Trac (e) ing geochemical processes and pollution in groundwater
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0 1 10 L i -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 0 0 1 10 Be 1 10 100 1000 B 0 1 101001000 10000 100000 Al 1000 1 0 0 0 01 0 0 0 0 0 1000000 Ca 0 0 1 T i 0 1 10 100 1000 Mn -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 1 0 10 0 1 0 0 01 0 0 0 0 1 0 00 0 0 F e 0 0 1 10 Co 0 0 1 10 100 Ni 0 1 10 Cu 1 10 100 Z n 0 0 1 10 100 As -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 1 10 Se 0 0 1 10 Rb 1 0 1 0 0 1 0 0 0 Sr 0 0 0 1 10 100 Y 0 0 0 1 Z r 0 0 0 1 10 100 Mo -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 0 0 1 Ag 0 0 0 0 1 10 Cd 0 0 0 0 1 Sn 0 0 0 1 Sb 0 0 0 1 Cs 0 0 0 0 Hf -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 0 1 10 Pb 0 0 0 0 Bi 0 0 0 0 1 T h 0 0 0 1 10 U 0 0 0 0 0 0 1 Eu 0 1 10 L i -4 5 -4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 0 Be 0 1 10 100 B 0 1 10 100 Al 10000 100000 1000000 Ca 0 0 1 10 T i 0 0 1 10 Cr 1 0 1 0 0 1 0 0 0 Mn -4 5 -4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 1000 10000 F e 0 0 1 Co 0 0 1 10 Ni 0 0 1 10 Cu 1 10 100 Z n 0 1 10 Ga 0 0 0 1 10 As -4 5 -4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 1 10 Se 0 1 10 Rb 10 1 0 0 1 0 0 0 Sr 0 0 1 Y 0 0 0 1 10 Z r 0 0 0 1 Nb 0 0 1 10 Mo -4 5 -4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 0 0 0 Ag 0 0 0 0 0 1 Cd 0 0 0 0 1 Sn 0 0 0 Sb 0 0 0 Cs 1 0 1 00 1 0 0 0 Ba 0 0 0 0 0 Hf -4 5 -4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -1 0 -5 0 5 0 0 1 Pb 0 0 0 0 Bi 0 0 0 0 0 T h 0 0 0 0 U 0 0 0 0 Eu 0 0 0 1 L a Trac Trac (e) (e) ing geochemical ing geochemical processes and pollution processes and pollution in groundwater in groundwater M.J.M. Vissers P.F.M. van Gaans S.P. Vriend
description
Trac (e) ing geochemical processes and pollution in groundwater. M.J.M. Vissers P.F.M. van Gaans S.P. Vriend. Multilevel wells have advantages over single level GWQ networks when studying trace elements. Many geochemical processes + The dynamic behavior of groundwater + - PowerPoint PPT Presentation
Transcript of Trac (e) ing geochemical processes and pollution in groundwater
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TracTrac(e)(e)ing geochemical processes ing geochemical processes and pollution in groundwaterand pollution in groundwater
M.J.M. Vissers
P.F.M. van Gaans
S.P. Vriend
Multilevel wells have advantages over single level GWQ networks when studying
trace elements
• Many geochemical processes +• The dynamic behavior of groundwater +• Changes in input (anthropogenic influence) i.e.
