The limnic ecosystems at Forsmark and Laxemar-Simpevarp

562 Pages·2011·30.81 MB·English

by  Eva Andersson

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Svensk Kärnbränslehantering AB
Swedish Nuclear Fuel
and Waste Management Co
Box 250, SE-101 24 Stockholm
Phone [phone]
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ISSN 1404-0344
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SKB TR-10-02
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ID 1273126
Updated 2013-01
The limnic ecosystems at Forsmark
and Laxemar-Simpevarp
Eva Andersson, Svensk Kärnbränslehantering AB
December 2010
Keywords: Lakes, Streams, Ecosystem model, Interaction matrix.
A pdf version of this document can be downloaded from www.skb.se
Update notice
The original report, dated December 2010, was found to contain both factual and editorial errors
which have been corrected in this updated version. The corrected factual errors are presented below.
Updated 2011-10
Location Original text Corrected text
Page 384, Table 11-3 Mean 122.7 Mean 126
Max 150 Max 220
Min 71.7 Min 72
n 9 n 8
Page 387, Table 11-10 Mean 166,7 Mean 138
Max 256,3 Max 256
Min 71,7 Min 72
Std 38,2 Std 38
n 35 n 12
Page 388, Table 11-12 Mean 0.94 Mean 0.93
Min 0.92 Min 0.90
Std 0.07 Std 0.02
n 14 n 7
Page 388, Table 11-13 Mean 662.0 Mean 663
Max 662 Max 664
Min 662.0 Min 662
n 7 n 3
Page 388, Table 11-14 Mean 0.96 Mean 0.64
n 14 n 10
Page 389, Table 11-16 Mean 2,110 Mean 2,132
Max 2,300 Max 2,200
Min 1,900 Min 1,980
Std 110 Std 87
N 18 n 5
Page 389, Table 11-17 Mean 0.25 Mean 0.21
Max 0.42 Max 0.27
Min 0.075 Min 0.18
Std 0,05 Std 0.04
n 15 n 4
Updated 2013-01
Location Original text Corrected text
Page 432, reference Avila and Models used in the SFR 1 Models used in the SFR 1 SAR-08
Pröhl 2008 SAR-08 and KBS-3H safety and KBS-3H safety assessments for
assessments for calculation of calculation of 14C doses. SKB R-08-16,
14C doses. Svensk Kärnbränslehantering AB.
Page 440, reference Larsson- SKB R-02-03 SKB TR-02-03
McCann et al. 2002
Page 440, reference Lundin SKB R-08-04 SKB R-04-08
et al. 2004
Summary
The overall objective of this report is to describe the limnic ecosystems at Forsmark and Laxemar-
Simpevarp, identify important processes in a radionuclide perspective and provide a description of
the radionuclide model for the biosphere used in SR-Site.
The report includes a thorough description of the lakes and streams in Forsmark and Laxemar-
Simpevarp and covers the following areas: catchment area characteristics, hydrology, climate,
sediment characteristics, physical characteristics of streams, habitat distribution in lakes, biotic
components (biomass as well as production), water chemistry, and comparison with other lakes and
streams in the region, and a historical description. Ecosystem models for carbon and mass balances
for a number of elements have been calculated to further improve the understanding of the lake
ecosystems. Important processes for the safety assessment are described and evaluated in the report.
A separate chapter is included to specifically describe how and where these processes are included
in the radionuclide model. The radionuclide model is described and parameterisation and guidance
to parameter calculation is provided. The last chapter of the report provides a summary of the
knowledge of the limnic systems at the two areas.
The Forsmark regional model area contains more than 25 permanent lakes and pools. All lakes are
small and shallow, and are characterized as oligotrophic hardwater lakes. Calcareous soils in the
area give rise to high calcium concentrations in the surface water, which in turn leads to high pH
and low nutrient concentrations in water as phosphorus often co-precipitates with calcium. The
shallow depths and moderate water colour permit photosynthesis in the entire benthic habitat of the
lakes, and the bottoms are covered by dense stands of the macroalgae Chara sp. Moreover, many of
the lakes also have a thick microbial mat (>10 cm), consisting of cyanobacteria and diatoms, in the
benthic habitat. Fish in the lakes are dominated by species resistant to low oxygen concentrations,
mainly due to poor oxygen conditions during the winter. The streams in Forsmark are all very small,
and long stretches of the streams are dry during summer. The downstream parts of some of the
streams may function as passages for migrating fish, and extensive spawning migration between the
sea and a lake has been observed. Human activities in the area have affected the limnic ecosystem,
and large parts of the streams in the Forsmark area consist of man-made ditches. Moreover, one of
the lakes has been lowered and one has been divided into two basins.
