115
The Science of the Total Environment, 62 (1987) 115-119 Elsevier Science Publishers B.V., Amsterdam - Printed in The
NATURE
C.
OF PLANT
COMPONENTS
SAIZ-JIMENEZI
and
IDENTIFIED
J.W.
'Institute de Recursos Sevilla (Spain) 2 Delft University of Engineering, Organic Delft (The Netherlands)
IN
SOIL
Netherlands
HUMIC
ACIDS
DE LEEUW'
Naturales
y Agrobiologia,
Technology, Geochemistry
C.S.I.C.,
Apartado
1052,
Department of Chemistry and Chemical Unit, De Vries van Heystplantsoen
2,
41080
2628
RZ
SUMMARY The chemical structure of two acid hydrolysed soil humic acids was investigated using analytical pyrolysis. A large part of the pyrolysis mixture consisted of a homologous series of straight chain alkanes, alk-l-enes and CL, w alkadienes probably derived from plant cuticles. The origin of other major components in the pyrolysate, phenols and aromatic hydrocarbons, is less clear.
INTRODUCTION The
origin
extensive
of
origins
have
tion
the
humic
acid
investigations
of
acids
are
proposed,
latest
between that
recent
the
peripheral
from
lignins, and
components
can
easily
be
structure
and
affected
by
drastic
removed
acid
humic
paper
with
based This
biopolymers
or
the
on
and
(ref.
mild
oxidations (ref.
chemical
has
geopolymers
of
pyrolysis-gas
(ref.
to 2,
melanins,
formation
of
and
protein
The
question
This
but
is
the
most
is
is
not
extensively
no
moieties
arises
core
humic
humus,
humic
acid
and
what
the
or
hardly
degraded
resistant
part
chromatography-mass
be
4,
of
the
soil
applicasoil
upon
3).
nature
proved
the
there
of
of
that
Although
sugar
is.
on
synthesis
core 2).
part
or
spite
Different
1).
lignin, so-called
resistant
Curie-point
technique
the
in
in 1).
proposed
and
involved
hydrolysis more
permanganate
describes
acids
analyses.
acid the
been
(ref.
that to
unclear (ref.
theory
has
activity
are
still years
recent it
etc.
demonstrated
hydrolysis
oxidation
This
of
is last
most
acids,
attached by
origin
the Thus,
mentioned
loosely
soils the
microbial amino
have or
on
method.
sugars
investigations
are
of over
based
analytical
derived
reaction doubt
been
the
fraction
accomplished
useful
in
the
of
soil
spectrometric
characterization
of
5).
METHODS Two was humic and
soil
samples
from
a Typic
Rend011
and
acid
fractions
NMR spectra
0048-9697/87/$03.50
the the
has of
the
been humic
0 1987
South other
of
Spain
a Typic
described acid
Elsevier
fractions
Science
were
used
Rhodoxeralft. previously have
Publishers
in
this
preparation
6).
Elemental
(ref. also
B.V.
study.
The
been
reported
One
of of
them the
analyses (ref.7).
The
116 analytical
pyrolysis
elsewhere
(ref.
RESULTS
pyrolysis
reported
the
acid
hydrolysis
have
been
described
2,
4).
of
unhydrolysed
Briefly,
products
humic
derived
from
humic acid
acids
fractions
have yield
polysaccharides,
been upon
proteins,
extensively flash
pyrolysis/
lignins,
lipids
pollutants. Figure
HCl
1 shows
and
comparison
istic
pyrolysis
extent, due
the
extraction
with
to
the
The
and
obtained
series
of
the
of
and
encountered
in
soil
humic
yield
such
as
acids
lignins,
the
of and
new
permanganate humic
acid
nols.
However,
difference of
character-
and,
to
some probably
is
upon
pyrolysis
the
biopolymer
has of
to after
the
n-alkanes,
present
in
cuticles
The
pat-
unhydrolysed
from
plant
components,
etc.
(ref.
4)
make
pyreand
hydrocarbon Since
derived
bio8).
I-alkenes
aliphatic
terpenoids,
have
homologous data).
(ref.
hydrolysis.
compounds
the
aliphatic,
reported of
Phe-
pyrograms case
highly
been
series
similar acids
present.
