7/77 - Institute of Oceanology, Polish Academy of Sciences (IO PAS)
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7/77 - Institute of Oceanology, Polish Academy of Sciences (IO PAS)
OCEANOLOGY No. 7 (1977) 105 R Y SZ A R D B O JA N O W SK I JA N U S Z PE M P K O W IA K P o lish A ca d em y of S c ien ces D ep a rtm en t of O cean ology — S op ot G O T FR Y D K U P R Y SZ E W SK I U n iv e r sity o f G dansk D ep a rtm en t o f C h em istry HUMIC SUBSTANCES IN THE BALTIC SEDIMENTS* I. ISO L A T IO N A N D P R E L IM IN A R Y C H A R A C T E R IZ A T IO N OF H U M IC SU BSTA NC ES C o n t e n t s : 1. In tro d u ctio n 105, 2. E x p erim en ts 106, 3. D iscu ssio n 110, 4. C o n c lu sio n s 117; S tr e szc ze n ie 118; R eferen ces 119. 1. INTRODUCTION Organic m atter plays an im portant role in physico-chemical and bio chemical processes taking place in the bottom sedim ents of shallow m a rine basins. The energy released upon decomposition of organic compounds is utilized by a v ariety of m arine organism s to m aintain th eir life activity. Organic substances contained in bottom deposits influence th eir physical, m echanical and chemical properties, such as hum idity, consistency, red-ox potential ec., and determ ine the direction of diagenetical reactions w ithin the sedim ents [3], N aturally occurring organic substances contain functional groups w hich are capable of binding ions of m etals, thereby expressing ionexchange properties [11], It is assum ed th a t hum ic substances, w hich usually represent a substantial p art of the m arine organic m atter in bot tom sedim ents, play a significant role in the turnover of a num ber of heavy m etals and transition elem ents in the m arine environm ent. In order to elucidate th e physical and chemical properties of hum ic substances and characterize th e ir ion-exchange capability, they have to be isolated from the bulk of m arine sedim ent in reasonably pure state. A common isolation procedure consists in the m ultiple extraction of the sedim ents w ith aqueous solutions of sodium or potassium hydroxide of various strengths (usually 0.1—0.5 M) [2—5, 7, 9], The crude alkaline ex * T h is w o rk w a s fin a n c ia lly su p p orted b y P A N o f IA E A R esearch A g reem en t N o 598/PO L/R2. p ro b lem N o 5 and is p art trac t containing humic and fulvic acids is then acidified to pH 2__3. The hum ic acids form an insoluble precipitate, which is separated by filtra tion or centrifugation from the m other solution containing fulvic acids. Purification of hum ic acids can be effected by consecutive dissolution — precipitation steps, high-speed centrifugation, dialysis and ion-exchange chrom atography [9, 11]. Humic substances are characterized by th eir elem entary composition and presence of functional groups [13, 15, 16], complexing properties [11, 12], isotope composition [9], grow th prom oting properties [8], etc. The use of strong hydroxide solutions has been reported to alter the n atu re of isolated compounds significantly [1], The alteration can even go fu rth er during th e subsequent purification steps, e.g. dialysis causes loss of substances w ith low m olecular weight, and ion exchange chrom atography leads to retention of some compounds on the resin bed due to adsorption effects. In this w ork an attem p t has been made to modify the commonly used extraction procedures for humic acids, the aim being to shorten the extraction tim e and reduce the num ber of extractions w ithout affecting the overall yield of humic acids. Efforts w ere made to find a suitable purification m ethod by which substantial losses of the m aterial could be avoided. 