The ecosystem carbon models for the Forsmark area show that the lakes that contain a microbial mat
have larger primary production than respiration, and thus show a positive net ecosystem production
(NEP). In lakes that lack a microbial mat, respiration is similar in magnitude as primary production
and net ecosystem production is close to zero. Carbon mass balance models for the Forsmark lakes
indicate, in accordance with the ecosystem models, that the larger lakes (with a microbial mat) in the
area have a positive NEP. However, in contrast to the ecosystem models, the mass balance models
indicate that the smaller lakes in the area have negative NEP, regardless of the occurrence of a
microbial mat. A low proportion (7–10%) of the carbon incorporated into primary producers in the
lake is transported upwards in the food web, and instead most carbon is consumed by bacteria in the
form of DOC and POC. The mass balances for a number of elements in Forsmark lakes show that
the proportions of different fluxes to and from the lakes are dependent on lake size and position in
the catchment, but also on the specific properties of the different elements.
A total of 6 lakes are situated partly or entirely within the regional model area of Laxemar-
Simpevarp. The Laxemar-Simpevarp lakes are small and all but one are characterized as brown-
water lakes. The lakes have moderate phosphorus concentrations, whereas the concentrations of
nitrogen and dissolved organic carbon tend to be high. Because of the brownish water, light penetra-
tion is poor and the depth of the photic zone is generally small. In accordance, macrophyte coverage
in the lakes is small and biota is dominated by heterotrophic organisms, particularly bacteria. Perch
is the predominant fish species in numbers, as well as in weight, in the lakes in the area. Most of
the streams in the Laxemar-Simpevarp area are small with mostly calm or slowly flowing water
and many of the streams have dry sections in the summer. Most lakes in the Laxemar-Simpevarp
area are affected by human activities; the water level in most lakes has been lowered, and one lake,
Söråmagasinet, was originally a sea bay but was dammed in order to ensure freshwater reserves to
TR-10-02 3
the nuclear power plant. Water is pumped from Laxemarån to Söråmagasinet in order to maintain the
available water storage in the lake.
Both the carbon ecosystem model and the mass balance for Lake Frisksjön in Laxemar-Simpevarp
indicate a negative NEP, i.e. higher respiration than primary production. The carbon mass balance
show that the lake receives large inputs of organic matter and that these inputs are to a large extent
mineralized to CO and emitted to the atmosphere. A large part of the carbon influx also contributes
2
to sediment accumulation in the lake. The annual amount of carbon transported to the lake via inflow
is of the same magnitude as the internal processes of primary production and consumption, and
there is a large probability that carbon entering the lake will be incorporated into the lake food web.
A relatively large part of the primary produced carbon (34%) is transported upwards in the food
web. Mass balances for a number of elements indicate that, in general, the most important influx
of different elements to the lake is via surface water and the most important outflux is via sediment
accumulation.
Interactions between different components of ecosystems have been listed in an interaction matrix.
In total, 51 processes are listed in the interaction of which 34 were identified as important to con-
sider in the safety analysis SR-Site. Accordingly, these processes are considered in the radionuclide
model. A description of the radionuclide model for the biosphere is provided together with a descrip-
tion of parameters used in the model. Calculations of limnic parameters are thoroughly described
and references are given to the reports where calculations of other parameters are described.
In conclusion, this report covers a description of the limnic ecosystems at Forsmark and Laxemar-
Simpevarp that has been applied on the SR-Site safety assessment but that also may be applied on
future safety analysis. In addition, important processes to consider in radionuclide modelling of the
biosphere are identified and the radionuclide model for the biosphere used in SR-Site is described.
