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1.
The purpose of this paper is to present a review of peat landslide events in Ireland since 2003, when two significant events
occurred. Since 2003, there have been at least 13 such events. Several of these events included more than one slide. It is
also likely that there have been unrecorded slides. It seems that there is an increasing incidence of such events, but they
seem to occur in clusters with intervening quiet periods. These clusters coincide with periods of intense rainfall. For many
slides, at least two causal factors can be identified. Primarily these comprised intense rainfall but human activities such
as road construction and peat cutting also contributed to the slides. Detailed geotechnical testing of the peat, including
laboratory direct simple shear tests (DSS), is reported for two of the slides. Back-analysis of these two failures suggests
that the mobilised strength of the material in the failure surface is similar to that measured in the DSS tests. However,
conventional geotechnical analyses need to be treated with caution as they fail to account for the complex interactions in
the sliding surface and in particular the lubricating role of water. 相似文献
2.
《Geomechanics and Geoengineering》2013,8(4):286-296
Peat deposits are comprised of high organic content substances primarily derived from dead plant vegetation. Peat itself is not inert but undergoes continuous biological decomposition that causes progressive destruction of the peat fabric, reductions in fibre and organic contents and biogas generation. Depending on the degree of decomposition, the organic solids can exist as fresh (intact) fibres, slightly decomposed or ultimately completely decomposed (amorphous) material. From a geotechnical perspective, an understanding of the relationship between degree of decomposition and engineering properties, including the level of compressibility, is important in dealing with such problematic deposits. However a review of the literature indicates that such relationships have not been sufficiently investigated. Moreover, potential impacts of uncontrolled or unexpected decomposition in-situ are regularly discounted in geotechnical practice. This paper reviews decomposition effects in peat and potentially significant knock-on effects in terms of the material’s physical properties and compressibility. Progressive reduction in solids volume and deterioration in the integrity of the organic structure due to on-going decomposition may cause significant additional settlement to occur over time. More decomposed peat generally undergoes lower primary consolidation and creep strains and is also less prone to future decomposition, compared with lesser decomposed peat. 相似文献
3.
A number of samples from a deep peat bog in Tierra del Fuego were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) in order to extract parameters that might be used to interpret the peat chemistry in terms of vegetation change, anaerobic and aerobic decomposition, and fire incidence. The choice of parameters was based on factor analysis of 177 pyrolysis products, quantified for 13 samples, separated into extract and residue, as well as the total samples. Factor analysis of extracts, residues and total samples yielded similar classifications in terms of vegetation and decomposition. Pyrolysis products and ratios that most clearly differentiated samples were used to interpret the depth profile. Although interpretation was not always straightforward, indications of parameters to describe vegetation shifts, aerobic and anaerobic decomposition, and fire largely coincided. These parameters will be used in a forthcoming study for a more complete interpretation of the peat profile. 相似文献
4.
Zhong Jianhua 《沉积学报》1997,15(1):128-134
Little is known about the geochemistry of peat and soft-brown coal The analytical chemical dataof forty eight samples have been obtained for the peat and soft-brow n coal in the 7henan basin, western Yunnan. njection of continental detritus into theswamp is favourable for the degradation of plant remains and thefor-oration of humic acid. The oxide compositions of the ash of the peat and soft一)rown coal and their distribution-typeshave indicated that the continental detritusome from two kinds of parent rocks.The Al2O3 and SiO2have a positive correlation with humic acid(Hmz)，showing that the organic matter is ad-vantageous to the formation of aluminosilic;ate mineral(mainly kaolinite, authigenic organic clay minerals). The TiO2 enrichment is mainly related to mineral materials. The Ge content in the peat and soft-brown coalranges from 0. 2- 2.6×10-6, and it is mainly bound to those minerals with Al2O3and organic matters. The GaContent is from 2. 3- 19.1×10-6，and it is associated with minerals that are MgO一Baring aluminosilicate minerals.The uranium (0.3- 4.9×10-6) is mainly bound in the Ca-and Mg-bearing minerals. They are not enriched andnot related to organic matter. 相似文献
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7.
