CC BY
51
УДК 631:417
L. W. Szajdak, M. Szczepanski
FUNCTION OF PEATLAND LOCATED ON SECONDARY TRANSFORMED PEAT-MOORSH SOILS ON THE RATES OF THE ELUTION OF ORGANIC MATTER
The elution of soil organic matter from 4.5 km long consisting peat-moorsh soils transect in broad range of pH was investigated. This transect is located in the Agroecological Landscape Park in Turew, 40 km South-West of Poznan, West Polish Lowland. There is this transect along Wyskoc ditch. pH and pseudo first-order reaction constants were measured. Peat-moorsh soils were described and classified according to Polish hydrogenic soil classification and World Reference Base Soil Notation. There are four investigated points along to Wyskoc ditch. Two times a month during entire vegetation season the following material was taken from this four chosen site - samples of peat, from the depth of 0-20 cm. The rates of the reaction were calculated from the kinetics of first order reaction model. All experiments were repeated at different pH 6.0, 6.5, 7.0, 8.0, 8.5 of 0.5 M ammonium acetate buffer solution. The rates of organic matter elution for all samples of peats were significant different at four used wavelengths X = 272 nm, X = 320 nm, X = 465 nm, and X = 665 nm. It was observed that the rates increased between X = 272 nm and X = 320 nm and decreased from X = 465 nm to X = 665 nm.
Key words: peat-moors soils, dissolved organic matter, kinetics of dissolved organic matter.
Peatland nitrogen, sulfur, phosphorus and carbon cycles are controlled by the sharp gradient in dissolved oxygen that occurs spatially, both on a horizontal and vertical scale and in time [1, 2]. Nitrate, ammonium and phosphate pollution caused by using of inorganic fertilizers are especially a great threats for rural areas and led to the eutrophication of ground water. Many physical, chemical, biochemical and biological processes control dispersion of these chemical compounds in soils and finally all these processes depend on the organic matter content and particularly on humic substances [1, 3-5]. Therefore, organic matter plays pivotal roles in several processes, conversions and mechanisms in peatlands, including detoxication of anthropogenic chemicals, C sequestration, water retention, nutrient cycling, soil structure formation and energy supply to soil microorganisms. These processes include biological conversion, biochemical and chemical degradation, reduction, and hydrolysis etc. [6, 7]. Thus they lie at heart of leading environmental and agricultural issues. Although humus of organic soils is affected by the great number of biological and chemical transformation mechanisms, including microbial processes and phytochemical degradation reactions, decomposition and loss of organic matter through biomineralization in surface layer [8]. Humics of different origins can differ significantly with respect to elemental composition, molecular weight, chemical structure etc. These substances represent a class of biogenic, heterogeneous and refractory organic compounds [9-11].
The goal of this study was to investigate impact of the pH solvent on leaching organic matter from soils in order to understand their role in functioning peatland as biogeochemical barriers.
The research site was a transect of peatland 4.5 km long located in the Agroecological Landscape Park host D. Chlapowski in Turew (40 km South-West of Poznan, West Polish Lowland) (Fig. 1).
The investigated points were located along to Wyskoc ditch. Two times a month during whole vegetation season the following material was taken from four chosen sites marked as Zb^chy (No 1), Bridge (No 2), Shelterbelt (No 3) and Hirudo (No 4) (Fig. 1): samples of peat - from the depth of 0-20 cm.
Peat-moorsh soils were described and classified according to Polish hydrogenic soil classification [12, 13] and World Reference Base Soil Resources [14] (Table 1).
Fig . 1. The map of the investigated peatland
The elution of soil organic matter from peat-moorsh soils in broad range of pH was investigated. The rates of the reaction were calculated from the kinetics of first order reaction model. All experiments were repeated at different pH 6.0, 6.5, 7.0, 8.0, 8.5 of
0.5 M ammonium acetate buffer solution. The investigations have shown the impact of the properties of secondary transformed peat-moorsh soils on the rates of the dissolution of organic matter.
