The transport and reaction behavior of arsenic in groundwater [Elektronische Ressource] : experiments and case studies / vorgelegt von Rouven Höhn

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The transport and reaction behavior of arsenic in groundwater: Experiments and case studies Inaugural – Dissertation zur Erlangung der Doktorwürde der Naturwissenschaftlichen-Mathematischen Gesamtfakultät der Ruprecht – Karls – Universität Heidelberg vorgelegt von Diplom - Geologe Rouven Höhn aus Worms, Rheinland – Pfalz Tag der mündlichen Prüfung: 22.07.2005 Gutachter: Prof. Dr. Margot Isenbeck-Schröter PD. Laurence Noel Warr Abstract The transport and reaction behavior of arsenic in the aquatic environment is of high importance, since arsenic in groundwater causes serious problems e.g. in Bangladesh. It is well known that elevated arsenic concentrations in drinking water lead to severe health risk. Various investigations have been carried out concerning the oxidation and adsorption of arsenic in the environment, but less is know about the reduction and release of arsenic. A continuous injection tracer test was conducted at the USGS Cape Cod research site (Mass.,USA) in order to investigate natural reduction of As(V) to As(III) in an iron reducing environment. As(V) reduction was observed to take place under the conditions of this aquifer. Furthermore retardation of As(III) turned out to be minor than the one of As(V).

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The transport and reaction behavior of arsenic
in groundwater:
Experiments and case studies




Inaugural – Dissertation



zur Erlangung der Doktorwürde
der Naturwissenschaftlichen-Mathematischen Gesamtfakultät
der Ruprecht – Karls – Universität
Heidelberg









