1.
Jarsjö, Jerker, et al.
(författare)
Projecting impacts of climate change on metal mobilization at contaminated sites: Controls by the groundwater level
2020
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 712
Tidskriftsartikel (refereegranskat) abstract
Heavy metal and metalloid contamination of topsoils from atmospheric deposition and release from landfills, agriculture, and industries is a widespread problem that is estimated to affect >50% of the EU's land surface. Influx of contaminants from soil to groundwater and their further downstream spread and impact on drinking water quality constitute a main exposure risk to humans. There is increasing concern that the present contaminant loading of groundwater and surface water systems may be altered, and potentially aggravated, by ongoing climate change, through large-scale impacts on recharge and groundwater levels. We investigated this issue by performing hydrogeological-geochemical model projections of changes in metal(loid) (As and Pb) mobilization in response to possible (climate-driven) future shifts in groundwater level and fluctuation amplitudes. We used observed initial conditions and boundary conditions for contaminated soils in the temperate climate zone. The results showed that relatively modest increases (0.2 m) in average levels of shallow groundwater systems, which may occur in Northern Europe within the coming two decades, can increase mass flows of metals through groundwater by a factor of 2–10. There is a similar risk of increased metal mobilization in regions subject to increased (seasonal or event-scale) amplitude of groundwater levels fluctuations. Neglecting groundwater level dynamics in predictive models can thus lead to considerable and systematic underestimation of metal mobilization and future changes. More generally, our results suggest that the key to quantifying impacts of climate change on metal mobilization is to understand how the contact between groundwater and the highly water-conducting and geochemically heterogeneous topsoil layers will change in the future.
2.
Fischer, Sandra, et al.
(författare)
Wide-spread microbial sulfate reduction (MSR) in northern European freshwater systems : drivers, magnitudes and seasonality
2023
Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 889
Tidskriftsartikel (refereegranskat) abstract
Microbial sulfate reduction (MSR), which transforms sulfate into sulfide through the consumption of organic matter, is an integral part of sulfur and carbon cycling. Yet, the knowledge on MSR magnitudes is limited and mostly restricted to snap-shot conditions in specific surface water bodies. Potential impacts of MSR have consequently been unaccounted for, e.g., in regional or global weathering budgets. Here, we synthesize results from previous studies on sulfur isotope dynamics in stream water samples and apply a sulfur isotopic fractionation and mixing scheme combined with Monte Carlo simulations to derive MSR in entire hydrological catchments. This allowed comparison of magnitudes both within and between five study areas located between southern Sweden and the Kola Peninsula, Russia. Our results showed that the freshwater MSR ranged from 0 to 79 % (interquartile range of 19 percentage units) locally within the catchments, with average values from 2 to 28 % between the catchments, displaying a non-negligible catchment-average value of 13 %. The combined abundance or deficiency of several landscape elements (e.g., the areal percentage of forest and lakes/wetlands) were found to indicate relatively well whether or not catchment-scale MSR would be high. A regression analysis showed specifically that average slope was the individual element that best reflected the MSR magnitude, both at sub-catchment scale and between the different study areas. However, the regression results of individual parameters were generally weak. The MSR-values additionally showed differences between seasons, in particular in wetland/lake dominated catchments. Here MSR was high during the spring flood, which is consistent with the mobilization of water that under low-flow winter periods have developed the needed anoxic conditions for sulfate-reducing microorganisms. This study presents for the first time compelling evidence from multiple catchments of wide-spread MSR at levels slightly above 10 %, implying that the terrestrial pyrite oxidation may be underestimated in global weathering budgets.
3.
Destouni, Georgia, 1961-, et al.
(författare)
Needs and means to advance science, policy and management understanding of the freshwater system : A synthesis report
2015
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Fragmented and inconsistent understanding of the freshwater system limits our ability to achieve water security and sustainability under the human-driven changes occurring in the Anthropocene. To advance system-level understanding of freshwater, gaps and inconsistencies in knowledge, data, representations and links of processes and subsystems need to be identified and bridged under consideration of the freshwater system as a continuous whole. Based on such identification, a freshwater system conceptualization is developed in this report, which emphasizes four essential, yet often neglected system aspects:i) Distinction of coastal divergent catchments.ii) Four main zones (surface, subsurface, coastal, observation) of different types of freshwater change.iii) Water pathways as system-coupling agents that link and partition water change among the four change zones.iv) Direct interactions with the anthroposphere as integral system pathways across the change zones.We explain and exemplify some key implications of these aspects, identifying in the process also distinct patterns of human-driven changes in large-scale water fluxes and nutrient loads.The present conceptualization provides a basis for common inter- and trans-disciplinary understanding and systematic characterization of the freshwater system function and its changes, and of approaches to their modeling and monitoring. This can be viewed and used as a unifying checklist that can advance science, policy and management of freshwater and related environmental changes across various scales and world regions.
4.
Hambäck, Peter A., et al.