2. EXPERIMENTS 2.1. M A T E R IA L S All experim ents w ere carried out on bottom m aterial from the Bay of Gdańsk (southern Baltic). Samples were taken w ith a snap m ud sam pler in the region of V istula riv er discharge, about 1 km off the river m outh, from a depth of 7 m. Geographical coordinates of the sampling site w ere as follows: 54° 22.3'Ni. e= 18° 59.5'E. P a rt of the sedim ent representing the upperm ost 10 cm layer was transferred to tw ist-off top glass jars and brought to the laboratory. Analyses w ere commenced on fresh m aterial w ithin 20 hours after col lection. The m oisture content of the sedim ent was 78.5% and th e organic carbon content was 5.45% d ry weight. P relim inary preparation of the sedim ent sample for the isolation of humic acids was made using a procedure described by Rashid and King [11], w ith slight modifications. A sam ple of n atu ral m oisture was centri fuged for 20 m inutes at 5,000 g and the supernate, which contained negligible am ounts of coloured substances, was discarded. The sedim ent was treated w ith an equal volume of 0.1 M HC1 to decompose carbonates and the m ixture was adjusted to pH 2 w ith 1 M HC1 while thoroughly swirling. A fter 16 hours th e m ixture was centrifuged, the supernate was discarded and the residue washed w ith distilled w ater and carefully neu tralized to pH 7.0 w ith 0.05 M KOH. The m ixture was centrifuged again, and after rem oving the liquid th e sample was homogenized and the m oisture determ ined. The sample was then divided into th ree sub samples on w hich subsequent extraction experim ents w ere perform ed using different extraction procedures. 2.2. E X T R A C T IO N — M ETH OD A A 145 g undried sub-sam ple w hich contained 31% m oisture, was m ixed w ith 300 cm3 0.5 M KOH solution and left for 16 hours w ith occasional stirring. The m ixture was centrifuged for 20 mins. at 5,000 g, and the residue washed w ith 100 cm3 0.5 M KOH and separated by centrifugation. The solutions w ere combined and the residue was m ixed w ith a second 300 cm3 portion of 0.5 M KOH, then the extraction and washing w ere repeated as above. The to tal num ber of extractions was ten. The solutions from each extraction w ere fu rth er processed to obtain pure preparations of hum ic acids. M inute m ineral particles w ere rem oved by centrifugation for 30 m inutes at 6,000 g then th e extracts w ere acidi fied w ith conc. HC1 to pH 2 and left overnight. The precipitates w ere separated by centrifugation and washed w ith 50 cm3 distilled w ater and the liquids saved to retriev e fulvic acids. Purification of hum ic acids was achieved by consecutive dissolution of the precipitates in 0.5 M KOH, centrifugation and re-precipitation w ith conc. HC1 to pH 2, this having been done four to six tim es to achieve a satisfactory degree of dem ineralization of the preparations. The final precipitates w ere washed w ith 0.01 M HC1 followed by redistilled w ater, u n til the w ashing solution was no longer acidic and w eighed after oven-drying at 70°C. The p re parations w ere th en analyzed for the to tal ash content and elem entary composition, and IR, VIS and UV absorption spectra w ere recorded. The solutions rem aining after the isolation of humic acids contained fulvic acids and large quantities of inorganic salts. They w ere joined and neutralized w ith 0.05 M KOH to pH 7 and vacuum -evaporated at 70°C in a rota-vapour device to about 100 cm3. The solution w as acid ified w ith a few drops of conc. HC1 to pH 2 and left overnight. A ny precipitate was rem oved by filtering the solution through a W hatm an GF/A glass-fibre filter. To remove salts the solution w as applied on th e top of a glass column 0 4 X 40 cm filled w ith Sephadex G — 10 and the column bed was washed w ith redistilled w ater. The eluate was collected in several fractions, and each fraction was checked for the presence of chloride ions. The salt-free fractions were combined and evaporated in Final HA product discard procedure Rye. 1. Schemat wyodrębniania Fig. 1 . Isolation Fina/ FA product osadów sed im en ts kwasy fu/winowe z morskich substances in bottom humusowe substancji humusowych for humic kwasy odrzut a rota-vapour at 70°C to dryness. The residue was then analyzed for the total