
therefore,
type the
of
3),
distribution
log-normality From
the
frequency
paper which show
of
histograms
in this
study,
in urban
surface
water
is shown, t w o are
a
almost
similar
obtained those
will
and benzo(a)pyrene.
for
data
straight
obtained
for
lines
parallel.
C27
being
These
two
far
as
the
is c o n c e r n e d
and
variability
distributions
25
distributions
distribution
concentrations
of these
analysed
pyrene
the
concentration
20
as
is c o n f i r m e d . the
aromatic
hydrocarbons
for compounds
with
a high
be highlighted,
such
as
incidence
fluoranthene,
471
Y
~
gg,llO-
C27
~
c29
90.
5O
L
I
I
. . . .
110¢ M+
Figure
The
3. Cumulative frequency distribution in urban runoff.
histogram
fluorantheneis
obtained
for
the
frequency
for C27 and C29
distributions
of
given in Fig. 4 and it can be seen that the values
are widely distributed over the different frequencies. The
variance,
6.6,
and
2.5,indicate that the variability high, and
with 3.1
ug/L.
approached seen which
the majority
of the
Distribution
more
closely
than
by the median values, are
fairly
close
is
the between
standard
deviation,
the results
is not very
concentrations not
for
symmetric, the
other.
although
aliphatic
2.0, the mean,
to each
being between
0.i
this
is
hydrocarbons,as
2.8 and the mode 3.2,
There
is a peak
and bias
towards the high values, with positive kurtosis and skewness
.
472
Count
Mi d p o i ryI2
':}
- 1.00
4
-.25
14 9
.50 1.25
1 ()
2. ()0
3
2.75
8
•~2 , .
2 5 1
I
~
| ,
!
I
I
I
!
I
~
I
I
"
I
~
I
~ {.)
4.2~5
C ~
5. < x ] 5.75
3
1
6.50 7, 25
3 0
8 ~ 75 9 ,, 5
I"
I IL~I|
10.25 i.
0
1
.... + .... I .... + .... I .... + .... I .... + .... I .... + .... I 4 8 12 16 20 Histogram Frequency
0
Figure
4. H i s t o g r a m distributions
Pyrene towards
the
variability deviation between ~cDurl t
!
P'.e.9~ /
(Fig.5) right is
0.45
shows and
not
2.0,
a
non
positive
very
with
and
of fluoranthene in road runoff.
the
2.45
normal
kurtosis
high,
with
majority
concentration
distribution, and
skewness
variance of
4.1,
concentration
with
bias
values.
Data
and
standard
values
being
ug/L.
i'l:t(:![]Oi riC
J7 3 J3 7 8 1 3
,,;2 .7
1.2 1.7 2.2 2,,7
~ t l i l l ~ . l
l
l
~
i
l
m
t
~
3.2
0
~
3. 7
3
~.
4.:~
1 4 ! 1 1 0 0
4.7 5.2 5.7 6.2 6.7
2
8.2
m I
m
7.2
7.7 ....
0
Figure
5.
+ ....
I ....
+ ....
4 Histogram
Histogram of pyrene in road runoff.
I ....
+ ....
8 Frequency
I ....
12
concentration
+ ....
I ....
+ ....
16
distributions
I
20
473 The
benzo(a)pyrene
that
it is n o t
being
between
in the data, The for
a symmetrical 0.25
with
and
accumulated the
but
establish
because main
pyrene
the
and gives
are
data three
(Fig.
with is
paper
to
obtained,
of
3
very
variability
of
2.1.
results
their
(Fig.
fluoranthene it
is
7), and
impossible
log-normality
separated
obtained
against lines
distribution its
indicates
of the values
much
benzo(a)pyrene rise
6)
deviation
of distributions
points
92%
not
and standard
benzo(a)pyrene
with
there
There
probability
log-normality
for
ug/L. 4.7,
on
frequencies
confirming
to
3.25
representation
histogram
distribution,
variance,
fluoranthene,
pyrene;
frequency
clearly,
in r e l a t i o n
to
the
line.
