Mercury distribution in tephra soil layers in Hokkaido, Japan, with reference to 34,000-year stratification

Tephra from volcanic eruptions contains only small amounts of mercury (Hg) right after the eruption because the high temperature at eruption evaporates Hg in volcanic ash. Thus, accumulation of Hg in tephra soil layers during the dormant periods of the volcano may reflect Hg deposition while the layer was exposed to the atmosphere. To estimate sequential changes in Hg deposition, we measured the Hg content and accumulation in tephra layers from 6 sites in Hokkaido known to have many tephra layers derived from volcanic eruptions over a 34,000-year period. Mercury content and accumulation rate in the soil profiles varied widely depending on the tephra. In each tephra layer, the Hg content and accumulation rates increased principally at the upper soil horizons and decreased at the lower depths. The Hg deposition rates calculated from the amount of Hg accumulated in the tephra layers were similar within the same tephra. These characteristics of Hg distribution indicate that Hg deposition accumulated on the surface of each tephra layer during the period the tephra layer was exposed to the atmosphere. Although physicochemical processes such as leaching out, wind erosion, and volatilization might lead to over- and/or underestimation of the deposition rates, our estimated amounts of Hg were markedly higher in the tephra soils after 1,600 year BP than before that time. The results of this study suggest that tephra layers in Hokkaido offer important implications for understanding of the historical changes in atmospheric Hg deposition.     

Mercury distribution in tephra soil layers in Hokkaido,Japan, with reference to 34,000-year stratification

Abstract

Tephra from volcanic eruptions contains only small amounts of mercury (Hg) right after the eruption because the high temperature at eruption evaporates Hg in volcanic ash. Thus, accumulation of Hg in tephra soil layers during the dormant periods of the volcano may reflect Hg deposition while the layer was exposed to the atmosphere. To estimate sequential changes in Hg deposition, we measured the Hg content and accumulation in tephra layers from 6 sites in Hokkaido known to have many tephra layers derived from volcanic eruptions over a 34,000-year period. Mercury content and accumulation rate in the soil profiles varied widely depending on the tephra. In each tephra layer, the Hg content and accumulation rates increased principally at the upper soil horizons and decreased at the lower depths. The Hg deposition rates calculated from the amount of Hg accumulated in the tephra layers were similar within the same tephra. These characteristics of Hg distribution indicate that Hg deposition accumulated on the surface of each tephra layer during the period the tephra layer was exposed to the atmosphere. Although physicochemical processes such as leaching out, wind erosion, and volatilization might lead to over- and/or underestimation of the deposition rates, our estimated amounts of Hg were markedly higher in the tephra soils after 1,600?year?BP than before that time. The results of this study suggest that tephra layers in Hokkaido offer important implications for understanding of the historical changes in atmospheric Hg deposition.     

The impact of environmental factors on early stage Andosol development south of Vatnajökull,Iceland

Icelandic soils develop in a dynamic environment affected by both natural processes and anthropogenic impacts. We present an extensive investigation of soil mineralogy and pedogenesis in a disturbed (i.e., by solifluction) pedon under such conditions. The study focuses on two distinct tephra layers, a rhyolitic tephra from the Öræfajökull eruption in 1362 CE (Ö1362) and a basaltic Veiðivötn tephra from 1477 CE (V1477). Both tephra layers form an important parent material in the study area south of Vatnajökull, Iceland. The Andosol developed from tephra and aeolian material, rich in volcanic glass. The pH (H₂O) values were between 5.5 and 6.6 and clay mineralogy displayed a predominance of allophanic material in both soil and tephra. The pedon can be seen in its early stage of chemical weathering and soil development. Despite the overall predominance of non- and poorly-crystalline short-range order secondary materials and Fe (hydr)oxides in the clay-size fraction, we found indication of smectite. High exchangeable Ca²⁺ and Mg²⁺ concentrations reflect enhanced aeolian input of volcanic material, while elevated exchangeable-Na⁺ concentrations are most likely caused by the oceanic composition of precipitation. The impact of erosion and aeolian processes on pedogenesis seemed to be higher between the deposition of Ö1362 and V1477, than in the soils above. Both, soil and tephra layers appeared disturbed by erosion–deposition processes over time. Characterised by a significantly coarser particle size composition, low soil organic carbon (SOC) content, and a more diverse mineralogy, a distinct fluvial sediment layer at 10–30 cm depth appeared sharply contrasting to the other soil layers in the profile. This possibly reflects the diverse composition of glaciofluvial material from a landslide originating from a Kvíárjökull moraine in the north. Changed weathering patterns and properties in the soils above the Ö1362 tephra indicated soil degradation following the deposition of the rhyolitic tephra.     