(författare)
Tradeoffs and synergies in wetland multifunctionality : A scaling issue
2023
Ingår i: Science of the Total Environment. - Amsterdam : Elsevier BV. - 0048-9697 .- 1879-1026. ; 862
Forskningsöversikt (refereegranskat) abstract
Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale.
5.
Mbanguka, René P., et al.
(författare)
Water Balance and Level Change of Lake Babati, Tanzania : Sensitivity to Hydroclimatic Forcings
2016
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 8:12
Tidskriftsartikel (refereegranskat) abstract
We develop and present a novel integrated water balance model that accounts for lake watergroundwater interactions, and apply it to the semi-closed freshwater Lake Babati system, Northern Tanzania, East Africa. The model was calibrated and used to evaluate the lake level sensitivity to changes in key hydro-climatic variables such as temperature, precipitation, humidity and cloudiness. The lake response to the Coupled Model Intercomparison Project, Phase 5 (CMIP5) output on possible future climate outcomes was evaluated, an essential basis in understanding future water security and flooding risk in the region. Results show high lake level sensitivity to cloudiness. Increased focus on cloud fraction measurement and interpretation could likely improve projections of lake levels and surface water availability. Modelled divergent results on the future (21st century) development of Lake Babati can be explained by the precipitation output variability of CMIP5 models being comparable to the precipitation change needed to drive the water balance model from lake dry-out to overflow; this condition is likely shared with many other East African lake systems. The developed methodology could be useful in investigations on change-driving processes in complex climatedrainage basinlake systems, which are needed to support sustainable water resource planning in data scarce tropical Africa.
6.
Sjöberg, Ylva, 1982-, et al.
(författare)
Scaling relations reveal global and regional differences in morphometry of reservoirs and natural lakes
2022
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 822
Tidskriftsartikel (refereegranskat) abstract
Water bodies provide essential ecosystem services linked to morphometric features that might differ between natural lakes and reservoirs. We use the HydroLAKES global dataset to quantitatively compare large (area > 1 km(2)) reservoirs and natural lakes in terms of scaling exponents between morphometric measures (volume, area, shore length). These exponents are further compared to those expected from geometrical assumptions and constraints. Lakes cover a larger range of volumes for the same range of surface areas than reservoirs, and have a larger volume-area scaling exponent. The volume-area scaling exponent for reservoirs (but not natural lakes) and the area-shore length exponent for all water bodies follow the predictions for self-affine surfaces. Land cover and terrain influence the scaling relations more for lakes than for reservoirs. These morphometric differences may be used to model the impact of reservoirs and lakes on hydrological processes and associated ecosystem services at regional to global scales.
7.
Alekseeva, I., et al.
(författare)
Reconstruction of historic changes of the Aral Sea water budget and sea-groundwater interactions by a coupled 3D sea-ice-groundwater model
2007
Ingår i: Geophysical Research Abstracts, Vol. 9, 10629, 2007.
Konferensbidrag (övrigt vetenskapligt/konstnärligt) abstract
A 3D coupled sea-ice-groundwater model has been developed and applied for an estimation of the water balance and groundwater-seawater interactions in the shrinking Aral Sea. The model developed combines the complete 3D sea-ice hydrodynamics model ECOSMO, including a mass and energy conserving wetting and drying scheme, and a simple groundwater model based on changes in hydraulic gradient in response to the sea surface variability. During the simulation period 1979-1993, the model successfully reproduced the rapid Aral Sea level drop, surface area decrease, coastline position changes and salinization. Model predictions of evaporation and groundwater inflow were also consistent with independent estimations. Model results indicated that within the 15 years period of simulations the net groundwater inflow to the Aral Sea might have increased by 10% or more as a direct effect of the sea level lowering.Furthermore, model scenario tests were carried out to examine effects of salinity on sea hydrodynamics and to estimate non-linear feedbacks of the sea thermo- and hydrodynamics, air-sea turbulent fluxes and the sea water balance. It was shown that a neglect of salinity in the sea hydro- and thermo dynamics resulted in considerable differences in the Aral Sea winter thermal conditions, which in turn influenced the air-sea exchange in the following spring and summer. As a result, the zero salinity scenario predicted higher evaporation rates and an considerably accelerated sea level lowering by up to 2 cm/yr, in comparison with the basic model run. An indirect influence of the fresh groundwater inflow in terms of water balance has been identified as less significant, however it was shown that the fresh groundwater input could influence the Aral Sea salinity distribution considerably since 1990’s.
8.
Cao, Feifei, et al.