COLII7"I
[' 1
"1 ~C'I~ n "
0
- 3.5
0
....2 . 0 -.5
14 36 1) 4 0 0 0
•
1. ( 2.5 4.0 ~ I1~ ~
0
'
o
m
5.5 7.0
8.5 1().C 11.5
0 0 0 0 1 0
14.5 16.0 17.5 19.0
0
2(:). 5
13.0
III .... + .... I .... + .... I .... + .... I .... +....i .... + .... I 8 16 24 32 40 Histogram Frequency
Figure
6. H i s t o g r a m o f b e n z o ( a ) p y r e n e , distributions in road runoff.
concentration
474
% benz o (a)pyrene pyrene .
sg.
~
,~fluoranthene
s0-1 ~ ....
I0-1 5
5
lo
Figure
lt£
X
7. C u m u l a t i v e f r e q u e n c y d i s t r i b u t i o n , b e n z o ( a ) p y r e n e , p y r e n e and f l u o r a n t h e n e in u r b a n runoff.
ReGression AnalYsis W i t h the p u r p o s e of d e t e r m i n i n g at all times the h y d r o c a r b o n levels
in
urban
calculated
expressing
existing
between
obtained
in this
and
total
surface
study.
aromatic
from C12 chosen
as
compounds
sum
of
to C34 total with
in
variables
the a r e a s studied, The
runoff,
The
a
a
straight
simple easy
total
hydrocarbons
fashion
to
the
calculate
linear
were
regression
chosen
was
relationship
from
aliphatic
line
the
data
hydrocarbons
as v a r i a b l e s
in all
since t h e s e c o m p o u n d s are a l w a y s present.
the
individual
and of the linear
isoalkanes,
aliphatic
molecular
benzo(g,h,i)perylene
concentrations
were
chosen
pristane
hydrocarbons.
weights to
of
the
n-alkanes
and p h y t a n e The
between represent
was
sum of those
naphthalene the
and
aromatic
475
hydrocarbon
fraction.
data
two
of
the
The
variables
correlation
coefficient
is
=
high,
r
0.725,
between
p
<
0.01
the
which
c o n f i r m s the r e l a t i o n s h i p e x i s t i n g b e t w e e n them. The squares
straight method;
dependent
line
equation
taking
total
variable
and
independent variable.
was
determined
by
the
minimum
aliphatic
hydrocarbons
as
the
aromatic
hydrocarbons
as
the
of
the
total
The f o l l o w i n g e q u a t i o n was obtained:
u g / L t o t a l a l i p h a t i c = -12.99 + 4.24 u g / L total a r o m a t i c hydrocarbons hydrocarbons
The straight
statistical
values
regression
line
obtained
which
relates
regression
equation,
other, can be
generalized
enable
for
the
correctness
to
be
the
two
a population
checked variables
greater
and
this
to
each
in size
than
ours w e r e d e t e r m i n e d .
X var constant
Standard which
are
B
SE-B
4.244 -12.992
.344 13.221
slope
estimates
and
constant
a
linear
population. obtaining which
Sig.T
12.333 -.983
errors
of the p o p u l a t i o n ' s
the s l o p e had a zero value, exist
T
.0000 .3300
appear standard
in
column
SE-B
deviation.
If
it w o u l d i n d i c a t e t h a t t h e r e d o e s not
relationship
between
the
To c h e c k t h a t this will not occur,
variables
in
the
the p r o b a b i l i t y of
a zero v a l u e was c a l c u l a t e d a c c o r d i n g to the s t a t i s t i c is
the
relation
between
the
slope's
value
plus
the
476
constant's
value
and the s t a n d a r d
Significance indicates observed
that when
this v a l u e
levels
postulating
statistical
model
fixed
value
of the c o e f f i c i e n t is
predicted value
to the
also
the
by
regression
indicates
total
variance.
