Masanori Okazaki

Effects of charcoal addition on N2O emissions from soil resulting from rewetting air-dried soil in short-term laboratory experiments

Abstract Laboratory experiments were conducted to examine the effect of charcoal addition on N2O emissions resulting from rewetting of air-dried soil. Rewetting the soil at 73% and 83% of the water-filled pore space (WFPS) caused a N2O emission peak 6 h after the rewetting, and the cumulative N2O emissions throughout the 120-h incubation period were 11 ± 1 and 13 ± 1 mg N m−2, respectively. However, rewetting at 64% WFPS did not cause detectable N2O emissions (−0.016 ± 0.082 mg N m−2), suggesting a severe sensitivity to soil moisture. When the soils were rewetted at 73% and 78% WFPS, the addition of charcoal to soil at 10 wt% supressed the N2O emissions by 89% . In contrast, the addition of the ash from the charcoal did not suppress the N2O emissions from soil rewetted at 73% WFPS. The addition of charcoal also significantly stimulated the N2O emissions from soil rewetted at 83% WFPS compared with the soil without charcoal addition (P < 0.01). Moreover, the addition of KCl and K2SO4 did not show a clear difference in the N2O emission pattern, although Cl− and SO2− 4, which were the major anions in the charcoal, had different effects on N2O-reducing activity. These results indicate that the suppression of N2O emissions by the addition of charcoal may not result in stimulation of the N2O-reducing activity in the soil because of changes in soil chemical properties.

Effects of successive soil freeze-thaw cycles on soil microbial biomass and organic matter decomposition potential of soils

Abstract Effects of soil freeze-thaw cycles on soil microbial biomass were examined using 8 soil samples collected from various locations, including 4 arable land sites and 2 forest sites in temperate regions and 2 arable land sites in tropical regions. The amounts of soil microbial biomass C and N, determined by the chloroform fumigation and extraction method, significantly decreased by 6 to 40% following four successive soil freeze-thaw cycles (- 13 and 4°C at 12 h-intervals) compared with the unfrozen control (kept at 4°C during the same period of time as that of the freeze-thaw cycles). In other words, it was suggested that 60 to 94% of the soil microorganisms might survive following the successive freeze-thaw cycles. Canonical correlation analysis revealed a significantly positive correlation between the rate of microbial survival and organic matter content of soil (r = 0.948*). Correlation analysis showed that the microbial survival rate was also positively correlated with the pore-space whose size ranged from 9.5 to 6.0 μm (capillary-equivalent-diameter; r = 0.995**), pH(KCI) values (r = 0.925**), EC values (r = 0.855*), and pH (H2O) values (r = 0.778*), respectively. These results suggested that the soil physicochemical properties regulating the amount of unfrozen water in soil may affect the rate of microbial survival following the soil freeze-thaw cycles. The potential of organic matter decomposition of the soils was examined to estimate the effects of the soil freeze-thaw cycles on the soil processes associated with the soil microbial communities. The soil freeze-thaw cycles led to significant 6% increase in chitin decomposition and 7% decrease in rice straw decomposition (p < 0.05), suggesting that the partial sterilization associated with the soil freeze-thaw cycles might disturb the soil microbial functions.

The chemical phase changes in heavy metals with drying and oxidation of the lake sediments

Abstract In order to understand the effects of oxidation on heavy metal behavior in sediments, the changes in chemical phase distributions of heavy metals with oxidation of sediments from Lake Teganuma were investigated using a sequential chemical extraction procedure for heavy metals. The exposure of sediments from the lake bottom to atmosphere caused the increase of Eh and the decrease of acid volatile-S in sediments. Most of the cadmium is expected to exist as relatively stable forms such as sulfides in original reduced sediments prior to exposure to the atmosphere. With the oxidation of sediments, Cd in the sulfidic/organic fraction were transformed to forms in the exchangeable and the reducible fractions which are easily dissolved. The chemical phase changes of Cu, Pb and Zn in sediments were less drastic than the case of Cd. Cadmium distinctly affected by the change in redox potential in sediments, and its behavior in the oxidized state is most mobile. Compared to Cd, the behavior of Cu and Pb are not so remarkably affected by the change in redox condition of sediments.

