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Identifying drivers of the molecular composition of dissolved organic matter (DOM) is essential to understand the global carbon cycle, but an unambiguous interpretation of observed patterns is challenging due to the presence of confounding factors that affect the DOM composition. Here, we show, by combining ultrahigh-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, that the DOM molecular composition varies considerably among 43 lakes in East Antarctica that are isolated from terrestrial inputs and human influence. The DOM composition in these lakes is primarily driven by differences in the degree of photodegradation, sulfurization, and pH. Remarkable molecular beta-diversity of DOM was found that rivals the dissimilarity between DOM of rivers and the deep ocean, which was driven by environmental dissimilarity rather than the spatial distance. Our results emphasize that the extensive molecular diversity of DOM can arise even in one of the most pristine and organic matter source-limited environments on Earth, but at the same time the DOM composition is predictable by environmental variables and the lakes’ ecological history.

The stability of black soil carbon in the deep layers of Japanese volcanic ash soil (i.e., buried A horizons) is often explained by its unique chemical (molecular structure) and physical (associate...

The response of soil organic matter (SOM) to global warming is a crucial subject. However, the temperature sensitivity of SOM turnover remains largely uncertain. Changes in the mineralization of na...

Dissolved organic matter (DOM) plays an important role in sustaining ecosystem services of mangrove forests through well-described biogeochemical and ecological functions. This study was conducted in the Fukido River (Ishigaki Island, Japan) to better understand the seasonal and episodic changes in DOM concentration and composition in a subtropical mangrove system. Water samples were collected seasonally along a headwater–mangrove–sea transect on 10 occasions from September 2014 through June 2016. DOM was fractionated based on hydrophobicity into two fractions (hydrophobic and hydrophilic) and also analyzed by excitation-emission matrix spectroscopy combined with parallel factor analysis (PARAFAC). Although seasonal changes in DOM concentration and composition were not observed, both hydrophobic and hydrophilic DOM concentrations and levels of the identified three PARAFAC components clearly increased during a typhoon event. It is suggested that episodic increases in freshwater input due to a typhoon caused enhanced leaching of DOM from mangrove litter and dissolution of mangrove soil organic matter (SOM), which was otherwise retained in the mangrove soil by salinity-induced aggregation. The aggregation–dissolution properties of SOM are crucial in determining the magnitude of DOM outwelling and possibly SOM accumulation rate by enhancing advective DOM exchanges. Future studies are needed to evaluate the size of the carbon pool and outwelling of DOM after classifying mangrove forests based on the hydrological regime that influences biogeochemical conditions in the forests. Regional Index Terms Japan, Okinawa, Ishigaki, Fukido.

The organic-Fe association in Scottish freshwater rivers has received little attention compared with in the estuarine mixing zone. We collected 201 water samples from rivers and lakes in Scotland across different sampling years and seasons. Relationships among the hydrophobic (HPO) fraction of dissolved organic matter (DOM), specific UV absorbance (SUVA254), and dissolved metals (Al and Fe) were examined to better understand their co-transportation in Scottish waters. The average DOM, HPO fraction, Fe, and Al concentrations for all the samples co-varied and were lower during winter than during summer. There was a strong positive correlation between DOM and HPO fraction concentrations (R2 = 0.99, p

The variation in CO2 flux from the forest floor is important in understanding the role of mangrove forests as a carbon sink. To clarify the effects of soil temperature and tidal conditions on variation in CO2 flux, sediment–atmosphere CO2 fluxes were measured between June 2012 and May 2013. We used the closed chamber method for two plots, with a 0.5 m difference in elevation (B, high elevation; R-B, low elevation), in a mangrove forest in south-western Japan. CO2 fluxes were highest in the warm season and showed a weak positive correlation with soil temperature in both forests. Estimated monthly CO2 flux showed moderate seasonal variation in accordance with the exposure duration of the soil surface under tidal fluctuation. Additionally, measured CO2 flux and soil temperature were slightly higher in the R-B plot than the B plot, although estimated annual CO2 flux was higher in the B plot than the R-B plot due to different exposure durations. These results suggest that variation in the exposure duration of the forest floor, which changes seasonally and microgeographically, is important in evaluating the annual CO2 flux at a local scale and understanding the role of mangrove ecosystems as regulators of atmospheric CO2.

