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Pyrogenic carbon (PyC) or black carbon (BC), the residue of grassland and forest fires and fossil fuel combustion, plays an important role in carbon storage and pollutant adsorption in soil. To und...

We examined the linkages between topography and electron donors for denitrification on in-stream NO3 − concentration in headwater catchments in the Lake Hachiro watershed having marine sedimentary ...

Sulfur-based denitrification may be a key biogeochemical nitrate (NO3−) removal process in sulfide-rich regions, but it is still poorly understood in natural terrestrial ecosystems. We examined sulfur-driven NO3− reduction using streambank soils in a headwater catchment underlain by marine sedimentary rock in Akita, Japan. In a catchment exhibiting higher sulfide content in streambed sediment, we sampled two adjacent streambank soils of streambank I (two layers) and of streambank II (eight layers). Anaerobic long-term incubation experiments (40 days, using soils of streambank I) and short-term incubation experiments (5 days, using soils of streambank II) were conducted to evaluate variations of N solutes (NO3−, NO2−, and NH4+), N gases (NO, N2O), and the bacterial flora. In both experiments, two treatment solutions containing NO3− (N treatment), and NO3− and S2O32− (N + S treatment) were prepared. In the N + S treatment of the long-term experiment, NO3− concentrations gradually decreased by 98%, with increases in the SO42−, NO2−, NO, and N2O concentrations and with not increase in the NH4+, indicating denitrification had occurred with a high probability. Temporal accumulation of NO2− was observed in the N + S treatment. The stoichiometric ratio of SO42− production and NO3− depletion rates indicated that denitrification using reduced sulfur occurred even without additional S, indicating inherent S also served as an electron donor for denitrification. In the short-term incubation experiment, S addition was significantly decreased NO3− concentrations and increased NO2−, NO, and N2O concentrations, especially in some subsoils with higher sulfide contents. Many denitrifying sulfur-oxidizing bacteria (Thiobacillus denitrificans and Sulfuricella denitrificans) were detected in both streambank I and II, which dominated up to 5% of the entire microbial population, suggesting that these bacteria are widespread in sulfide-rich soil layers in the catchment. We concluded that the catchment with abundant sulfides in the subsoil possessed the potential for sulfur-driven NO3− reduction, which could widely influence N cycling in and NO3− export from the headwater catchment.

This chapter presents characteristics of soils of the Chubu region, which encompasses between the Sea of Japan and the Pacific Ocean in the middle of Honshu. In the region, there is Mt. Fuji, the active volcano and the highest mountain in Japan. Not only that, the geology of the region is diverse. The region has several mountain ranges, diverse climates and vegetation. So, you can see a lot of different type of soils in the region. In this chapter, we will first give an overview of the soil formation factors and the existing soils in the region. The chapter then describes the agriculture and forestry for the three distinct regions of the Chubu region. The northern part of the Chubu region, called Hokuriku, centers on paddy production on wet and clayey soil by virtue of snow-meltwater and summer high temperature. For the central part of the Chubu region consisting of highland, the sustainable soil management for forestry is described. As for the southern part of the Chubu region, Tokai, characteristics of agriculture for cultivation of vegetables and tea on mainly Red-Yellow soil under mild climate are described, including efforts toward effective use of fertilizers.

Saltpetre (KNO3; potassium nitrate) is one of the major ingredients of gunpowder which often served as a driving force during the political changes in historical times. Before development of chemical synthesis which involves the fixation of atmospheric dinitrogen followed by oxidation of NH3 with atmospheric oxygen, natural occurrence of nitrate minerals in sediments and soils was the sole source of the saltpetre. Reworking historic saltpetre manufacture was conducted in five locations from Lao PDR, a landlocked country in the Indochina Peninsula. The overall manufacturing processes involved the extraction with water of economic nitrous-earth (so-called bat guano deposits) collected from limestone caves, followed by addition of potash (potassium carbonate in form of wood-, grass- and bottom-ashes) to convert native nitrates (mostly Ca-salts) into saltpetre, evaporative removal of excess water from the elutes by pro-longed boiling (evaporative concentration), removal of floating scum and finally differential crystallization from the concentrates. The process was tested by use of stable isotopic analyses of nitrogen and oxygen isotope of the relevant chemical constituents (ambient water and nitrate). The analytical results for δ15N-δ18O values of nitrates collected at each step of the manufacturing processes verify limited isotopic modification, even in the prevailing conditions under strong alkaline media (pH: up to 11) and repeated evaporative removal of the ambient water which accompanies selective removal of 16O from the fluids. Slight negative/positive changes up to 2‰ in nitrate isotopic signatures of saltpeter concentrates were observed during the repeated removal of scum due to co-precipitation of nitrates with associated insoluble sulfates. Significance of the stable isotopic fingerprinting for the source identification as applied for saltpetre in the historic gunpowder was emphasized.

