Charakterystyka widm absorpcyjnych w podczerwieni kwasów huminowych wydzielonych z czarnej ziemi

R O C Z N IK I G L E B O Z N A W C Z E T. X X V , D O D A T E K , W A R S Z A W A 1974

P IO T R S K Ł O D O W S K I

C H A R A C T E R IS T IC S O F A B S O R P T IO N S P E C T R A

IN IN F R A R E D O F H U M IC A C ID S IS O L A T E D F R O M B L A C K E A R T H Pedological Laboratory Institute of Economical Geodesy,

W arsaw Technical U niversity

IN T R O D U C T IO N

Humic acids constitute a group of humus compounds of soil, the structure and properties of which have not been exactly determined hitherto, despite recently intensified efforts in this direction. Therefore the further investigations on recognition of humic acid structure is very purposeful. Particularly many informations concerning the structure of humic acids can be obtained at the infrared spectroscopy application.

The aim of the present investigations was to determine by means of spectra in infrared of function groups occurring in the humic acid fractions obtained from three subsequent extractions after thier sepa­ ration on columns filled up with the Sephadex G-75 gel.

These measures should give the answer to the following two ques­ tions: (

1

2

IN V E S T IG A T IO N M E TH O D S

For isolation of humus compounds a soil sample from the accumu­ lation horizon A 1 of black earth developed from medium silty lacustrine loam in the state of Michigan, U S A , was taken.

The soil in air-dry state w as ground in an agate mortar, passed through a sieve with the meshes of 0,5 mm in dia. and then w as subject to three subsequent extractions : A, B, C.

— In the extraction A — 0.1M N a

4

2

7

2

4

2

— in the extraction В — 0.1M N a

4

2

7

— in the extraction С— 0.1N N aO H with pH 13.4, w ere applied.

Soil samples were poured with the extract solution (at soil^solution ratio 1:10) and left for 24 hours, stirred up from time to time and next centrifuged at 4000 r.p.m. for 10 min.

In the extractions obtained humic acids w ere precipitated by acidi­ fication with HC1 to pH 1.0 and then separated from fulvic acids by centrifugation. The humic acids precipitated w ere solved in a little amount of 0.1N N aO H and subjected to a dialysis. The dialysis was accomplished in cellophane tubes— at use of great amounts of redistilled water, ex­ changed initially 2-3 times and then 1 time a day. The dialysis was carried out till the moment when w ater ceased to colour and reached pH 7.0 (average

8

In further investigations, from the obtained humic acid preparations 0.5% solutions were made and subjected to fractioning at the Sephadex gel use. The columns with the dimension of

2.2

20

In consequence of the fractioning

8

1— with the molecular weight of over 70 thous., 2— with the molecular weight of 4.5-3.5 thous., 3— with the molecular weight less than 3.5 thous.

Humic acid of the extraction В has been divided into two fractions: 1— with the molecular weight of over 70 thous,

2— -with the molecular weight les than 3.5 thous.

Humic acids of the extraction С have been divided into three fractions similarly as humic acids of the extraction A.

The obtained humic acid fractions w ere condensed on the water bath at the temperature of about 35 °C under lowered pressure and then lyophilized.

From such humic acid preparations tablets w ere made for determin­ ing spectra in infrared. For this purpose 600 mg K B r and 3 mg o f the preparation obtained w ere weighed up. The weighed portions were placed in a special grinder for finer grinding and mixing up 400 mg of weighed portion of the mixture w ere transferred into the press, in which under pressure of

10

Characteristics of absorption spectra... 77

In the tablets obtained spectra in infrared on the Peririn-Elmer In­ frared Spectrophotometer, model 21, w ere determined.