vorgelegt von
Diplom - Geologe Rouven Höhn
aus Worms, Rheinland – Pfalz

Tag der mündlichen Prüfung: 22.07.2005






























Gutachter:
Prof. Dr. Margot Isenbeck-Schröter
PD. Laurence Noel Warr Abstract
The transport and reaction behavior of arsenic in the aquatic environment is of high
importance, since arsenic in groundwater causes serious problems e.g. in
Bangladesh. It is well known that elevated arsenic concentrations in drinking water
lead to severe health risk. Various investigations have been carried out concerning
the oxidation and adsorption of arsenic in the environment, but less is know about the
reduction and release of arsenic.
A continuous injection tracer test was conducted at the USGS Cape Cod research
site (Mass.,USA) in order to investigate natural reduction of As(V) to As(III) in an iron
reducing environment. As(V) reduction was observed to take place under the
conditions of this aquifer. Furthermore retardation of As(III) turned out to be minor
than the one of As(V). Microbial investigations showed that arsenic reducing
microorganism as well as iron reducers and sulfate reducers were present in the
aquifer. Arsenic was assumed to be reduced by microbial reduction as well as by
dissolved sulfide. To support this theory batch experiments with As(V) and sulfide
were conducted. In preliminary experiments at pH 3, up to 30 % was reduced
depending on the sulfide. Water samples buffered a pH 6.8 showed lower reduction
rates. Batch experiments with MnO apparently indicated manganese reduction to 2
prevent arsenic reduction. In batch experiments with Fe(III), a simultaneous reduction
of Fe(III) and As(V) was observed.
The third part of the work deals with the arsenic release from ore and mine dumps.
For a better understanding of the flow and the reaction path of arsenic sediment
samples from two sites on Sardinia highly influenced by ore and mine dumps were
analyzed. In all sediment samples the total amount of arsenic as well as of Ca, Mn,
Fe, S and Pb were measured. Different elution methods were conducted to make
predictions of the mobility as well as the arsenic binding. In the first study area, the
arsenic is transported in a stream in which the flow rate differs extremely over the
year. High flow rates cause translocation processes of the tailing material and the
stream sediments. During periods with low flow rates the arsenic transport is
dominated by the dissolved fraction. In the other study area the arsenic is released in
a wetland and in this case the transport is mostly controlled by geochemical
conditions. Thus the As transport velocity is slow and the accumulation rates are
much lower compared to the other study area. Zusammenfassung
Arsen verursacht in vielen Ländern große Probleme bei der Einhaltung der
Trinkwassergrenzwerte. Es ist bekannt, dass Arsen Krankheiten verursacht. Aus
diesem Grund ist es wichtig das Reaktions- und Transportverhalten von Arsen zu
kennen.
Ein Tracer Test mit kontinuierlicher Injektion wurde auf dem Versuchsgelände des
USGS auf Cape Cod (Mass., USA) durchgeführt, um die Reduktion von As(V) zu
As(III) unter natürlichen Bedingungen in der Eisenreduktionszone zu beobachten.
Außer der Reduktion von As(V) wurde ein schnellerer Transport von As(III)
gegenüber dem von As(V) festgestellt. Mikrobiologische Untersuchungen an Proben
aus dem Aquifer deuten auf eisen-, arsen- und sulfidreduzierende Organismen hin.
In Anbetracht aller Ergebnisse kann das Arsen sowohl von Mikroorganismen als
auch von Sulfid reduziert worden sein.
Um die Reduktion von Arsen durch Sulfid genauer zu untersuchen wurden im
Labor Schüttelversuche durchgeführt. In ersten Experimenten bei einem pH-Wert
von 3 wurde eine Reduktion, je nach eingegebener Sulfidkonzentration, von bis zu
30 % festgestellt. Bei einem pH-Wert von 6,8 waren die Reduktionsraten deutlich
geringer. Bei einer Zugabe von Manganoxid war keine Reduktion zu As(III)
erkennenbar. Wohingegen bei der Zugabe von Eisenoxid eine gleichzeitige
Reduktion von Eisen und Arsen stattfand.
Der dritte Teil der Arbeit befasst sich mit der Freisetzung von Arsen aus
Abraumhalden von Erzminen. Um mehr über das Reaktions- und Transportverhalten
nach einer Freisetzung von Arsen zu erfahren wurden Sedimentproben aus zwei von
Minen stark beeinflussten Gebieten analysiert. Des Weiteren wurden die Proben mit
verschieden Chemikalien eluiert, um Aussagen über die Bindung und die Mobilität zu
treffen. Im ersten Untersuchungsgebiet wird das Arsen als As(V) bei hoher
Fließgeschwindigkeit des Baccu Locci Flusses partikulär an Mineralien und in Zeiten
von geringer Fließgeschwindigkeit in gelöster Form transportiert. Im zweiten
Untersuchungsgebiet wird Arsen in ein Feuchtgebiet freigesetzt und in gelöster Form
transportiert. Die Ausbreitung vom Arsen ist dabei stark von den ändernden
geochemischen Bedingungen des Feuchtgebietes abhängig. So wird es während
oxischen Bedingungen als As(V) adsorbiert und während anoxischen Bedingungen
zu As(III) reduziert und transportiert. Die Akkumulationsraten sind im zweiten
Untersuchungsgebiet deutlich geringer als im Ersten. Index of Contents
1. Introduction........................................................................................................................................ 1
2. Arsenic in the atmosphere and the aquatic cycle.......................................................................... 4
2.1. Atmospheric deposition................................................................................................................ 4
2.2. Rivers ........................................................................................................................................... 4
2.3. Lake water.................... 5
2.4. Groundwater ................................................................................................................................ 6
3. Processes concerning arsenic cycling in the environment.......................................................... 8
4. Intentions of the studies................................................................................................................. 11
4.1 Tracer test with As(V) to study transport and reaction rates in an iron-reducing environment at
the USGS Cape Cod site .................................................................................................................. 11
4.2 Mobilization of arsenic from ore and mine dumps ...................................................................... 12
4.3 Mobilization of arsenips 12
5. Arsenic speciation in the presence of dissolved sulfide ............................................................ 14
6. Summary of results......................................................................................................................... 20
6.1 Tracer test with As(V) to study transport and reaction rates in an iron-reducing environment at
the USGS Cape Cod site .................................................................................................................. 20
6.2 Arsenic reduction by dissolved sulfide at MnO and Fe O surfaces ......................................... 21 2 2 3
6.3 Mobilization of arsenic from ore and mine dumps: Two case studies from Sardinia (Italy)........ 22
7. Tracer test with Arsenic (V) to study transport and reaction rates in an iron-reducing
environment at the USGS Cape Cod Site (Mass., USA) .................................................................. 23
7.1 Abstract: ...................................................................................................................................... 23
7.2 Introduction ................................................................................................................................. 24
7.3 Materials and Methods................................................................................................................ 26
7.4 Results and Discussion............................................................................................................... 31
7.5 Conclusions................................................................................................................................. 46
7.6 Acknowledgements..................................................................................................................... 47
8. Arsenic reduction by dissolved sulfide at MnO and Fe O surfaces........................................ 48 2 2 3
8.1 Abstract ....................................................................................................................................... 48
8.2 Introduction ................................................................................................................................. 49
8.3 Materials and methods................................................................................................................ 50
8.4 Results and discussion ............................................................................................................... 52
8.5. Conclusions................. 56
8.6 Acknowledgements.......... 58
9. Mobilization of Arsenic from Ore and Mine Dumps: Two Case Studies from Sardinia (Italy). 59 9.1 Abstract ....................................................................................................................................... 59
9.2 Introduction ................................................................................................................................. 60
9.3 Description of the study areas and sampling.............................................................................. 62
9.4. Analytical methods..................................................................................................................... 66
9.5 Results and interpretation ........................................................................................................... 67
9.6 Comparison of the two Sardinian Case Studies ......................................................................... 76
9.7 Acknowledgements..................................................................................................................... 77
10. Literature ........................................................................................................................................ 78