Tephra-mulched soils irrigated with reclaimed urban wastewater in former dry-farming systems of Lanzarote (Spain)

On the island of Lanzarote, under extreme conditions of aridity and water scarcity, a certain amount of rainfed agriculture has been possible due to the use of tephra mulching, a system known locally as arenados, which is a very effective water and soil conservation system. The natural arenados are associated to already present tephra from recent volcanic eruptions. In artificial arenados a 5 to 20 cm layer of pyroclasts is placed over the soil. Over the last decade, the availability of urban reclaimed water (RW) has allowed irrigation networks to be established in artificial arenados with significant increases in crop yields. In this work, a preliminary evaluation of the sustainability of this new form of management was performed. Field plots irrigated with tertiary effluent for almost a decade were studied and compared with adjacent dry-farming fields, both cropped with sweet potatoes. In both cases, the soils had a covering of basaltic tephra mulch. The irrigation lines are placed on top of the mulch. Although this was not a controlled field experiment, since water and soil management was not exactly the same in the studied plots, some significant effects of RW irrigation on soil chemical properties were identified. Crop yields in the irrigated fields can be up to three times the yields obtained under rainfed conditions. The RW quality posed some restrictions for irrigation, particularly as regards salinity, sodicity and boron, although their buildup in soils appears to have been reduced by the mulch effect. In some field plots, crop critical threshold values of soil salinity and boron were reached with no harmful consequences. This developing soil degradation suggests that the sustainability of arenados systems under RW irrigation would appear to be under threat in the mid- to long-term based on current management practices. Further research is required on the salt and boron dynamics in this system, which is an example of conservation agriculture that also helps combat desertification.     

Initial Carbon Storage in New Tephra Layers of Mt. Talang in Sumatra as Affected by Pioneer Plants

To date, no global data on carbon sequestration at the initial weathering phase of tephra deposits are available. To study carbon storage in the new volcanic deposit, tephra layers were reconstructed for a period of 46 months. The tephra samples were collected immediately after eruption of Mount (Mt.) Talang on 12 April 2005, over portions of the Solok District in West Sumatra, Indonesia. Pot experiments were filled with and without soil materials and covered with the collected tephra. The pot experiments were conducted in a wired house. The tephra was applied in 0, 2.5 and 5 cm depths to simulate natural tephra deposition. Every day 250 ml of filtered water was added and allowed to percolate. Solid fraction from the tephra layer was collected and analyzed at regular intervals and primary plant succession was observed over a period of 4 years. After 2 months, blue-green algae (cyanobacteria) started to colonize the bare surface tephra layer to form an algae mat. After 16 months, the surface was transformed into a green biofilm of lichen. Vascular plants (grasses and shrubs) started to be established after 2 years. Total carbon (TC) content of the tephra layer was increased significantly from 0.19 to 1.75% or eight times higher after 46 months of incubation. Higher TC storage was found in the 2.5 cm compared to that of the 5.0 cm tephra layer, which was reconstructed above the soil, with values of 1.75 and 0.89%, respectively. On the contrary, lesser amount of TC was accumulated in the single tephra layer (without soil underneath). Between 71 and 90% of TC was considered as total organic carbon (TOC). The labile organic carbon (LOC) content in the 2.5 cm and 5.0 cm of tephra layer was found to be 0.22 and 0.77%, respectively, at the end of incubation. This experiment confirmed the potential of tephra to capture carbon from the atmosphere with the help of nonvascular plants and then by vascular plants and finally sink them in the tephra layer.     

The formation of tephra layers in peatlands: An experimental approach

Tephrochronology provides a valuable method of dating peat deposits but results may be compromised if tephra undergoes significant post-depositional movement. This study takes an experimental approach to investigate the processes of tephra taphonomy. Tephra was applied to peats and movement monitored over periods of up to 6 years. Experiments combined field studies on six British peatlands with rainfall simulation experiments in the laboratory. Tephra moved up to 15 cm down through the peat but the vast majority remained at the surface at time of deposition, forming a layer which accurately recorded the palaeo-surface. Tephra moved both down, by shards sinking through the peat, and up, with shards probably being moved by plant growth or with water table variability. The extent of tephra movement most likely depends on the density and porosity of the surface peat; there is no simple relationship with wetness. There is some indication that the extent of tephra movement depends on the tephra particle size but this will require further work to confirm. The taphonomy of tephra is an important issue which should be considered in all tephrochronology studies in peatlands.     