With global population growth, substantial increases in food demand have aggravated the problem of methane emissions, which most researchers have been focusing on reducing in paddy fields. Since methane is a clean energy source and the main component of natural gas, we established a novel and efficient on-site biomethane production and collection system using rice straw in the paddy field without any other methane fermentation tan, implying that this system will contribute to reduction of the greenhouse effect. We have termed this the “GET system”: the efficient production of biomethane gas (G) as renewable energy (E) from a tanbo (T), which means “paddy field” in Japanese. The results showed that, during mesophilic (20–40 °C) digestion, the GET system could generate up to 100 L/day m−2 of biomethane at a methane concentration of more than 60% from rice straw, which was at the optimum application amount of 14 kg m−2 in the study. Moreover, the resulting 25.7% of carbon in rice straw was simultaneously stored in the soil as fermentation residue, improving soil fertility during the next rice-growing season and creating a carbon sink. The GET system is therefore a game-changing technology, offering a potential solution to the demand for food and energy without the emission of methane, thus reducing atmospheric carbon dioxide (CO2). Promotion and use of the GET system as effective clean technology will play a key role in global sustainable development in the near future.

The classification systems for soil particle size ranges and soil texture differ among countries and/or associations. Unique systems have also endured in Japan over the last six decades. However, the original reports explaining the rationale for these systems have gradually been lost, so there is no source written in either Japanese or English for authors to reference the origin of the Japanese soil classification systems. In this light, we reviewed the origin of the Japanese classification systems for soil particle size ranges and soil texture. The size range system was adopted from International Society of Soil Science (ISSS) standards. The soil texture classification system was introduced by Tommerup in his paper at the ISSS Commission I (Soil Physics) meeting in 1934. This soil texture classification system was modified by Yamanaka in 1955, and was henceforth adopted as the conventional soil texture classification system in Japan. This ISSS-defined soil texture classification system has been i...

Large amounts of marine-derived nitrogen are carried ashore by seabirds in their feces (ornithogenic N). Various topological, meteorological, and environmental factors can affect microbial transformation of ornithogenic N altering the physical and biochemical conditions of the soils. Tsunami may be a factor affecting ornithgenic soil N dynamics leading to changes in soil conditions. We examined the effects of the tsunami triggered by the 11 March 2011 earthquake off the East Coast of Honshu, Japan, on ornithogenic soil N in the Black-tailed Gull Larus crassirostris breeding colony on Kabushima (Kabu Island) four months after the disaster. There were no differences in the total N content in soils between tsunami splashed (upper half of the island) and flooded areas (lower half), and the visual topography was comparable to that reported before the tsunami. It seems that the tsunami may not have extensively removed accumulated ornithogenic N in the soils, nor did it induce deposition of organic matt...

Humic substances (HS) in soil and sediments, and surface water influence the behavior of organic xenobiotics in the environment. However, our knowledge of the effects of specific HS fractions, i.e., humic acids (HAs), fulvic acids (FAs), and humin (HM), on the sorption of organic xenobiotics is limited. The neonicotinoid insecticide acetamiprid is thought to contribute to the collapse of honeybee colonies. To understand the role that soil organic matter plays in the fate of acetamiprid, interactions between acetamiprid and the above HS fractions were examined. Batch experiments were conducted using various combinations of a field soil sample and the above 3 HS fractions prepared from the same soil, and differences in isotherm values for acetamiprid sorption were investigated based on the structural differences among the HS fractions. The sorption of acetamiprid to soil minerals associated with HM (MHM) (Freundlich isotherm constant, Kf: 6.100) was reduced when HAs or FAs were added (Kf: 4.179 and 4.756, respectively). This can be attributed to hydrophobic interactions between HM and HAs or FAs in which their dissociated carboxyl and phenolic groups become oriented to face the soil solution. The amount of acetamiprid that was adsorbed to (MHM+HA) or (MHM+FA) increased when aluminum ions were added (Kf: 6.933 and 10.48, respectively), or iron ions were added (Kf: 7.303 and 11.29, respectively). Since acetamiprid has no affinity for inorganic components in soil, the formation of HS-metal complexes by cation bridging may have oriented the hydrophobic moieties in the HAs or FAs to face the soil solution and may also have resulted in the formation of dense structures, resulting in an increase in the amount of acetamiprid that becomes adsorbed to these structures. These results highlight the importance of interactions among soil components in the pedospheric diffusion of acetamiprid.

