Nature of plant components identified in soil humic acids

Nature of plant components identified in soil humic acids

115 The Science of the Total Environment, 62 (1987) 115-119 Elsevier Science Publishers B.V., Amsterdam - Printed in The NATURE C. OF PLANT COMPO...

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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).