4 TR-10-02
Contents
1 Introduction 11
1.1 Background 11
1.2 Aims 13
2 This report 15
2.1 This report in a broader context 15
2.2 Report content 16
2.3 Definitions 17
2.3.1 Model area 17
2.3.2 Delimitations of the ecosystems and common terms 17
3 Description of lakes and streams in the Forsmark area 21
3.1 General description of the lakes and streams 21
3.2 Catchment characteristics 22
3.3 Hydrology 25
3.3.1 Discharge 25
3.3.2 Water levels in lakes 29
3.3.3 Groundwater discharge/recharge 29
3.3.4 Inflow of marine water to lakes 30
3.3.5 Flooded areas 32
3.4 Climate 33
3.4.1 Air temperature 33
3.4.2 Precipitation 34
3.4.3 Snow cover 35
3.4.4 Ice cover 36
3.4.5 Global radiation 36
3.5 Lake bathymetry 37
3.6 Lake sediments 39
3.6.1 Stratigraphy 39
3.6.2 Redox zone 40
3.6.3 Carbon content 40
3.6.4 Sedimentation, resuspension and long term accumulation 42
3.6.5 Chemical composition 43
3.7 Habitat distribution in the lakes 45
3.8 Physical characteristics of streams 47
3.8.1 Bottom substrate 48
3.8.2 Morphometry 48
3.8.3 Shading 49
3.9 Hydrochemical characteristics of lakes, streams and shallow groundwater 50
3.9.1 Water chemistry in lakes 51
3.9.2 Water chemistry in streams 58
3.9.3 Chemistry in groundwater 64
3.10 Biota 68
3.10.1 Biota in lakes 68
3.10.2 Biota in streams 78
3.10.3 Threatened species in lakes and streams 82
3.10.4 Edible biota in lakes and streams 83
3.10.5 Chemical characteristics of biota 84
3.11 Land use and human impact 87
3.11.1 Human impact on lakes 87
3.11.2 Human impact on streams 87
3.12 Streams and lakes in the region 88
3.12.1 Lakes 88
3.12.2 Streams 103
3.13 Confidence and uncertainties in site data 106
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4 Description of lakes and streams in the Laxemar‑Simpevarp area 111
4.1 General description of the lakes and streams 111
4.2 Catchment characteristics 112
4.3 Hydrology 114
4.3.1 Discharge 114
4.3.2 Water levels in lakes 116
4.3.3 Groundwater discharge/recharge 117
4.3.4 Flooded areas 118
4.4 Climate 118
4.4.1 Air temperature 119
4.4.2 Precipitation 119
4.4.3 Snow cover 120
4.4.4 Ice cover 121
4.4.5 Global radiation 121
4.5 Lake bathymetry 122
4.6 Lake sediments 124
4.6.1 Stratigraphy 124
4.6.2 Redox zone 125
4.6.3 Carbon content, accumulation rate and chemical composition 125
4.7 Habitat distribution in the lakes 128
4.8 Physical characteristics of streams 129
4.8.1 Bottom substrate 130
4.8.2 Morphometry 130
4.8.3 Shading 131
4.9 Hydrochemical characteristics of lakes, streams and shallow groundwater 131
4.9.1 Water chemistry in lakes 131
4.9.2 Water chemistry in streams 138
4.9.3 Chemistry in groundwater 144
4.10 Biota 147
4.10.1 Biota in lakes 147
4.10.2 Biota in streams 153
4.10.3 Edible biota in lakes and streams 157
4.10.4 Chemical characteristics of biota 158
4.11 Land use and human impact 161
4.11.1 Human impact on lakes 161
4.11.2 Human impact on streams 163
4.12 Lakes in the region 163
4.13 Confidence and uncertainties in site data 164
5 The lake ecosystem – conceptual and quantitative carbon models 169
5.1 Conceptual models 169
5.1.1 Carbon mass balances 169
5.1.2 Ecosystem carbon models 171
5.2 Model parameterization for the mass balances 174
5.2.1 Carbon influx from the catchment via water (TOC , DIC ) 174
IN IN
5.2.2 Carbon influx/exchange with the atmosphere (DOC and CO ) 175
DEP 2FLUX
5.2.3 Carbon outflux by sediment accumulation (TC ) 176
SED
5.2.4 Carbon outflow via water (TOC + DIC ) 177
OUT OUT
5.2.5 Carbon outflux by birds feeding in the lake (TC ) 177
BIRD
5.3 Model parameterization for ecosystem models 178
5.3.1 Abiotic carbon pools 178
5.3.2 Biomass 178
5.3.3 Primary production 181
5.3.4 Respiration 182
5.3.5 Consumption 183
5.4 Quantitative mass balances and ecosystem carbon models 184
5.4.1 Lakes in Forsmark 184
5.4.2 Lakes in Laxemar-Simpevarp 198
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5.5 Conclusions from the carbon models 202
5.5.1 Forsmark 202
5.5.2 Laxemar-Simpevarp 205
5.5.3 Comparison between Forsmark and Laxemar-Simpevarp 205
5.6 Confidence and uncertainties 206
5.6.1 Forsmark 206
5.6.2 Laxemar-Simpevarp 209
6 The stream ecosystem – conceptual model and model assumptions
for carbon 213
6.1 Habitats and functional groups 213
6.1.1 Primary producers 213
6.1.2 Consumers 214
6.1.3 Transport and accumulation in stream ecosystems 214
7 Pools and fluxes of different chemical elements into, out of
and within lakes 215
7.1 Conceptual model and model assumptions 215
7.1.1 Elements considered in the evaluation 216
7.2 Model parameterization 217
7.2.1 Chemical composition of biotic and abiotic components 217
7.2.2 Mass balances 219
7.3 Evaluation of elemental pools and fluxes for a number of elements
in Forsmark 221
7.3.1 Chemical composition of different ecosystem components 221