Uptake of six particle-reactive and/or redox-sensitive radionuclides (210Pb, 234Th, 7Be, 59Fe, 237Np and 233Pa) by 14 humic acids (HAs) was investigated in artificial groundwater under mildly acidic conditions (pH~5.5). In HA-groundwater slurry, Pb, Be, Fe and Pa bound strongly to particulate HA (>0.45 µm), supporting their application as tracers of soil erosion. Th bound strongly to the colloidal HA (3 kDa-0.45 µm) and as such, would not be a good candidate as a tracer for monitoring soil erosion. HAs likely reduced the oxidized neptunyl form (Np(V)O4+) to Np(IV) based on its enhanced particle-reactivity and Np uptake by particulate HAs, partially retarding the movement of anthropogenic 237Np in field polluted environments. Particulate/colloidal carbonyl/O-aryl (likely through hydroquinone/quinone) functionalities in the HA correlated to Np and Pa uptake, but only particulate O-aryl functionalities was responsible for Fe uptake. The carboxylate- and carbonyl/O-aryl-containing organic functionalities in the HA correlated strongly with Th uptake. In contrast, no significant correlations between organic parameters and Pb or Be uptake implied their predominance of uniform surface adsorption onto particles. This study provides novel insight into the binding of six radionuclides with different organic functionalities of three size fractions, as well as its possible impact on their application in the soil-tracing research.

In order to assess how environmental factors are affecting the distribution and migration of radioiodine and plutonium that were emitted from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, we quantified iodine and (239,240)Pu concentration changes in soil samples with different land uses (urban, paddy, deciduous forest and coniferous forest), as well as iodine speciation in surface water and rainwater. Sampling locations were 53-63 km northwest of the FDNPP within a 75-km radius, in close proximity of each other. A ranking of the land uses by their surface soil (4 cm) stable (127)I concentrations was coniferous forestdeciduous foresturbanpaddy, and (239,240)Pu concentrations ranked as deciduous forestconiferous forestpaddy ≥ urban. Both were quite distinct from that of (134)Cs and (137)Cs: urbanconiferous forestdeciduous forestpaddy, indicating differences in their sources, deposition phases, and biogeochemical behavior in these soil systems. Although stable (127)I might not have fully equilibrated with Fukushima-derived (129)I, it likely still works as a proxy for the long-term fate of (129)I. Surficial soil (127)I content was well correlated to soil organic matter (SOM) content, regardless of land use type, suggesting that SOM might be an important factor affecting iodine biogeochemistry. Other soil chemical properties, such as Eh and pH, had strong correlations to soil (127)I content, but only within a given land use (e.g., within urban soils). Organic carbon (OC) concentrations and Eh were positively, and pH was negatively correlated to (127)I concentrations in surface water and rain samples. It is also noticeable that (127)I in the wet deposition was concentrated in both the deciduous and coniferous forest throughfall and stemfall water, respectively, comparing to the bulk rainwater. Further, both forest throughfall and stemflow water consisted exclusively of organo-iodine, suggesting all inorganic iodine in the original bulk deposition (∼ 28.6% of total iodine) have been completely converted to organo-iodine. Fukushima-derived (239,240)Pu was detectable at a distance ∼ 61 km away, NW of FDNPP. However, it is confined to the litter layer, even three years after the FDNPP accident-derived emissions. Plutonium-239,240 activities were significantly correlated with soil OC and nitrogen contents, indicating Pu may be associated with nitrogen-containing SOM, similar to what has been observed at other locations in the United States. Together, these finding suggest that natural organic matter (NOM) plays a key role in affecting the fate and transport of I and Pu and may warrant greater consideration for predicting long-term stewardship of contaminated areas and evaluating various remediation options in Japan.

A nonionic macroporous resin, Amberlite(®) XAD-8, or its substitute, Supelite™ DAX-8, is used when isolating or quantifying aquatic humic substances (AHS). However, the effect of salinity on the adsorption behavior of AHS onto the resin is yet to be confirmed, rendering the possibility of salinity-induced changes in the values of quantified amounts or characteristics of AHS obtained from a salty system. To verify the results of quantification and isolation of AHS using the resin in different salinity systems, the effect of salinity on such quantitative analyses of AHS has been examined. It has been concluded that the salinity effect is in general trivial and will not hinder comparison of results regardless of sample solution salinity.