ADSORPTION-DESORPTION CHARACTERISTICS OF HIGH LEVELS OF COPPER IN SOIL CLAY FRACTIONS

Copper adsorption and desorption under acid conditions by soil clay fractions separated from Vertisol, Planosol and Gleyic Acrisol has been studied in 0.01 M Ca(NO3)2. A Freundlich equation was appropriate to describe Cu adsorption. Within the range of 150 to 2600 mg of copper per kg of soil clay fraction the proportions of Cu not displaced during 5 successive 48-hour desorptions with 0.01 M Ca(NO3)2 decreased with increasing adsorption density and at the lower pHs. The proportions ranged from as high as 0.98 in th case of the Vertisol clay (pH 5.3) to as low as 0.12 (88% desorption) in the Planosol clay (pH 4.5). Measurement of separation factors (ga Cu/Ca) showed that the preference of the clay surface for Cu over Ca decreased in the order: Gleyic Acrisol > Planosol > Vertisol. A considerable amount of sorbed copper could be solubilized by decreasing pH values to 4 when in the Planosol clay 39% was desorbed and 45% was desorbed in the Gleyic Acrisol clay.

Adsorption of Heavy Metal Cations on Hydrated Oxides and Oxides of Iron and Aluminum with Different Crystallinities

The adsorption of Cu2+, Zn2+, and Mg2+ on the hydrated oxides and oxides of iron and aluminum with different crystallinities was investigated. The effects of pH, ionic strength of the bulk solution, competing metal cations, metal cation concentration on the adsorption were evaluated. The adsorption of Cu2+, Zn2+, and Mg2+ on the hydrated oxides and oxides of iron and aluminum increased with increasing pH of the bulk solution, and the adsorption sequence was in the order Cu2+>Zn2+>Mg2+. The ionic strength of the bulk solution did not affect the adsorption of Cu2+ and Zn2+. Competitive adsorption of Zn2+ and Mg2+ was observed in the presence of Cu2+. The X-ray amorphous hydrated oxides and oxides of iron and aluminum with a low crystallinity showed a larger adsorption capability for heavy metal cations than those with a high crystallinity.

Acidification in nitrogen-saturated forested catchment

Abstract Continuous monitoring studies focused on nitrogen saturation were conducted at the Rolling Land Laboratory (RLL) of the forest experimental station located in the Tama Hill region in Central Japan. Based on the nitrate concentration in stream water, it was estimated that the forest ecosystems at RLL could be classified into Stage 2 of nitrogen saturation. The stream water pH decreased when the nitrate concentration increased. Proton production due to N transformation (= ([NH4 +]th-[NH4 +]out)-([N03 -]th-[N03 -]out) amounted to 1.24 kmolc ha-1 y-1 in 1991–1992, a value 1.5 times as high as the total atmospheric proton input. Sulfate adsorption buffered the impact of the acid load. Protons were mainly consumed by ion exchange with base cations and weathering processes. Both acidic deposition and N transformation accelerated base cation mobilization. Nevertheless, soil pH values at RLL did not decrease due to the abundance in base cations.

Development of Damage Function of Acidification for Terrestrial Ecosystems Based on the Effect of Aluminum Toxicity on Net Primary Production