7.3.2 Mass balances 225
7.3.3 Detailed description of phosphorus pools and mass balances 228
7.3.4 Detailed description of pools and mass balances of iodine,
uranium and thorium 231
7.4 Evaluation of elemental pools and fluxes for a number of elements
in Laxemar-Simpevarp 235
7.4.1 Chemical composition of different ecosystem components 235
7.4.2 Mass balances 240
7.4.3 Detailed description of phosphorus pools and mass balances 243
7.4.4 Pools and mass balances for iodine, thorium and uranium 245
7.5 Comparison of element pools and fluxes between Forsmark and the
Laxemar-Simpevarp lakes 247
7.5.1 Pools of elements in different components of the lake ecosystems 247
7.5.2 Fluxes of elements 248
7.6 Confidence and uncertainties in the mass balance results 248
7.6.1 Forsmark 248
7.6.2 Laxemar-Simpevarp 250
8 Long‑term development of lakes and streams 253
8.1 Shoreline displacement 254
8.2 Successional processes 255
8.2.1 Successional processes in lakes in the Forsmark area 257
8.3 Climate change 259
8.3.1 Climate cases 259
8.3.2 Climate conditions during different climate domains 260
8.3.3 Ecosystem functioning in different climate domains 263
8.3.4 Transitions between different climate domains 275
8.4 Historical development 275
8.4.1 The Forsmark area 275
8.4.2 The Laxemar-Simpevarp area 277
8.5 Future development of limnic systems in the Forsmark area 279
8.5.1 Future lakes 279
8.5.2 Future streams 286
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9 Important processes for transport and accumulation of radionuclides
– a comparison with the radionuclide model 289
9.1 Introduction 289
9.2 Concept of the interaction matrix 290
9.3 The limnic/marine/terrestrial interaction matrices 290
9.4 Diagonal elements in the interaction matrix 296
9.5 Processes in the interaction matrix 298
9.6 Interactions in the ecosystems 302
9.7 Concluding discussion 364
10 The radionuclide model for derivation of landscape dose
conversion factors (LDF) 367
10.1 Source terms 367
10.2 The conceptual model 368
10.2.1 Temporal development of biosphere objects 370
10.2.2 Releases to drilled wells 372
10.2.3 Modelling spatial distribution of radionuclides in the landscape 372
10.3 The mathematical model 373
10.3.1 Calculation of activity concentrations in the environment 374
10.4 Exposure assessments 375
10.4.1 Exposure from external irradiation and inhalation 376
10.4.2 Exposure from water consumption 376
10.4.3 Exposure from food consumption 376
11 Radionuclide model parameterization 379
11.1 Reader’s guide to parameter calculation 379
11.1.1 Parameter statistics and representation 379
11.1.2 Future conditions 381
11.2 The limnic biosphere object in Forsmark 381
11.2.1 Lakes 381
11.2.2 Streams 382
11.3 Dose model parameterization for Forsmark 382
11.3.1 Regolith parameters 382
11.3.2 Hydrological and meteorological parameters 390
11.3.3 Chemical and biological parameters 394
11.3.4 Human food parameters 405
11.4 Dose model parameterisation for Laxemar-Simpevarp 408
11.4.1 Regolith parameters 408
11.4.2 Hydrological parameters 412
11.4.3 Chemical and biological parameters in Laxemar 413
11.4.4 Human food parameters 418
11.5 Uncertainties in the parameterization 419
11.5.1 Spatial and temporal variation 419
11.5.2 Future conditions 420
12 Concluding descriptions of the limnic ecosystems in Forsmark and
Laxemar‑Simpevarp and comparison between the two areas 421
12.1 Characterization of the limnic ecosystems in Forsmark and
Laxemar-Simpevarp 421
12.1.1 Lake size and influence of the catchment 421
12.1.2 Water chemistry 422
12.1.3 Biota 423
12.2 Major pools, fluxes and sinks of elements in the lake ecosystems 424
12.2.1 Pools of elements 424
12.2.2 Fluxes within the lake ecosystems 425
12.2.3 Fluxes to and from the lake ecosystems 425
12.2.4 Sinks of elements 426
12.3 Human impact on the limnic ecosystem 426
12.4 Long-term development of lakes 427
12.5 Processes of importance to the safety assessment SR-Site 428
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13 References 431
Appendix 1 Map Forsmark 449
Appendix 2 Map Laxemar-Simpevarp 451
Appendix 3 Input data table 453
Appendix 4 Species list 455
Appendix 5 Fish histograms 461
Appendix 6 Available data for models 473
Appendix 7 Chemical composition of the dissolved fractions of water 479
Appendix 8 Chemical composition of the particulate component of water 483
Appendix 9 Chemical composition in the sediment component 485
Appendix 10 Chemical composition of the biotic component 489
Appendix 11 Pools of elements per unit area 495
Appendix 12 Fluxes of elements 501
Appendix 13 Equations in the radionuclide model for the biosphere 513
Appendix 14 Parameters in the radionuclide model for the biosphere 573
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