ash content, elem entary composition, and IR, VIS and UV absorption spectra w ere recorded. The schem atic diagram of th e isola tion of hum ic and fulvic acids from sedim ents is shown in Fig. 1 and the course of alkaline extraction in Fig. 2. Corg m extraction number numer ekstrakcji F ig. 2. C han ges o f o rg a n ic carb on con ten t in th e sed im e n t sa m p le in th e cou rse o f e x tra c tio n w ith 0.5 M K O H (m eth od A) R ye. 2. Z m ian y w za w a rto ści w ę g la o rgan iczn ego w p róbce o sad ów ek stra h o w a n ej p rzy u ży ciu 0,5 M (m etod a A) 2.3. E X T R A C T IO N — M ETH OD BI A portion of th e sedim ent, which had been p re-treated as described in paragraph 2.1. was consecutively extracted w ith eight 300 cm3 portions of 0.1 solution of EDTA (disodium salt). The extracts w ere dialysed through a cellophane bag (Kalle A ktiengesellschaft, West G erm any) against distilled w ater, the dialysates w ere evaporated under reduced pressure to 1/4 of th e original volume, and acidified w ith conc. HC1 to pH 2. A fter 24 hrs. the precipitate of humic acids was centrifuged, washed w ith diluted HC1 and distilled w ater, and dried. The yield of hum ic acids for each extraction w as determ ined gravim etrically, and th e p rep arations w ere thoroughly m ixed to obtain a homogeneous composite sample. On this sam ple the determ ination of the total ash content and elem entary composition was carried out, and absorption spectra in IR, VIS and UV light w ere taken. The sedim ent, after the Na2EDTA extractions, was w ashed four tim es w ith 400 cm3 of distilled w ater and brought in contact w ith 300 cm 3 of 0.2 M KOH for 16 hrs., w ith occasional stirring. The alkaline extraction was repeated three times and the humic and fulvic acids w ere isolated using the same procedure as in Method A. 2.4. E X T R A C T IO N — M ETH OD B2 An aliquot portion of the p re-treated sedim ent sample was extracted w ith two 300 cm3 portions of 0.1 M Na2EDTA for 16 hrs. each, the residues w ere washed th ree tim es w ith distilled w ater and the extrac tion was continued using th ree 300 cm3 portions of 0.2 M KOH for each extraction. Subsequent separations w ere perform ed on the combined alkaline extracts as described in 2.1.2. 3. DISCUSSION The data characterizing extraction efficiency of hum ic and fulvic acids by the three different methods are presented in Table 1. The results indicate th a t all methods tested yield sim ilar quantities of both th e acids, and for the sedim ent sample used in this tria l the am ounts of humic and fulvic acids were 2.4 to 3.1 and 0.49 to 0.54 percent of dry sedim ent, respectively. The higher values for both acids w ere obtained when alkaline extractions w ere made on the NaaEDTA p re-treated samples. T ab le 1 T ab ela 1 R eco v ery o f h u m ic and fu lv ic acid s from sed im e n t sa m p les b y d iffe r en t e x tra ctio n m eth o d s W yd ajn ość k w a só w fu lw in o w y c h i h u m u so w y ch u z y sk a n y ch z osad u d en n ego po za sto so w a n iu ek str a k cji m etod ą A oraz m eto d ą B 1 i B 2 E xtraction m ethod S a m p le size (dry) M etoda e k stra k cji Ilo ść osadu R eco v ery W yd ajn ość C org. C org. FA KF HA KH E x tra ctio n co n d ition s HA KH FA KF W arunki e k stra k cji g % A 100 5,45 2,420 0,485 22,4 4,5 0.5M ,K O H 8x BI 100 5,45 0,255 — 2,3 — N a 2E D T A 8x 2,715 0,525 24,9 4,8 0.2M K O H 3x — — — — N A 2E D T A 2 x 3,070 0,540 28,1 5,0 0.2M K O H 3x B2 100 5,45 g % Assuming the to tal organic m atter in th e sedim ent to be tw ice the am ount of organic carbon, hum ic acids constitute about 28% of the organic m atter, w hereas fulvic acids are m uch less abundant and am ount to some 5% of th e to tal organic m atter. The to tal ash content in the respective fractions of humic and fulvic acids is shown in Table 2. The results for humic acids vary w ith in a narrow range of 2.2 to 2.8% irrespective of the m ethod of extraction. The only result