The aim of this paper was to determine the ultimate vertical bearing capacity of rectangular rigid footings resting on homogeneous peat stabilized by a group of cement deep mixing (CDM) columns. For this purpose, a series of physical modeling tests involving end-bearing and floating CDM columns were performed. Three length/depth ratios of 0.25, 0.5, and 0.75 and three area improvement ratios of 13.1, 19.6, and 26.2 % were considered. Bearing capacity of the footings was studied using different analytical procedures. The results indicated that compared to unimproved peat, the average ultimate bearing capacity (UBC) improvement of floating and end-bearing CDM columns were 60 and 223 %, respectively. The current study found that simple Brom’s method predicted the UBC of the peat stabilized with floating CDM columns with reasonable accuracy, but underestimated the UBC by up to 25 % in the case of end-bearing CDM columns. Published laboratory experiences of stabilizing soft soils using soil–cement columns were also collated in this paper. 相似文献
8.
The influence of volcanism on paleoclimate in the northeast of China： Insights from Jinchuan peat, Jilin Province, China 总被引：3，自引：0，他引：3
Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic
activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A
section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with
surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According
to the peat characteristics of uniform deposition, the tephra was dated at 2002–1976 a B.P. by way of linear interpolation,
so the time of volcanic eruption was 15 B.C.–26 A.D. (the calibrated age). While the geochemical characteristics of tephra
in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic
magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption
events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent
or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these
volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result,
there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of
volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact
of volcanism on climate change. 相似文献
9.
Harm Jan Pierik Jelle I. M. Moree Karianne M. van der Werf Lonneke Roelofs Marcio Boechat Albernaz Antoine Wilbers Bert van der Valk Marieke van Dinter Wim Z. Hoek Tjalling de Haas Maarten G. Kleinhans 《Sedimentology》2023,70(1):179-213
In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco-engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal bp , and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back-barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back-barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large-scale crevassing along the Old Rhine River – driven by tidal backwater effect – only started as nutrient-rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal bp , likely due to a reduced tidal backwater effect. The insights from this data-rich Holocene study showcase the dominant role that vegetation may have in the long-term evolution of coastal wetlands. It provides clues for effective use of vegetation in vulnerable wetland landscapes to steer sedimentation patterns to strategically adapt to rising water levels. 相似文献
10.
The purpose of this study was to determine the history of paleosalinity over the past 6000+ years in the Sacramento-San Joaquin Delta (the Delta), which is the innermost part of the San Francisco Estuary. We used a combination of Sr and U concentrations, δ87Sr values, and 234U/238U activity ratios (AR) in peat as proxies for tracking paleosalinity. Peat cores were collected in marshes on Browns Island, Franks Wetland, and Bacon Channel Island in the Delta. Cores were dated using 137Cs, the onset of Pb and Hg contamination from hydraulic gold mining, and 14C. A proof of concept study showed that the dominant emergent macrophyte and major component of peat in the Delta, Schoenoplectus spp., incorporates Sr and U and that the isotopic composition of these elements tracks the ambient water salinity across the Estuary. Concentrations and isotopic compositions of Sr and U in the three main water sources contributing to the Delta (seawater, Sacramento River water, and San Joaquin River water) were used to construct a three-end-member mixing model. Delta paleosalinity was determined by examining variations in the distribution of peat samples through time within the area delineated by the mixing model.The Delta has long been considered a tidal freshwater marsh region, but only peat samples from Franks Wetland and Bacon Channel Island have shown a consistently fresh signal (<0.5 ppt) through time. Therefore, the eastern Delta, which occurs upstream from Bacon Channel Island along the San Joaquin River and its tributaries, has also been fresh for this time period. Over the past 6000+ years, the salinity regime at the western boundary of the Delta (Browns Island) has alternated between fresh and oligohaline (0.5–5 ppt). 相似文献
11.
The results of investigations (SEM/EDS and AAS) of a peat deposit, spanning 13,000 years of peat accumulation, are shown. The peat deposit is located in a region of shallow occurrence of Zn–Pb ores, near Tarnowskie Góry town, within the Cracow–Silesia district (southern Poland). Exploitation of lead, silver and iron during the medieval times (Twelfth and thirteenth century) was confirmed by historical documents whereas there are no unambiguous data showing that there was metal mining during the Romanian or earlier times in the region. The peat deposit is located within the influence of atmospheric Pb and Zn emission from a nearby Zn–Pb smelter. Two vertical peat profiles were investigated (120 and 140 cm depth of profile) showing variable concentrations of Zn up to 713 mg kg?1, Pb up to 317 mg kg?1, Cd up to 13 mg kg?1 and Tl up to 31 mg kg?1. The highest concentrations were recorded for the uppermost peat layers. SEM and EDS investigations revealed the occurrence of metalbearing, submicroscopic mineral components: Fe, Mn, Ti and Zn oxides and Zn and Pb carbonates. The top layer of the deposit contained Zn, Pb and Cd sulphides. The occurrence of aggregates of Au–Ag, Cu–Zn and Au–Ag–Cu alloys can be possibly related to pre-historical mining and smelting or be explained by geochemical transformations. The preservation of carbonates and oxides in the peat is discussed, indicating a generally neutral to alkaline peat water chemistry and maintenance of an oxidized environment in the fen. 相似文献
12.
