Wildfire Effects on the Quantity and Composition of Suspended and Gravel-Stored Sediments

In August of 2003 a severe wildfire burnt the majority of Fishtrap Creek, a 170 km² catchment in central British Columbia, Canada. The objective of this study was to determine the short-term (15-month) influence of the wildfire on the amount and composition of fine sediment delivery and retention in the system and to compare it to a similar unburnt catchment. In the spring of 2004 automatic water samplers were installed at a gauging site on Fishtrap Creek to collect suspended sediments from the snowmelt runoff and gravel traps were deployed on the channel bed surface to collect composite samples of suspended fine sediment. Jamieson, the reference creek, exhibits similar geology and pre-burn vegetation and was sampled in the same manner for comparison. Composite suspended sediment collected in the traps was removed from the streams in mid-summer and early September. Quantitative estimates of the amount and particle size structure of the naturally stored fine sediment in, and on, the gravel creekbed were obtained in pre-melt, mid and late-summer conditions. Estimates of suspended sediment yields indicated that while the burnt system delivered 66% more material per unit area, the total seasonal suspended sediment yield was low (855 kg km⁻²) compared to other fire-disturbed systems. While the burnt catchment was primed to deliver sediment, the hydrologic drivers were not of sufficient magnitude to generate a substantial response, suggesting that in this first post-fire year the system was transport-limited, not supply-limited. Differences were noted in the spatial and seasonal composition of the <500 more OM% composite suspended sedimentswith the burnt catchment having significantly (P≤0.05) more OM%. Seasonally a significant increase of OM% in late summer samples was associated with instream biofilms and possible delivery of black carbon. The system’s post-fire response was not geomorphically substantial but significant biological differences were noted in the short-term.     

The Input and Transmission of Fallout Radionuclides Through Redó, a High Mountain Lake in the Spanish Pyrenees

Fallout radionuclides have increasing value as tracers of pathways for pollutant transport through catchment/lake systems, in addition to their more traditional role in dating sediment records. The objectivesof this study, carried out within the EU MOLAR project, were tomeasure atmospheric fluxes of fallout ²¹⁰Pb, ¹³⁷Cs and ⁷Be at Redó, to establish mass balances for theseradionuclides, and test and validate models of pollutant transport through the lake and its catchment. This was achieved by comparing measured fluxes and concentrations in the water column with theoretical estimates using simple compartment models. Several interesting points emerged. Differences betweensoil core and rainwater measurements suggest that Saharan dust may be an important source of fallout ²¹⁰Pb. Fluxes throughthe water column had a clear seasonal trend reflecting winter icecover. Significant concentrations of ¹³⁷Cs are still presentin the water column, due to continued inputs from the catchment and/or remobilisation from the bottom sediments.     

Temporal Trends in Mercury Accumulation in Lake Sediments in Sweden

Lake sediment cores were analyzedto study the history of mercury (Hg) pollution andparticularly to determine whether recent sedimentconcentrations have declined in response todeclining atmospheric deposition of Hg. Sedimentcores from 6 forest lakes distributed fromsouthern to northern Sweden and 3 northernmountain lakes were analyzed for Hg using CVAAS. A400 cm sediment profile from Måkevatten insouthwest Sweden indicates that the onset of Hgpollution occurred in the 18th century. Anindisputable increase in Hg concentrationsoccurred concurrent with the appearance ofspheroidal carbonaceous flyash particles (SCP)derived from fossil-fuel combustion, in themid-19th century. There is a strong correlationbetween Hg and SCP concentrations in the sedimentcores (r=0.67 to 0.91), which suggests a strongrelationship between historical Hg pollution andfossil fuel burning. In contrast to sediment corestaken in 1979, maximum Hg concentrations are nowobserved below the sediment surface and declinetowards the sediment surface. This study confirmsthat reductions in atmospheric deposition of Hgover Sweden have resulted in a decreased transferof total Hg to aquatic environments as reflectedby lake sediments, and that lake sediment profilesof Hg concentrations reflect relative trends inthe atmospheric deposition of Hg rather thanpost-depositional diagenetic processes.     