BackgroundAcidification is one of the important impact categories for life cycle impact assessment. Although its characterization has progressed during this decade through the employment of midpoint approaches, only limited studies of endpoint approaches have been performed. Objective. This study aimed at developing damage function of acidification for terrestrial ecosystems in Japan. Damage function expresses a quantitative relationship between the inventory and endpoint damage.MethodsThe geographical boundary was limited in Japan both for emission and impact. In this study, sulfur dioxide (SO2), nitrogen monoxide (NO), nitrogen dioxide (NO2) (NO and NO2 collectively mean NOx), hydrogen chloride (HC1), and ammonia (NH3) were considered as major causative substances of acidification. Net primary production (NPP) of existing vegetation was adopted as an impact indicator of terrestrial ecosystems. The aluminum toxicity was adopted as the major factor of effect on terrestrial ecosystems due to acidification. The leachate concentration of monomeric inorganic aluminum ions was selected to express the plant toxicity of aluminum.Results and DiscussionThe results of damage function gave utilizable factors both for a midpoint approach and an endpoint approach; Atmospheric Deposition Factor (ADF) and Damage Factor (DF) applicable to the former and the latter, respectively. The ADF indicates an increase of H+ deposition per unit area to an additional emission of causative sustance. The additional emission corresponds to some alternatives in industry, not the baseline emission. The DF indicates the total NPP damage in all of Japan due to the additional emission of causative substances. The derived NPP damage is on the order of one millionth of the NPP itself. HC1 and NH3 showed larger ADFs and DFs than that of SO2 and NOx. The reason was ascribed to the relatively large source-receptor relationships (SRR) of HC1 and NH3. However, since the method applied to determine the SRR of HC1 and NH3 has larger uncertainties than that of SO2 and NOx, attention is needed to handle the difference.ConclusionThe damage function easily defines the concrete NPP damage due to an additional emission. The impact indica tor, NPP, also has an advantage in its mass unit that is directly summable through the entire impact categories. Expansion of endpoints, such as in aquatic ecosystems, material degradation, human health, and biodiversity aspects of terrestrial ecosystems, is an important subject for future work. Further, uncertain analyses for major parameters will provide helpful information on the reliability of damage function.

Effect of acidic deposition on forested andisols in the Tama Hill region of Japan

Abstract Acid deposition and its effect on Andisols was investigated in the forest experimental station, the Rolling Land Laboratory, the Tama Hill region, central Japan. The annual volume-weighted mean pH value of open bulk precipitation was 4·8. The acidity of stemflow from coniferous trees was attributed to dry deposition of air pollutants. The acidic stemflow affected the chemical composition of the soil solution and the pH of soils around the coniferous trees. The concentration of aluminum in the soil solution was accompanied by nitrate which was provided by nitrification in the low soil pH range. The concentration of aluminum in the soil solution, which ranged from 0·02 to 0·12 mmolc liter−1 is similar to the critical levels for the roots of the trees. Andisols in the surface horizon are acidified due to the atmospheric acid deposition, even though seepage from the catchment is still neutral.

Effect of converting wetland forest to sago palm plantations on methane gas flux and organic carbon dynamics in tropical peat soil

The effect of changing wetland forest to sago palm plantations on methane gas flux and organic carbon dynamics in tropical peat soil was studied in the field and the laboratory using soil samples from the Peat Research Station, Sarawak, Malaysia. A small amount of methane was released from the soil surface of both the forest and plantation field, with no significant difference between the two sites (1.1 ± 0.61 and 1.39 ± 0.82 mg CH 4 m -2 hr -1 , respectively); thus, the amount of methane emission from the total area of tropical peat soil was estimated, preliminarily, as 2.43 Tg yr - 1 , contributing 0-45% of the total global methane emission and 2.1% of methane emissions from global natural wetland. However, large amounts of methane were accumulated in the deeper soil layers. Sago palm contained much less carbon as biomass, but lost more as the carbon dissolved in groundwater. Laboratory experiments showed that incorporation of rice straw into tropical peat soil increased methane formation significantly. Conversely, ammonium sulfate suppressed methane formation in tropical peat soil.

Distribution of heavy metals among different bonding forms in tropical peat soils

Abstract The objective of this study is to analyze the characteristics of the macro- and micro-nutrient status of tropical peat soils under natural swamp forest and their changes after reclamation. We sampled peat soils from the coastal swamps in southern Thailand and southern Peninsular Malaysia. These soils were at varying stages of reclamation. Soil Fe, Mn, Zn, and Cu were sequentially divided into water soluble, Ca exchangeable, free-oxide-associated, weakly complexed, strongly complexed, carbonate-associated, and sulfide-associated extractable forms. Peat soils sampled in Malaysia were classified into Oligotrophic peat soils due to their low N, P, K, and Ca contents. The Ca, Mg, K, and Na contents did not change appreciably with the soil depth, though the Mn, Zn, and Cu contents decreased with the soil depth down to 30 cm and subsequently the decrease was negligible. Based on the analysis of the distribution of the metal forms, most of Cu and Fe occurred in strongly chelated and non-extractable forms...