C H A R A C T E R IS T IC S OF A B S O R P T IO N S P E C T R A

Below the most characteristic bands occmring an the spectra in in­ frared of all the fractions of humic adds {Figs 1,

2

-Fig. 2. Extraction B: 0.1 M N a4P207 — pH 10.3 I — m o l e c u l a r g r a v i t y > 70 000, H — m o l e c u l a r g r a v i t y < 3500

% T Ш I

i

of i-Lo nzsb iEpsrt:-jrt a-rcrpticr. oszis in the inTrsred

spectra cx hvj;J.c acids izivestir:atccl

Pernsability T in ^ ü атэ e.v.d';cj*

-Л i extraction A cr.-ürr.ctior. 3 extraction С c:i i 35 С 0-3250 0 0 0 0 1 0 0 0 3000-2330 23 37 42 40 56 17 35 41 2>00—2JC0 - 81 63 - 74 90 80 73 2360-2330 £8 69 82 - 7S - 83 SO 21S0 91 89 £6 91 91 90 90 90 i?;-:c-i70O 25 24 10 - 37 - 29 25 lec-c-icco p 5 0 • 2 6 0 0 3 1595'0.575 - » - 15 - 2 7 -1570-1333 - - 21 22 - 10 14 26 1520-1500 - 56 36 - 54 24 30 42 1495-1485 50 - - - - - ~ 1470-1455 - 50 - - - - 30 -1420-1360 22 29 34 - 25 39 13 15 28 1360-1340 - - - ~ - - 25 35 1265-1210 23 » - 34 - 17 - -1200-1100 9 0 0 - 0 - 2 0 1100-1C00 2 7 9 0 1 2 11 6 Ç40-se0 42 8 14 20 4 41 15 7 850-815 50 - 35 34 - - 27 -800-780 41 47 - 29 - 37 - -760-700 34 38 - 76 33 - 24 30 6'i 0-610 16 24 13 12 19 14 16 37

Characteristics of absorption spectra... ₇₉

B A N D W IT H IN T H E R A N G E OF W A V E N U M B E R S O F 3250-3550 C M -*

In all the spectra a district and broad absorption band occurred within the range of w ave numbers 3250-5350 cm-1, corresponding with valence vibrations of the bounded O H groups as the components of alcohols, acids and phenols. This band according to some authors might be also ascribed to valence vibrations of the N — H bounds belonging to amides [2, 3, 4, 7,

8

In thiis band no significant differences were observed in the adsorption between particular humic acid preparations.

B A N D W I T H I N T H E R A N G E O F W A V E N U M B E R S O F 2880-2940 C M -*

In the humic acid preparations investigated the absorption band within the w ave numbers of 2880-2940 cm

-1

3

2

The analysis of the above band has proved that along with the mo­ lecular weight growth of humic acids the number of C H

3

2

3

2

B A N D W IT H IN T H E R A N G E OF W A V E N U M B E R S OF 2300-2500 C M - i

Within the range o f w ave numbers of 2330-2500 cm

"1

On the basis of the results obtained it can be stated thait along with a drop of the molecular weight of humic acids their acidity is growing.

The latter band is somewhat w eaker than the former, what can be ascribed to valence vibrations of the P — H bound [3]. The absorption in the case of w ave numbers of 2330-2380 cm

-1

B A N D A T T H E W A V E N U M B E R OF 2180 C M - i

In all the humic acid spectra an occurrence of very w eak absorption band of equal intensity at the w ave num ber of 2180 cm

-1

B A N D S W I T H I N T H E W A V E N U M B E R S OF 1500-1800 C M - i

Within the range of wave numbers of 1500-1800 cm

-1

A very w eak absorption occurs within 1700-1720 cm“ 1. This ab­ sorption is as if covered by a very strong absorption from the 'band of 1600-1650 c m -1.

The absorption within the range of w ave numbers of 1700-1720 cm

-1

One of the most characteristic features of the humic acid preparations investigated is obtaining maximal absorption within the w ave numbers of 1600-1650 cm-1 . This absorption is very strongly marked in all the spectra obtained.

The absorption occurrence is ascribed to valence vibrations o f the oarbonylic group C = 0 of chinones as w ell as to valence vibrations of double bounds C = C [1,

2

12

Characteristics of absorption spectra... 81

C = C of the aromatic ring and to those C = 0 of chinon es. R o s o c h a c- k a [

8

Moreover, there occur here the absorption bands caused b y valence vibrations C = N and the bands giving bending vibrations N — H of amides and other nitrogen compounds containing the C = N group [3, 4]. Accord­ ing to D y e r [3] the absorption in question can be caused also by valence vibrations C = 0 of the carboxylate ion.