福建旅游型海岛水土保持措施研究——以妈祖圣地湄洲岛为例

 旅游型海岛作为福建重要的旅游目的地,以独特旅游景观和旅游环境得到旅游者的青睐,但旅游开发不当引发的水土流失加剧影响了海岛旅游景观质量和环境质量,必须引起高度重视。以湄洲岛为例,分析湄洲岛水土流失现状及对旅游发展的影响,提出福建旅游型海岛水土保持原则和植物、工程、政策、技术等6方面具体的水土保持措施,努力实现"旅游促水保、水保促旅游"的良性循环。     

1980 tephra from Mount St. Helens: Spatial and temporal variation beneath forest canopies

Summary Tephra and underlying litter and soil were sampled in 1980, 1982, and 1987 beneath subalpine forests where 4.5 and 15 cm of tephra fell during the 1980 eruption of Mount St. Helens, Washington State, USA. Coarse pumice had a higher initial pH and less total N, less exchangeable K, Ca, and Mg, and less extractable B and S than finer textured layers. Tephra pH and concentrations of cations and S decreased rapidly with time, especially during the first 2 years in the finer layers. Total N, Bray-Kurtz P, and organic C concentrations in the tephra increased with time. Changes within a site in total N, pH, organic C, P, Ca, Mg, and S from 1980 to 1987 exceeded the differences among sites at any one time. By 1987 a forest floor covered much of the tephra surface, and differences in Ca associated with site vegetation and seepage had developed in tephra layers of a similar depth. In 15 cm deep tephra at one site in 1987, the tephra crust beneath the forest canopy was thicker and had higher concentrations of coarse particles, organic C, total N, and cations than beneath forest openings. In concave microsites the crust was thicker, with higher pH, organic C, and total N but lower S than in adjacent convex microsites. Spatial and temporal chemical differences are sufficient to affect patterns of vegetation recovery.     

崇明岛土壤资源评价初探

根据上海市崇明岛资源调查结果,首先选择了土壤质量等级,土壤限制型为评价系统。其次,综合考虑崇明岛的实际情况和演变趋势,同时,在上海市土壤资源评价标准的基础上,制定了适合崇明岛土壤资源评价标准和评价因素权重。最后,采用了模糊聚类的方法,对崇明岛的土壤资源进行了分等划级,当λ=0.7797时,可把崇明岛土壤资源划分为4个土壤质量等级和7个限制型,分析和评论了模糊聚类的结果。揭示了崇明岛土壤质量的递变规律,并指出了加速土壤正向演化的措施。     

The soil cover of Central Kamchatka (GIS model)

The spatial distribution of major soil horizons and layers of pyroclastic deposits in Kamchatka was analyzed with the use of GIS technologies. For this purpose, the attribute soil database and the computer-supported cartographic database were developed. Their analysis with the help of GIS technologies made it possible to study the dependence of the morphology of soil profiles on the bioclimatic conditions and on the stratification of ash layers in the particular areas of Kamchatka and to develop the cartographic model of the areas of soil horizons. The concept of tephra stratotypes—the particular combinations of ash layers in the profiles of volcanic soils—was verified on the basis of factual materials. It was shown that tephra stratotypes affect many important soil properties and specify the direction of soil formation in Kamchatka. Several major tephra stratotypes differing in their morphology and environmentally important features were distinguished in Central Kamchatka. The method of soil mapping on the basis of the concept of tephra stratotypes with due account for the specificity of surface organic horizons of soils was developed. It is argued that this method makes it possible to reflect the specificity of soil formation in volcanic regions.     

三江平原不同类型湿地土壤酶活性及其与营养环境的关系

对三江平原3种典型湿地(毛苔草湿地、小叶章湿地、岛状林湿地)的土壤酶活性、土壤养分进行了研究,探讨了不同湿地土壤酶与土壤养分及酶活性间的相关性。结果表明:不同湿地土壤酶活性和土壤养分含量有较大差异。土壤蔗糖酶、脲酶、过氧化氢酶、淀粉酶活性与土壤有机质、全氮、碱解氮含量变化趋势一致,表现为毛苔草湿地>小叶章湿地>岛状林湿地。酸性磷酸酶活性表现为岛状林湿地>毛苔草湿地>小叶章湿地;纤维素酶活性则表现为毛苔草湿地>岛状林湿地>小叶章湿地。经分析,土壤酶活性和养分密切相关,且酶活性间存在一定的相关关系,其中脲酶、过氧化氢酶、淀粉酶活性与土壤养分相关性最好,呈显著或极显著正相关。并且这3种酶活性之间也呈显著或极显著正相关,因此脲酶、过氧化氢酶、淀粉酶活性可以作为该地区较为理想的湿地营养状况的表征指标。     