Table 1
Some properties of peat-moorsh soils
Place of sampling Type of peat-moorsh Stage of soil moorshification, degree of decomposition Kind of moorsh formation
Zb^chy Wooden-sedge moorsh soil with peat, light degree of moorsh process Mtl, deep soil developed with low Carex-Phragmiteti strongly decomposed (sapric) peat, 10YR 2/1 black, amorfic-fibrus structure. The upper peat horizon have thin 1-2 mm mineral layers. Peaty muck horizon with subangular blocky structure with low fiber content. Moorsh horizon Mt 0-10 cm depth. Polish hydrogenic soil classification [12]: Mtlcc. World Reference Base [14] soil notation: Sapri-Eutric Histosols MtIcc 0-20 cm, R3 Z1
Bridge Alder, moorsh soil with peat, medium degree of moorsh process MtII, deep soil developed with low strongly decomposed (sapric) wood peat, 10YR 2/1 black, angular blocky structure. Humic muck horizon with subangular blocky microstructure. Very good developed M1 moorsh sod subhorizon and subangular blocky M2 muck undersod subhorizon. Moorsh horizon Mt 0-20 cm depth. Polish hydrogenic soil classification [12]: MtIIcc. World Reference Base [14] soil notation: Sapri-Eutric Histosols MtIIcc 0-20 cm R3 Z2
Shelterbelt Sedge-rushes, moorsh soil with peat, strong degree of moorsh process MtIII, deep soil developed with low Carex-wood decomposed (sapric) peat, 10YR 3/1 very dark gray, angular-fibrus blocky structure. Moorsh horizon strongly draied, subangular blocky microstructure. Good developed subhorizons M1, M2. Degraded moorsh M3 subhorizon have light identificable. Moorsh horizon Mt 0-32 cm depth. Polish hydrogenic soil classification [12]: MtIIIcc. World Reference Base [14] soil notation: Sapri-Eutric Histosols MtIIIcc 0-20 cm R3 Z2 Z3
Hirudo Alder, moorsh soil with peat, medium degree of moorsh process MtII, deep soil developed with low wood decomposed (sapric) peat, 10YR 2/2 very dark brown, angular blocky structure. Moorsh horizon strongly draied, subangular blocky macro and microstructure. Good developed sod and undersod subhorizons M1 and M2. Moorsh horizon Mt 0-20 cm depth. Polish hydrogenic soil classification [12]: MtIIcc. World Reference Base [14] soil notation: Sapri-Eutric Histosols MtIIcc 0-20 cm R3 Z2
Mt - stage of soil moorshification, Mtl - weakly moorshified, MtII - medium moorshified, MtIII - strongly moorshi-fied; a - according to classification [14] - Sapri-Eutric Histosols, Zj - grain moorsh, Z2 - peaty moorsh, Z3 - humic moorsh.
7 grams of peat were filled to the fixed level equaled to 50 ml in the glass column (ID = 1 cm). The solvent as mobile phase was pumped at the rate 2 cm3 min-1 and developed a pressure of 2.5 MPa. Samples of
5 ml were collected at suitable time intervals. The absorbances of these samples were monitored at four following wavelengths X = 272 nm, X = 320 nm, X = 465 nm, and X = 665 nm. BECKMAN DU®-68 spectrophotometer with 1 cm thickness of layer was used for spectrometric measurements. In order to determine the reaction order of organic matter release it’s the Ostwald’s equation was applied for the calculation of the reaction order. All the kinetic experiments were run triplicate and the results averaged.
Peatlands are areas which share ecosystem properties with both terrestrial and aquatic systems. Aquifers are vulnerable to contamination by agricultural, residential, and industrial pollutants. Sources of ground water contamination are numerous and include among many others agricultural activities, accidental spills, landfills, storage tanks and pipelines. Agriculture-related activities are well-known for causing nonpoint sources pollution in small to large watersheds especially due to fertilizers and various substances found in pesticides [15].
The investigated peatland represents a different kind of peat-moorsh soils (Table 1). Our earlier investigations shown that organic soils of the transect represent a different stage of moorshification [16]. Zb^chy located at the beginning of peatland is characterized by weak moorshfied soil. The farther the soils were located from the edge the more were they moorshified. The most moorshified is the soil of Shelterbelt, representing peaty and humic moorsh. All the soils represented from slightly acidic (No 2 and 4) to neutral properties (No 1 and 3). In peat moorsh soils the values of pH’s ranged from 5.82 to 7.56 (Table 2) [3]. The highest pH was measured in peat from Shelterbelt while the lowest in Hirudo.