A very weak absorption was found within the wave numbers of 1575-1595 cm-1. This absorption is ascribed to valence vibration of. double bounds C = C of the aromatic rings as w ell as to those C = 0 of the carboxylate ion [3, 4]. As a characteristic feature there can be mentioned a lack of any absorption within this spectra sector of all the humic acid preparations obtained in the extraction A (sodium pyro­ phosphate with pH 7.0) as w ell as in low-molecular humic acid pre­ parations of the extractions В and C.

A very w eak absorption band within the w ave numbers of 1535- 1570 cm

-1

02

Similarly as above, also the absorption band within the w ave numbers of 1500-1520 cm

-1

B A N D S W IT H IN T H E R A N G E OF W A V E N U M B E R S O F 1300-1500 C M - i

In the humic acid spectra obtained in the extraction A with the molecular weight of 4.5-3.5 thous. there occur single weak bands within the w ave numbers of 1455-1495 cm-1. These bands cannot be observed in any other spectra of the humic acids investigated. The absorption occurring within this spectre sector may be ascribed to deforming v i­ brations С— H of the methyl C H

3

2

-1

In all the spectra of the humic acids investigated an absorption band very distinctly manked can be observed within the w ave numbers of 1360-1420 cm-1. This absorption is ascribed to deforming vibrations

С— Н of the methyl C H

3

Which analyzing the spectra obtained it m ay 'be easily noted that the absorption growth takes place along with a increase of the molecular weight of humic acids. The most intensive absorption has been found in humic acids with the highest molecular weight. Moreover, significant differences in absorption occur between particular extractions. It con­ cerns also humic acids of the extraction C. Humic acids of this extraction show much more intensive absorption than those of the extractions A and B. It leads to the conclusion that humic acids obtained in the exr- traction С would have much more C H

3

A very w eak absorption band within w ave numbers of 1340-1360 cm

-1

Moreover, it should be stressed that within the w ave numbers of 1300-1400 cm

-1

B A N D S W I T H I N T H E R A N G E OF W A V E N U M B E R S OF 1200-1265 C M - 1

Two absorption bands occur within the range of w ave numbers of 1200-1265 cm-1 : one at 1250-1265 cm

-1

B A N D S W IT H IN T H E R A N G E O F W A V E N U M B E R S OF 1000-1200 C M - i

In all spectra of the humic acids investigated a very w ide and in­ tensive absorption band within the wave numbers of

1000-1200

-1

This band is undoubtedly connected with bending vibrations О— О of the OCH3 and С— О— H groups of various alcohols, carboxylic acids and cyclic ethers containing the С— О— С group [

2

3

4

1100

1200

Characteristics of absorption spectra.., 83

or only w eak one occurs in this spectre sector and the strongest ab­ sorption is observed too within the w ave numbers of

1000-1100

It is to stress that within the range of w ave numbers of 1000-1100 cm

-1

B A N D W IT H IN T H E W A V E N U M B E R S OF 880-940 C M - i

In all spectra of the humic acids investigated a very distinct ab­ sorption band within the wave numbers of 880-940 cm

-1

2

8

"1

B A N D S W IT H IN T H E R A N G E OF W A V E N U M B E R S OF 700-850 C M - ‘

A number of single absorption bands occurs within the range of w ave numbers of 700-850 c m "1. A ll they are ascribed to bending vi­ brations С— H of aromatic compounds [3, 4]. This absorption occurs here mainly in the case of humic acids with the highest molecular weight, no absorption being observed in those with the lowest molecular weight.

B A N D S W IT H IN T H E R A N G E OF W A V E N U M B E R S OF 610-640 C M - i

The band within the wave numbers of 610-640 cm

-1

C O N C L U S IO N S

Basing on the absorption spectra observed the following conclusions can be draw n:

1

function groups and molecular weights of humic acids.

of methyl C H

3

2

-1

-1

— Simultaneously, along with the molecular weight growth of humic acids a drop of carboxylic groups in them is observed. Of it the absorption growth within the range of w ave numbers of 2380-2500 cm

-1

— Humic acids with the highest molecular weight show, moreover, a weak absorption, which can be caused by the groups of aromatic compounds. O f it the occurrence of absorption bands within the range of w ave numbers of 1575-1595 cm-1, 1210-1265 cm

-1

-1

2. A ll the humic acid fractions contain most probably sugars. Of it the occurrence of intensive absorption bands within the ranges of 3250- 3500 cm-1, 1000-1200 cm

