Tomoyoshi Murata

Pollution of montane soil with Cu, Zn, As, Sb, Pb, and nitrate in Kanto, Japan.

Soil cores and rainwater were sampled under canopies of Cryptomeria japonica in four montane areas along an atmospheric depositional gradient in Kanto, Japan. Soil cores (30cm in depth) were divided into 2-cm or 4-cm segments for analysis. Vertical distributions of elemental enrichment ratios in soils were calculated as follows: (X/Al)(i)/(X/Al)(BG) (where the numerator and denominator are concentration ratios of element-X and Al in the i- and bottom segments of soil cores, respectively). The upper 14-cm soil layer showed higher levels of Cu, Zn, As, Sb, and Pb than the lower (14-30cm) soil layer. In the four areas, the average enrichment ratios in the upper 6-cm soil layer were as follows: Pb (4.93)>or=Sb (4.06)>or=As (3.04)>Zn (1.71)>or=Cu (1.56). Exogenous elements (kg/ha) accumulated in the upper 14-cm soil layer were as follows: Zn (26.0)>Pb (12.4)>Cu (4.48)>or=As (3.43)>or=Sb (0.49). These rank orders were consistent with those of elements in anthropogenic aerosols and polluted (roadside) air, respectively, indicating that air pollutants probably caused enrichment of these elements in the soil surface layer. Approximately half of the total concentrations of As, Sb, and Pb in the upper 14-cm soil layer were derived from exogenous (anthropogenic) sources. Sb showed the highest enrichment factor in anthropogenic aerosols, and shows similar deposition behavior to NO(3)(-), which is a typical acidic air pollutant. There was a strong correlation between Sb and NO(3)(-) concentrations in rainfall (e.g., in the throughfall under C. japonica: [NO(3)(-)]=21.1 [dissolved Sb], r=0.938, p<0.0001, n=182). Using this correlation, total (cumulative) inputs of NO(3)(-) were estimated from the accumulated amounts of exogenous Sb in soils, i.e., 16.7t/ha at Mt. Kinsyo (most polluted), 8.6t/ha at Mt. Tsukuba (moderately polluted), and 5.8t/ha at the Taga mountain system (least polluted). There are no visible ecological effects of these accumulated elements in the Kanto region at present. However, the concentrations of some elements are within a harmful range, according to the Ecological Soil Screening Levels determined by the U.S. Environmental Protection Agency.

Microbial biomass and nitrogen transformations in surface soils strongly acidified by volcanic hydrogen sulfide deposition in Osorezan, Japan

Abstract Volcanic acidification has created unique ecosystems that have had to adapt to the acidic environments in volcanic regions. To characterize the primary microbial properties of strongly acidified soils in such environments, we investigated microbial biomass, nitrogen transformations and other relevant chemical properties in the surface soils of solfatara and forests from Osorezan, a typical volcanic region in Japan, and compared the results to common Japanese forest soils. Soil microbial biomass C (MBC) and N (MBN) were determined using the chloroform fumigation–extraction method. Potential net N mineralization and net nitrification were measured in aerobic laboratory incubations. Long-term acidification in the Osorezan soils by volcanic hydrogen sulfide deposition caused low soil pH (3.0–3.8), base cation deficiency and increased concentrations of toxic ions such as Al3+. The proportions of MBC to total carbon (MBC/TC ratio) and MBN to total nitrogen (MBN/TN ratio) were lower than those in common Japanese forest soils. The extreme acidic conditions may have inhibited microbial survival in the Osorezan acid soils. Net N mineralization occurred at rates comparable to those in common Cryptomeria japonica forest soils, probably because of the presence of acid-tolerant soil microorganisms. Net nitrification was completely inhibited and autotrophic ammonia oxidizers were not detected by the MPN method. The inhibition of nitrification prevents nitrogen leaching from the soils, thus maintaining a nitrogen cycle in the volcanic acid region in which NH+ 4 (and NH3) is recycled among microorganisms and plants.