To relate the isotopic composition of soil humic acids (HAs) to their source plants and their degree of humification (as indicated by the degree of darkening), as well as to soil type, we determined the stable isotope ratios for carbon (δ13C) and nitrogen (δ15N) of HAs extracted from 26 virgin soil samples (14 Andisols and 12 non-Andisols) and from leaf samples from ten C3 plants and seven C4 plants. The high absorption coefficients (estimated at 600 nm for 1% solutions), low hydrogen and nitrogen contents, low H/C ratios, low alkyl C and O-alkyl C contents, high O/H and C/N ratios, high aryl C contents, and high aromaticity of the Andisol HAs indicated a high degree of humification. The δ13C and δ15N values of the non-Andisol HAs increased along with the progression of humification of C3 plant-derived HAs. A significant correlation was observed between the δ15N and δ13C values of the non-Andisol HAs, but not for the Andisol HAs. Most of the Andisol HA δ13C values were higher than the highest non-Andisol HA δ13C value, and δ13C values were distributed between the δ13C values for the C3 and C4 plants. The contributions of C4 plant-derived carbon to total Andisol HA carbon (CRC4) are usually calculated on the assumption that the δ13C values are not substantially altered during the decomposition of plant materials and the formation of soil organic matter. However, if 13C enrichment occurs during organic matter decomposition, CRC4 will be overestimated. Therefore, we suggest a new method to calculate CRC4 values of Andisol HAs with a correction for isotopic fractionation associated with microbial degradation; the corrected CRC4 values ranged from − 5% to 58% and were approximately 22% lower than the uncorrected values.

Humic substances (HSs) are ubiquitous in various aquatic systems and play important roles in many geochemical processes. There is increasing evidence of the presence of HSs in deep groundwater; nevertheless, their ion binding properties are largely unknown. In this study we investigated the physicochemical and ion-binding properties of humic and fulvic acids extracted from deep sedimentary groundwater. The binding isotherms of protons (H(+)) and copper (Cu(2+)) were measured by potentiometry and fitted to the NICA-Donnan model, and the obtained parameters were compared with the generic parameters of the model, which are the average parameters for HSs from surface environments. The deep groundwater HSs were different from surface HSs, having high aliphaticities, high sulfur contents, and small molecular sizes. Their amounts of acidic functional groups were comparable to or slightly larger than those of surface HSs; however, the magnitude of Cu(2+) binding to the deep groundwater HSs was smaller. The NICA-Donnan model attributed this to the binding of Cu(2+) to chemically homogeneous low affinity sites, which presumably consist of carboxylic groups, via mono-dentate coordination at relatively low pH. The binding mode tended to shift to multi-dentate coordination with carboxylic groups and more heterogeneous alcoholic/phenolic groups at higher pH. X-ray absorption spectroscopy also revealed that Cu(2+) binds to O/N containing functional groups and to a lesser extent S containing functional groups as its divalent from. This study shows the particularity of the deep groundwater HSs in terms of their physicochemical and ion-binding properties, compared with surface HSs.

The molecular composition of soil organic matter (SOM) is important in understanding the elemental cycling of mangrove forests. The aim of the study was to investigate the SOM compositional changes with time in a mangrove mineral soil, which is rarely reported in the literature. A 1-m soil core was collected in the subtropical Fukido River mangrove forest (Okinawa, Japan) and separated into 25-cm sections. Humic acids (HA) and fulvic acids (FA) were extracted from the soil, and their relative abundance and chemical characteristics were analyzed by elemental analysis, stable carbon analysis, spectrophotometric measurement, liquid-state 13C nuclear magnetic resonance spectroscopy, and radiocarbon dating. HA exhibited a clear depth trend in the chemical characteristics, with lower H/C and N/C ratios, higher aromaticity, and higher phenolic 13C NMR peaks in the deeper sections. FA did not show such a clear depth trend, and was enriched in O-containing functional groups. A combination of radiocarbon dating and structural analysis of HA indicated that the rapid structural changes in HA (H/C and N/C) occurred during the first years–decades, followed by a gradual change over a time scale of several hundred (~500) years, and these structural changes were best explained by an increase in the relative phenolic C contents. These results show that mangrove SOM is a complex mixture of organic fractions with different biogeochemical reactivities.