Terrestrial ecosystems near breeding/roosting colonies of piscivorous seabirds can receive a large amount of marine-derived N in the form of bird feces. It has been well demonstrated that N input from seabirds strongly affects plant communities in forests or coastal grasslands. The effects of nutrient input on plant communities in agricultural ecosystems near seabird colonies, however, have rarely been evaluated. This relationship was examined in rice-paddy fields irrigated by a pond system located near a colony of the Great Cormorant Phalacrocorax carbo in Aichi, central Japan. In the present study, spatial variations in N content (N %) and N stable isotope composition (δ15N) of soils and wild grass species together with the growth height of plants in paddy fields in early spring (fallow period) were examined. Soils had a higher N % and δ15N values in fields associated with an irrigation pond that had N input from cormorants. The δ15N values tended to be higher around the inlet of irrigation waters, relative to the outlet. These results indicate that cormorant-derived N was input into the paddy fields via the irrigation systems. Plants growing in soil with higher δ15N had higher δ15N in the above-ground part of the plants and had luxurious growth. A positive correlation in plant height and δ15N of NO3–N was observed in soil plough horizons.

We investigated the adsorption and mobility of aromatic arsenicals (AAs) in two types of Japanese agricultural soils in batch and column leaching experiments. The amounts of AAs adsorbed onto a Fluvisol (a sandy loam) and an Andosol (a light clay) decreased in the order of phenylarsonic acid (PAA) > methylphenylarsinic acid (MPAA) > diphenylarsinic acid (DPAA) > methyldiphenylarsine oxide (MDPAO) > dimethylphenylarsine oxide (DMPAO). The amounts of all AAs adsorbed onto the Andosol, which had more amorphous minerals and organic carbon, were higher than those adsorbed onto the Fluvisol. The adsorbability of AAs increased with both an increasing arsenate proportion and a decreasing hydrophobicity. This result suggests that the mechanisms of adsorption of AAs onto soil are due mainly to ligand exchange reactions and less to hydrophobic interactions. Mobility in the Fluvisol decreased in the order of DMPAO (30 cm) > MDPAO (25 cm) > MPAA (20 cm) > DPAA (15 cm) = PAA (15 cm). Mobility in the Andosol was less: D...

It has been known that the Cucurbitaceae family takes up a large amount of persistent organic pollutants from soils and that the translocation of those compounds in cucurbits is higher than those in non-cucurbits. To understand the persistent organic pollutant uptake mechanisms of plant species, we compared the dieldrin absorption and transportation potentials of several plants in hydroponic medium. Sorghum (Sorghum vulgare Moench), sunflower (Helianthus annuus L.), soybean (Glycine max), komatsuna (Brassica rapa var. peruviridis), white-flowered gourd (Lagenaria siceraria var. hispida), cucumber (Cucumis sativus L.), and zucchini (Cucurbita pepo L.) were grown in a dieldrin-added hydroponic medium for 10 d, and then the amount of dieldrin in their shoots and roots was measured. All of the roots contained dieldrin, whereas only the cucurbits (white-flowered gourd, cucumber, and zucchini) contained considerable amounts of dieldrin in their shoots. The dieldrin uptake to the roots depended on the concentration of the n-hexane soluble components in the roots, regardless of whether the dieldrin in the roots was translocated to shoots or not. The dieldrin uptake from the solution to the roots was thought to be due to a passive response, such as adsorption on the roots. The translocation of dieldrin from the roots to the shoots was probably through the xylems. The amounts of dieldrin in the shoots per transpiration rates were higher for cucurbits than for non-cucurbits. It seems likely that cucurbits have uptake mechanisms for hydrophobic organic chemicals. Environ. Toxicol. Chem. 2010;29:142–148. © 2009 SETAC

