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M Van De Broek - One of the best experts on this subject based on the ideXlab platform.

  • soil organic carbon stocks in a tidal marsh landscape are dominated by human marsh Embankment and subsequent marsh progradation
    European Journal of Soil Science, 2019
    Co-Authors: M Van De Broek, L Baert, Stijn Temmerman, Gerard Govers
    Abstract:

    Tidal marshes are coastal and estuarine ecosystems that store large amounts of sedimentary organic carbon (OC). Despite the valuable ecosystem services they deliver, tidal marshes have been converted to other land‐use types over the past centuries. Although previous studies have reported large decreases in soil organic carbon (SOC) stocks after tidal marsh Embankment, knowledge on the magnitude and rate of OC losses is still limited. Here, we studied the effect of stepwise Embankments of brackish and salt marshes and subsequent marsh progradation on SOC stocks in the Scheldt estuary (the Netherlands). We collected samples from soil profiles along tidal marsh–reclaimed tidal marsh chronosequences and determined total OC stocks and the stable carbon signature of the OC. Our results showed that large losses of previously sequestered SOC occur on a decadal timescale with the Embankment of brackish (−8.7 ± 0.7 kg OC m⁻²) and salt marshes (−6.7 ± 0.8 kg OC m⁻²). The (incomplete) replacement of tidal marsh OC by agricultural OC is substantially faster in topsoils (ca. a century) compared with subsoils (multiple centuries). Simulations with a coupled land use–SOC model showed that large rates of marsh progradation following Embankment Construction resulted in a substantial increase in landscape‐scale SOC storage, whereas large SOC losses occurred in landscapes dominated by embanked tidal marshes. The findings of our study might help to assess how these management practices affect regional SOC stocks. HIGHLIGHTS: We studied how OC stocks in tidal marsh sediments are affected by Embankment Construction OC stocks of both brackish and salt marsh sediments were reduced by ca. 60% with Embankment Gains in landscape‐scale SOC storage occurred with marsh progradation after Embankment If no marsh progradation occurs, Embankments always lead to SOC loss at the landscape scale

Gerard Govers - One of the best experts on this subject based on the ideXlab platform.

  • soil organic carbon stocks in a tidal marsh landscape are dominated by human marsh Embankment and subsequent marsh progradation
    European Journal of Soil Science, 2019
    Co-Authors: M Van De Broek, L Baert, Stijn Temmerman, Gerard Govers
    Abstract:

    Tidal marshes are coastal and estuarine ecosystems that store large amounts of sedimentary organic carbon (OC). Despite the valuable ecosystem services they deliver, tidal marshes have been converted to other land‐use types over the past centuries. Although previous studies have reported large decreases in soil organic carbon (SOC) stocks after tidal marsh Embankment, knowledge on the magnitude and rate of OC losses is still limited. Here, we studied the effect of stepwise Embankments of brackish and salt marshes and subsequent marsh progradation on SOC stocks in the Scheldt estuary (the Netherlands). We collected samples from soil profiles along tidal marsh–reclaimed tidal marsh chronosequences and determined total OC stocks and the stable carbon signature of the OC. Our results showed that large losses of previously sequestered SOC occur on a decadal timescale with the Embankment of brackish (−8.7 ± 0.7 kg OC m⁻²) and salt marshes (−6.7 ± 0.8 kg OC m⁻²). The (incomplete) replacement of tidal marsh OC by agricultural OC is substantially faster in topsoils (ca. a century) compared with subsoils (multiple centuries). Simulations with a coupled land use–SOC model showed that large rates of marsh progradation following Embankment Construction resulted in a substantial increase in landscape‐scale SOC storage, whereas large SOC losses occurred in landscapes dominated by embanked tidal marshes. The findings of our study might help to assess how these management practices affect regional SOC stocks. HIGHLIGHTS: We studied how OC stocks in tidal marsh sediments are affected by Embankment Construction OC stocks of both brackish and salt marsh sediments were reduced by ca. 60% with Embankment Gains in landscape‐scale SOC storage occurred with marsh progradation after Embankment If no marsh progradation occurs, Embankments always lead to SOC loss at the landscape scale

Altug Saygılı - One of the best experts on this subject based on the ideXlab platform.