Table 2
The pH of peat-moorsh soils
Place of sampling pH in 1 M KCl
Zb^chy 6.22-6.97
Bridge 6.00-6.46
Shelterbelt 7.05-7.56
Hirudo 5.82-6.41
The rates of organic matter elution for all samples of peats were significant different at four used wavelengths X = 272 nm, X = 320 nm, X = 465 nm, and X = 665 nm.
Kinetic modeling studies of organic matter release from peat were performed. The absorbances of organic matter release were characterized by an exponential equation (1) as a function of time (Fig. 2).
ln(A„ - A,) = ln A0 - kt,
(2)
Am - A, = A0e-
(1)
Its transformations lead to linear relationship in agreement with the first-order reaction model (2) (Fig. 3) [17-19]:
were A„ is the value of maximum absorbance, At - absorbance at the time , A0 - absorbance at the time 0, k - pseudo first-order reaction rate constant, t - time.
The absorbances of organic matter releases by different pHs 0.5 M ammonium acetate buffer measured at four following wavelengths as a function of time follows the equation (1) and their graphical illustration is a linear curve. The correlation coefficients measured
Fig . 2 .Typical changes of A„ - A, at □ = 272 nm of organic mater released by 0 . 5 M ammonium acetate buffer at pH 7 . 0 from Zb^chy, Bridge, Shelterbelt and Hirudo in accordance with the eq . (1)
at □ = 272 nm ranged from -0.844 to -0.994 (Table 3), at □ = 320 nm ranged from -0.828 to -0.993 (Table 4), at □ = 465 nm ranged from -0.809 to -0.993 (Table 5), at □ = 665 nm ranged from -0.874 to -0.995 (Table 6). However, they yield linear relationships according to equation (2) (Tables 3-6). The slopes of the equation describe the rates of leaching process. It appeared that the rates of organic matter elution for all samples of peats were significant different at four used wavelengths X = 272 nm, X = 320 nm, X = 465 nm, and X = 665 nm. It was observed that the rates decreased between pH 6.0 and pH 7.0 and increased from pH 7.0 to pH 8.5.
The values of the pseudo first-order rate constants
2000 4000 6000 aooo 10000 12000 14000 16000
t[s]
Fig . 3 . Semilogarithmic plots ln (AM - A,) = ln A0 -kt for first order reaction of organic matter release by 0 5 M ammonium acetate buffer at pH 7 . 0 from Zb^chy, Bridge, Shelterbelt and Hirudo measured at □ = 272 nm in accordance with eq (2)
measured for all samples of peats from four places at X = 272 nm ranged from 1.7999 10-4 s'1 to 2.3697 10-4 s-1 (Table 3), at X = 320 nm ranged from 1.7455 10-4 s-1 to 2.5811 10-4 s-1 (Table 4), at X = 465 nm ranged from
1.6816 10-4 s-1 to 2.4017 10-4 s-1 (Table 5), at X = 665 nm ranged from 1.5841 10-4 s-1 to 2.7939 10-4 s-1 (Table 6).
The highest values of to.5 ranged from 48.7 to 64.2 min measured at X = 272 nm (Table 3), at X = 320 nm values of t05 ranged from 44.6 to 66.2 min (Table 4), at X = 465 nm values of t05 ranged from 48.1 to 68.7 min (Table 5), at X = 665 nm values of t05 ranged from 41.3 to 72.9 min (Table 6) for all samples from Zb^chy. Bridge, Shelterbelt and Hirudo (Tables 3-6).
