Surface-active properties of particle size fractions in two humic acids

The relationships between surface active properties and humic acid (HA) particle sizes were investigated. Two HAs from an Ando soil and a Brown forest soil were separated into 6 particle size fractions by gel permeation chromatography. Surface-active properties characterized by surface excess value (\gT mol cm^-2), cross-sectional surface area per molecule (A nm²), critical micelle concentration (CMC g L^-1), efficiency and effectiveness of water surface tension reduction were obtained by the measurement of the surface tension of HA solutions from different particle size fractions. For the HA from the Ando soil, except for the smallest particle size fraction, increasing particle size enhanced the efficiency of reduction of the water surface tension and decreased the CMC, while the effectiveness of reduction of the water surface tension was about the same. The surface activity of the HA from the Ando soil increased with increasing particle size. This phenomenon was similar to the surface activity of a homologous series of surfactants, which increased with increasing alkyl chain length. For the HA from the Brown forest soil, the smallest particle size fraction and three large fractions showed a high efficiency, namely a high surface activity. The smallest fraction from the Brown forest soil showed the highest efficiency and the lowest CMC value. In both HAs, the smallest particle size fraction showed exceptional surface-active properties compared with the other fractions and three fractions with large particle size showed a higher surface activity than other smaller fractions.     

Relationship between viscosity and molecular weight in an andosol humic acid

Viscosity and molecular weight of particle size fractions obtained from an Andosol humic acid (HA) were determined. Viscosity was determined both in solutions with and without the addition of 0.1 M NaCl (Cs 0.1 and Cs 0, respectively) at pH 7.0. Polyelectrolytic character was observed in the particle size fractions based on the changes in the concentration dependence of reduced viscosity with NaCI concentrations. The use of a Cs 0.1 solution was suitable for the determination of the values of intrinsic viscosity ([η]) of the particle size fractions. The [η] value increased with increasing weight average molecular weight ( M _w) determined by gel permeation chromatography (GPC), and ranged from 4.3 to 12.9 X 10-3 (L g^-1) in the Cs 0 solution and from 3.5 to 6.6 × 10^-3 (L g^-1) in the Cs 0.1 solution. A linear relationship between [η] in the Cs 0.1 solution and M _w on a logarithmic scale, which was similar to the MarkHouwink equation, was observed. The value of the constant a calculated from the relationship, which reflected the polymer morphology, was 0.75 in the Cs 0.1 solution, and it corresponded to a polymer with flexible chains.     

Transgenic rice plants expressing human CYP1A1 remediate the triazine herbicides atrazine and simazine

The human cytochrome P450 CYP1A1 gene was introduced into rice plants (Oryza sativa cv. Nipponbare). One-month-old CYP1A1 plants grown in soil clearly showed a healthy growth and tolerance to 8.8 microM atrazine and 50 microM simazine, but nontransgenic plants were completely killed by the herbicides. Although transgenic and nontransgenic plants metabolized the two herbicides into the same sets of compounds, CYP1A1 plants metabolized atrazine and simazine more rapidly than did control plants. In small-scale experiments, residual amounts of atrazine and simazine in the culture medium of CYP1A1 plants were 43.4 and 12.3% of those in control medium; those of nontransgenic Nipponbare were 68.3 and 57.2%, respectively. When cultivated in soil with 2.95 microM atrazine and 3.15 microM simazine for 25 days, CYP1A1 plants eliminated 1.3 times more atrazine and 1.4 times more simazine from the soil than did control plants. Thus, CYP1A1 rice plants make it possible to remove atrazine and simazine more rapidly from the culture medium and soil than can nontransgenic Nipponbare.     

Impact of farmland reclamation on soil distribution in Japan: the case of Andosols in Nagano Prefecture

Journal of Soils and Sediments - In modern times, farmlands in Japan have been reconstructed at a large-scale through the cutting and filling of soils. In principle, such reconstruction should be...     

Phytoremediation of metolachlor by transgenic rice plants expressing human CYP2B6

We introduced the human cytochrome P450 gene CYP2B6 into rice plants (Oryza sativa L. cv. Nipponbare), and the CYP2B6-expressing rice plants became more tolerant to various herbicides than nontransgenic Nipponbare rice plants. In particular, CYP2B6 rice plants grown in soil showed tolerance to the chloroacetanilide herbicides alachlor and metolachlor. We evaluated the degradation of metolachlor by CYP2B6 rice plants to confirm the metabolic activity of the introduced CYP2B6. Although both CYP2B6 and nontransgenic Nipponbare rice plants could decrease the amount of metolachlor in plant tissue and culture medium, CYP2B6 rice plants could remove much greater amounts. In a greenhouse, the ability of CYP2B6 rice plants to remove metolachlor was confirmed in large-scale experiments, in which these plants appeared able to decrease residual quantities of metolachlor in water and soil.     