-1

-1

-1

3. It can be supposed that in the humic acids investigated, particular­ ly in those with the lowest molecular weight, no higher quantities of aromatic compounds could be found. Of it the character of absorption within the range of 1500-1660 cm

-1

4. In the humic acids investigated nitrogen compounds, such as amides and peptides, can occur. However, it is difficult to interpret precisely the results in this respect, as the occurrence range of valence vibrations N — H (3100-3500 cm-1) is covered by the absorption of the OH groups, while the strong absorption within the w ave numbers of 1600-1660 cm

-1

ing vibrations N — H. Nevertheless the absorption occurrence within

1535-1570 cm“ 1, which can be ascribed to bending vibrations of the N — H groups of peptides, can be observed.

5

3

2

Characteristics of absorption spectra. ₈₅

Moreover, it seems that the quantitative relations between humic acids with the lowest molecular weight and those with the highest molecular weight are different for particular extractions. In humic acids of the extraction A the content of compounds w ith the highest molecular value is much lower than in humic acids of the etxraction C. This ques­ tion requires, however, further investigations.

REFERENCES

[1] C z u c h a j o w s k i L . , K r z e c z e k J. J.: U dział chinonów w strukturze k w a ­ sów huminowych w św ietle w idm absorpcyjnych w podczerwieni nowych zw iązków modelowych. Rocz. glebozn. 16, 1966, 3.

[2] D r o z d J.: Physico-chem ical properties of humus substances of soil utilized differen tly. Polish J. Soil Sei., 4, 1971.

[3] D y e r J. R.: Spektroskopia absorpcyjna w chemii organicznej. Warszawa, 1967, PW N .

[4] F a r m e r V. C., M o r r i s o n R. J., Chemical and infrared studies on phrag- mites peat and its humic acid. Sei. Proc. Roy. Dublin Soc., Ser. A 1, 4, 1960, 85.

[5] K o n o n o w a M. M.: Substancja organiczna gleby. W arszawa 1968, P W R iL . [6] K u m a d a K., A i z a w a K.: The infrared spectra of humic acids. Soil Plan t

Fe. 3, 1958, 152.

[7] P o s n e r A. M., T h e n g В. K. G., W a k e J. R. H.: The extraction of soil organic m atter in relation to humification. Trans. 9th Congr. Int. Soil. Sei. Soc. 3, 1968, 153.

[8] R o s o c h a c k a J.: Charakterystyka widm absorpcyjnych w podczerw ieni czterech fra k c ji kwasów fu lw ow ych w ydzielonych metodą W. G. C. Forsytha. Rocz. glebozn. 20, 1969, 335.

[9] S h a r p e n s e e l H. W.: Tracer investigations on synthesis and radiom etric combination of soil organo-m ineral complexes. Trans. Soil Chem istry and F ertility. M eeting of Commissions I I and IV of The Int. Soc. of Soil Sei., Aberdeen 1966.

[10] S ł a w i ń s k a D., S ł a w i ń s k a J.: Chemiluminescencja w procesie degrada- cyjnego utleniania kwasów huminowych. I. K in etyka i skład spektralny. Rocz. Chem. 44, 1970, 1995.

[11] Tokudom e S h o i с h i, Kanno I c h i r o : Nature of the humus of some Japanese soils. Trans. 9th Congr. Int. Soil Sei. Soc. 3, 1968, 163.

[12] T u r s k i R., W i n c e n c i a k C.: Studies in in frared on humic acids of soil on eroded areas. Polish J. Soil Sei. 2, 1969, 21.

[13] T u r s k i R., F l i s - B u j a k M.: The influence of m ineral fertilizin g and the w ay of m anuring of soil on humic acids. Polish J. Soil. Sei. 3, 1970.

[14] T u r s k i R., N g o V a n P h u : The characteristics of humus compounds of soil form ed from solid calcareous rocks in various clim atic zones. Polish J. Soil Sei. 4, 1971, 93.