Table 3
Pseudo first-order rate constants (k x 10-4 s-1), half-times (min), and correlation coefficients (r) for the reaction of the release of organic matter from peat by 0.5 M ammonium acetate buffer at pH: 6.0, 6.5, 7.0, 8.0, 8.5 for wavelengths X = 272 nm
pH Zbqchy Bridge Shelterbelt Hirudo
k t0.5 r k ^0.5 r k ^0.5 r k ^0.5 r
6.0 1.7999 64.17 -0.855 1.8434 62.66 -0.975 1.9384 59.59 -0.844 1.8552 62.26 -0.976
6.5 1.8675 61.85 -0.974 1.8758 61.57 -0.975 2.2354 51.67 -0.990 1.8830 61.34 -0.974
7.0 1.8603 62.09 -0.975 1.8438 62.64 -0.974 2.2787 50.69 -0.988 1.8456 62.58 -0.970
8.0 1.8932 61.01 -0.967 1.8887 61.15 -0.976 2.3697 48.74 -0.990 1.8657 61.91 -0.976
8.5 1.8779 61.50 -0.977 1.8736 61.65 -0.977 2.5817 44.74 -0.994 1.8585 62.15 -0.971
Table 4
Pseudo first-order rate constants (k x 10-4 s-1), half-times (min), and correlation coefficients (r) for the reaction of the release of organic matter from peat by 0.5 M ammonium acetate buffer at pH: 6.0, 6.5, 7.0, 8.0, 8.5 for wavelengths X = 320 nm
pH Zb^chy Bridge Shelterbelt Hirudo
k t0.5 r k t0.5 r k t0.5 r k t0.5 r
6.0 2.3055 50.10 -0.833 1.8093 63.84 -0.971 2.5811 44.75 -0.828 1.7933 64.41 -0.968
6.5 1.9405 59.52 -0.970 1.8569 62.20 -0.973 2.2005 52.49 -0.989 1.9870 58.13 -0.973
7.0 1.8577 62.17 -0.970 1.8222 63.38 -0.966 2.2543 51.24 -0.988 1.7455 66.17 -0.964
8.0 1.9137 60.35 -0.977 1.9880 58.10 -0.980 2.3361 49.44 -0.989 1.9634 58.83 -0.979
8.5 1.9581 58.99 -0.979 1.9654 58.77 -0.979 2.4473 47.19 -0.993 1.8343 62.97 -0.974
Table 5
Pseudo first-order rate constants (k x 10-4 s-1), half-times (min), and correlation coefficients (r) for the reaction of the release of organic matter from peat by 0.5 M ammonium acetate buffer at pH: 6.0, 6.5, 7.0, 8.0, 8.5 for wavelengths X = 465 nm
pH Zb^chy Bridge Shelterbelt Hirudo
k t0.5 r k t0.5 r k t0.5 r k t0.5 r
6.0 2.2611 51.08 -0.865 1.7818 64.82 -0.968 2.2739 50.79 -0.809 1.6816 68.68 -0.958
6.5 1.8027 64.07 -0.963 1.7222 67.06 -0.965 2.0809 55.51 -0.987 1.8552 62.26 -0.966
7.0 1.7632 65.51 -0.963 1.7039 67.79 -0.956 2.1930 52.67 -0.986 1.7946 64.36 -0.957
8.0 1.7980 64.24 -0.970 1.8629 62.00 -0.974 2.2430 51.49 -0.986 1.8402 62.77 -0.972
8.5 1.8378 62.85 -0.972 1.8595 62.11 -0.974 2.4017 48.09 -0.993 1.9802 58.33 -0.976
Kablitz [20, 21] suggested that properties of dissolved organic matter determine its biodegradation. In turn, biodegradation changes the properties of the remaining dissolved organic matter, which may be decisive for the formation of stable organic carbon in soil. Increasing UV absorption and humification indices, and increasing portions of aromatic H indicated relatively enrichment of aromatic compounds during biodegradation. This enrichment significantly correlated with the amount of dissolved organic carbon mineralized suggesting that aromatic compounds were relatively stable and slowly mineralized. The partial degradation of higher-molecular, lignin-derived dissolved
organic matter compounds was accompanied by relative increases in the proportions of lower-molecular degradation products and microbial metabolites. Carbohydrates, especially when some microbial production of carbohydrates and peptides during dissolved organic matter degradation. The authors concluded that dissolved organic matter biodegradation seems to result in organic matter properties being preconditions for the formation of stable carbon. These structural changes induced by dissolved organic matter biodegradation should also result in stronger dissolved organic matter sorption to the soil matrix additionally affecting dissolve organic matter stabilization.