The use of heptachlor, a cyclodiene-type insecticide, has been banned since the 1970s because of its carcinogenic potential. However, its metabolite, heptachlor exo-epoxide (HEPX), has still been detected in the fruit of cucurbits produced in some areas. It is important to reduce the daily intake of HEPX contained in food. To address this issue, the effects of carbonaceous adsorbents on the uptake of HEPX from the soil by Cucurbita maxima Dutch. (winter squash) were investigated. Amorphous organic carbons, such as peat moss and wood chips, did not affect the concentration of HEPX in the soil solution or the amount present in the shoots. In contrast, relatively condensed carbon, such as activated carbons, decreased the concentration of HEPX in the soil solution and in the shoots. The uptake amount in the shoot was closely correlated with the concentration of HEPX in the soil solution, which suggests that its uptake by C. maxima depends on its concentration in the soil solution. Activated carbons d...

The relationship between the behavior of clomeprop ([RS]-2-[2,4-dichloro-m-tolyloxy]propionanilide) and its residual phytotoxic activity in the soil was investigated in the laboratory with special emphasis on the concentration in the soil water. The phytotoxic activity of clomeprop on radish seedlings (Raphanus sativus L. var. radicula cv. Akamaruhatsukadaikon), as the test plant, became greater with time after application but the inhibition was different between the two soils, which had different properties. The amount of 2-(2,4-dichloro-3-methylphenoxy)propionic acid (DMPA), a hydrolyzed and active metabolite of clomeprop, in the soil water and total soil increased with time, corresponding to the decrease in the amount of clomeprop under non-water leakage conditions. The residual phytotoxic activity of clomeprop in the soil was more highly correlated with the concentration of DMPA in the soil water than with the amount of DMPA in the total soil. In addition, a leaching column test was conducted with clomeprop and DMPA. The DMPA easily moved downward and the concentration in the soil water in the upper layer decreased with time after application. It is supposed that the downward movement of DMPA was one of the factors influencing the lasting effect of clomeprop in the field.

Samples of river waters containing high concentrations of zinc and other heavy metals but low concentrations of other anthropogenic contaminants were collected to investigate the relationship between toxicity of heavy metals and naturally present organic matters or hardness, as well as the effects of heavy metals on aquatic organisms. Acute toxicity tests were conducted for the water samples using Daphnia magna and medaka Oryzias latipes. Almost all the D. magna died in river waters containing high concentrations of zinc, but O. latipes in the same waters were hardly affected. Since the test organisms were not only exposed to zinc but also other heavy metals in the river waters, we examined the toxicity using toxic units composed of zinc, copper, lead, and cadmium. The results of a bioassay with the river waters showed that the mortality of D. magna did not depend solely on the total number of toxic units of heavy metals. The organic matters and the hardness of the river waters could decrease the acute toxicity of zinc and other heavy metals to D. magna.

The phytotoxic activity of soil-applied thenylchlor (2-chloro-N-[3-methoxy-2-thenyl]-2′,6′-dimethylacetanilide) on the growth of rice seedlings and its behavior in two different types of soil, Ryugasaki soil and Tsukuba soil, after application was investigated with emphasis on the concentration in the soil water. The greatest inhibition of thenylchlor on the growth of rice seedlings was found immediately after application to both the Ryugasaki and Tsukuba soils. The phytotoxic activity decreased with time in both soils. However, the rate of decrease in phytotoxic activity was slower in the Ryugasaki soil than in the Tsukuba soil. The concentration of thenylchlor in soil water, the amount adsorbed on the soil solid, and the amount in the total soil reduced with time after application to both soils. The amount of thenylchlor adsorbed on the soil solid phase was more persistent than that in the soil water in both soils and the concentration in the soil water was higher in the Ryugasaki soil than in the Tsukuba soil at any given time. The residual phytotoxic activity of thenylchlor on the growth of the rice seedlings in the soil was highly correlated with its concentration in the soil water but not with the amount in the total soil. These results suggested that the residual phytotoxic activity of thenylchlor in the soil is determined by its concentration in the soil water after application.

