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

More documents

Recommendations

Info

Jessen et al., manuscript to be submitted to Geochim. Cosmochim. Acta the supernatant were withdrawn by a needle and a polypropylene (PP) syringe, and transferred to polyethylene (PE) vials. After sampling, the bottles received aliquots of the As-free 10 mM NaHCO3 solution, and/or a spike of a 10 mg/L As(III) stock solution. The mass of samples and amendments was determined gravimetrically. Again the bottles were shaken and left for particle settling for the next sampling session. This cycle was concluded up to five times for each bottle. 2.2.3. Analysis Arsenic was analyzed on a Perkin Elmer graphite furnace AAS 600 using an EDL lamp and a Pd-Mg matrix modifier with an As detection limit (DL) of 0.013 μM. No interferences were found in standard addition tests. Aqueous As(V) and As(III) were separated by passing 2 mL of freshly collected sample through first a membrane filter and then a disposable anion exchange cartridge at a rate of approximately 3 mL/min using a syringe. The cartridges contained 0.8 g aluminosilicate adsorbent that selectively adsorbs As(V) but not As(III) (Meng and Wang, 1998). As(V) was calculated as the difference between As(III) and As(tot). The combined syringe, filter and cartridge were flushed five times by N2 gas before processing a sample. Samples were acidified by 0.5vol% HNO3 suprapur. Si was analyzed on a Shimadzu UV-160A by the ammonium molybdate method (DL 1.7 μM). 2.3. Field experiment Three pumping wells (Fig. 1 and 2) were constructed by rotary drilling (Ø170 mm) in May-June 2007 and equipped with a Ø140 mm PVC casing, and a Ø90 mm screen. 13 observation wells were constructed in May 2006 by water-jet drilling and equipped with 7
Jessen et al., manuscript to be submitted to Geochim. Cosmochim. Acta a Ø60 mm PVC casing and a 1 m screen. A quartz sand filter pack and a clay sealing along the casing were installed around the screen and casing, respectively. Immediately after completion the well was pumped to remove the water affected by the drilling. The top end of the PVC-casing was sealed by a rubber cap, to prevent the entrance of surface water during flooding. During high channel stage, the PVC casing was extended with a flexible spacer with a PVC thread, and the casing was then elongated with an appropriate number of 1 m sections of Ø60 mm PVC, each threaded at both ends. The thread connections were tested to be waterproof at pressure differences of >3 m water column. The top end section was sealed by a rubber cap. Sampling could then be conducted from a small boat. The combined pumping rate of the three pumping wells was 33.6 m 3 /h, as determined by daily readings of inline flow meters. The pumped water was discharged 50 m downstream in the channel. 2.3.1 Water level measurements Water levels in the channel, and observation wells N1 and N4 were recorded by data loggers with an uncertainty of ±1.5 cm. In addition, the error introduced by the flexibility of the wells when equipped for sampling during flooding is estimated to roughly ±3 cm. The latter error likely depends on the flex angle of the spacer which in turn depends on the channel stage, causing a shift in the relative head between N1 and N4. 2.3.2 Water sampling and field analysis Sampling was conducted by a Grundfos MP1 using Ø10 mm PE tubing. Before sampling, three well volumes of water were pumped with the MP1 positioned in the 8
Page 1 and 2:
Groundwater arsenic in the Red Rive
Page 3 and 4:
Søren Jessen Groundwater arsenic i
Page 5 and 6:
organic matter may prevent As mobil
Page 8 and 9:
Resumé Naturligt frigivet arsen (A
Page 10 and 11:
efterfølgende forsøgt at opstille
Page 12 and 13:
Preface This PhD thesis deals with
Page 14:
Table of contents 1 INTRODUCTION: T
Page 17 and 18:
The PhD research presented in this
Page 19 and 20:
educed form as As(III), which is al
Page 21 and 22:
A more complex and intimate relatio
Page 23 and 24:
sedimentary As content (Postma et a
Page 25 and 26:
(Anawar and Mihaljevi, 2009), and g
Page 28 and 29:
3 Regional As distribution in the R
Page 30 and 31:
in large part by changes in the eus
Page 32:
In the Red River delta, the Pleisto
Page 35 and 36:
the Red River delta, which are not
Page 38 and 39:
5 The mitigation potential of bank
Page 40:
Noteworthy is, that the ratio of Fe
Page 43 and 44:
trend in the distribution of the RF
Page 45 and 46:
2008) or the Hach or Merck test kit
Page 47 and 48:
Badloe C., Nguyen T. P. T. and Nguy
Page 49 and 50:
Driehaus W., Seith R. and Jekel M.
Page 51 and 52:
Islam F. S., Boothman C., Gault A.
Page 53 and 54:
Mondal D. and Polya D. A. (2008) Ri
Page 55 and 56:
A. Ali and Z. Adeel). ITN Centre, B
Page 57 and 58:
Ahmed K. M. (2006) A transect of gr
Page 60:
Arsenic in groundwater of the Red R
Page 63 and 64:
In short, there is a consensus amon
Page 65 and 66:
The local geology shows mainly sand
Page 67 and 68:
ane concentration and P CO2 values
Page 69 and 70:
Fig. 7. The distribution of arsenic
Page 71 and 72:
H3AsO3 þ H2O $ H2AsO4 þ 3H þ þ
Page 73 and 74:
Fig. 12. The relative composition o
Page 75 and 76:
of the Fe-oxides in the upper 3 m c
Page 77 and 78:
found that while As(V) coprecipitat
Page 79 and 80:
desh: further evidence of decouplin
Page 82 and 83:
Controlling geological and hydrogeo
Page 84 and 85:
Here the results of the geological
Page 86 and 87:
sediments. In general, the coarser
Page 88 and 89:
Fig. 5. Thickness of the clay-rich
Page 90 and 91:
a b c The groundwater head distribu
Page 92 and 93:
Table 2 Total As and stable isotope
Page 94 and 95:
delayed yield from the fine grained
Page 96 and 97:
that the situation in Dan Phuong co
Page 98:
Mathers, S., Zalasiewicz, J., 1999.
Page 102 and 103:
0883-2927/$ - see front matter © 2
Page 104 and 105:
3118 S. Jes sen et al. / Applied Ge
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112:
Page 116 and 117:
Postma et al., submitted to Geochim
Page 118 and 119:
Postma et al., submitted to Geochim
Page 120 and 121: Postma et al., submitted to Geochim
Page 162: The mobility of arsenic in a Red Ri
Page 165 and 166: Jessen et al., manuscript to be sub
Page 169: Jessen et al., manuscript to be sub
Page 207 and 208: Table 1
Page 209 and 210: Fig. 1
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?