Table 6
Pseudo first-order rate constants (k x 10-4 s-1), half-times (min), and correlation coefficients (r) for the reaction of the release of organic matter from peat by 0.5 M ammonium acetate buffer at pH: 6.0, 6.5, 7.0, 8.0, 8.5 for wavelengths X = 665 nm
pH Zb^chy Bridge Shelterbelt Hirudo
k t0.5 r k V5 r k V5 r k V5 r
6.0 1.8484 62.49 -0.915 1.7815 64.83 -0.968 2.2841 50.57 -0.874 1.5905 72.62 -0.952
6.5 1.6939 68.19 -0.956 1.6332 70.72 -0.961 2.0566 56.16 -0.994 1.7406 66.36 -0.962
7.0 1.6762 68.90 -0.960 1.5841 72.91 -0.947 2.4677 46.80 -0.991 1.6727 69.05 -0.948
8.0 1.7283 66.83 -0.964 1.7627 65.52 -0.970 2.1321 54.17 -0.982 1.7529 65.89 -0.967
8.5 1.7368 66.50 -0.968 1.7400 66.38 -0.969 2.7939 41.34 -0.995 1.8579 62.17 -0.971
Well documented solvent systems for the isolation of organic components from soils were presented by Hayes [22]. Author shows the properties of organic and inorganic solvents systems, the separation of organic matter components in aqueous media, and an isolation of organic matter in organic solvents. This author postulated, that applying of the combinations of aqueous and organic solvents for isolation the components of organic matter that have special growth pro-
moting or inhibition effects on plants could help resolve the debate regarding whether or not dissolved organic matter components can influence plant growth by hormones or by enhanced uptake of nutrients.
Conclusions. Our research has revealed the impact on the rates of the elution of organic matter from secondary transformed peat-moorsh soils at different pH.
The values of half-time t05 were connected with the humification processes in peat.
Acknowledgements. This work was supported by tion and Science (№ 02.740.11.0325). a grant № N N305 320436 and № N N310 310039 Thanks are also given to Mrs. Teresa Stachecka for founded by Polish Ministry of Education and by RFFR technical support.
(№№ 09-05-00235, 09-05-00395), Minister of Educa-
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Szajdak L. W.
Institute for Agricultural and Forest Environment, Polish Academy of Science.
Street Bukowska, 19, Poznan, Poland, 60-809.
E-mail: [email protected]
Szczepanski M.
Institute for Agricultural and Forest Environment, Polish Academy of Science.
Street Bukowska, 19, Poznan, Poland, 60-809.
Л. В. Шайдак, М. Щепаньский
влияние торфяных залежей
НА ВЫМЫВАНИЕ ОРГАНИЧЕСКИх ВЕщЕСТВ ИЗ ТОРФЯНЫх ПОЧВ
Направление использования торфяных болот определяет скорость трансформации органического вещества торфов. Исследования рН и состава органического вещества торфяных почв проводились на трансект катене, которая расположена в агроэкологическом ландшафтом парке в 40 км на ЮЗ от Познани. Торфяные почвы описаны по польской классификации и на основании медународного классификатора. Выбрано 4 пункта исследования. Два раза в месяц проводился отбор образцов на глубине 0-20 см. Скорость реакции кинетики вычислялась по уравнению первого порядка. Оптические плотности органических веществ определялись при разных длинах волн. Опыт проводился при разных значениях рН 6.0, 6.5, 7.0, 8.0, 8.5.
Ключевые слова: торфяные почвы, растворенное органическое вещество, кинетика растворенного органического вещества.
Шайдак Л. В., профессор.
Институт сельскохозяйственной и лесной охраны окружающей среды Польской академии наук.
Ул. Буковска, 19, г. Познань, Польша, б0-809.
E-mail: [email protected]
Щепаньский М., магистр.
Институт сельскохозяйственной и лесной охраны окружающей среды Польской академии наук.
Ул. Буковска, 19, г. Познань, Польша, б0-809.
Материал поступил в редакцию 20.10.2010.
