Depositional environment and geotechnical properties of Shanghai clay: a comparison with Ariake and Bangkok clays

Wu, Changying; Ye, Guanlin; Zhang, Lulu; Bishop, Daniel; Wang, Jianhua

doi:10.1007/s10064-014-0670-0

Cited by 49 publications

(13 citation statements)

References 51 publications

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“…Assuming a high groundwater CO 2 (51,900 μatm [ Johnson et al , ]), lateral groundwater inflow would need to be about 12% of surface water discharge to support 70% of the remaining CO 2 evasion (i.e., 2.8 g C m −2 d −1 ) after accounting for the contribution of longitudinal input (i.e., 43%) along the Huangpu River main stem. Such high lateral influx is unrealistic on an annual basis in this lowland watershed where downwelling events frequently occur especially during the wet season [ Yin et al , ; Wu et al , ]. Second, substantial OC and NH 4 + inputs from nonpoint urban runoffs and WWTP effluents [ Yu et al , ] might stimulate metabolic CO 2 production.…”

Section: Discussionmentioning

confidence: 99%

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Carbon dioxide and methane dynamics in a human-dominated lowland coastal river network (Shanghai, China)

Wang

et al. 2017

J. Geophys. Res. Biogeosci.

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Evasion of carbon dioxide (CO2) and methane (CH4) in streams and rivers play a critical role in global carbon (C) cycle, offsetting the C uptake by terrestrial ecosystems. However, little is known about CO2 and CH4 dynamics in lowland coastal rivers profoundly modified by anthropogenic perturbations. Here we report results from a long‐term, large‐scale study of CO2 and CH4 partial pressures (pCO2 and pCH4) and evasion rates in the Shanghai river network. The spatiotemporal variabilities of pCO2 and pCH4 were examined along a land use gradient, and the annual CO2 and CH4 evasion were estimated to assess its role in regional C budget. During the study period (August 2009 to October 2011), the overall mean pCO2 and median pCH4 from 87 surveyed rivers were 5846 ± 2773 μatm and 241 μatm, respectively. Internal metabolic CO2 production and dissolved inorganic carbon input via upstream runoff were the major sources sustaining the widespread CO2 supersaturation, coupling pCO2 to biogeochemical and hydrological controls, respectively. While CH4 was oversaturated throughout the river network, CH4 hot spots were concentrated in the small urban rivers and highly discharge‐dependent. The Shanghai river network played a disproportionately important role in regional C budget, offsetting up to 40% of the regional terrestrial net ecosystem production and 10% of net C uptake in the river‐dominated East China Sea fueled by anthropogenic nutrient input. Given the rapid urbanization in global coastal areas, more research is needed to quantify the role of lowland coastal rivers as a major landscape C source in global C budget.

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Section: Discussionmentioning

confidence: 99%

“…The geology of this region is typical of tidal‐dominated deltas with the Quaternary deposits consisting of five confined and one unconfined aquifers. The unconfined aquifer is about 8 m thick and has an annual mean water level of 0.5 to 1.5 m belowground surface [ Wu et al , ].…”

Section: Methodsmentioning

confidence: 99%

Carbon dioxide and methane dynamics in a human-dominated lowland coastal river network (Shanghai, China)

Wang

et al. 2017

J. Geophys. Res. Biogeosci.

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“…The reported fractured clay aquitards are generally composed of stiff Pleistocene (Q 3 ) deposits, which underwent a desiccation cracking process at late Q 3 . The coastal areas of Southeast Asia is widely distributed the marine soft clay formed in Holocene (Q 4 ), which includes Ariake (Japan), Bangkok (Thailand), Busan (South Korea), Singapore, Mekong River Delta (Vietnam), and China's coastal areas [15]. The marine soft clays are generally homogenous deposits characterized with large void ratio (over 1.0) and flocculated structure [16].…”

Section: Introductionmentioning

confidence: 99%

A Case Study of Deep DNAPL Contamination in Marine Soft Clays

Gao

2023

Geofluids

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Aquifers in China’s southeast coastal areas are protected by the overlying marine soft clays formed in Holocene transgression. However, a fundamental understanding of the characteristics of DNAPL (dense nonaqueous phase liquid) contamination in marine soft clays is limited. The study was conducted on the site of a former pharmaceutical factory in Shanghai, where serious 1,1,2-trichloroethane (DNAPL) contamination was detected up to the depth of 22.0 m below the existing grade. Partitioning calculation method was used to identify the presence of pure phase, and the results showed that pure 1,1,2-trichloroethane was accumulated at the interface of the upper soft silty clay and lower soft clay. The vertical transport was believed to be the pure DNAPL displacing pore water following the principle of two-phase flow, rather than the convection and diffusion of aqueous phase. The contamination (NAPL-soil interaction) impacted the soil properties slightly, and this effect could not account for the deep contamination. Soil structure analysis showed that these clays contained a proportion of large interaggregate pores, providing pathways for the transport of pure DNAPL. Considering their flocculated structure, the marine soft clays are not capable to perform as a barrier to prevent the downward migration of pure DNAPL.

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“…The higher the activity of clay, the more pronounced the influence of the clay fraction on its engineering behavior and the more susceptible it is to changes in pore fluid composition [51]. The high activity of clay is also related to greater smectite presence [28]. (Table 1) shows the significant amount of smectite.…”

Section: Geotechnical Index Properties Of Claymentioning

confidence: 99%

“…Some marine clays with saline porewaterare known to be soft and vulnerable to excessive settlements, posing threats to construction and the maintance of infrastructure, for example, the marine clays fromBangkok [27,28], Shanghai [29,30], Pusan [31], and Kansai [32]. Land subsidence of marine clays has been widely analyzed in the light of one-dimensional consolidation theory [5,14,33,34]; however, the effect of groundwater salinity on the subsidence process (e.g., consolidation parameters) tends to be overlooked.…”

Section: Introductionmentioning

confidence: 99%

A Physical Study of the Effect of Groundwater Salinity on the Compressibility of the Semarang-DemakAquitard, Java Island

et al. 2018

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Semarang-Demak and other cities along the coast of North Java are vulnerable to land subsidence. The presence of saline groundwater in the coastal region is thought to affect the high subsidence rate, in this case the compressibility of the aquitard layer. We aimed to analyze the effects of groundwater salinity on the compression characteristics of the Semarang-Demak clay using physical analysis. Methods included the determination of groundwater salinity, clay mineralogy and fabrics, and consolidation tests under various salinity conditions. The Semarang-Demak clay is dominated by smectite of high activity, and saline clay exists at the depth of 10 to 35 m. Consolidation tests revealed that the increase insalinity increases the average consolidation rate and hydraulic conductivity up to 42% and 37.5%, respectively. Clay fabric analysis showed that the groundwater salinity modified the interconnectivity of pores by changing the fabric into parallel alignments, facilitating faster porewater dissipation, hence the clay is more readily compressed. These findings are useful for explaining the mechanism of the fast-subsiding coastal plains of North Java.

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Depositional environment and geotechnical properties of Shanghai clay: a comparison with Ariake and Bangkok clays

Cited by 49 publications

References 51 publications

Carbon dioxide and methane dynamics in a human-dominated lowland coastal river network (Shanghai, China)

Carbon dioxide and methane dynamics in a human-dominated lowland coastal river network (Shanghai, China)

A Case Study of Deep DNAPL Contamination in Marine Soft Clays

A Physical Study of the Effect of Groundwater Salinity on the Compressibility of the Semarang-DemakAquitard, Java Island

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