Finnish Lake Survey: The Role of Catchment Attributes in Determining Nitrogen, Phosphorus, and Organic Carbon Concentrations

This study is based on a Finnish lake survey conducted in 1995, a dataset of 874 statistically selected lakes from the national lake register. The dataset was divided into subgroups to evaluate lake water-catchment relationships in different geographical regions and in lakes of different size. In the three southernmost regions, the coefficients of determination in multiple regression equations varied between 0.40 and 0.53 for total nitrogen (TN) and between 0.37 and 0.53 for total phosphorus (TP); the best interpreters were agricultural land and water area in the catchment. In the two northernmost regions, TN concentrations in lake water were best predicted by the proportion of peatlands in the catchment, the catchment slope, and TP concentrations by lake elevation and latitude. Coefficients of determination in multiple regression equations in these northern regions varied between 0.39 and 0.67 for TN and between 0.41 and 0.52 for TP. For all the subsets formed, the best coefficients of determination explaining TN, TP, and total organic carbon (TOC) were obtained for a subset of large lakes (>10 km²), in which 72–83% of the variation was explained. This was probably due to large heterogeneous catchments of these lakes.     

Spatial and Temporal Variations in the Sediment Habitat of Ranunculus spp. in Lowland Chalk Streams – Implications for Ecological Status?

Ranunculus spp. are the dominant plants of lowland chalk stream habitats in England. The spatial variability of sediment characteristics (silt–clay, organic matter, total phosphorus and total nitrogen content) within stands of Ranunculus spp. was investigated in 12 rivers in lowland England. Variability was found to be high and there were no discernible differences between samples taken from within Ranunculus and a limited number of samples from bare substrate. For two of these rivers, comparisons were also made between reaches upstream and downstream of waste water treatment works outfalls in terms of the characteristics of the sediments within Ranunculus stands. In one river a clear increase in sediment nutrient, fine and organic material content was observed downstream but in the other there was no consistent difference. Temporal variability was considered for two rivers in the Frome catchment, Dorset, by analysing the monthly variability in sediment organic matter and silt–clay content beneath Ranunculus stands over an annual cycle of growth and die-back. Whilst a clear pattern of fine and organic material retention consistent with seasonal plant growth patterns was evident at one site, the three sites displayed different temporal patterns. This inconsistency is believed to reflect differences in sediment supply at the three sites.     

Atmospheric Metal Pollutants-Archives, Methods, and History

Pollution of the atmosphere with cadmium (Cd), mercury (Hg), and lead (Pb) is a consequence of human activities. Natural archives are necessary to reconstruct the long-term history of metal deposition because accurate measurement of atmospheric deposition is a recent accomplishment. Reconstructions require: (1) accurate determination of concentrations of elements and isotopes, (2) accurate chronology of archives, and (3) archives that faithfully record atmosphere deposition. The most useful long-term archives are accumulations of ice and snow, peat, and lake sediment. Quantification of Cd deposition is uncommon because of its low concentration and substantial chemical mobility. Nonetheless, trends in peat and lake sediment are similar to those of Hg and Pb since ca. 1800 a.d. Both Hg and Pb are relatively chemically immobile and thus the peat and lake archives are believed to record historic trends of atmospheric deposition. Isotopic and concentration studies of Pb indicate a history of northern hemisphere atmospheric pollution extending back prior to 0 a.d. Although measurements of Hg concentration are now routine, isotopic measurements are in their infancy. Some Hg pollution sources have unique isotopic ratios, thereby contributing unique signals to the total Hg. Maximum accumulation rates of Hg and Pb occur up to 10 years later than for Cd (1970s versus 1960s in eastern North America, perhaps slightly later in Europe). By 2004, deposition of Cd, Hg, and Pb had declined from peak values in eastern North America more than 75, 75, and 90%, respectively.     

Application of Static Critical Load Models for Acidity to High Mountain Lakes in Europe

Critical load models for acidityprovide a measure of the sensitivity of surfacewaters to acid deposition, and can be used todetermine critical load exceedance and potentiallong-term harmful effects. Three static models,the Steady-State Water Chemistry model, diatommodel and First-order Acidity Balance model, arehere applied to 11 high mountain lakes in Norway,Scotland, the Alps, the Pyrenees and the Tatras.Between five and seven of the lakes show criticalload exceedance, depending on the model used.Nitrogen as well as sulphur deposition isimportant in causing exceedance. Since soil andvegetation cover are generally sparse, geologyand lake retention time appear to be key factorsin the determination of critical load. Retentionof nitrogen is observed, but it is unclearwhether this occurs within the lake or theterrestrial part of the catchment.     