Analysis
line
for
model
which
data
the
model
value
column
slope is
however,
being
of
matches the
is
the
0.8549
of
correctness
which
that with
is the
The
between
absolute
the
values
observed.
confirms
R square
regression
of the
the two v a r i a b l e s
which
that
value
explains
=
73%
The the 0.73
of
the
is correct,
the
Mean Squares
760546.19 280009.18
In o r d e r to see w h e t h e r proportion
of
can
be
calculated.
the
total
explained
Thus
squares
760546.19 5000.16
Signif
F=152.1
mean
than
of V a r i a n c e
Regression Residual
the
0.0000
0.00005,
and the v a l u e s
Sum of S q u a r e s
that
the
between
results.
line
less
than
correlation
of r e g r e s s i o n
T:
0.3300.
is the R multiple, of c o r r e l a t i o n
Siq.
being
less
describing
R multiple
that
in
of the
coefficient
the
obtained
shown
the p r o b a b i l i t y
for the constant,
Another
and
are
error.
the of
the
statistic the
obtained
of F = 152.1
confirms
that
there
the r e g r e s s i o n
variability by
F
exists
a level a
of
model
the
dependent
independent
variable
expresses
regression
with
F= 0.0000
and
the
the
residual.
relation
is
relation
of s i g n i f i c a n c e
linear
variable
The
below
between
also
between value 0.00005 the
two
477 variables to
the
which
mean
is
square
residual's
to
calculated.
The
difference
between
dependent
t h e data,
whether
the
the
the
residuals
the
as r e s i d u a l
PRED. PRED.Z RESID.Z
PRED.:
Value
such
Z in the
observed
that
bigger
line
of
residual
line
of
than
those
line
the
regression
values
regression
and
if the
according
were
is
the
calculated
adapts
for
perfectly
to
are zero. been
its
are
standardized
standard
large
following
Minimum
Maximum
i0.000 -180.42 0.97 2.55
532.89 212.46 3.72 3.00
predicted
a
much
the
several
in
estimated
being
matching
values
by
residuals
Difference
RESID.:
of
have
-
RESID.
regression
residual
value
variability
results,
variable
each
the
aim
all r e s i d u a l s
The dividing
to
of the
With
determined
the
due
in
deviation
or small,
and
in they
this
study,
order are
to
find
expressed
table:
Mean
Std.
103.10 0.000 0.000 0.000
Dev.
Cases
115,51 70.08 1.00 0.99
58 58 58 58
from the l i n e a r model.
between
the
value
observed
and
that
calculated. PRED.Z.: RESID.Z.:
Prediction Residual
There were 6.5%
value divided
4 samples
of t h e v a l u e s The
v a l u e d i v i d e d b y the s t a n d a r d
with a RESID.Z
error.
o v e r 2, w h i c h m e a n s
only
studied.
histogram
standardized
by the s t a n d a r d
error.
residuals
obtained (Fig.
for 8)
shows
the that
frequencies the
for
distribution
the of
478
residuals
is
normally
also
normal,
distributed
independent
to
observed
the
of
on
the
straight
coefficient
were
NExD
i,
N
.09 5. ()0 .2:3 2.67 *
dependent for
variable
each
value
is
of
the
0
.52
1.Oh
2..3:7: ":~.( )
0
1.9~
I.([~7
4 4.68 1 3.18
regression
would
to
occur
the
a graph if
X
axis
and
very
the
similar
correlation
I Ca~es,
:
= Normal
Curve)
.
"',~
:~;~i~,~
-I.L)(.! : ~ : ~ . -1.33 * .
.04
may
rise
on
9).
