Folia Geographica 10. sÄjums - Latvijas UniversitÄte

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DABAS PĒTĪJUMIsources on the structure and properties of humic substances. Humic substances from soils have ahigher degree of aromaticity and molar absorption than those from water.Light Absorbance Properties and Aromaticity of Humic SubstancesHumusvielu sorbcijas raksturojumsTable 2Molar absorption,L (mole C) -1 cm -1 E4/E6 Aromaticity, % M wFA Missouri River a 247 13.9 20.4 -FA Ohio River a 274 17.2 24.3 -FA Minnesota groundwater a 122 3.53 12.6 -FA Suwannee River a 389 20.7 24.8 880FA Lake Fryxell a 150 - 13.0 -FA Coal Creek b 401 20.7 27.4 -FA Lake Burtnieku b 214 8.6 17.4 2200FA Lake Liepājas b 189 9.4 16.1 1650HA-soilBrown soilsPodzolic soilsAnthrosolsHydromorphic soilsa – Chin et al., 1994;b – Kļaviņš et al., 19975014442696815.46.57.85.641.436.732.456.31300180035001500Direct evidence of the structural features of humic substances provides their 13 C NMRspectra. The signals in these NMR spectra represent different types of carbon atoms. The13 C NMR spectra can be divided into several chemical shift ranges (Figure 3), indicating thepresence of different major structural elements into structure of the humic substances. Region A(0-50 ppm) consists primarily of aliphatic carbon resonances (methyl, methylene and methinecarbons). Region B (50 to 60 ppm) consists of methoxylcarbon (-OCH 3 ) resonance signals.Region E (110 to 140 ppm) is assigned to the resonance of unsubstituted and alkysubstitutedaromatic carbons. Region F (140 to 160 ppm) consists of the resonance of the aromatic carbonssubstituted by oxygen and nitrogen (e.g., phenols, aromatic ethers or amines). This analysisallows the direct evaluation of the substantial differences among humic substances of differingorigins and the substantially lower aromaticity of aquatic humic substances in comparison withcommercial humic substances.It can be concluded that the properties of humic substances depend on the origin of thehumic matter. The similarities existing among humic substances reflect not so much theenvironment from which they has been isolated but rather the conditions of their formation.These differences may be explained by the proportions of production and transformationprocess intensities in the relevant environments.The distinctive distribution of functional groups and the major building blocks of humicsubstances may reflect their production and structure alteration due to microbial degradation andgeochemical alteration. Fulvic acid formation may occur through condensation reactionsinvolving compounds derived from their precursor organic materials or through the productionof residual recalcitrant compounds in the microbial degradation of their precursor organicmaterial. For peat humic acids, lignin is not included in the set of precursor materials, andcarbohydrates and aliphatic structures are relatively abundant. Carbohydrate structures,however, are the most labile and are rapidly degraded by microorganisms. Similarity betweenhumic substances from peat and soil indicate either the dominance of allochtohonous peathumus or the deep transformation of autochthonous humic material.4. ConclusionsThe elemental, functional, mass-molecular and spectral characterisation of humicsubstances stresses the role of their origin on the properties of these humic substances. Humicsubstances from different soil, water and peat types differ in their properties. The similarity inthe structure and properties of humic substances suggests the importance of the intensity of52
NATURE RESEARCHbiological transformation of organic matter on their structure. The pattern of differences amongLatvian humic substances, peat, soil, the IHSS reference and commercial samples, demonstratesthat even within such a territory as Latvia it is impossible to isolate one reference sample thatwould be representative of humic substances.Figure 3.13 C-NMR spectra of humic substances: 1– humic acid from the Daugava; 2 – humic acid from LakeBaltezers; 3 – humic acid from groundwater; 4 – commercial humic acid (Aldrich)3. attēls. Humusvielu 13 C KMR spektri: 1 Daugavas humīnskābe; 2 Baltezera humīnskābe; 3 pazemes ūdeņuhumīnskābe; 4 rūpnieciski ražota humīnskābeKopsavilkumsNo dažādām <strong>Latvijas</strong> augsnēm un kūdras izdalītām humusvielām analizēts elementsastāvsun funkcionālo grupu sastāvs, veikta sastāva analīze (UV, fluorescences, EPR). To īpašībassalīdzinātas ar dažādas izcelsmes humusvielu vispārīgajām īpašībām, novērtējot humifikācijasprocesa raksturu. Parādīta humusvielu īpašību atkarība no humifikācijas procesa apstākļiem.53
Page 1 and 2: ĢEOGRĀFISKI RAKSTIFOLIA GEOGRAPHI
Page 3 and 4: CILVĒKS UN VIDESatursAija MellumaA
Page 5 and 6: MAN AND ENVIRONMENTAinava kā attī
Page 7 and 8: MAN AND ENVIRONMENTun (2) ka dažā
Page 9 and 10: MAN AND ENVIRONMENT1. attēls. Kurz
Page 11 and 12: MAN AND ENVIRONMENTKā atsevišķs
Page 13 and 14: MAN AND ENVIRONMENTautoceļa aizsar
Page 15 and 16: MAN AND ENVIRONMENTKurzeme region t
Page 17 and 18: NATURE RESEARCH2. attēls. Eiropas
Page 19 and 20: NATURE RESEARCHautonomais (neatkar
Page 21 and 22: NATURE RESEARCHtemperatūra nav zem
Page 23 and 24: NATURE RESEARCHietekmei - pie tam,
Page 25 and 26: NATURE RESEARCHpirmajām - arī “
Page 27 and 28: NATURE RESEARCHveģetācijas period
Page 29 and 30: NATURE RESEARCHputekšņu diagramma
Page 31 and 32: NATURE RESEARCHdabas liegumā. Skā
Page 33 and 34: NATURE RESEARCHparādās divos neda
Page 35 and 36: NATURE RESEARCHsadalījušos nobiru
Page 37 and 38: NATURE RESEARCHRhytiadelphys trique
Page 39 and 40: NATURE RESEARCHTādējādi lielai d
Page 41 and 42: NATURE RESEARCHatrasts - tāpat kā
Page 43 and 44: NATURE RESEARCHAugsnes rakums izdar
Page 45 and 46: NATURE RESEARCHcodominant species o
Page 47 and 48: NATURE RESEARCHKiršteins K., Eiche
Page 49 and 50: NATURE RESEARCH3. Results and discu
Page 51: NATURE RESEARCHConcentrations of ca
Page 55 and 56: HUMAN GEOGRAPHYMigrācijas procesi
Page 57 and 58: HUMAN GEOGRAPHYSavukārt republikas
Page 59 and 60: 592. attēls. Migrācijas reģioni
Page 61 and 62: HUMAN GEOGRAPHYvirzītas uz vietām
Page 63 and 64: HUMAN GEOGRAPHYMarkausa I.M. (2001)
Page 65 and 66: HUMAN GEOGRAPHYRaugoties no augšan
Page 67 and 68: HUMAN GEOGRAPHYSociālekonomisko r
Page 69 and 70: HUMAN GEOGRAPHYsadalījums Latvijas
Page 71 and 72: HUMAN GEOGRAPHY3. attēls. Latvijas
Page 73 and 74: HUMAN GEOGRAPHYSecinājumiKoncentr
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DEVELOPMENT OF PLACES AND REGIONS8.
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CHRONICLELatvijas Ģeogrāfijas bie
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AUTORIAUTHORSAndris Bauls, Dr.geogr
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Folia Geographica 10. sÄjums - Latvijas UniversitÄte

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Folia Geographica 10. sÄjums - Latvijas UniversitÄte