п. склодовски Х А Р А К Т Е Р И С Т И К А А Б С О Р Б Ц И О Н Н Ы Х С П Е К Т Р О В В И Н Ф Р А К Р А С Н Ы Х Л У Ч А Х Г У М И Н О В Ы Х К И С Л О Т В Ы Д Е Л Е Н Н Ы Х ИЗ Ч Е Р Н О Й П О Ч В Ы Почвоведческая лаборатория Института хозяйственной геодезии Варшавской П олитехники Р е з юм е Д ля вы деления гуминовы х кислот бы л отобран образец из аккум уляцион­ ного горизонта A i черной почвы образованной из озерной пы леватой глины в Ш тате Мичиген, С Ш А. Образец почвы подвеграли трем очередным экстракциям: эстракция А — 0,1 M N a ^ O ? + 7,5 N a2S 0 4 (рН-7,0), В — 0,1 М N a4P 20 7, С — 0,1 Я NaOH. В получен н ы х экстрактах осаж дали гуминовуто кислоту с помощью НС1, а затем подвергали ее диализу в пластмассовы х трубках при использовании различн ы х количеств редистиллированной воды. Затем диализированные гуми- новые кислоты фракционировали при применении ж е л я Сефадекс G-75. В р езультате фракцонирования гуминовая кислота экстракции А разд ели ­ лась на три фракции, гуминовая кислота экстракции В — на две фракции и гуминовая кислота экстракции С — на три фракции. Д еление на фракции происходило в соответствии с м олекулярны м весом ф ракционируемых соеди­ нений. И з получен н ы х таким образом препаратов гуминовых кислот изготовляли таблетки д ля определения спектров в инфракрасны х лучах. Спектры в инфракрасных л у ч а х проводились на спектрофотометре П ер- кин-Эльмер-И нф раред, м одель 21. А н а ли з п олучен ны х спектров показал, что по мере повышения м олек у­ лярного веса гуминовы х кислот повышается содержание в них м етиловы х групп СН3 и м етиленовы х групп СН2. Одновременно с ростом м олекулярн ого веса гуминовы х кислот сниж алось в них содержание карбоксиловы х групп. Сверх того установлено, что гуминовые кислоты с наивысшим м олек уля р ­ ным весом показывают слабую абсорбцию в этих пределах, что может бы ть связано с влиянием группы ароматических веществ. П о всей вероятности фракции гуминовы х кислот содержат сахары. Об этом свидетельствует наличие интенсивных абсорбционных полос в пределах волновы х чи сел 1000-1200 с м ~1 и 880-940 с м - 1. Не бы ли установлены значительны е различия м еж ду препаратами гуми­ новых кислот получаемыми в трех очередны х экстракциях. М ож но при этом заметить, что гуминовые кислоты получаем ы е в экстракции С (0,1 н. N aO H ) содержат наивысшее количество групп СН3 и С Н 2, а меньше всего карбокси­ лов ы х групп, а такж е показывают абсорбцию в этих пределах, которая может свидетельствовать о значительном участии в них ароматических веществ и азот­ н ы х соединений.

Characteristics of absorption spectra., ₈₇

P. S K Ł O D O W S K I

C A R A C T E R IS T IQ U E DES S PE C TR E S A B S O R P T IF S À L ’IN F R A R O U G E DES A C ID E S H U M IQ U E S E X T R A IT S D ’U N E TE R R E N O IR E

L aboratoire de Pédologie, Institut de la Géodesie Économique à l ’Ecole Polytechnique de V arsovie

R é s u mé

Pour extraire des acides humiques on a pris un échantillon du sol l ’horizon d’accumulation A i de la terre noire form ée de l ’argile de lac d’une texture lim o ­ neuse de l ’Etat Michigan, U SA.

On a soumis cet échantillon du sol aux trois extractions successives: extraction A — 0,1m Ш 4 Р г0 7, + 7,5% N a2S 0 4 (pH 7,0),

extraction B — 0,1m Ш 4 Р г0 7, extraction С — 0,ln NaOH.

Dans les extraits obtenus on a précipité des acides humiques en utilisant l ’acide HC1 qu’on a soumis ensuite à la dialyse dans les tubes de celophane, en usant de grandes quantités d’eau redistillée.

On a soumis ensuite des acides humiques dialyses au fractionem ent avec le gel Sephadex G-75. À la suite du fractionnem ent on a divisé l’acide humique de l ’extraction A entre trois fractions, l ’acide humique de l ’extraction B en deux fractions et l ’acide humique de l ’extraction С en trois fractions.