w hich fell outside this range was for the B1 (OHA) fraction, w hich had not been subjected to m ultiple purification proce dure. The ash content in the fulivc acids is m uch greater and am ounts to up to 15.3%, w hich can be indicative of g reater affinity of this tow ard cations. T a b le 2 T ab ela 2 E lem en ta ry co m p o sitio n o f h u m ic and fu lv ic acid s iso la ted fro m B a ltic se d im en ts S k ła d e lem e n ta r n y k w a só w h u m u so w y ch i fu lw in o w y c h w yo d ręb n io n y ch z o sad ów d en n y ch M orza B a łty ck ieg o E xtraction m eth od (fraction num ber) M etoda ek stra k cji (nr frak cji) A A A A B B B B B A B B (1KH**) (3KH) (5KH) (7KH) 1 (OKH) 1 (1KH) 1 (2KH) 2 (1KH) 2 (2KH) (K F ***) 1 (KF) 2 (KF) A sh co n ten t E lem en ta ry co m p o sitio n * Z a w a r tość p op iołu S k ła d elem en ta rn y % C% H% N% 0 + S% 2,2 2,7 2,3 2,8 5,28 2,8 2,4 2,3 2,2 15,1 13,3 12,9 53,94 55,39 55,96 56,61 53,63 55,73 56,92 55,17 56,81 47,32 46,59 46,68 6,31 6,75 6,26 6,28 6,49 6,41 6,17 6,35 6.14 7,77 7,38 7,75 5,74 6,44 5,98 5,88 5,50 5,83 6,02 5,93 5,96 5,61 5,88 6,13 34,01 31,42 31,80 31,23 33,98 32,33 30,89 32,55 31,09 39,30 40,15 30,84 C /H C/'N 8,54 8,20 8,93 9,01 8,26 8,60 9,22 8,61 9,26 6,09 6,31 6,35 9,39 8,60 9,35 9,62 9,08 9,52 9,41 9,30 9,53 8,43 7,92 7,61 C, H a n d N co n te n ts a re ex p ressed on ash fre e substance. Z aw artość C, H, N podano w % p rzeliczonych d la su b sta n c ji pozbaw ionych popiołu. * O + S v alues w ere obtain ed by su b tra c tio n of th e sum of C + H -f N fro m 100%. W artość O + S w yliczono z różnicy: 100%> — (%>C + %H + %N). ** H um ic acids K w asy hum usow e *** F ulvic acids K w asy fulw inow e The course of alkaline extraction of the sedim ent in m ethod A is shown in Fig. 2. Num bers on the ordinate show the to tal organic carbon left in the sedim ent after consecutive extraction steps. The overall decrease of C org. in the sedim ent after ten extractions was 43%. It should be pointed out th a t a little higher recovery of hum ic and fulvic acids w as obtained when Na2EDTA treatm en t was applied prior to alkaline extraction, even though few er extractions w ith m ore diluted KOH solutions w ere carried out. The effectiveness of Na2EDTA alone in solubilizing hum ic acids in the sedim ent proved to be negligible in the first th ree extractions and appreciable quantities of hum ic substan ces began to appear startin g from the fo u rth extract. The rate of ex traction was slow though, the overall yield of eight Na2EDTA extractions having been but 250 mg per 100 g of d ry sediment. The enhancing effect of Na2EDTA on th e alkaline extraction of humic acids can presum ably be attrib u ted to complexing properties of ethylen diam ine tetraacetic acid molecules tow ard positively charged ions of metals. Humic m a tter is 'known to form insoluble compounds w ith m ultivalent cations, and adsorb on m ineral particles [10, 12, 16]. In the presence of Na2EDTA exchange of ligands takes place and m ultivalent cations complexed w ith EDTA are no longer capable of rendering the hum ic m a tter in insoluble form. If adsorption of hum ic acids on clay particles is effected via cations loosely bound to alum inosilicate stru c tures [16] by complexing these cations w ith Na2EDTA th e bonds are broken and hum ic anions are m ade available for alkaline extraction. The results of elem entary analysis of hum ic and fulvic acids are given in Table 2. They are expressed on an ash-free substance basis. The results indicate th a t th e carbon content of consecutive humic acids fractions obtained in m ethod A increases gradually from 53.94% to 56.61%. A t th e same tim e th e hydrogen cointent decreases in th e same order, w hereas the values for nitrogen are w ith in th e range of 5.74 to 6.44%, the variation being irregular. The C/H ratio, w hich is regarded as indicative of the degree of condensation of hum ic acids [2], increases w ith the increase of th