This study characterized dissolved organic matter (DOM) obtained from 47 lakes and 2 streams on ice-free areas at Lutzow-Holm Bay and Amundsen Bay in East Antarctica (n = 74), where few biogeochemical studies have been historically conducted. Samples were analyzed for basic water chemistry and by resin fractionation, UV–vis spectroscopy, and excitation emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). Salinity of the samples ranged very broadly from fresh to hypersaline as a result of evaporative concentration. There was a clear positive correlation between log-salinity and the spectral slopes of DOM (S275–295), an indicator of photodegradation. Thus, we interpreted the correlation as a progression of photodegradation by prolonged water retention time. Of the identified seven PARAFAC components, three ubiquitous humic-like components decreased as photodegradation progressed, while a photorefractory UVC humic-like component increased its relative abundance. A non-humic component, traditionally defined as Peak N, did not show a trend depending on photodegradation, and its level was high in nutrient-rich lakes, presumably due to high in-situ production. We found robust correlations between the relative abundance of the ubiquitous humic-like components and that of the Peak N component in the bulk DOM irrespective of water types or ice-free areas. We proposed there were common processes that generated the ubiquitous humic-like components from the Peak N component in the Lutzow-Holm Bay and Amundsen Bay lakes and streams, such as bacterial processing of primary production-derived DOM and photochemical transformation of microbial DOM.

The dynamics of the polyaromatic structures of black humic acids (HAs), which are presumably derived from charred materials, are of significant interest for the global carbon cycle. However, the details of those dynamics are not yet well understood. We investigated differences in the degree of darkness (A600/C values), isotopic ratios (δ13C, δ15N, and Δ14C values), and 13C NMR spectra of size-separated black HAs extracted from Japanese volcanic ash soils in order to estimate the variations in the polyaromatic structures of black HAs during ca. 100 years of natural reforestation of Japanese pampas grassland. For several hundred years, all the study sites were managed similarly as grassland by burning. Subsequently, their management differed: at site G (Miscanthus sinensis: C4 plant), maintenance as of the time of this study was still performed by mowing, while at sites P (Pinus densiflora: C3 plant) and Q (Quercus crispula: C3 plant), maintenance was discontinued ca. 30 and 100 years ago, respectively. Thus, the sites range from grassland (site G) to coniferous forest (site P) to broad-leaved forest (site Q). For all HA size fractions at all sites, we found that δ13C values correlate positively with δ15N values, although the gradients are much lower for fractions of small to medium molecular size than for fractions of medium to large molecular size (denoted as lower-size and higher-size fractions, respectively). Overall, for the lower-size fractions, the contribution ratio of C4-plant-derived carbon shows a significant positive correlation with A600/C values and a negative correlation with Δ14C values, and their aromatic characteristics are greater than those of higher-size fractions within the same black HA. Furthermore, the relative proportion of lower-size fractions decreases with reforestation, especially from site P to Q. The δ13C values for all size fractions are similar for sites G and P, but are relatively low for site Q. The aryl C contents of the lower-size fractions are lower and the O-alkyl C contents and the aliphaticity (alkyl C:O-alkyl ratio) are clearly higher for sites P and Q than for site G. These results strongly suggest that stimulation of HA biodegradation might be achievable by continuous input of new plant litter during reforestation, even for lower-size HA polyaromatic structures, despite the fact that lower-size HAs biodegrade more slowly than higher-size HAs.

A five-step sequential extraction procedure was developed for the partitioning of soil aluminum (Al) into five fractions: exchangeable, weakly organic bound, strongly organic bound, inorganic non-crystalline and crystalline. The results obtained by the sequential extraction method for Al were compared with those estimated from single extractions using identical operating conditions applied in each individual sequential fraction. The Al content in the extracts was measured by inductively coupled plasma optical emission spectrometry. The results indicated that the first four steps [potassium chloride (KCl), copper chloride (CuCl2), sodium pyrophosphate (Na4P2O7), acid ammonium oxalate ((NH4)2C2O4)] in the sequential procedure could be as effective as single extraction methods at estimating exchangeable Al, weakly organic bound Al, strongly organic bound Al, and non-crystalline Al. However, the crystalline Al content by sequential procedure was not in agreement with single extraction procedures. Further, the...