(unpublished
saponifiable,
C31.
alkylbenzenes are
that
C6 to
up
a part
it
is
of
the
acids.
The
phenolic
aliphatic
oxidation
of
humic
on flash origin
non
of
Similar in
prominent
chlorophylls,
chain
which
products.
consist
humic
series
of
from
hydrocarbons
although
cuticles
series
ranging
homologous
less
a new,
soil
humic
oxidation core
6 J-
drastically,
a homologous
aromatic
were
plant
long
permanganate biopolymer.
as
acids,
pattern
the
the
core
alkaline this
of
tocopherols,
that
short
main
proteins
shows
pyrolysis
biopolymers
tern
The
major
fossil
cuticle
~1 , w-alkadienes
so-called
The
with
dissapearance
C( , w -alkadienes
such
components
and
acids
and
fulvic
occurrence
modern
speculated
the
decreased
polycyclic
also
aliphatic
this
hydrolysis
polysaccharides,
humic
some
hydrolysed
the in
the
hydrocarbons
are
for
Recently,
grams
of
and
alkylphenols
been
is
concentrations
alk-1-enes
aromatic
no1
from
after
2 x 10 min.).
samples
acid
mixture
alkylnaphthalenes
acids
process.
alkanes,
addition,
humic
(sonication,
derived fatty
extraction
and
the
unhydrolysed
Also
chain
of
hexane
the
products
pyrolysis
polymer
pyrograms
with to
lignins.
straight In
as
4).
behaviour
(ref.
evaporation and
2,
as well
DISCUSSION
AND
The
method
and
mono-
of
humic
acids
and
acids
yield of
dicarboxylic (ref.
acids
3)
might
benzenecarboxylic might
pyrolysis nature
acids
and
these
the
be derived
acids
originate
from
from upon in
hydrocarbons is
upon
identified
substances
aromatic
substances
obtained
as yet
the and
unclear.
phe
117
I.1
94
61 I
76 I
37
1
I
0
10
0
20
30
Lo
so
60
MIN
Figure 1. Flash pyrolysis-gas chromatography-mass spectrometric analysis of 6 i HCl hydrolysed and hexane extracted humic acids. A: Typic Rend011 humic acid, B: Typic Rhodoxeralft humic acid. Curie-point temperature 770°C. Peak identifications are given in Table 1. Owing to the vast number of identified compounds in each pyrolysate only major peaks are indicated in the figures. GC conditions: Fused silica column (28 m x 0.5 mm I.D.) coated with CP-sil 5 held at O°C for 5 min. and subsequently programmed to 300°C at a rate of 5oC/min The chromatograph (Varian 3200) was coupled to a Varian MAT 44 quadrupole mass spectrometer operated in the EI mode at 80 eV.
118 TABLE Pyrolysis
1 products
of
I Carbon monoxide 2 Carbon dioxide 3 Methane 4 Ethene 5 Ethane 6 Propene 7 Propane 8 Sulphur dioxide 9 But-l-ene 10 Butane 11 Acetone 12 Pent-l-ene 13 Furan 14 Pentane 15 Hex-l-ene 16 Z-Methylfuran 17 Hexane 18 3-Methylfuran 19 Benzene 20 Cyclohexene 21 Hept-1-ene 22 Heptane 23 Methylcyclohexa ne 24 Toluene 25 Acetic acid 26 Ott-1-ene 27 Octane 28 Ethylbenzene 29 m- and/or e-xylene 30 Styrene 31 o-xylene 32 Non-1-ene 33 Nonane 34 C3-alkylbenzene 35 C3-alkylbenzene 36 C -alkylbenzene 37 Ptenol 38 Dee-l-ene 39 Decane 40 C3-alkylbenzene 41 Indane 42 Indene 43 C4-alkylbenzene 44 cresol 45 -I- 4-alkylbenzene 46 C$t;;;:ylbenzene 47 48 o-cresol 49 T: 4.I-alkylbenzene 50 ~1; w-undecadiene 51 Undec-1-ene 52 Undecane 53 C4:I-alkylbenzene 54 C4-alkylbenzene 55 C4,I-alkylbenzene 56 C4:I-alkylbenzene
6 5
HCl
hydrolysed
