| 1. |
- Björkvald, Louise, et al.
(författare)
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Hydrogeochemistry of Fe and Mn in small boreal streams : The role of seasonality, landscape type and scale
- 2008
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 72:12, s. 2789-2804
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Tidskriftsartikel (refereegranskat)abstract
- Stream water from a stream network of 15 small boreal catchments (0.03–67 km2) in northern Sweden was analyzed for unfiltered (total) and filtered (<0.4 μm) concentrations of iron (Fetot and Fe<0.4) and manganese (Mntot and Mn<0.4). The purpose was to investigate the temporal and spatial dynamics of Fe, Mn and dissolved organic carbon (DOC) as influenced by snow melt driven spring floods and landscape properties, in particular the proportion of wetland area. During spring flood, concentrations of Fetot, Fe<0.4, Mntot, Mn<0.4 and DOC increased in streams with forested catchments (<2% wetland area). In catchments with high coverage of wetlands (>30% wetland area) the opposite behavior was observed. The hydrogeochemistry of Fe was highly dependent on wetlands as shown by the strong positive correlation of the Fetot/Altot ratio with wetland coverage (r2 = 0.89, p < 0.001). Furthermore, PCA analysis showed that at base flow Fetot and Fe<0.4 were positively associated with wetlands and DOC, whereas they were not associated during peak flow at spring flood. The temporal variation of Fe was likely related to varying hydrological pathways. At peak discharge Fetot was associated with variables like silt coverage, which highlights the importance of particulates during high discharge events. For Mn there was no significant correlation with wetlands, instead, PCA analysis showed that during spring flood Mn was apparently more dependent on the supply of minerogenic particulates from silt deposits on the stream banks of some of the streams. The influence of minerogenic particulates on the concentration of, in particular, Mn was greatest in the larger, lower gradient streams, characterized by silt deposits in the near-stream zone. In the small forested streams underlain by till, DOC was of greater importance for the observed concentrations, as indicated by the positive correlation of both Fetot and Fe<0.4 with DOC (r2 = 0.77 and r2 = 0.76, p < 0.001) at the smallest headwater forest site. In conclusion, wetland area and DOC were important for Fe concentrations in this boreal stream network, whereas silt deposits strongly influenced Mn concentrations. This study highlights the importance of studying stream water chemistry from a landscape perspective in order to address future environmental issues concerning mobility of Fe, Mn and associated trace metals.
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| 2. |
- Buffam, Ishi, et al.
(författare)
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Landscape-scale variability of acidity and dissolved organic carbon during spring flood in a boreal stream network
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- Acidity is well known to influence stream biota, but the less well-studied spatial and temporal distributions of acidity are likely to play a larger ecological role than average values. We present data on spatial variability of chemical parameters contributing to acidity during winter baseflow and spring flood periods in Krycklan, a fourth-order boreal stream network in northern Sweden. Fifteen stream sites were monitored in subcatchments spanning 3 orders of magnitude in size and representing a wide range of percent wetland. At baseflow, pH ranged from 3.9 to 6.5 at the different sites. Baseflow dissolved organic carbon (DOC) concentration varied by an order of magnitude and was positively correlated with subcatchment percent wetland, resulting in high spatial variability in dissociated organic acids (OA(-)). During spring flood, DOC and OA(-) increased in forested sites and decreased in wetland sites, resulting in reduced spatial variability in their concentrations. In contrast, base cations and strong acid anions diluted throughout the stream network, resulting in decreased acid neutralizing capacity (ANC) at all sites. The spatial variability of base cations increased slightly with high flow. As a result of the changes in OA(-) and ANC, pH dropped at all but the most acidic site, giving a slightly narrowed pH range during spring flood (4.2-6.1). The transition from winter to spring flood stream chemistry could largely be explained by: (1) a shift from mineral to upper riparian organic soil flow paths in forested catchments and (2) dilution of peat water with snowmelt in wetland catchments.
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| 3. |
- Buffam, Ishi, et al.
(författare)
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Spatial heterogeneity of the spring flood acid pulse in a boreal stream network.