L a division en fractions a eu lieu conform ém ent au poids m oléculaire des composés fractionnés. On a préparé des tablettes de préparation d’acides humiques ainsi obtenues à la determ ination des spectres à l ’infrarouge.

On a exécuté des spectres à l ’infrarouge à P erk in -E lm er In frared Spectro- photometre, m odèle 21.

A ya n t analysé des spectres obtenus on a constaté que le contenu de groupes de m ethyle C H 3 et de ceux de m etylène CH 2 augmente au fu r et à mesure que s’accroit le poids m oléculaire d’acides humiques.

En même temps, avec l ’accroissement du poids m oléculaire diminue le contenu de groupes de carboxylène.

En outre on a constaté que les acides humiques aux plus gramdspoids m olé­ culaires démontrent une absorption faib le dans ces sphères ce qui peut être causé par des groupes de combinaisons aromatiques.

Probablem ent toutes les fractions des acides humiques contiennent des sucres. L ’apparition des bandes inteuses d’absorption en sphères de nombres ondés: 1000-1200 c m - 1, 880-940 c m -1 en est le témoignage.

On n’a pas trouvé de plus grandes différences parm i des préparations d’acides humiques obtenues en résultat de 3 extractions successives.

Néanmoins on peut observer que les acides humiques obtenus en résultat d ’e x ­ tractions С (0,1 n N aO H ) contiennent le plus de groupes CH 3 et ’,CH2 et le moins de groupes de carboxylèle et aussi dem ontrent-ils une absorption dans ces sphères qui peut y prouver une part considérable des combinaisons aromatiques et azoteux.

P. S K Ł O D O W S K I

C H A R A K T E R IS T IK DER A B S O R P T IO N S S P E K T R E N IN DEN IN F R A R O T S T R A H L E N V O N D EN A U S DER SC H W A R Z E R D E IS O L IE R T E N H U M IN S Ä U R E N

Laboratorium für Bodenkunde des Institutes für W irtschaftsgeodäsie der Technischen Hochschule in W arszawa

Z u s a m m e n f a s s u n g

Um die Huminsäuren zu isolieren w urde eine Bodenprobe aus dem A kku m u ­ lationshorizont A i der von dem m ittleren staubigen Lehm entw ickeletn Schwarzerde im Staat Michigan, U SA, entnommen.

Die Bodenprobe wurde den 3 sukzessiven Extraktionen unterworfen, und zw ar: E xtraktion A — 0,1m N a4P207 + 7,5% N a 2S 0 4 (pH 7,0),

,, В — 0,1m N a4P 20 7, C — 0,ln NaOH.

In den erhaltenen Extraktionen waren die Humussäuren m ittels H C l ausge­ fällt, die darauf einer Dialyse in den Zellophanrohren, bei Anwendung grosser Mengen des redistillierten Wassers, unterworfen werden. D ie dialysierten H um in­ säuren waren dann bei Anwendung des Sephadex-G-75-Gels fraktioniert.

Im Ergebnisse der Fraktionierung wurde die Huminsäure der Extraktion A auf drei Fraktionen, diese der Extraktion В — auf zw ei und diese der Extraktion С — auf drei Fraktionen eingeteilt. Die Teilung auf Fraktionen erfolgte nach dem M olekulargew icht der fraktionierten Verbindungen. Aus den auf solche W eise erhaltenen Huminsäurepräparaten wurden die Tabletten zur Spektrenbestimmung in Infrarotstrahlen ausgefertigt. Die Spektren in den Infrarotstrahlen wurden auf dem Perkin-E lm er-Infrarot-Spektrophotom eter, M odel 21, ausgeführt.

Inden die erhaltenen Spektren analysiert waren, ergab es sich, dass je nach der Erhöhung des Hum insäure-M olekulargewichtes sich der Gehalt der M eth yl- C H 3- und M ethylen- C H 2-Gruppen in denselben erhöht. G leichzeitig m it der Z u ­ nahme des M olekulargewichtes der Huminsäuren erniedrigte sich der K arb oxylgru p - pengehalt in denselben.

Überdies wurde festgestellt, dass die Huminsäuren m it dem höchsten M olek u ­ largew icht eine schwache Absorption in diesen Bereichen zeigen, die durch die Gruppen von aromatischen Verbindungen verursacht werden kann.