11. Appendix……………..……………….………………………………………………..………………….A1


List of Figures

Fig. 1 a. Keratosis on the soles of an arsenic exposed Bangladeshi man. b. Black foot Disease from a
patient in Taiwan ......................................................................................................................... 1
Fig. 2 Partial Eh – pH stability diagram for dissolved arsenic species (VINK, 1996). .............................. 8
Fig. 3 Dionex series 4000i to separate As(III), As(V) and sulfide.......................................................... 15
-1Fig. 4 Separation with 3.45 g L Ammoniumdihydrogenphospahte ..................................................... 15
-1Fig. 5 Separation with 12 g Logenphospahte ........................................................ 16
-1Fig. 6 Separation with 6 g L .......................................................... 16
Fig. 7 Separation of As(III), As(V) and sulfide in 5 bottles ....................................................................17
Fig. 8 Automatic sampler collecting samples in five bottles.................................................................. 17
Fig. 9 Arsenic standards spiked with eluent.......................................................................................... 18
Fig. 10 Recovery of arsenic standards separated with IC and measured with FIAS - AAS ................. 19
Fig. 11 Test site with the 10 multilevel sampling wells ( ) and two core locations ( )..................... 27
Fig. 12 Breakthrough of bromide, nitrate and iron 1 m downstream..................................................... 34
Fig. 13 Fe and Mn concentrations in M2 (injection well) and M3. The concentrations decreased during
injection due to an input of small amounts of oxygen ............................................................... 36
Fig. 14 Map of wells with different H S intensities................................................................................. 37 2
thFig. 15 Profiles of the arsenic plumes along the flow path directly after stopping the injection at the 30
day. a) As(V) b) As(III). ............................................................................................................. 38
thFig. 16 Profiles of the arsenic plumes along the flow path at the 45 day. a) As(V); b) As(III)............. 38
thFig. 17 Profiles of the arsenic plumes alpath at the 63(III)............. 39
Fig. 18 Breakthrough curves of As(V) and As(III) measured in the injection well and in the three
sampling wells in the levels with the highest concentrations. a) M2 (2.27 m MSL) b) M3
(2.12 m MSL) c) M5 (2.24 m MSL) d) M9 (2.24 m MSL). ......................................................... 39
Fig. 19 As (tot) concentration from three cores after the sampling was stopped. C0 is a reference core
taken upstream of the test area. CM2-3 and CM5 are in the flow path of the arsenic plume .. 43
Fig. 20 As(V) concentrations accumulated in the aquifer sediment at three core locations: C0:
reference core, C2-3: between M2 and M3, C5: near M5; the four extraction methods
represent different mobilities of As(V). a) H O; b) hydroxyl ammonium chloride; c) sodium 2
ammonium hydrogen phosphate; d) HCl .................................................................................. 44
Fig. 21 Schematic model of As(V) reduction by dissolved sulfide in an iron-dominated system.......... 50
Fig. 22 As(III) production from As(V) reduction by different H S concentrations in two different setups 2
(* single container setup 2 with 500 ml bottle) .......................................................................... 53
Fig. 23 As(III) production from As(V) reduction by H S and Na S at pH 6.8......................................... 54 2 2
Fig. 24 Iron dissolution from iron oxides by sulfide ............................................................................... 55
Fig. 25 As(III) formation from arsenate reduction by sulfide on iron oxides.......................................... 55
Fig. 26 Schematic model of an iron-dominated system with sulfate reduction with possible overall
reactions.................................................................................................................................... 57
Fig. 27 Schematic map of the Baccu Locci Stream region with indication of the sampling points ....... 63 Fig. 28 Schematic map of the Palude Sa Masa region with indication of the sampling points and the
flow path.................................................................................................................................... 65
Fig. 29 Handling of the samples and analyzed parameters.................................................................. 66
Fig. 30 As(V) concentrations in the supernatant water of the BLS sediment samples ......................... 68
Fig. 31 Iron concentration extracted by hydroxyl ammonium chloride.................................................. 69
Fig. 32 Total arsenic concentrations in the sediments of the BLS ........................................................ 70
Fig. 33 Arsenic concentrations, given as percentage of the total amount, extracted from the BLS
sediments with (a) H O; (b) hydroxyl ammonium chloride; (c) sodium ammonium hydrogen 2
phosphate. Samples A and B are tailings. ................................................................................ 71
Fig. 34 (a) Arsenic release over time from a sediment sample by long-term extraction. (b) Arsenic
release over time from a tailing sample by long-term extraction. ............................................. 72
Fig. 35 Correlation between iron and arsenic in samples 1-4............................................................... 74
Fig. 36 Extracted As(V) and As(III) concentrations of the “source samples” calculated as percentage of
the total arsenic concentration. ................................................................................................. 75

List of Tables

Tab. 1 The main arsenic containing minerals.......................................................................................... 3
Tab. 2 Recovery of arsenic standards in eluent solution ...................................................................... 18
Tab. 3 Small scale hydrodynamic properties of the anoxic test site at Cape Cod estimated by the
bromide breakthrough curves ................................................................................................... 32
Tab. 4 Background geochemical conditions in the anoxic zone at the Cape Cod aquifer.................... 33
Tab. 5 Composition of the samples in the tests of As(V) reduction by dissolved sulfide at reactive
surfaces..................................................................................................................................... 51
Tab. 6 Determined rate constants for arsenate reduction by sulfide .................................................... 56
Tab. 7 Chemical composition of the supernatant water of the BLS sediment samples........................ 68
Tab. 8 Total concentrations of calcium, iron, sulfur, lead and arsenic from the four groups of the
Palude Sa Masa samples ......................................................................................................... 74