and 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 ^_
2 8 88 89 90 91 92 93 94 nr
extracted
Methylindene Methylindene C4-alkylbenzene C5-alkylbenzene Naphthalene C5:I-alkylbenzene Methylguaiacol CL ,w-dodecadiene Dodec-1-ene Dodecane Methylnaphthalene Branched tridecane Vinylphenol CA-alkylbenzene CE-alkylbenzene Methvlnaohthalene Ethylgua;acol Methylnaphthalene o ,i-tridecadiene Tridec-1-ene Methylnaphthalene Tridecane C7-alkylbenzene CT-alkvlbenzene /Acenaphthene C2-alkylnaphthalene IMethylbiphenyl ~1 ,u-tetradecadiene Tetradec-1-ene C2-alkylnaphthalene Tetradecane C2-alkylnaphthalene C2-alkylnaphthalene trans-isoeugenol wkylnaphthalene C8-alkylbenzene o,a-pentadecadiene Pentadec-1-ene Pentadecane C3-alkylnaphthalene C3-alkylnaphthalene Cg-alkylbenzene Fluorene CI2 fatty acid C3-alkylnaphthalene -hexadecadiene Ht;awdec-1-ene Hexadecane Xanthene CIO-alkylbenzene C4-alkylnaphthalene a,~ -heptadecadiene Heptadec-i-ene Heptadecane Prist-1-ene Prisf-Z-ene
i;: 2
1;: 101 102 103 104 105 106 107 108 109 110 111 II2
hexane
soil
humic
acids
119 TABLE
1 (continued)
;;;
;ghf;;geacid
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
a,w-octadecadiene Octadec-1-ene Octadecane C fatty acid P&adiene cc,w-nonadecadiene Nonadec-1-ene Nonadecane Methylanthracene Dialkyl phthalate CI6 fatty acid a,w-eicosadiene Eicos-1-ene Eicosane a,w-heneicosadiene Heneicos-1-ene Heneicosane Docos-1-ene
133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152
Docosane Tricos-l-ene Tricosane Tetracos-1-ene Tetracosane Pentacos-1-ene Pentacosane Dialkyl phthalate Hexacos-1-ene Hexacosane Heptacos-1-ene Heptacosane Octacos-1-ene Octacosane Nonacos-1-ene Nonacosane Triacont-1-ene Triacontane Hentriacont-1-ene Hentriacontane
ACKNOWLEDGEMENT This
research
has
been
funded
by
the
C.S.I.C.,
Spain
(Project
No.
781).
REFERENCES F.J. Stevenson, Humus Chemistry, Wiley, New York, 1982. C. Saiz-Jimenez and J.W. de Leeuw, The chemical nature of a soil humic acid as revealed by analytical pyrolysis. J. Anal. Appl. Pyrol. (in press). M. Schnitzer and S.U. Khan, Humic Substances in the Environment, Marcel Dekker, New York, 1972. C. Saiz-Jimenez and J.W. de Leeuw, Chemical characterization of soil organic matter fractions by analytical pyrolysis-gas chromatography-mass spectrometry, J. Anal. Appl. Pyrol. 9 (1986) 99-119. C.Saiz-Jimenez and J.W. de Leeuw, Pyrolysis-gas chromatogra hy-mass s ectrom etry of isolated, synthetic and degraded lignins. Org. Geoc R em. 6 (I9 E 4) 417-422. C. Saiz-Jimenez, K. Haider and H.L.C. Meuzelaar, Comparisons of soil organic matter and its fractions by_._pyrolysis _ mass spectrometry, Geoderma 22 (1979) 25-37. C. Saiz-Jimenez B.L. Hawkins and G.E. Maciel, Cross polarization, magic angle spinning 13 C nuclear magnetic resonance of soil humic fractions. Org. Geochem. (in press). M. Nip, E.W. Tegelaar, J.W. de Leeuw, P.A. Schenck and P.J. Holloway, A new non saponifiable highly aliphatic and resistant biopolymer in plant cuticles: evidence from pyrolysis and I3C NMR analysis of present-day and fossil plants, Naturwissenschaften (in press).