Ethyl-2-hydroxy-4-methylpentanoate (ethyl leucate) contributes to a fruity flavor in Japanese sake. The mold Aspergillus oryzae synthesizes leucate from leucine and then the yeast Saccharomyces cerevisiae produces ethyl leucate from leucate during sake fermentation. Here, we investigated the enzyme involved in leucate synthesis by A. oryzae. The A. oryzae gene/cDNA encoding the enzyme involved in leucate synthesis was identified and expressed in E. coli and A. oryzae host cells. The purified recombinant enzyme belonged to a D-isomer-specific 2-hydroxyacid dehydrogenase family and it NADPH- or NADH-dependently reduced 4-methyl-2-oxopentanate (MOA), a possible intermediate in leucine synthesis, to D-leucate with a preference for NADPH. Thus, we designated this novel enzyme as MOA reductase A (MorA). Furthermore, an A. oryzae strain overexpressing morA produced 125-fold more leucate than the wild-type strain KBN8243. The strain overexpressing MorA produced 6.3-fold more ethyl leucate in the sake than the wild-type strain. These findings suggest that the strain overexpressing morA would help to ferment high-quality sake with an excellent flavor. This is the first study to identify the MOA reductase responsible for producing D-leucate in fungi.

The uptake ability of hydrophobic organic chemicals by plants and the nature of xylem sap of the plants were studied. The plants were grown in soil contaminated with dieldrin. High amounts of dieldrin were detected in the shoots of Cucurbita pepo and Cucumis sativus, but little was seen in the shoots of Brassica oleracea var. italica, Solanum lycopersicum, Glycine max, Zea mays, and Helianthus annuus. The xylem saps of C. pepo and C. sativus leached dieldrin adsorbed on C8 granules, but those of the other plants did not. The xylem saps of C. pepo and C. sativus eluted high amounts of dieldrin from the size-exclusion chromatography column near the fractions of RNase A (13.7 kDa) after Aprotinin (6.5 kDa), which has a larger molecular weight than dieldrin (381). The enhancement of dieldrin solubility by xylem sap was reduced by proteinase and heating. It was suspected that the protein-like materials in the xylem sap delivered dieldrin from the roots to the shoots. Environ. Toxicol. Chem. 2010;29:2269–2277. © 2010 SETAC

To prevent the distribution of cucumbers with dieldrin contamination exceeding the limit set by the Japanese Food Sanitation Law, the extraction solvent for dieldrin-contaminated soil was selected prior to cultivation so that the dieldrin residue level in cucumber could be predicted. The exhaustive extraction from soil could not explain the dieldrin uptake by cucumber plants. However, significant correlation (R(2) = 0.966, P < 0.001) was observed between dieldrin concentrations in cucumber and dieldrin concentrations extracted with 50% (v/v) methanol-water solution from soils. This was a result of the phytoavailability of dieldrin to the cucumber plants. The extractability of soil dieldrin with the methanol-water solution decreased as the organic carbon content in the soils increased. This suggested that a 50% (v/v) methanol-water solution is the optimal solution for predicting dieldrin concentrations in cucumbers by soil analysis.

The adsorption of 2-(2,4-dichloro-3-methylphenoxy)propanoic acid (DMPA) on the surface horizon of a humus-rich Andosol was examined. To investigate the mechanisms of adsorption, chemically treated Andosols, such as organic matter removed Andosol, organic matter and active metals removed Andosol, and clay minerals of the Andosol, were prepared. Furthermore, humic acid was extracted from the Andosol. The mechanisms of the DMPA adsorption were identified by using those untreated and chemically treated Andosols and the humic acid. The amount of DMPA adsorbed increased with decreasing equilibrium pH value. Active surface hydroxyl groups were identified as the most important soil functional group in DMPA adsorption. The predominant mechanism of DMPA adsorption on the Andosol is a ligand-exchange reaction, in which an active surface hydroxyl on Al and/or Fe is replaced by a carboxylic group of DMPA. A comparative study revealed that the amount of DMPA adsorbed was slightly greater than that of (2,4-dichlorophenoxy)acetic acid (2,4-D), especially at equilibrium pH values below 5. This is because the octanol-water partition coefficient (log Kow) of DMPA in the equilibrium pH range is higher than that of 2,4-D, and SOM participates in the adsorption process through a hydrophobic interaction.