Spectra of the REE distribution in the Quaternary–Recent peat bog ore of southern Karelia and Leningrad region are characterized by LaN/YbN < 1.0, presence of positive Eu and negative Ce anomalies, and higher Y enrichment (relative to Ho and Dy) because of the REE sorption by Fe-bearing minerals in acid boggy waters. The 87Sr/86Sr ratio is 0.7175 in iron oxyhydroxides of the Somino deposit (Leningrad region) and 0.7283 in the Polovinkino ore (southern Karelia). The 143Nd/144Nd ratio in them is 0.511844 and 0.511617, respectively. 相似文献
13.
The most widely accepted origin of n-alkan-2-ones in peats is the microbial oxidation of the related n-alkanes and/or oxidative decarboxylation of fatty acids derived from plant input. The distributions of n-alkanes and n-alkan-2-ones in 48 samples from the Roñanzas 6000 cal. yr BP peat bog profile (N Spain) do not justify a single source. The n-alkan-2-ones typically dominate the n-alkanes, maximizing at C19 or C25/C27, whereas the n-alkanes maximized either at C23 or at C31/C33. The averaged δ13C values of the n-alkanes ranged from −32.3‰ to −33.1‰, but those of the n-alkan-2-ones were consistently higher (−29.2‰ to −29.9‰), suggesting a different, probably bacterial, source for the ketones. 相似文献
14.
A total of 233 samples from the upper 16 m of the Toushe peat core retrieved in central Taiwan were measured for TOC and δ13CTOC values. From these samples, 17 selected samples with large δ13CTOC fluctuations were analyzed for n-alkane and δD of the C27 and C29 n-alkanes. Combining with the detailed high-resolution pollen and geochemical records, this study reveals more detailed climatic variations in terms of temperature and precipitation as well as abrupt climatic events during the past 30 Kyrs. Before the Last Glacial Maximum (LGM), climate was cold and damp with predominantly woodland vegetation in Toushe Basin, and turned to cold and dry after 25 Kyr BP. Climatic conditions there were the worst during LGM over the past 30 Kyrs, especially around 23 and 18 Kyr BP when the woodland was diminished and C4 grass was dominated. Although short durations of relatively wet conditions could be found at 17, 16 and 14 Kyr BP, cold and dry climates were prevailing during 29.5–28, 24–22, 17–15 and 13–11.5 Kyr BP, corresponding to Heinrich (H) Events 3, 2, 1, and Younger Dryas (YD), respectively. During the early Holocene, dry climate occurred at ∼11, ∼10, 9.7–9.2 and ∼8 Kyr BP; whereas wet condition appeared at 10.3, 9.8, 9–7.5 Kyr BP. In the middle Holocene, climate kept warm and moderate wet in the first half period, but many dry events existed in the second half following a cold and dry event at 6 Kyr BP. After a sharply warm peak at 5.2 Kyr BP, the climate in Toushe turned to cold quickly, and tree/shrub vegetation disappeared completely with the replacement of C3 grasses. In the late Holocene, climate was relatively wetter with predominant C3 grasses in the basin. Our climatic interpretations based on the peat records agree well with the Greenland ice core and Chinese speleothem records on millennium time scales during the last glacial period. Dry climates corresponding to weakening of the East Asian Summer Monsoon (EASM) during the Heinrich events and Younger Dryas in central Taiwan and eastern China demonstrate the climatic forcing on such long time scales in concert with regional monsoon climate. However, the discrepancies exist between our peat record and the Dongge/Hulu stalagmite record on: (1) the age of H2; (2) climate intensities of LGM and H1; and (3) wetness condition during Holocene. These observations call for further study on high-resolution climatic changes especially on moisture budget in the East Asian monsoonal region. 相似文献