浙江省生态旅游区的水土保持问题

生态旅游区已经成为浙江省旅游开发的新天地，它以其提供自然性和原始性的环境深受游客青睐。水土流失是降低旅游区环境质量和资源质量的重要因素，必须引起高度重视。水土流失对旅游区的影响方式可分为自生型和外来型两种。按区域地理特征不同，浙江省生态旅游区水土保持类型可分为山区丘陵型、江河湖泊型、平原型、海岛型4类。     

Origin and nature of halloysite in Ando soils from Towada tephra,Japan

The origin and nature of halloysite in Ando soils from Towada tephra were investigated. These soils were formed from five tephras: Towada-a (1,000 years old), Towada-b (2,000 years old), Chuseri (4,000 years old), Nanbu (8,600 years old) and Ninokura (10,000 years old).Formation of halloysite took place only in the buried soils from Nanbu and Ninokura tephras occurring in an “accumulating zone”, where thicknesses of overburden tephra deposits were mostly 2.5 m or greater and silica enrichment of the clay fractions could occur.The amounts of halloysite were greater in (1) the soils from Ninokura tephra than in those from Nanbu tephra, and greater in (2) the humus horizons as compared to the nonhumus horizons of these same soils. The mean sizes of spheroidal halloysite particles and the ratios of numbers of tubular to spheroidal forms differed with differences in soil horizons and age.High-resolution electron micrographs of glycerol-solvated spheroidal halloysite particles had lattice images of 11 Å due to (001) from the exterior to the interior and had no indications of layer separation. Moreover, the central core of spheroidal halloysite with a diameter of 150 Å showed neither layer structure nor allophane spherules.Results obtained in this study thus indicate that spheroidal and tubular forms of halloysite were formed concurrently in these Ando soils.     

基于SOTER的海南岛土壤水侵蚀模拟

The actual and potential water erosion rates of soils with different land covers in Hainan Island,China,were estimated based on the universal soil loss equation(USLE) and a 1:200000 Soils and Terrain digital Database(SOTER) Ddatabase,from which soil water erosion factors could be extracted.92.8% of the whole island had a current erosion rate of lowerthan 500t km^-2 a^-1.Soil erosion risk was considered to be high because of its abundant rainfall.Without vegetation tcover,the potential soil erosion ratewould be extremely high and 90.8% ofthe island would have a soil erosion rate higher than 2500t km^-2a^-1.Relative erosion vulnerability of different soil zones,landform types,and lithological regions of the island was compared by introducing a relative erosion hazard parameter α.Cambosols developed from siltstone and mudstone in low hill regions were pinpointed as soils with the highest erosion risk in the island.     

Some applications of paleopedology in Japan

Paleosols in Japan consist of buried soils and relict soils. The former occur primarily in tephra deposit, whereas the latter occupy old land surfaces in various parts of the country. The buried soils affect construction of highways and urban development. The relict soils pose problems in forestry.The paleosols formed in tephra and buried by subsequent volcanic eruptions are chiefly Andosols with their low bulk densities, low solid ratios, high specific surfaces and high water losses. These characteristics are responsible for poor engineering performance of the paleosols and tephras. These have been especially troublesome in the Kanto plain near tokyo and around the Ashitaka Volcano. Some buried soils in tephra, as for example those in the San'in district, are exceptions to the general rule and have desirable properties for construction. Those tephras have clay fractions low in allophane and high in layer-silicate minerals.The buried soils have provided approximate ages of human artifacts through radiocarbon dating of humic horizons. Conversely, identification of artifacts found in buried soils has helped to bracket their ages.Paleosols that are relicts are chiefly members of a Red-Yellow group, many of which seem to be Udults (Ultisols). The soils apparently began forming in warmer past periods but still persist on the land surface. Such soils are strongly acid and very low in plant nutrients, with resulting low productivity when used for forestry or farming. Moreover, such soils are readily subject to erosion because of their landscape positions and poor plant cover.     