Effects of Bismuth Contamination on the Growth and Activity of Soil Microorganisms Using Thiols as Model Compounds

The present study was undertaken to obtain information about the effects of Bi contamination on soil microbial growth and activity using a series of Bi complexes with thiol compounds, including mercaptoethanol, thioglycerol, mercaptoethylamine, thioglycolic acid, thiomallic acid, reduced glutathione, 2-mercaptopropionic acid, and L-cysteine. We found that Bi complexes with mercaptoethanol, thioglycerol, and mercaptoethylamine, all of which showed lipophilicity, markedly inhibited bacterial growth in 1/10 TSB liquid media in both Eutric Cambisol (brown forest soil) and Eutric Fluvisol (brown lowland soil), with relative CFU of less than 2% at 50 μ M Bi and 6% at 25 μ M Bi. However, none of the Bi-thiols, including Highly lipophilic complexes, at 200 μ M Bi in rosebengal agar medium inhibited fungal growth, possibly because fungi have a metabolic system that protects against Bi uptake or detoxifies Bi compounds. When soil was contaminated experimentally with Bi-thiol, these complexes suppressed soil dehydrogenase activity, particularly in brown forest soil, which contains large amounts of easily decomposable organic matter. These results indicate that the effects of Bi on soil microbes may depend on mutual reactions with organic matter in the environment.

Effects of mefenacet and pretilachlor applications on phospholipid fatty acid profiles of soil microbial communities in rice paddy soil

Abstract The effects of herbicide (mefenacet and pretilachlor) applications on soil microbial communities in rice paddy soil were investigated in a laboratory study using phospholipid fatty acid (PLFA) profiles. Soils with or without herbicide application were incubated separately under oxidative or reductive conditions for 30 d. Half-life (DT50) of mefenacet was 14 d under oxidative conditions and 9.8 d under reductive conditions. DT50 of pretilachlor was 17 d under oxidative conditions and 8.8 d under reductive conditions. PLFA contents did not seem to be affected by the residual levels of herbicides. The composition of PLFAs under in both the oxidative and reductive conditions fluctuated during the incubation period. However, the effects of applications of herbicides (mefenacet and pretilachlor) under oxidative and reductive conditions in rice paddy soil did not affect appreciably the soil microbial biomass and the structure of the soil microbial communities, as determined by PLFA profiles. Fluctuations in the composition of PLFAs during the incubation period were rather conspicuous.

Effect of structural modification on heat transfer through man-made soils in urban green areas

Abstract This study examined the characteristics of heat and water transfer in structurally modified urban soils. To satisfy our goals, we measured the temperature and moisture content of anthropogenic soils to a depth of 50 cm. Field observations was carried out for three sets (each of two pedons) of soils in the Tokyo Metropolitan area. Each pedon had the same turf coverage but different profile modifications in the green areas. Soil temperature, soil moisture, and precipitation data were collected during the summer (July–Sept) and winter (Oct–Feb) every 10 min. From the results, we calculated the thermal diffusivity and thermal conductivity in each pedon. Soil temperature showed a clear daily variation down to 30 cm depth. Temperature transmission to deeper layers was faster in pedon having stronger soil compaction and more artificial fragments than in pedons with weaker soil compaction and fewer concrete fragments. This finding suggests that strongly compacted soil has a relatively high thermal conductivity, and easily transfers heat to deeper soil. In pedons composed of soft, organic-rich, and clay-rich soil, water retention impedes the increase in soil temperature during daytime, whereas nighttime cooling is prevented by the lower heat transmission due to the larger porosity. Throughout the observations, the water content ranged from 0.1 to 0.45 m3 m−3. The thermal diffusivity was obtained as 1.2–5.0 × 10−3 cm2 s−1 in pedons without artifacts, but was higher (2.5–7.3 × 10−3 cm2 s−1) in all pedons containing larger volumes of concrete artifacts. Although the directions of heat flow by time within the profiles having lithological disturbance was not much different with that of natural soils, the observation data revealed that heat flow per time differed by structural properties of the profiles. Furthermore, thermal properties such as thermal diffusivity and thermal conductivity of the soils characterized with lithological disturbance were significantly higher than those of natural soils and it was notable that they were not influenced by either volume fraction of water or air in the soil. The fact suggested that the anthropogenic soils containing a large amount of modifiers and concrete artifacts have small capacity of water retention due to specific macro pores. Artificial materials and compaction regulate the drainage and water retention of the soil, although the water transfer behavior in the studied pedons could be rather complicated.