e carbon content. Such results m ay speak in favour of the belief th a t during the consecutive alkaline extractions hum ic acids of increasingly condensed molecules pass into th e solution. The elem entary composition of hum ic acids extracted using the th ree different m ethods is m uch th e same, which can be regarded as evidence th a t no substantial alteration of th e natu re of extracted substances has occurred. In comparison w ith humic acids fulvic acids contain higher proportions of hydrogen and a low er carbon content, w hich results in great differences in the C/H ratio for both acids. Absorpion spectra, in visual and u ltraviolet light, of selected humic and fulvic acid fractions are shown in Figs. 3 and 4. Spectra of hum ic acids bear the same character for all th e fractions, and indicate two def lections on the absorption curves, one at 405 nm and th e other at 665 nm, w ith continual increase of absorbance tow ards a shorter w avelength region. On absortion spectra of fulvic acids no such deflecwove length dtugość fa li r„i I 1 wave number liczba falo wa F ig. 3. A b sorp tion sp ectra o f h u m ic (K H ) an d fu lv ic (K F) acid s in v is ib le lig h t R ye. 3. W idm o a b so rp cy jn e k w a só w h u m u so w y ch (KH) i k w a só w (K F) w za k resie w id z ia ln y m wave length długość fa li fu lw in o w y c h r i 1 1 wave number U f '. / t f '] l/czba falowa L J F ig. 4. A b sorp tio n sp ectra o f h u m ic (KH) an d fu lv ic (KF) acid s in u ltr a v io le t lig h t R ye. 4 W idm o a b so rp cy jn e k w a só w h u m u so w y ch (KH) i k w a só w fu lw in o w y c h (KF) w za k resie n a d czerw o n y m 8 — O ceanologia n r 7 tions can be seen in visible light, and absorbance values are generally m uch lower th an for humic acid solutions of th e same concentration. Spectra in visible light provide some inform ation about th e m olecular structure of hum ic acids. Skopintsev [17] has shown th a t the absorbance ratio: K = —■465 nm depends on the degree of condensation of humic -^•665 nm acid molecules, this being higher for stru ctu res w ith a low er degree of condensation, and vice versa. The validity of this finding was confirm ed by Nissenbaum and K aplan [9], T a b le 3 T ab ela 3 K = A 4e5nm : A 665nm v a lu e s fo r d iffe r e n t fu lv ic and h u m ic acid fra ctio n s W artości K = E465nm : E665nm d la p o szczeg ó ln y ch fra k cji su b sta n c ji h u m u sow y ch E xtra ctio n m eth od (fractio n num ber) K M etoda ek str a k c ji A (I K H ) Ą (3KH) A (5KH) A (7KH) E x tra ctio n m eth od (fra ctio n num ber) K M etoda e k stra k cji 4.8 4.65 4.55 4.25 B B B B B 1 (1KH) 1 (2KH) 2 (1KH) 2 (2KH) 1 (OKH) E x tra ctio n m eth od (fraction num ber) K M etoda e k stra k cji 4.7 4.3 4.6 4.35 4.75 A (K F) B 1 (KF) B 2 (KF) 5.8 6.1 5.95 The K values for hum ic acids obtained by consecutive alkaline ex tractions of the bottom sedim ent are shown in Table 3. It can be seen from these data th a t the K values decrease w ith the increasing num ber of extractions, which indicate the growing contribution of more conden sed molecules in each subsequent alkaline extract. The same general conclusion can be draw n from the results of elem entary analyses perform ed on the respective fractions of hum ic acids (Table 2). Fulvic acids show higher K values th an hum ic acids which m ay be associated w ith lower m olecular w eight of the form er [9], Both hum ic and fulvic acids comprise a v ariety of chem ical com pounds w ith different m olecular sizes and elem entary composition [10, 15] which fact makes them a difficult object of study. In frared spectrom etry provides useful m eans of elucidating th e functional composition of such complex substances. In exam ining IR spectra of hum ic and fulvic acids attention is given to th e following w ave num ber regions: 3200 cm-1 — stretching vibrations of — OH and — NH2 bonds, 1720 cm-1 stretching vibrations of > C = 0 in esters and aliphatic aoids, 1650 