  • a new technique to improve freeze thaw durability of fly ash
    Fuel, 2012
    Co-Authors: Gokhan Baykal, Altug Saygılı
    Abstract:

    Abstract High volume utilization of industrial wastes and by products is the solution for high disposal costs. Acceptable durability levels in addition to environmental factors are a key factor for safe utilization of wastes and by products of coal burning power plants in road Construction activities. The durability levels of most fly ashes are similar to concrete if the strength and air content are kept constant. To obtain a better freeze–thaw performance from the fly ash samples, an air entraining agent must be added into the matrix. Snow can be added to the fly ash samples as an air entraining agent as presented. In this study a new technique involving the use of snow as an additive to the fly ash is presented. Compaction of fly ash is very sensitive to water content which complicates the use of fly ash in highway Embankment Construction. One or two percent additional water over optimum moisture content makes compaction of the fly ash impossible. On the other hand, an excess amount of water is needed to enhance the reactions leading to formation of cementitious products, which increases strength. The extra water is added in solid phase as snow, which allows compaction of the samples without liquefying. The 10% extra water added in the solid phase caused a 30% increase in the void ratio. The main objective of this investigation is to evaluate whether the increased void ratio causes a similar behavior expected from air entraining agents on the freeze thaw durability of fly ash. Type C fly ash at optimum moisture content and fly ash with additional 10% by weight snow are compacted, sealed and cured for 90 and 180 days at the curing room. After the curing period, freeze–thaw durability tests are conducted with a freeze–thaw cabinet. The development of deterioration, resonant frequency variation and weight losses of fly ash and snow added fly ash samples compacted at optimum moisture content are determined throughout the test period. The relative dynamic modulus of elasticity of the control samples decreased to 55% of their original value after 90 freeze thaw cycles, for snow added fly ash samples the same amount of reduction occurred after 120 freeze thaw cycles for 90 and 180 days cured samples. Higher freeze–thaw performance of the snow added samples is related to the increased void ratio after melting of snow and densification of the matrix around the pores due to higher level of cementitious mineral formation. The increase in the freeze–thaw performance of snow added fly ash samples will allow utilization of fly ash in highway Embankment Construction activities where large surface area exposure and large volume usage makes it more critical for the service life and longevity of the constructed road in cold regions. Another advantage of the developed technique is the reduction of transportation costs by more than 10% by using less material for Construction.

  • influence of different processing techniques on the mechanical properties of used tires in Embankment Construction
    Waste Management, 2010
    Co-Authors: Ayse Edincliler, Gokhan Baykal, Altug Saygılı
    Abstract:

    Use of the processed used tires in Embankment Construction is becoming an accepted way of beneficially recycling scrap tires due to shortages of natural mineral resources and increasing waste disposal costs. Using these used tires in Construction requires an awareness of the properties and the limitations associated with their use. The main objective of this paper is to assess the different processing techniques on the mechanical properties of used tires-sand mixtures to improve the engineering properties of the available soil. In the first part, a literature study on the mechanical properties of the processed used tires such as tire shreds, tire chips, tire buffings and their mixtures with sand are summarized. In the second part, large-scale direct shear tests are performed to evaluate shear strength of tire crumb-sand mixtures where information is not readily available in the literature. The test results with tire crumb were compared with the other processed used tire-sand mixtures. Sand-used tire mixtures have higher shear strength than that of the sand alone and the shear strength parameters depend on the processing conditions of used tires. Three factors are found to significantly affect the mechanical properties: normal stress, processing techniques, and the used tire content.

  • highway Embankment Construction using fly ash in cold regions
    Resources Conservation and Recycling, 2004
    Co-Authors: Gokhan Baykal, Ayse Edincliler, Altug Saygılı
    Abstract:

    Abstract Mineral wastes or by products provide great potential to alleviate demand for large volumes of low cost mineral resources for highway Construction. Fly ash, the inorganic residue of coal burning thermal power plants, has been used widely in the Construction industry. However, compaction of fly ash is very sensitive to water content which complicates use of fly ash in highway Embankment. One or two percent over optimum water content makes compaction impossible. On the other hand, an excess amount of water is needed to enhance reactions leading to formation of cementitious products, which increases strength. This paper presents a new technique for adding water to fly ash samples to enhance the conditions for cementitious mineral formation without sacrificing compactibility. Fly ash at optimum water content, and fly ash with additional 10% by weight crushed ice were compacted, sealed and cured for 1, 7, 14, 28, and 90 days at 21 °C. Unconfined compression tests and splitting tensile tests were conducted after completion of each curing period. Cementitious mineral formation, and changes in microfabric with curing time were observed using powder X-ray diffraction (XRD) analysis and environmental scanning electron microscopy (ESEM). The addition of snow into fly ash increased the unconfined compressive strength and splitting tensile strength noticeably beginning from 14 days of curing. X-ray diffractograms and ESEM micrographs are used to explain the mechanisms leading to increase in shear strength. More important than the higher performance obtained by using snow, the new technology will allow Construction of highway Embankments, bases and subbases during wintertime at cold regions, where Construction activities are ceased normally due to snow and low temperatures.