Effect of the Geological Factor on Polyarenes in Soils

The study, generalization, and comparative analysis of data on the content and composition of polyarenes have been performed for the soils subjected to the impact of the following factors: (1) approach of bituminous material to the surface along the fault zone from the deep layers of sedimentary rocks with the formation of bituminous sandstones and asphalt lenses (Bakhilovo asphalt deposit, Zhiguli dislocations, Samara region); (2) periodical discharge of large amounts of volcanic tephra into the atmosphere resulting in the formation of pyroclastic deposits (near the Avacha Volcano, Kamchatka region); (3) increased geodynamic activity within the area of the recent blocky structure of the earth crust, where a spontaneous upward flux of fluids into the soil is possible (Istra morphostructural node, Moscow region); and (4) high fumarolic activity resulting in the impact of hot water and vapor on the surrounding soils (Golovnin caldera, Island Kunashir, Kuril region). It has been found that the considered manifestations of geological factors can be arranged into the following increasing order: (a) exposure of volcanic tephra as a parent rock (20 ng/g); (b) increased hydrodynamic and fumarolic activity (85–90 ng/g); and (c) penetration of asphalt into the sedimentary rocks (4800 hg/g). According to the diversity of polyarenes identified in the soils, the considered situations form the following increasing series: (a) 9 out of 11 identified polycyclic aromatic hydrocarbons (PAHs) are found in the area of increased geodynamic activity and in the region of volcanic tephra fallouts; (b) 10 PAHs are identified in the asphalt deposit; and (c) all 11 PAHs are identified in the area of fumarolic activity.     

Long-term biogenic soil mixing and transport in a hilly,loess-mantled landscape: Blue Mountains of southeastern Washington

In soil-mantled landscapes, downslope sediment transport occurs via disturbance-driven processes that vary with climate and vegetation change. To help constrain the long-term (? 10 yr) pattern and rate of soil mixing and transport in forests, we analyzed the distribution of tephra grains in soil along a hillslope transect in the Blue Mountains, SE Washington. Deposited within a loess mantle, tephra associated with Mt. Mazama (7.7 cal. kyr B.P.) serves as a marker bed for estimating erosion and transport rates. Moving downslope, the buried tephra horizon is progressively exhumed and becomes increasingly mixed in the upper soil layer, reflecting disturbance and transport via tree root growth and turnover. This pattern also implies increasing erosion rates downslope and our hillslope transect becomes increasingly convex coincident with progressive exhumation of the tephra layer. This systematic correspondence between topographic form, specifically, local convexity, and surface lowering is consistent with theoretical models for which soil transport rates depend on slope inclination. From our analysis, calibrated coefficients for a linear, slope-dependent transport model are on the order of 10^− 3 m²yr^− 1, consistent with previous work in forested loess-mantled landscapes. In addition, our results reveal both the high degree of soil mixing over millennial timescales and the local variability of mixing in forested landscapes. Furthermore, the results enable us to quantify the amount of energy expended by trees in mixing and transporting soil and the net sediment transport fraction of the net primary productivity NPP of the ecosystem.     

Characteristics of the induration of tephra-derived soils in Kyushu,Japan

The physical, chemical, and mineralogical properties as well as the micromorphology of five indurated volcanic ash soils in Kyushu, Japan were investigated. The indurated soils were divided into two types based on the physical and chemical properties. Type 1 was not indurated in its moist state, but shrank and became very hard by air-drying. Type 1 included the buried volcanic ash soils whose physical and chemical properties were similar to those of other buried volcanic ash soils except for the property of induration by air-drying. The mechanism of the induration is still unknown, although it is considered to have occurred during the long period after the deposition of tephra under the influence of soil formation processes. Type 2 included the tephra layers that were indurated in both moist and air-dried states. The carbon and clay contents of type 2 were remarkably lower than those of type 1. Type 2 had not been affected by the soil formation process but had undergone induration soon after the deposition of the tephra. Neither type 1 nor type 2 could be classified into any indurated horizons that are defined in the present soil classification system. For the improvement of soil productivity, type 1 should be harrowed thoroughly soon after its exposure to the surface, and type 2 should be harrowed or removed using farm machinery.     

Note on local applications of paleopedology in central North Island,New Zealand

Paleosols at the land surface and others that are buried are formed almost entirely from tephra parent materials. Current information on nutrient uptake by trees, on highway construction, pipe corrosion, and construction of earthworks is summarized briefly in this paper.     

青海湖防沙治沙区土壤微生物特征初步研究

选择了青海湖防沙治沙措施区,通过野外调查、采样和室内实验分析,对该措施区及流动沙区的土壤微生物数量及垂直分布特征进行研究。结果表明:(1)微生物总数量为沙岛半固定沙丘> 克土丘间地> 克土灌丛> 沙岛灌丛> 湖东种羊场草方格区> 流动沙丘> 克土沙棘草方格> 克土青杨草方格> 示范区近年设置的草方格区。(2)早期治理区,植被覆盖较高,微生物数量垂直分布表现为上层的高于下层,微生物含量也较其他点高。(3)流动沙丘及草方格治理的沙丘,微生物数量非常少,而且下层的稍高于上层,这是因为流动沙丘下层土壤水分状况较好。