Influence of historical manmade alterations on soil-forming processes in a former imperial estate (Shirogane-goryouchi), the Institute for Nature Study: Development of a soil evaluation technique and importance of inventory construction for urban green areas

Abstract The influence of historical land use on soil-forming processes was assessed in a former imperial estate (Shirogane-goryouchi), the Institute for Nature Study, as one of the urban green areas where many records on land use and vegetation history have been maintained. The area of study was divided into several subsections and categorized based on land use history. Results from a soil survey in each categorized area showed that Andosols were dominant across all areas, and that past construction activities, creation of artifacts, and soil cutting and banking resulted in a disruption of horizon sequences and shifts in soil components. Soil was characterized using chemical analyses of oxalate-extractable Al (Alo) and Fe (Feo), the melanic index (MI) of soil organic matter (SOM), and the carbon stable isotope ratio (δ13C) of soil. These parameters helped researchers assess the influence of land use on soil and vegetation over time. After land use ceased, newly accumulated organic horizons, the development of soil structures, and horizon differentiation due to forest regeneration were apparent. δ13C of soil suggested that SOM in surface horizon (A, A1) was primarily derived from present-day forest vegetation (C3 plants) with MI values >1.7. The origins of SOM in subsurface horizon (A2, AB) were mixed with present-day C3 plants and past grass vegetation from C4 plants. MI values were lower in subsurface horizons due to a higher degree of humification as compared to surface horizon values. The absence of fresh organic matter supply after deforestation and lack of soil material mixing between surface and subsurface horizons after land use changed affected the state of soil organic matter in the subsurface horizon. Alo leached from surface to deeper horizons via large inputs of organic material over the long term (approximately 400 years), even on sections of earthworks. Even though the soil in this urban green area had a complex land use history, it was still possible to evaluate the soils in terms of pedogenesis with a multidisciplinary approach that explored land use and vegetation history, and used soil surveys and soil chemical characteristics to answer our questions.

Bismuth solubility through binding by various organic compounds and naturally occurring soil organic matter

The present study was performed to examine the effects of soluble organic matter and pH on the solubility of Bi in relation to inference with the behavior of metallic Bi dispersed in soil and water environments using EDTA, citric acid, tartaric acid, l-cysteine, soil humic acids (HA), and dissolved organic matter (DOM) derived from the soil organic horizon. The solubility of Bi by citric acid, tartaric acid, l-cysteine, HA, and DOM showed pH dependence, while that by EDTA did not. Bi solubility by HA seemed to be related to the distribution of pKa (acid dissociation constant) values of acidic functional groups in their molecules. That is, HA extracted at pH 3.2 solubilized Bi preferentially in the acidic range, while HA extracted at pH 8.4 showed preferential solubilization at neutral and alkaline pH. This was related to the dissociation characteristics of functional groups, their binding capacity with Bi, and precipitation of Bi carbonate or hydroxides. In addition to the dissociation characteristics of functional groups, the unique structural configuration of the HA could also contribute to Bi-HA complex formation. The solubility of Bi by naturally occurring DOM derived from the soil organic horizon (Oi) and its pH dependence were different from those associated with HA and varied among tree species.