L Baert - One of the best experts on this subject based on the ideXlab platform.

  • soil organic carbon stocks in a tidal marsh landscape are dominated by human marsh Embankment and subsequent marsh progradation
    European Journal of Soil Science, 2019
    Co-Authors: M Van De Broek, L Baert, Stijn Temmerman, Gerard Govers
    Abstract:

    Tidal marshes are coastal and estuarine ecosystems that store large amounts of sedimentary organic carbon (OC). Despite the valuable ecosystem services they deliver, tidal marshes have been converted to other land‐use types over the past centuries. Although previous studies have reported large decreases in soil organic carbon (SOC) stocks after tidal marsh Embankment, knowledge on the magnitude and rate of OC losses is still limited. Here, we studied the effect of stepwise Embankments of brackish and salt marshes and subsequent marsh progradation on SOC stocks in the Scheldt estuary (the Netherlands). We collected samples from soil profiles along tidal marsh–reclaimed tidal marsh chronosequences and determined total OC stocks and the stable carbon signature of the OC. Our results showed that large losses of previously sequestered SOC occur on a decadal timescale with the Embankment of brackish (−8.7 ± 0.7 kg OC m⁻²) and salt marshes (−6.7 ± 0.8 kg OC m⁻²). The (incomplete) replacement of tidal marsh OC by agricultural OC is substantially faster in topsoils (ca. a century) compared with subsoils (multiple centuries). Simulations with a coupled land use–SOC model showed that large rates of marsh progradation following Embankment Construction resulted in a substantial increase in landscape‐scale SOC storage, whereas large SOC losses occurred in landscapes dominated by embanked tidal marshes. The findings of our study might help to assess how these management practices affect regional SOC stocks. HIGHLIGHTS: We studied how OC stocks in tidal marsh sediments are affected by Embankment Construction OC stocks of both brackish and salt marsh sediments were reduced by ca. 60% with Embankment Gains in landscape‐scale SOC storage occurred with marsh progradation after Embankment If no marsh progradation occurs, Embankments always lead to SOC loss at the landscape scale

Stijn Temmerman - One of the best experts on this subject based on the ideXlab platform.

  • soil organic carbon stocks in a tidal marsh landscape are dominated by human marsh Embankment and subsequent marsh progradation
    European Journal of Soil Science, 2019
    Co-Authors: M Van De Broek, L Baert, Stijn Temmerman, Gerard Govers
    Abstract:

    Tidal marshes are coastal and estuarine ecosystems that store large amounts of sedimentary organic carbon (OC). Despite the valuable ecosystem services they deliver, tidal marshes have been converted to other land‐use types over the past centuries. Although previous studies have reported large decreases in soil organic carbon (SOC) stocks after tidal marsh Embankment, knowledge on the magnitude and rate of OC losses is still limited. Here, we studied the effect of stepwise Embankments of brackish and salt marshes and subsequent marsh progradation on SOC stocks in the Scheldt estuary (the Netherlands). We collected samples from soil profiles along tidal marsh–reclaimed tidal marsh chronosequences and determined total OC stocks and the stable carbon signature of the OC. Our results showed that large losses of previously sequestered SOC occur on a decadal timescale with the Embankment of brackish (−8.7 ± 0.7 kg OC m⁻²) and salt marshes (−6.7 ± 0.8 kg OC m⁻²). The (incomplete) replacement of tidal marsh OC by agricultural OC is substantially faster in topsoils (ca. a century) compared with subsoils (multiple centuries). Simulations with a coupled land use–SOC model showed that large rates of marsh progradation following Embankment Construction resulted in a substantial increase in landscape‐scale SOC storage, whereas large SOC losses occurred in landscapes dominated by embanked tidal marshes. The findings of our study might help to assess how these management practices affect regional SOC stocks. HIGHLIGHTS: We studied how OC stocks in tidal marsh sediments are affected by Embankment Construction OC stocks of both brackish and salt marsh sediments were reduced by ca. 60% with Embankment Gains in landscape‐scale SOC storage occurred with marsh progradation after Embankment If no marsh progradation occurs, Embankments always lead to SOC loss at the landscape scale