cm-1 — s tre t ching vibrations of peptide bonds in proteins and > C = C < in arom atic rings 1530 cm-1 —• amide II bonds in proteins, 1240 cm 1 — usually accompanied w ith 1530 cm-1 absorption band, 1200 cm-1 — usually wave number r -n liczba ptowa J F ig. 5. In frared tr a n sm issio n sp ectra o f sep a ra te fra ctio n s of h u m ic (KH) and fu lv ic (KF) acid s R ye. 5. W idm o a b so rp cy jn e p o szczeg ó ln y ch fra k c ji k w a só w h u m u so w y ch i k w a só w fu lw in o w y c h (KF) w za k resie p od czerw o n y m (KH) accompanied w ith a carbonyl band at 1720 c m '1, 1200 — 1100 cm -1 cyclic ethers, 1050 cm -1 — a band characteristic fo r > C = 0 in polysa ccharides, 1000 700 cm-1 — a band characteristic for silicoorganic compounds. Specimen exam ples of IR spectra taken for selected fractions of humic and fulvic acids are shown in Fig. 5, and the m ore im portant absorption bands are tab u lated in Table 4. Interp retatio n of the spectra is compliT ab le 4 T ab ela 4 M ore im p o rta n t in fra red a b sorp tion b an d s fo r h u m ic su b sta n ces iso la ted from B a ltic sed im en ts W ażn iejsze m a k sim a a b sorp cji w p o d czerw o n y m za k resie w id m a dla su b sta n cji h u m u so w y ch z o sa d ó w d en n y ch M orza B a łty ck ieg o E xtraction m ethod (fraction num ber) IR M etoda ek strak cji 3200 1720 n e w o il m ax (cm -1 ) IR n u jol m ax (cm -1) 1650 1530 1240 1260 1200-1100 1030 A (1KH) S ( v e r y w id e ) S M M W M A (3KH) S S S M M A (5KH) S s s M (w ide) szer. M M W M A (7KH) S s s M M W M S M B 1 (1KH) S B 1 (2KH) S B 2 (1KH) S B 2 (2KH) S A (KF) S B 1 (KF) S B 2 (KF) S S b. sz e r . S (v e r y w id e ) b. sz e r . ( v e r y w id e ) S b. sz e r . S ( v e r y w id e ) b. sz e r . S (v e r y w id e ) b . sz e r . s ( v e r y w id e ) b. sz e r . s ( v e r y w id e ) b . sz e r . s (v e r y w id e ) b. sz e r . (very w id e) M b. szer. (v ery w id e) M b. szer. (v ery w id e) M b. szer. S tro n g silne S (w ide) szer. S (w ide) szer. S M s M M w M (w ide) szer. M M S (w ide) szer. M S s S s s s M — m edium śre d n ie S (w ide) szer. M (w ide) M (w ide) szer. szer. M S M W S(ujide) S (w ide) S (w ide) szer. S (w ide) szer. szer. szer. M M M M S (w ide) b. szer. S (w ide) szer. w _w eak słabe ■ cated by the presence of strong and wide absorption bands. It can be seen, however, th a t the spectra of fulvic acid fractions are all alike, w ith all the aforem entioned bands being w ell visualized. The more pronounced absorption peaks occur at 1050-1 and w ithin a range of 1200 — 1100 cm-1 , w hich w ere not observed in th e hum ic acid spectra. T here are also some additional peaks in hum ic acid spectra, at 1240 cm -1 and 1200 cm“ 1 w hich are not seen in the spectra of fulvic acids. Humic acids do not seem to undergo alteration in the course of alkaline ex tra ct ion significant enough to be revealed by the IR spectra. 4. CONCLUSIONS A comparison of different extraction m ethods for isolating hum ic substances from m arine sedim ents indicates th a t treatm en t of th e sedi m ents w ith 0.1 M solution of Na2EDTA prior to alkaline extraction w ith 0.2 M KOH solution results in faster dissolution rate and greater yield of hum ic substances com pared w ith m ethods th a t m ake use of hydrox ide solutions alone. The resu lts of elem entary analysis and IR, VIS and UV spectra show no substantial differences in the physical and chem ical properties of the hum ic substances isolated by both the m eth ods. The effectiveness of N a2EDTA in enhacing solubilization of organic m a tter contained in sedim ents m ay be due to com plexation of heavy m etal ions th a t form insoluble compounds w ith hum ic substances. A nother factor th a t m ay contribute is th e action of Na2EDTA on organo-m ineral aggregates, w hich brings th e organic com ponent to solution. An advontage of the p re-tre atm e n t of sedim ent sam ples w ith Na2EDTA solution is th a t by using more dilute hydroxide