Soils in Historical Urban Parks

Urban parks are one of the large infrastructures that enhance quality of life in a metropolis. It is therefore important to maintain a record of soil history, including the development and alteration of land in urban areas. Three historical urban parks were surveyed to obtain information of the land use history. The Institute for Nature Study, designated as a national monument and historical landmark in 1949, is a particularly important site for the study of pedogenesis in urban green spaces. As compared to a reference site, “the Meiji Shrine”, past construction activities, production of artifacts, and land cutting and banking resulted in a disruption of natural soil horizons. Horizon sequences were relatively similar among sites on earthworks but not on terrace surfaces, reflecting the high frequency of change in land use on these areas. Accumulation of total organic carbon decreased with increasing soil depth probably due to forest regeneration. Non-crystalline components increased with increasing soil depth mainly as a result of leaching of non-crystalline components by complexation with soil organic matter under forest vegetation. δ13C values of soil increased with increasing soil depth reflecting vegetation succession. The δ13C values of soil were significantly negatively correlated with a color index of extracted organic matter, indicating that C4 plants have contributed to accumulated carbon, mainly after episodes of fire. Shinjuku-Gyoen site has experienced changes in its land use history during the past four centuries. There were several drastic differences in general soil properties with depth. These soil characteristics reveal signatures of anthropogenic impact such as banking and cutting in the soil profiles. Short and frequent complex anthropogenic alterations were observed in the historical park. High variability of soil properties in the Shinjuku Gyoen site indicates high frequency of land use changes within its history. In the Kitanomaru Garden connected to the East Gardens of the Imperial Palace, three large-scale constructions were performed from the Edo era (1603–1868) to the present. Soils in Kitanomaru Garden are classified as Urbic Technosols, and feature artifacts such as bricks, tiles, concrete, or potteries originating from buildings from the past 400 years. Soils in Kitanomaru Park had a higher soil pH, lower total carbon content and relatively high cation exchange capacity (CEC) compared with natural volcanic ash soils. Moreover, the vertical distribution of soil compactness was characterized by disorders of the compaction layers or having a consolidated layer within 1 m deep. The spatial distribution of the soils having non-intrusive and densely-compacted layers correspondences with the restoration position of a building and land-grading works.

Degradation of the urban ecosystem function due to soil sealing: involvement in the heat island phenomenon and hydrologic cycle in the Tokyo metropolitan area

ABSTRACT We reviewed the role of the soil function of urban green space in mitigating the heat island phenomenon and urban flood damage, which are important issues in the modern urban environment. Urban sprawl has progressed remarkably in the southern part of the Kanto District of Japan, especially since the 1960s. The grassland/bare land area ratio in the center of Tokyo was more than 70% in the 1930s but less than 40% in 1990. On the other hand, the paving area ratio was ~2% in the 1930s but more than 10 times that amount in 1990. Thus, cities, such as Tokyo, in the southern part of the Kanto District have been significantly sealed soil throughout time, and the heat island phenomenon has intensified. Urban green space helps to mitigate the heat island phenomenon based on the water retention and heat dissipation function of plants and unsealed soil. A cool island effect was reported during summer days in urban green spaces in Tokyo. The mitigation of the heat island effect seems to be large, even when conditions, such as the park area, land use, afforestation area ratio, and soil type, differ. Soil sealing and compaction affect urban flooding by hindering the penetration of rainwater and increasing surface runoff. According to a survey in the hilly basin (1 km2) of the western part of Tokyo, the proportion of farm- and forestland decreased due to development. The urban area increased from ~10% in the 1970s to ~60% in the 1980s. As a result, the flood arrival time shortened. Green spaces have a high rainwater permeability. The forest soil structure and presence of O horizons further increase the permeability. By promoting permeability to the underground, it is possible to reduce and delay the water runoff on the land surface. To develop urban green space as green infrastructure, it is necessary to accumulate more information on the current situation and agenda for the future of urban green space.

What Does “Soil Is Valuable” Mean? Institutional Design and Ethics for Sustainable Use of Soil Resources

This paper is intended to be a practical and ethical recommendation to policies surrounding soil and agriculture. It addresses how soil resources are in the process of transitioning from the base for food production to the base for ecosystem services in the past roughly 30 years.