Groundwater arsenic in the Red River delta, Vietnam ... - Fiva

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Jessen et al., manuscript to be submitted to Geochim. Cosmochim. Acta without ruling out Fe hydro(oxide) surfaces as a host for As in the reduced sediment. Instead, possibly the surface sites controlling the As adsorption to the iron oxides for the observed As concentration range are not characterized in the models (Ponthieu et al., 2006). 5. IMPLICATIONS FOR BANK INFILTRATION The results of the present study can be used to assess the potential of bank infiltration to mitigate the groundwater As problem in floodplains. The results indicate that bank infiltration of low-As surface water can immediately reduce the As concentration in the pumped water to an expected As concentration of 1-2 μM (75 to 150 μg/L) provided that the pumped water consists primarily of the infiltrated surface water. An As concentration below the 0.13 μM (10 μg/L) WHO guideline will, however, not immediately be obtained and therefore the pumped water with a reduced As concentration still requires treatment. Clearly, further research on bank infiltration as an As mitigation technique is needed. Firstly, the present study indicates that As is released by the bed sediments. Previous studies suggest that the release may be continuous (Polizzotto et al., 2008) and in practice not related to the infiltration rate (Schlieker et al., 2001). Secondly, if the As release from the bed sediment ceases, a low As concentration in the pumped water might be obtained only after prolonged periods (years) of continuous pumping. Finally, within the aquifer, mobilization of solid bound As by reductive dissolution of Fe oxides appears to become important at residence times greater than one month. 31
Jessen et al., manuscript to be submitted to Geochim. Cosmochim. Acta 6. CONCLUSIONS Reduced Holocene aquifer sediments reversibly adsorbs/desorbs As(III), indicating the existence of a labile pool of As(III). The isotherm for As(III) sorption to the reduced aquifer sediment is highly convex at a low aqueous As concentration (
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Groundwater arsenic in the Red Rive
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Søren Jessen Groundwater arsenic i
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organic matter may prevent As mobil
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Resumé Naturligt frigivet arsen (A
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efterfølgende forsøgt at opstille
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Preface This PhD thesis deals with
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Table of contents 1 INTRODUCTION: T
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The PhD research presented in this
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educed form as As(III), which is al
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A more complex and intimate relatio
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sedimentary As content (Postma et a
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(Anawar and Mihaljevi, 2009), and g
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3 Regional As distribution in the R
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in large part by changes in the eus
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In the Red River delta, the Pleisto
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the Red River delta, which are not
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5 The mitigation potential of bank
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Noteworthy is, that the ratio of Fe
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trend in the distribution of the RF
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2008) or the Hach or Merck test kit
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Badloe C., Nguyen T. P. T. and Nguy
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Driehaus W., Seith R. and Jekel M.
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Islam F. S., Boothman C., Gault A.
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Mondal D. and Polya D. A. (2008) Ri
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A. Ali and Z. Adeel). ITN Centre, B
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Ahmed K. M. (2006) A transect of gr
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Arsenic in groundwater of the Red R
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In short, there is a consensus amon
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The local geology shows mainly sand
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ane concentration and P CO2 values
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Fig. 7. The distribution of arsenic
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H3AsO3 þ H2O $ H2AsO4 þ 3H þ þ
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Fig. 12. The relative composition o
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of the Fe-oxides in the upper 3 m c
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found that while As(V) coprecipitat
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desh: further evidence of decouplin
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Controlling geological and hydrogeo
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Here the results of the geological
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sediments. In general, the coarser
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Fig. 5. Thickness of the clay-rich
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a b c The groundwater head distribu
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Table 2 Total As and stable isotope
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delayed yield from the fine grained
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that the situation in Dan Phuong co
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Mathers, S., Zalasiewicz, J., 1999.
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0883-2927/$ - see front matter © 2
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3118 S. Jes sen et al. / Applied Ge
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Postma et al., submitted to Geochim
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Groundwater arsenic in the Red River delta, Vietnam ... - Fiva

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