Japanese volcanic ash soils have very thick and dark-colored A horizons with large amounts of black humic acids which are characterized by their extremely high aromatic structure and stabilities such as black carbon. Nevertheless, the disappearance of the melanic epipedon with a decreasing aromatic C and increasing alkyl C proportion of humic acids was observed in ecological succession for only over 20–30 years. To obtain further details regarding the chemical characteristics of this extraordinary changing process quantitatively, humus quantitative analysis, high-performance size exclusion chromatography (HPSEC), and liquid-state 13 C nuclear magnetic resonance ( 13 C NMR) analysis were performed, including those for fulvic acids at the surface of mineral soils (0–20 cm), in the grassland/forest ecotone of volcanic ash soil in Japan. In addition, to obtain information regarding the stability and origin of C which gives the key of changing mechanism of humus along with ecological succession, resistance to hydrogen peroxide oxidation (percent decolorization) and the stable isotope ratio of carbon (δ 13 C) were measured, respectively. The study sites were managed as grassland for several hundred years. Grassland at site 1 was still being maintained by mowing, while the maintenance of sites 2 and 3 was discontinued approximately 30 and more than 100 years ago, respectively. The dominant vegetative cover at site 1 was Miscanthus sinensis , that at site 2 was Pinus densiflora with an understory of Sasa spp., and the vegetation comprised mainly Quercus crispula with an understory of Sasa spp. at site 3.The concentration of humic acids decreased significantly from 60.4 to 47.4 C g kg − 1 in site 2, and then decreased continuously from 47.4 to 30.2 C g kg − 1 in site 3. These trends paralleled those of the total C and N content in soils, and C:N ratio increased along with succession from 11.1 to 17.0 to 19.2, respectively, supporting the hypothesis that changing vegetation from grassland to forest may promote N losses by plant uptake. Simultaneously, the concentration of fulvic acids and humin decreased only slightly throughout the series relative to humic acids. Physicochemical properties appeared to be affected by the succession especially in humic acids. In particular, the apparent content of aryl C moieties in the humic acids of site 2 decreased significantly from 30.0 to 14.9 C g kg − 1 , a level similar to site 3. Percent decolorization of humic acids corresponded to their aromaticity; site 1 had a lower value (55.3%) than those of sites 2 and 3 (65.8% and 66.4%, respectively). The δ 13 C values of humic acids ranged from − 19.6 to − 22.6‰; however, the values for sites 1 and 2 were exactly the same. The findings of this study point to the fact that humic acids, but not other humus fractions, significantly changed with decreasing aryl C moieties and stability over the first 30 years of conversion from managed grassland to forest. Furthermore, the disappearance of the melanic epipedon in the surface volcanic ash soil evidently contributed to the aryl C, but not alkyl C, content of humic acids, and there might be a difference in the major mechanism of chemical change of humic acids before 30 years and more than 100 years. At least for the first 30 years, it is strongly suggested that C losses and changes in chemical properties of humic acids could be due to extraordinary microbial degradation processes through accelerated plant N uptake along with ecological succession from grassland to forest in earlier stages.

Anthraquinones are widely present in plant kingdom, and clinically used as laxatives. Environmental contaminants, dioxins, develop various adverse effects through transformation of a cytosolic aryl hydrocarbon receptor (AhR). We investigated the effects of 18 anthraquinones and 7 of their structurally related compounds on transformation of the AhR estimated by its DNA-binding activity in the cell-free system. 1,4-Dihydroxyanthraquinone (quinizarin), 1,5-dihydroxyanthraquinone (anthrarufin), 1,8-dihydroxyanthraquinone (danthron), and 5-hydroxy-1,4-naphthoquinone (juglone) strongly suppressed DNA-binding activity of the AhR induced by 0.1 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), with their IC(50) values around 1 muM. On the other hand, anthraquinone, 2,6-dihydroxyanthraquinone (anthraflavic acid), and 2-hydroxy-1,4-naphthalendione (lawsone) showed moderate effects. Quantitative structure-activity relationships analysis demonstrated that hydroxyl groups at C1 or C4 but not C3 position of anthraquinone structure are critical for the suppressive effects. In addition, all compounds except lawsone had no agonistic effect. The suppressive effects of anthraquinones in a cultured cell system were also confirmed. In human hepatoma HepG2 cells, chrysophanol, danthron, and rhein also suppressed the DNA-binding activity in a dose-dependent manner, although aloe-emodin showed a moderate effect. The findings of this study may be useful for the design of the novel antagonists of the AhR.

To find a certain relation between the composition of carbon functional groups of humic acids derived from liquid state 13C nuclear magnetic resonance (NMR) spectra acquired with inverse-gated decoupling (IGD), known as a quantitative pulse sequence, and that by solid-state 13C NMR with cross polarization/magic angle spinning (CPMAS) techniques, fifteen soil humic acid samples with a wide range of aromaticity were analyzed. Relationships between the proportions of humic acid carbon as alkyl, O-alkyl, and aromatic carbon assessed by the two methods could be regressed to y = ax (r = 0.932–0.956; P < 0.005), respectively. The contents of alkyl, O-alkyl, and aromatic carbon assessed by CPMAS method were larger than those found by IGD method. However, the differences between the two methods were small and exclusive regression to y = x was also significant (r = 0.775–0.941; P < 0.005). Aromaticity calculated from 13C CPMAS NMR data also did not differ significantly from those computed from 13C NMR spectra with IGD. These observations indicated the comparability of the relative content of carbon functional groups in humic acids except for carboxyl and carbonyl carbon.