no steady state +• (Analytical / sampling errors )
I will show this by presenting:
Study area and processes that (may) occur
Two example elements– Rubidium– Uranium
Study area and processes Map of the study area
Sandy, unconsolidated aquifer, with ice-pushed ridge in the east Mainly Agricultural land use, eastern part cultivated in the 1920’s 10 Borings, total of 244 mini screens
NZwolle
Deventer
210 212 214 216 218 220 222 224
482
484
486
A1A2A3A4A5
A6
A7A8
A10
A11
Heeten
Wesepe
HaarleBroekland
Village ForestH eather
X -coord ina te
Y-c
oord
ina
te
G rass / agricultu re
++
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Boring with mini well screens
Calcite saturated waters
NO3/Fe redox boundary
SO4 redox boundary
Groundwater level
Streamlines
Pine / deciduous forest
Arable land (mostly corn)
2 km
Clay
Clay
A5A10
Study area and processes Cross-section of the study area
Filtrated over 0.45μm, analyzed on ICP-MS Sampled in 1989 (no trace elements), 1996 (½), and 2002 (all) Randomly analyzed on > 70 inorganic components and DOC
Study area and processes Processes and number of observed boundaries
> 60 11 9 4 5
Pollution / changes in inputIron reductionMn reduction
Sulphate reductionpH changes / carbonate bufferingMineral Dissolution / Precipitation
Coprecipitation / CodissolutionAdsorption / Desorption
KineticsAnalytical problems
In m
ajor
ele
men
ts
Rubidium and Uranium Two example elements
• Rubidium: “No” mineral phases, input from either recharge or sediment, and adsorption processes are expected to play role
• Uranium: Many saturation phases, depending on redox conditions.
What is needed for interpretation?• Concentration – depth profiles of trace element• Knowledge derived from macro-chemistry• Geochemical knowledge
RubidiumConcentration (μg/l) - depth profiles of all borings
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A 1
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0 1 10A 2
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A 3
0 1 10A 4
0 1 10
A 5
0 1 10A 6
0 1 10 100
A 7
0 1 10A 8
0 1 10
A10
0 1 10A11
Legend
2002
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“Noisy profiles”Base level
RubidiumInput and adsorption, and influence of pH and redox in boring A7
• Rubidium 0.3 μg/l in pristene water• Adsorption plays a role (retention): boring A5 and A8• Input by recharge (up to 100 μg/l)• No (direct) influence of redox and pH boundaries
0 0 0 1 10
B e
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C s
0 0 1 10S b
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F e
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R b
1 0 1 0 0 1 0 0 0H f
468p H
“Ox”Red
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U3O8(C)
U4O9(C)
UO2(am)
Uraninite
USiO4(C)
MnNO3FeSO4
UraniumSI – Eh dependence of a 6 ppb groundwater
Log
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n in
dex Eh (mv)
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0.01 0.1 1 10A2
0.01 0.1 1 10
A3
0.01 0.1 1 10
A70.01 0.1 1 10
A100.01 0.1 1
A10.01 0.1 1 10
A5
0.01 0.1 1A11
UraniumConcentration (μg/l) – depth profiles of all borings
0.01 0.10A4
0.01 0.10A6
0.01 0.10A8
Low concentrations as complete boring is reduced: Uraninite
U (µg/l)
Uranium
0.01 0.1 1
A10.01 0.1 1 10
A5
0.01 0.1 1A11
Oxic waters: Undersaturation, concentrations determined by recharge
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0.01 0.1 1 10A2
0.01 0.1 1 10
A3
0.01 0.1 1 10
A70.01 0.1 1 10
A10
U (µg/l)
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0.01 0.1 1 10A2
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A3
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A70.01 0.1 1 10
A10
Uranium
High concentrations, not related to input
U (µg/l)
UraniumConcentration – depth profiles of boring A7 in μg/l
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p Hμ
Uranium
• Iron reduced waters have concentrations of 0.001 – 0.05 μg/l (uraninite saturation)
• Input in recently recharged water: 0.1μg/l• In deeper oxic water lower concentrations are found• At reduction boundary (manganese reduced) concentrations
reach 1 – 8 μg/l• Source is the sediment
Conclusions
In the examples, multilevel wells give possibility to:– Determine background concentration for Rb– Exclude redox and pH as important process for Rb– Show input and retention are important for Rb– Accuratly determine redox zone of high U– Exclude pollution as potential U-source– Estimate input of U from recharge and from sediment
Conclusions II
• Even with the help of multilevel wells, it is hard to determine trace element systematics