Wahrscheinlich sind in sämtlichen Hum insäurefraktionen Zucker enthalten. Darüber zeugt das A u ftreten von intensiven Absorptionsbändern innerhalb der W ellennum m erbereiche von 1000-1200 c m - 1 und 880-940 cm -1.

Es wurden keine signifikanten D ifferen zen zwischen den Huminsäurepräparaten, die im Ergebnisse der drei sukzessiven Extraktionen erhalten worden sind, fe s t­ gestellt. Allerdin gs kann man bemerken, dass die in der Extraktion С (0,ln N aO H ) erhaltenen Huminsäuren die höchsten M engen von СНз- und C H 2- Gruppen und die kleinsten Mengen von K arboxylgruppen enthielten sowie die Absorption innerhalb dieser Bereiche aufwiesen, was über den wesentlichen A n teil der aro­ matischen und Stickstoffverbindungen zeugen kann.

Characteristics of absorption spectra... ₈₉

P. S K Ł O D O W S K I

C H A R A K T E R Y S T Y K A W ID M A B S O R P C Y J N Y C H W P O D C Z E R W IE N I K W A S Ó W H U M IN O W Y C H W Y D Z IE L O N Y C H Z C Z A R N E J Z IE M I

Laboratorium Gleboznawstwa Instytutu G eodezji Gospodarczej Politechniki W arszawskiej

S t r e s z c z e ń ie

W celu w ydzielen ia kwasów huminowych pobrano próbkę gleby z poziomu akum ulacyjnego A i czarnej ziemi, w ytw orzon ej z gliny pojeziornej średniej pylastej Stanu Michigan, USA.

Próbkę gleby poddawano trzem kolejnym ekstrakcjom: — ekstrakcja A — 0,lm N a 4P 20 7 + 7,5% N a 2S 0 4 (pH 7,0), — ekstrakcja В — 0,lm N a4P207,

— ekstrakcja С — 0,ln NaOH.

W otrzym anych ekstraktach strącano kwasy huminowe za pomocą HC1 i pod­ dawano je następnie dializie w tubach celofanowych przy użyciu dużych ilości w ody redestylowanej. Dializow ane kwasy huminowe poddawano frakcjonow aniu przy użyciu żelu Sephadex G-75.

W w yniku frakcjonow ania kwas hum inowy ekstrakcji A rozdzielono na trzy frakcje, kwas hum inowy ekstrakcji В — na dw ie frak cje i kwas hum inowy ekstra­ kcji С — na trzy frakcje. Podział na frak cje następował zgodnie z ciężarem cząsteczkowym frakcjonow anych zw iązków . Z tak otrzym anych preparatów kwasów huminowych przygotow ano tabletki do oznaczeń w idm w podczerwieni. W idm a w podczerw ieni wykonano na P erkin -E lm er In frared Spectrophotometr, m odel 21.

Analizując otrzym ane w idm a stwierdzono, że w m iarę jak wzrasta ciężar cząsteczkowy kwasów huminowych, wzrasta w nich zawartość grup m etylow ych CH 3 i m etylenow ych CH 2. Równocześnie w raz ze wzrostem ciężaru cząsteczkowego kwasów huminowych m aleje w nich zawartość grup karboksylowych.

Stw ierdzono ponadto, że kwasy huminowe o największych ciężarach cząsteczko­ w ych w ykazują w tych zakresach słabą absorpcję, która może być powodowana przez grupy zw iązk ów aromatycznych.

Najpraw dopodobniej wszystkie frakcje kwasów huminowych zaw ierają cukry. Św iadczy o tym w ystępow anie intensywnych pasm absorpcyjnych w zakresach liczb falow ych : 1000-1200 i 880-940 cm-1.

N ie stwierdzono większych różnic m iędzy preparatam i kwasów huminowych otrzym anych w w yniku trzech kolejnych ekstrakcji. M ożna jednak zauważyć, że kwasy huminowe otrzym ane w wyniku ekstrakcji C(0,ln N aO H ) zaw ierają n a j­ w ięcej grup C H 3 i C H 2, a najm niej grup karboksylowych, oraz w ykazu ją w tych zakresach absorpcję, która może świadczyć o znacznym udziale w nich zw iązków aromatycznych i zw iązków azotowych.

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