1.33 1.0(~ *** . .67 ~*~*:~ .~:':3 * ~ . ().0 ~ $ ~ -.~;?5 * ~ $ *
0 1.~'4-1.07 2 1.Oh -2.00 0 .52 -2.3:5 1 .2.3-2.67 0 .09 -3.00
Figure
give
values
0u t
2
7 6.16
expected
which
~:t =
l I
6 7.27 7.68 4 7.27
because
the
population
Y axis
(Fig.
.0~
U
the
the
line
0
0 3.18 3 4.68
It
over
that
variable.
Representation those
i.e.,
:* .
Out
8. H i s t o g r a m
be
said
equation
of standarized
from
the
established
residuals.
previous for
these
discussion variables
that is
the
correct
of:
-
the
statistical
-
the
small
Z value.
number
values
confirming
of standardized
it residual
values
exceeding
the
479
-
The m e a n
of
103.1 ug/L,
95.4
concentration
of total
linear aliphatic hydrocarbons
o b t a i n e d by the equation,
ug/L being determined
w i t h the annual m e a n of
from the r e s u l t s of this study,
which
m e a n s a d i f f e r e n c e of only 7.5%.
Standaralzed 8~si~ual 1.0
"I
$$$$$ $$$ $$ $ $$8
• 75
. .
• .
$$$
0 b e
I
.
.5
$
V e
$$
d • 25
Expected
F i g u r e 9. The r e l a t i o n s h i p between e x p e c t e d and o b s e r v e d v a l u e s for a l i p h a t i c and a r o m a t i c h y d r o c a r b o n s .
CONCLUSIONS The
statistical
study
aliphatic
and a r o m a t i c
sampling
programme
expression, and
which
hydrocarbons
during relates
anthropogenic
carried
the
out
origins a with
data
o b t a i n e d for
in u r b a n r u n o f f of M a d r i d in a
year,
aliphatic
on
indicates
hydrocarbons, aromatic
a from
linear natural
hydrocarbons
from
a n t h r o p o g e n i c origin. B a s i c a l l y t h o s e are in this u r b a n r u n o f f and have
noxious
environment. hydrocarbons
and On
harmful considering
of
the
effects in
areas
on
this of
human work,
Madrid
health
and
concentrations with
the of
different
480
characteristics, linear
distinct
expression
compounds
is
whenever
traffic
very
level
useful
qualities
of
in
along
order
the
city
all to
are
seasons,
determine the
same
this these
as
in
t h i s study. Although
values
hydrocarbon, aromatic, each
in
are
one
of
positive
vary
general,
grouped them
as
kurtosis data
too
it has
obtained
from
of
normal
distributions
between
hydrocarbon
toward
and
much
lower
as
values
demostrated
skewness these
data,
them both
of
those
found
Frequency
compound
showed
that
it
possible
the
aliphatic
by h i s t o g r a m
values.
was
for
shapes
and for and
histograms
they to
same
are
non
check
in
r e p r e s e n t a t i o n s on p r o b a b i l i s t i c paper.
REFERENCES 1 2 3 4 5
A.G. Barbancho. E s t a d i s t i c a e l e m e n t a l moderna, N a t i o n a l Public A d m i n i s t r a t i o n School (ed.) Madrid, 1967. R°E. Parker. E s t a d i s t i c a para biologos, O m e g a S.A. (ed.), Barcelona, 1981. F. Moller. M a n u a l of m e t h o d s in a q u a t i c e n v i r o n m e n t research. Part 5. S t a t i s t i c a l Test. F.A.O. F i s h e r i e s T e c h n i c a l p a p e r no. 182, F.A.O., Rome, 1979. M.T. B o m b c i and A. Hernandez. H y d r o c a r b o n s in u r b a n runoff: T h e i r c o n t r i b u t i o n to w a s t e water, Madrid, 1989. In press. N.H. Nie, C.H. Hull, J e n k i n s J. G., K. S t e i n b r e n n e r and D.H. Bent, S t a t i s t i c a l p a c k a g e for the social sciences, 2nd. edition, M c G r a w Hill Company, N e w York, 1975, pp320-365.