(författare)
Large-scale arsenic mobilization from legacy sources in anoxic aquifers : Multiple methods and multi-decadal perspectives
2023
Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 892
Tidskriftsartikel (refereegranskat) abstract
While geogenic arsenic (As) contamination of aquifers have been intensively investigated across the world, the mobilization and transport of As from anthropogenic sources have received less scientific attention, despite emerging evidence of poor performance of widely used risk assessment models. In this study we hypothesize that such poor model performance is largely due to insufficient attention to heterogeneous subsurface properties, including the hydraulic conductivity K and the solid-liquid partition (Kd), as well as neglect of laboratory-to-field scaling effects. Our multi-method investigation includes i) inverse transport modelling, ii) in-situ measurements of As concentrations in paired samples of soil and groundwater, and iii) batch equilibrium experiments combined with (iv) geochemical modelling. As case study we use a unique 20-year series of spatially distributed monitoring data, capturing an expanding As plume in a Chromated Copper Arsenate (CCA)-contaminated anoxic aquifer in southern Sweden. The in-situ results showed a high variability in local Kd values of As (1 to 107 L kg−1), implying that over-reliance of data from only one or few locations can lead to interpretations that are inconsistent with field-scale As transport. However, the geometric mean of the local Kd values (14.4 L kg−1) showed high consistency with the independently estimated field-scale “effective Kd” derived from inverse transport modelling (13.6 L kg−1). This provides empirical evidence for the relevance of using geometric averaging when estimating large-scale “effective Kd” values from local measurements within highly heterogenous, isotropic aquifers. Overall, the considered As plume is prolonged by about 0.7 m year−1, now starting to extend beyond the borders of the industrial source area, a problem likely shared with many of the world's As-polluted sites. In this context, geochemical modelling assessments, as presented here, provided a unique understanding of the processes governing As retention, including local variability in, e.g., Fe/Al-(hydr)oxides contents, redox potential and pH.
9.
Shibuo, Yoshihiro, et al.
(författare)
Hydrologic responses to climatic changes and irrigation expansion within the Aral Sea basin
2007
Ingår i: Geophysical Research Abstracts, Vol. 9, 09963, 2007.
Konferensbidrag (övrigt vetenskapligt/konstnärligt) abstract
Quantitative understanding of the Aral Sea’s water budget and its dynamics is not straightforward because the magnitude of groundwater discharge into the sea is very uncertain. From a catchment-scale water balance perspective, groundwater recharge may be approximately estimated by closing the water balance equation and treating the groundwater term as a fitting parameter. However, then the predicted groundwater flow can be considerably affected by the estimated evapotranspiration, which is also uncertain due to measurement difficulties.Furthermore, in the specific case of the Aral Sea, evapotranspiration and groundwater recharge may have changed considerably in the past decades, due to the enormous expansion of irrigation in the region. We here aim at quantifying changes in total discharge into the Aral Sea by using GISbased, basin scale hydrological modeling. Aral Sea catchments are delineated based on elevation data. This allows us to quantify unmonitored discharges as well as Amu Darya and Syr Darya river runoff. Then we investigate how the hydrological system has responded to the observed climatic changes and anthropogenic activities, through scenario analyses. From observed temperature and precipitation data, we reproduce representative hydrological conditions in the beginning of the last century, before the intensive irrigation started, and in the end of the last century, after a considerable Aral Sea shrinkage. The impact of anthropogenic activities is considered by adding an irrigation unit to the model.Our model results reveal physically different characteristics between Amu Darya and Syr Darya catchments, and comparisons of model scenarios show considerably increased evapotranspiration within the basin, suggesting that most of the irrigation water does not add to groundwater flows.
10.
Thorslund, Josefin, et al.
(författare)
Speciation and hydrological transport of metals in non-acidic river systems of the Lake Baikal basin : Field data and model predictions
2017
Ingår i: Regional Environmental Change. - : Springer Science and Business Media LLC. - 1436-3798 .- 1436-378X. ; 17:7, s. 2007-2021
Tidskriftsartikel (refereegranskat) abstract
The speciation of metals in aqueous systems is central to understanding their mobility, bioavailability, toxicity and fate. Although several geochemical speciation models exist for metals, the equilibrium conditions assumed by many of them may not prevail in field-scale hydrological systems with flowing water. Furthermore, the dominant processes and/or process rates in non-acidic systems might differ from well-studied acidic systems. We here aim to increase knowledge on geochemical processes controlling speciation and transport of metals under non-acidic river conditions. Specifically, we evaluate the predictive capacity of a speciation model to novel measurements of multiple metals and their partitioning, under high-pH conditions in mining zones within the Lake Baikal basin. The mining zones are potential hotspots for increasing metal loads to downstream river systems. Metals released from such upstream regions may be transported all the way to Lake Baikal, where increasing metal contamination of sediments and biota has been reported. Our results show clear agreement between speciation predictions and field measurements of Fe, V, Pb and Zn, suggesting that the partitioning of these metals mainly was governed by equilibrium geochemistry under the studied conditions. Systematic over-predictions of dissolved Cr, Cu and Mo by the model were observed, which might be corrected by improving the adsorption database for hydroxyapatite because that mineral likely controls the solubility of these metals. Additionally, metal complexation by dissolved organic matter is a key parameter that needs continued monitoring in the Lake Baikal basin because dependable predictions could not be made without considering its variability. Finally, our investigation indicates that further model development is needed for accurate As speciation predictions under non-acidic conditions, which is crucial for improved health risk assessments on this contaminant.