Chemical properties of hydrophobic acid (HoA) fractions in water-soluble organic matter in soil and water are concerned with its interactions with mineral soil surfaces and organic pollutants. In 2004 we examined the seasonal and vertical changes in chemical properties of the HoA fraction in a Cambisol profile and compared these properties with those in the HoA fraction of an adjacent stream (aquatic humic substances) in a temperate forested watershed using high performance size exclusion chromatography (HPSEC) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The HoA fractions from Oi, Oe/Oa, A and B horizon soils in summer had lower O-alkyl C proportions than those recorded in samples in other seasons. The proportions of aromatic C in HoA fractions from A and B horizons were highest in summer. These seasonal variations were less significant than variations with soil depth. O-alkyl C proportions in HoA fractions decreased with increasing soil depth from the Oi to the A horizon. The H...

Carbon isotopes (13C and 14C) were used to study the characteristics and origin of humic substances in water samples from Lake Biwa in Japan. Humic substances were isolated from surface lake waters in each season by the XAD extraction method and their carbon isotopic ratios were measured by accelerator mass spectrometry. The Δ14C values of Biwa humic and fulvic acids indicate that these substances consist mainly of pre-bomb 14C. There is a negative correlation between Δ14C and δ13C values for the Biwa fulvic acids. The fulvic acid consists of younger organic materials with lower δ13C value in January, but older organics with higher δ13C in April and October. The major part of fulvic acid may be supplied from soil solution and/or groundwater in the watershed and their contribution varies with season.

14C ages and δ13C were examined for sclerotium grains to elucidate the characteristics of these grains distributed in forest soils. The ages of the grains from surface A horizons and buried A horiz...

To clarify the formation condition of Type A humic acids (HAs) from plant residues and to contribute to reducing CO2 emission, three plant residues were incubated for 0, 25, 50, 100 and 160 days with fresh volcanic ash and water at 90°C to produce humic acid like substances (HALS). The HALS of all incubation samples showed a decrease in log (A 400 /A 600 ) values and an increase in A 600 /C values with increasing incubation time. When HALS were classified, only rice straw HALS of 160 days (RS160) belonged to Type A, whereas broad leaf HALS of 160 days (BL160) and Japanese cedar sawdust HALS of 160 days (JCSD160) belonged to Type B. For elemental and nuclear magnetic resonance (NMR) analysis, the HALS samples were prepared according to the International Humic Substances Society (IHSS) method. Data from the elemental composition of all HALS showed high contents (45.98 to 56.55) of carbon (C), low (3.19 to 5.16) hydrogen (H), and low (0.33 to 2.36) nitrogen (N). Carbon content increased in RS and BL...

The vertical distribution of the content of the chloroform-extractable green fraction (CEGF) in the soil profiles of four Japanese Andosols, one Japanese Cambisol and one Nepalese Cambisol was examined using a colorimetric method with an ultraviolet and visible spectrophotometer. In addition, the relationship between the CEGF content and the soil chemical properties was examined by statistical analysis. CEGF was detected in all the soil samples, and the content ranged from 0.02 to 1.16 g kg−1. The CEGF content in the surface A horizon of the Andosol tended to be higher than in the Cambisol. The vertical distribution of the CEGF content in three soil profiles (two Andosol profiles and one Nepalese Cambisol) revealed maximum values in the subsurface horizon. In the Japanese Cambisol, the content of the CEGF was highest in the surface horizon. In the remaining two Andosol profiles containing a buried humus horizon, the content of the CEGF was highest in the buried humus horizon and the distribution ...

A high-performance liquid chromatographic method for the determination of chrysotalunin (1,1′, 8,8′-tetrahydroxy-3,3′-dimethyl-7,7′-bianthraquinoyl), the main hydroxyanthraquinone pigment in soils, is proposed. This method is based on the acetylation of chrysotalunin, and separation and determination of its tetraacetate by liquid chromatography. The minimum detectable amount of chrysotalunin expressed as chrysotalunin acetate was 10 pg. Seventeen samples of different soil types in Japan containing various amounts of carbon were examined. Chrysotalunin amounts ranged from 0.5 ppm (Orthic Acrisols) to 27.7 ppm (Humic Andosols). In addition, for comparison, all samples were assayed using a colorimetric method. From the results of these analyses, the chromatographic method was found to be suitable for the determination of chrysotalunin in soils of various types.