- 2008
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 407:1, s. 708-22
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal patterns in streamwater acidity are ecologically important, but difficult to measure in parallel. Here we present the spatial distribution of streamwater chemistry relevant to acidity from 60 stream sites distributed throughout a 67 km(2) boreal catchment, sampled during a period of winter baseflow (high pH) and during a spring flood episode (low pH). Sites were grouped based on pH level and pH change from winter baseflow to spring flood. The site attributes of each pH group were then assessed in terms of both stream chemistry and subcatchment landscape characteristics. Winter baseflow pH was high throughout most of the stream network (median pH 6.4), but during the spring flood episode stream sites experienced declines in pH ranging from 0-1.6 pH units, resulting in pH ranging from 4.3-6.3. Spring flood pH was highest in larger, lower altitude catchments underlain by fine sorted sediments, and lowest in small, higher altitude catchments with a mixture of peat wetlands and forested till. Wetland-dominated headwater catchments had low but stable pH, while the spring flood pH drop was largest in a group of catchments of intermediate size which contained well-developed coniferous forest and a moderate proportion of peat wetlands. There was a trend with distance downstream of higher pH, acid neutralizing capacity (ANC) and base cation concentrations together with lower dissolved organic carbon (DOC, strongly negatively correlated with pH). This apparent scale-dependence of stream chemistry could be explained by a number of environmental factors which vary predictably with altitude, catchment area and distance downstream-most notably, a shift in surficial sediment type from unsorted till and peat wetlands to fine sorted sediments at lower altitudes in this catchment. As a result of the combination of spatial heterogeneity in landscape characteristics and scale-related processes, boreal catchments like this one can be expected to experience high spatial variability both in terms of chemistry at any given point in time, and in the change experienced during high discharge episodes. Although chemistry patterns showed associations with landscape characteristics, considerable additional variability remained, suggesting that the modeling of dynamic stream chemistry from map parameters will continue to present a challenge. (C) 2008 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
- Cory, Neil, et al.
(författare)
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Particulate aluminium in boreal streams : Towards a better understanding of its sources and influence on dissolved aluminium speciation
- 2009
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 24:9, s. 1677-1685
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Tidskriftsartikel (refereegranskat)abstract
- The adverse impacts of the inorganic labile monomeric Al (Al-i) fraction on aquatic organisms have meant that Al (Al-tot) determination and even speciation has become a routine part of environmental monitoring and assessment. However, if samples are not filtered prior to analysis then particulate Al (Al-tot(p)) could influence the determination of Al-tot, and therefore the determination of the more toxicologically important (Al-i), both when it is measured analytically or modelled from Al-tot. This paper shows that the Al/DOC ratio in unfiltered samples can identify the Al-tot(p) fraction, and thus improve the speciation of Al-i. These findings are based on data from a study in a 67 km(2) catchment in northern Sweden during the snowmelt-driven spring flood of two consecutive years. Filtered and unfiltered samples were studied to determine the spatial and temporal patterns in Al-tot(p). The concentrations of Al-tot(p) were greatest in larger downstream sites where significant silt deposits are located. The sites with no silt in their drainage area showed a mean difference between filtered (Al-tot(f)) and unfiltered (Al-tot(uf)) samples of 6%, while sites with silt deposits had a mean difference of 65%. The difference between filtered and unfiltered samples was greatest at peak flow. Spikes in Al-tot(p) did not behave consistently during fractionation with a cation exchange column, resulting in increases in either measured Al-i(f) or non-labile monomeric Al (Al-o(f)). Al-tot(p) spikes were associated with sharp increases in the Al:DOC ratio. The baseflow Al:DOC ratio could be used to model filtered Al-tot from DOC with a Spearman rho of 0.75.
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| 6. |
- Erlandsson, Martin, et al.
(författare)
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Thirty-five years of synchrony in the organic matter concentrations of Swedish rivers explained by variation in flow and sulphate
- 2008
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Ingår i: Global Change Biology. - : Blackwell Publishing. - 1354-1013 .- 1365-2486. ; 14:5, s. 1191-1198
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Tidskriftsartikel (refereegranskat)abstract
- Increasing concentrations of organic matter ( OM) in surface waters have been noted over large parts of the boreal/nemoral zone in Europe and North America. This has raised questions about the causes and the likelihood of further increases. A number of drivers have been proposed, including temperature, hydrology, as well as SO42 - and Cl (-) deposition. The data reported so far, however, have been insufficient to define the relative importance of different drivers in landscapes where they interact. Thirty-five years of monthly measurements of absorbance and chemical oxygen demand ( COD), two common proxies for OM, from 28 large Scandinavian catchments provide an unprecedented opportunity to resolve the importance of hypothesized drivers. For 21 of the catchments, there are 18 years of total organic carbon (TOC) measurements as well. Despite the heterogeneity of the catchments with regards to climate, size and land use, there is a high degree of synchronicity in OM across the entire region. Rivers go from widespread trends of decreasing OM to increasing trends and back again three times in the 35-year record. This synchronicity in decadal scale oscillations and long-term trends suggest a common set of dominant OM drivers in these landscapes. Here, we use regression models to test the importance of different potential drivers. We show that flow and SO42 - together can predict most of the interannual variability in OM proxies, up to 88% for absorbance, up to 78% for COD. Two other candidate drivers, air temperature and Cl (-) , add little explanatory value. Declines in anthropogenic SO42 - since the mid-1970s are thus related to the observed OM increases in Scandinavia, but, in contrast to many recent studies, flow emerges as an even more important driver of OM variability. Stabilizing SO42 - levels also mean that hydrology is likely to be the major driver of future variability and trends in OM.