Transgenic rice containing human CYP2B6 detoxifies various classes of herbicides

The human gene for CYP2B6, a cytochrome P450 monooxygenase that inactivates xenobiotic chemicals, was introduced into Oryza sativa cv. Nipponbare by Agrobacterium-mediated transformation. At germination, R(1) seeds of transgenic rice plants expressing CYP2B6 (CYP2B6 rice) showed a high tolerance to 5 microM metolachlor, a preemergence herbicide that is degraded by CYP2B6. Thin-layer chromatography after culture with (14)C-labeled metolachlor revealed that the amounts of residual metolachlor decreased in plant tissues and the medium of CYP2B6 rice faster than those of untransformed Nipponbare. CYP2B6 rice plants were able to grow in the presence of 13 out of 17 herbicides: five chloroacetamides and mefenacet, pyributicarb, amiprofos-methyl, trifluralin, pendimethalin, norflurazon, and chlorotoluron. These herbicides differ in their modes of action and chemical structures. Transgenic rice expressing a xenobiotic-degrading human CYP2B6, which has broad substrate specificity, should be good not only for developing herbicide tolerant rice but also for reducing the environmental impact of agrochemicals.     

Phytoremediation of the herbicides atrazine and metolachlor by transgenic rice plants expressing human CYP1A1, CYP2B6, and CYP2C19

This study evaluated the expression of human cytochrome P450 genes CYP1A1, CYP2B6, and CYP2C19 in rice plants (Oryza sativa cv. Nipponbare) introduced using the plasmid pIKBACH. The transgenic rice plants (pIKBACH rice plants) became more tolerant toward various herbicides than nontransgenic Nipponbare rice plants. Rice plants expressing pIKBACH grown in soil showed tolerance to the herbicides atrazine, metolachlor, and norflurazon and to a mixture of the three herbicides. The degradation of atrazine and metolachlor by pIKBACH rice plants was evaluated to confirm the metabolic activity of the introduced P450s. Although both pIKBACH and nontransgenic Nipponbare rice plants could decrease the amounts of the herbicides in plant tissue and culture medium, pIKBACH rice plants removed greater amounts in greenhouse experiments. The ability of pIKBACH rice plants to remove atrazine and metolachlor from soil was confirmed in large-scale experiments. The metabolism of herbicides by pIKBACH rice plants was enhanced by the introduced P450 species. Assuming that public and commercial acceptance is forthcoming, pIKBACH rice plants may become useful tools for the breeding of herbicide-tolerant crops and for phytoremediation of environmental pollution by organic chemicals.     

Soils, vegetation, and climate of the southern Transural region in the Middle Bronze Age (by the example of the Arkaim fortress)

Paleosols of the unique fortress of Arkaim located in the steppe zone of the southern Transural region (Chelyabinsk oblast) were investigated. The dating of the buried soils was performed using the radiocarbon method. The time of building this archeological monument is the Middle Bronze Age (the Sintashta culture; the calibrated dating with 1σ confidence is 3700–4000 years ago). Seven pits of paleosols and ten pits of background ordinary chernozems were studied. The soils are loamy and sandy-loamy. The morphological and chemical properties of the buried and background ordinary chernozems are similar; they differ by the lower content of readily soluble salts in the paleosols as compared to the background ones. The sporepollen spectrum of the Arkaim paleosol is transitional from the steppe to the forest-steppe type. During the existence of this settlement, pine forests with fern ground cover grew, and hygrophytic species (alder and spruce) that nowadays are not recorded in the plant cover occurred. The main feature of the paleosols is the presence of pollen of xerophytic and halophytic herbaceous plants there. The few pollen grains of broad-leaved species testify to a higher heat supply as compared to the current one. Judging by the results of the spore-pollen and microbiomorphic analyses, the climate during the time of building the walls of the settlement was somewhat moister and warmer (or less continental) than the present-day climate. The duration of this period appeared to be short; therefore, soil properties corresponding to the changed environment could not be formed. They reflect the situation of the preceding period with the climatic characteristics close to the present-day ones.     

Effect of fire on solute release from organic horizons under larch forest in Central Siberian permafrost terrain

To evaluate the effects of forest fire and post-fire stand recovery on the organic layer chemistry and solute release within mound and trough microrelief elements (termed earth hummock microtopography) that mainly distribute permafrost affected area, we chose five fire plots (larch forests burned in 1951, 1981, 1990, 1994 and 2005) paired with adjacent control plots in mature larch forests in Central Siberian permafrost terrain. We determined total carbon, nitrogen and ash content in solid organic soils, and analyzed total carbon, nitrogen, bases and major anions in water extracts. There was a significant correlation between water-extracted organic carbon (WEOC) and total carbon (kg m⁻²) in area basis, implying that the quantity of total carbon was a major factor in WEOC production. WEOC correlated negatively with pH, indicating strong control by organic horizons (organic solute leaching) on soil acidity and base cation dynamics. The sum of water extractable base cations was also correlated significantly to total carbon, indicating that cations can be released through organic matter decomposition. Organic horizons in troughs in burned plots released greater amounts of Ca, Mg and K than those in mounds, probably due to greater content of organic matter as a cation source. Anions including nitrate and phosphate and WEOC also accumulated in trough depressions, due probably to organic matter degradation. The contrasting distribution of solutes between mounds and troughs in burned plots seems to be controlled by organic horizon development via changes in microtopography after forest fires.