extractants and shortening th e extraction procedure organic compounds are less exposed to the adverse environm ent, thereb y yielding products which resem ble m ore closely th eir original structure. OCEANOLOGIA N r 7 (1977) 118 R Y SZ A R D B O JA N O W SK I J A N U S Z P E M P K O W IA K P o lsk a A k a d em ia N a u k Z akład O cea n o lo g ii — S op ot G O T FR Y D K U P R Y SZ E W SK I U n iw e r sy te t G dański In sty tu t C h em ii — G d ań sk S U B S T A N C J E H U M U SO W E W O S A D A C H D E N N Y C H M O RZA B A Ł T Y C K IEG O I. W Y O D R Ę B N IE N IE I W S T Ę P N A C H A R A K T E R Y ST Y K A S U B S T A N C J I H U M U SO W Y C H S tresz cz e n ie S u b sta n c je org a n iczn e za w a rte w o sad ach d en n y ch m órz o d g ry w a ją w a ż n ą rolę w fizy k o ch em ic zn y ch i b io ch em iczn y ch p rocesach zach od zących w ty ch osadach. N a jw ię k sz ą fra k cję su b sta n cji o rg a n iczn y ch o sa d ó w d en n y ch sta n o w ią su b sta n cje h u m u sow e. W ła sn o ści su b sta n cji h u m u so w y ch p ozn an e zo sta ły w m a ły m stop n iu ; w iad om o jed n ak , że w sk ła d fr a k c ji h u m u so w ej za w a rtej w m orsk ich osa d a ch d en n y ch w ch od zą zw ią z k i zn a czn ie ró żn ią ce się ciężarem czą steczk o w y m , p osia d a ją ce szereg gru p fu n k c y jn y c h , ta k ich jak h y d ro k sy lo w e, k a rb o n y lo w e, k a rb o k sy lo w e, a m in o w e, u g ru p o w a n ia a ro m a ty czn e i h etero cy k liczn e. P o ró w n a n ie w y n ik ó w badań nad su b sta n cja m i h u m u so w y m i, k tó re z o sta ły u z y sk a n e przez różn ych badaczy, sp ra w ia tru d n o ści ze w z g lęd u n a sto so w a n ie różn ych m etod izo lo w a n ia ty ch zw ią zk ó w z o sa d ó w oraz m o żliw o ści zm ia n w n a tu rze w y o d ręb n io n y ch su b sta n cji. W p racy p rzed sta w io n o m eto d ę szy b k ieg o w y o d r ęb n ia n ia su b sta n cji h u m u so w y c h z osad ó w i o czy szcza n ia u z y sk a n y ch su b sta n c ji w w a ru n k a ch za ch o w a w czy ch . M etoda p o leg a n a w stę p n e j ob rób ce osad u 0,1 M ro ztw o rem w erse n ia n u d w u so d o w eg o (N a2E DTA ), a n a stę p n ie ek str a k c ji osad u 0,2 M ro ztw o rem w o d o ro tlen k u p o ta so w eg o (KOH). T a k i sp osób iz o la cji p o zw a la z w ię k sz y ć w y d a jn o ść e k stra k cji oraz ogran iczy ć ilo ść d estru k c y jn y ch e k stra k cji a lk a liczn y ch W w y p a d k u sto so w a n ia w y łą c z n ie ek stra k cji a lk a liczn y ch k o n ieczn a je st d z ie się ciok rotn a ek stra k cja 0,5 M ro ztw o rem KO H, co sp raw d zon o ozn aczając za w a rto ść w ę g la organ iczn eg o (corg) w o sa d zie po k o lejn y ch ek stra k cja ch . U z y sk a n e su b sta n c je h u m u so w e rozd ziela n o n a k w a sy h u m u so w e i k w a sy fu lw in o w e w y k o rzy stu ją c różn icę rozp u szcza ln o ści ty ch zw ią zk ó w w śro d o w isk u k w a śn y m (pH 2). K w a sy h u m u so w e oczyszczan o drogą w ir o w a n ia , a k w a sy fu lw in o w e — na k o lu m n ie w y p ełn io n ej S ep h a d e x e m G -10. W celu sch a ra k tery zo w a n ia u z y sk a n y ch w tra k cie k o le jn y c h e k stra k cji fra k cji k w a só w h u m u so w y ch i k w a só w fu lw in o w y c h w y k o n a n o w id m a ab so rp cy jn e w o d n y ch roztw orów ty ch k w a só w w ś w ie tle w id z ia ln y m i n a d fio le c ie oraz w id m a w p od czerw ien i. W yk on an o r ó w n ież a n a lizę sk ła d u elem en ta r n e g o p o szczeg ó ln y ch frak cji, ozn aczając za w a rto ść w ę g la , w od oru i azotu. W idm o a b so rp cy jn e w ś w ie tle w id z ia ln y m o trzy m a n e d la ro ztw o ró w k w a só w h u m u so w y ch w y k a z u je d w a p u n k ty p rzegięcia: p rzy d łu g o ści fa li 405 n m i 665 nm . N a to m ia st w id m o k w a só w fu lw in o w y c h m a ch a ra k ter m o n o to n iczn y w ty m z a k re sie . W idm o a b so rp cy jn e w n a d fio le c ie d la k w a só w