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| 7. |
- Fölster, Jens, et al.
(författare)
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A Novel Environmental Quality Criterion for Acidification in Swedish Lakes - An Application of Studies on the Relationship Between Biota and Water Chemistry
- 2007
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Ingår i: Acid Rain - Deposition to Recovery. - Netherlands : Springer. - 9781402058844 ; , s. 331-338
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden's Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.
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| 8. |
- Fölster, Jens, et al.
(författare)
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A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry
- 2007
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Ingår i: Water, Air, & Soil Pollution: Focus. - : Springer Science and Business Media LLC. - 1567-7230 .- 1573-2940. ; 7:1-3, s. 331-338
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Tidskriftsartikel (refereegranskat)abstract
- The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.
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| 9. |
- Köhler, S. J., et al.
(författare)
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Dynamics of stream water TOC concentrations in a boreal headwater catchment : Controlling factors and implications for climate scenarios
- 2009
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 373:1-2, s. 44-56
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Tidskriftsartikel (refereegranskat)abstract
- Two different but complementary modelling approaches for reproducing the observed dynamics of total organic carbon (TOC) in a boreal stream are presented. One is based on a regression analysis, while the other is based on riparian soil conditions using a convolution of flow and concentration. Both approaches are relatively simple to establish and help to identify gaps in the process understanding of the TOC transport from soils to catchments runoff. The largest part of the temporal variation of stream TOC concentrations (4-46 mg L-1) in a forested headwater stream in the boreal zone in northern Sweden may be described using a four-parameter regression equation that has runoff and transformed air temperature as sole input variables. Runoff is assumed to be a proxy for soil wetness conditions and changing flow pathways which in turn caused most of the stream TOC variation. Temperature explained a significant part of the observed inter-annual variability. Long-term riparian hydrochemistry in soil solutions within 4 m of the stream also captures a surprisingly large part of the observed variation of stream TOC and highlights the importance of riparian soils. The riparian zone was used to reproduce stream TOC with the help of a convolution model based on flow and average riparian chemistry as input variables. There is a significant effect of wetting of the riparian soil that translates into a memory effect for subsequent episodes and thus contributes to controlling stream TOC concentrations. Situations with high flow introduce a large amount of variability into stream water TOC that may be related to memory effects, rapid groundwater fluctuations and other processes not identified so far. Two different climate scenarios for the region based on the IPCC scenarios were applied to the regression equation to test what effect the expected increase in precipitation and temperature and resulting changes in runoff would have on stream TOC concentrations assuming that the soil conditions remain unchanged. Both scenarios resulted in a mean increase of stream TOC concentrations of between 1.5 and 2.5 mg L-1 during the snow free season, which amounts to approximately 15% more TOC export compared to present conditions. Wetter and warmer conditions in the late autumn led to a difference of monthly average TOC of up to 5 mg L-1, suggesting that stream TOC may be particularly susceptible to climate variability during this season.
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| 10. |
- Laudon, Hjalmar, et al.
(författare)
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Impact of changing DOC concentrations on the potential distribution of acid sensitive biota in a boreal stream network
- 2007
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 4, s. 3145-3173
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Tidskriftsartikel (refereegranskat)abstract
- DOC concentrations have increased in many surface waters in Europe and North America over the past few decades. As DOC exerts a strong influence on pH this DOC increase could have detrimental effects on acid sensitive biota in many streams and lakes. To investigate the potential implications of changes in the DOC concentration on stream water biota, we have used a mesoscale boreal stream network in northern Sweden as a case study. The network was sampled for stream water chemistry at 60 locations during both winter base flow and spring flood periods, representing the extremes experienced annually in these streams both in terms of discharge and acidity. The effect of changing DOC on pH was modeled for all sampling locations using an organic acid model, with input DOC concentrations for different scenarios adjusted by between –30% and +50% from measured present concentrations. The resulting effect on pH was then used to quantify the proportion of stream length in the catchment with pH below the acid thresholds of pH 5.5 and pH 5.0. The results suggest that a change in stream water DOC during base flow would have only a limited effect on pH and hence on the stream length with pH below the acid thresholds. During the spring flood on the other hand a change in DOC would strongly influence pH and the stream length with pH below the acid thresholds. For example an increase in DOC concentration of 30% at all sites would increase the proportion of stream length with pH below 5.5 from 37% to 65%, and the proportion of stream length with pH below 5.0 would increase from 18% to 27%. The results suggest that in poorly-buffered high DOC waters, even a marginal change in the DOC concentration could impact acid sensitive biota in a large portion of the aquatic landscape.
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