h u m u so w y ch i fu lw in o w y c h p osiada p u n k t p rzeg ię cia p rzy ok oło 280 nm . W idm a ab sorp cyjn e w ś w ie tle w id z ia l nym i n a d fio lecie w y k a z u ją w z ro st absorp cji w ra z ze z m n iejsza n iem d łu g o ści fa li. Z n aczn ie bardziej in te r e su ją c e są w id m a a b so rp cy jn e w p o d czerw ien i. P om im o u tru d n ion ej, ze w z g lęd u n a bardzo siln e i bardzo szero k ie p asm a, in te r p r e ta c ji w e w sz y stk ic h a n a lizo w a n y ch fra k cja ch w y k a za n o is tn ie n ie pasm ab sorp cji w y w o ła n ych o b ecn ością gru p h y d ro k sy lo w y ch , k a rb o n y lo w y ch , k a rb o k sy lo w y ch , a m in o w y ch , a tak że w ią z a ń p ep ty d o w y c h u gru p ow ań a ro m atyczn ych i p olicu k rów . A n a liza elem en ta rn a w y k a za ła , że k w a sy h u m u so w e za w iera ją 53,94— 56,61% w ę gla, 6,14— 6,75% w o d o ru oraz 5,74— 6,44% azotu. S k ła d elem e n ta r n y k w a só w fu lw in o w y ch je st n ieco in n y . Z a w a rto ść w ę g la w y n o si 46,68—47,32%, za w a rto ść azotu 5,61— 6,13%, a zaw a rto ść w o d o ru 7,35— 7,77%. N ie stw ierd zo n o z a leż n o ści p o m ięd zy ch a rak terem w id m w p o d czerw ien i a sk ła d em elem en ta rn y m b a d a n y ch zw ią zk ó w . W zrost w y d a jn o śc i e k stra k cji po w stę p n y m u ży ciu w e r sen ia n u d w u so d o w eg o w y tłu m a czo n o k o m p lek so w a n iem jo n ó w m e ta li przez siln y lig a n d , ja k im je s t w e r sen ia n d w u sod ow y . N ie b ez zn a czen ia m oże b y ć ró w n ież w p ły w w e r se n ia n u na stru k tu rę m in era łó w ila sty c h , k tó re są g łó w n y m c zy n n ik iem a d sorb u jącym su b sta n cje h u m u so w e z w o d y m orsk iej. REFEREN CES LITERATURA 1. A k i r a O tsu k i, T a k a n i s h a H an ya, S o m e P re c u rso rs o f H u m ic A c id in R e c e n t L a k e S e d im e n t, S u g g e ste d b y In fra -R e d S p e c tr a , G eoch im . C osm ochim . A cta, 1967, 31, 1505. 2. B o r d o w s k i O.K., A c c u m u la tio n o f O rga n ic M a tte r in B o tto m S e d im e n ts , Mar. G eol., 1965, 3, 33. 3. B o r d o w s k i O.K., O rg a n ic ze sk o je w ie s z c z e s tw o so w rie m ie n ń y c h o sa d k o w B e rin g o w o M oria, T ru d y Inst. O k iean oł., 1960, 42, 89. 4. D e g e n s E.T., R e u t e r J.H., S h a w N.T., B io ch e m ic a l C o m p o u n d s in O ffsh o re C a lifo rn ia S e d im e n ts a n d S ea W a te r, G eoch im . C osm ochim . A cta, 1964, 28, 45. 5. E a rly d ia g e n e sis in S p a n ish In le t, a red u cin g fjo r d , B r o w n E.S., B o e d e c k e r M.J., N i s s e n b a u m A. , K a p l a n I.R., G eoch im . C osm ochim . A cta, 1972, 36, 1185. 6. G o l d b e r g E.D., A r r h e n i u s G.O.S., C h e m is tr y o f th e P a c ific P e la g ic S e d im en ts, G eochim . C osm och in . A cta, 1958, 13, 153. 7. 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R a s h i d M .A., C o n trib u tio n o f H u m ic S u b sta n c e s to th e C a tio n E x ch a n g e C a p a c ity o f D iffe re n t M a rin e S e d im e n ts , M ar. S edim ., 1969, 5, 44. 12. R a s h i d M .A., R o le o f H u m ic A c id s o f M a rin e O rig in a n d th e ir D iffe re n t M o lecu la r W e ig h t F ra ctio n s in C o m p le x in g D i-a n d T r iv a le n t M eta ls, S o il Sci., 1971, 111, 298. 13. R a s h i d M .A., Q u in o n e C o n te n t o f H u m ic C o m p o u n d s Is o la te d fr o m th e M a rin e E n v iro n m e n t, S o il Sci., 1972, 113, 181. 14. R a s h i d M .A., B a c 1 a y D.E., R o b e r t s o n K.R., W z a im o d ie js tw ije h u m in o w y c h k is lo t s r o z lic z n y m i g lin is ty m i m in ie r a la m i i p r ir o d n y m i o sa d k a m i w ilow y c h w o d a c h b lizk ic h k w o d a m e stu a rie w , I M iezdun arodn yj G ieoch im iczesk ij K on griess. O sadocznoje p rocessy. Tom . IV , K n iga 2, 125. M o sk w a 1973. 15. 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