Reconstruction of Long-Term Changes in Lake water Chemistry,Zooplankton and Benthos of a Small,Acidified High-Mountain Lake: Magic Modelling and Palaeolimnogical Analysis

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericusPalaeolimnological investigations show changes in cladoceran zooplankton and chironomid zoobenthic assemblages since about 1920 and a major change in 1970–1980. The dynamic acidification model MAGIC was used to reconstruct changes in water chemistry over the past 150 years. The results from MAGIC agree well with the sediment record; pH levels gradually decreased from 6.5 in the mid-1800s to about 5.6 in 1920 (first response in biota) to below 5.0 by 1970, and concentrations of inorganic aluminium rose dramatically beginning about 1960. In the 1990s the lake water chemistry showed clear signs of reversal in acidification brought about by a major decline in S deposition.     

Assessment of the Ecological Integrity of Traunsee (Austria) Via Analysis of Sediments and Benthic Microbial Communities

Since nearly one hundred years Traunsee experiences the import of tons of liquid and solid waste originating from salt and soda production. Today, the lake exhibits chloride concentrations of up to 170 mg L^-1 and 19% of the lake floor are directly or indirectly influenced by industrial deposits (ID). Based on the comparison of several microbial parameters in unaffected, directly affected and intermediate lake bottom sediments, the ecological integrity of the lake was evaluated. The highly alkaline ID, which were exclusively colonized by microorganisms, harbored a bacterial community reduced by a factor of 10 in abundance and biomass compared to undisturbed sediment areas within the lake. The bacterial community of ID was furthermore characterized by a reduced content of actively respiring cells (INT-formazan reduction), a lower frequency of dividing cells (FDC) and a significantly reduced cell and biomass production. A 80 to 90% reduction in carbon recycling is estimated for the area exclusively covered by ID. Protists, although occasionally absent from the industrial sediments, were in general found to be less sensitive to the contaminant stress. Differences in alkalinity and dissolved organic carbon (DOC) concentrations of sediment porewaters as well as the total organic content and C/N ratios of sediments partly explain the microbial pattern observed at the various sampling sites. Possible consequences of the continuous industrial tailings for the whole lake ecosystem and the validation of the ecological integrity are discussed.     

Mercury and Methylmercury in Runoff from a Forested Catchment – Concentrations, Fluxes, and Their Response to Manipulations

Measurements of TotHg (total mercury) and MeHg (methylmercury) in runoff from the covered catchment G1 and the reference catchment F1 at Lake Gårdsjön, Sweden, have been performed and evaluated. The roof over the covered catchment limits atmospheric deposition input of TotHg and MeHg and a response in runoff concentrations and transport was expected. Based on data from 10 yr of monitoring, no statistically significant change in runoff flux of TotHg or MeHg can be observed. A slight decrease in MeHg output in the covered catchment was observed after 2 yr of the experiment. This can be explained as a temporary effect caused by the roof construction. The main conclusion is that release of TotHg and MeHg from the forest soil is controlled by factors other that wet deposition input, for example the mineralisation of organic matter. Furthermore, there is no indication of a depletion of the Hg pool in the soil. In spring 1999, the reference catchment F1 was affected by forestry machinery significantly disturbing the forest soil layer in a limited area. This caused MeHg concentrations to increase dramatically in runoff and led to an increase of the annual transport by at least a factor of 3. This indicates that forestry and other activities that disturb forest soils may be important for controlling MeHg fluxes to aquatic ecosystems.     

Modelling Acidification and Recovery of Swedish Lakes

The MAGIC model was calibrated to 143 lakes in Sweden, all of which are monitored in Swedish national monitoring programmes conducted by the University of Agricultural Sciences (SLU). Soil characteristics of the lake catchments were obtained from the National Survey of Forest Soils and Vegetation also carried out by SLU. Deposition data were provided by the Swedish Meteorological and Hydrological Institute (SMHI). The model successfully simulated the observed lake and soil chemistry at 133 lakes and their catchments. The fact that 85% of the lakes calibrated successfully without being treated in an individual way suggests that data gathered by the national monitoring programmes are suitable for modelling of soil and surface water recovery from acidification. The lake and soil chemistry data were then projected into the future under the deposition scenario based on emission reductions agreed in the Gothenburg protocol. Deposition of sulphur (sea salt corrected) was estimated to decrease from 1990 to 2010 by 65–73%; deposition of nitrogen was estimated to decrease by 53%. The model simulated relatively rapid improvements in lake water chemistry in response to the decline in deposition from 1990 to 2010, but the improvements levelled off once deposition stabilised at the lower value. There was a major improvement of simulated lake water charge balance acid neutralising capacity (ANC) from 1990 to 2010 in all lakes. The modelled lakes were divided into acidification sensitive and non-sensitive. The modelled sensitive lakes are representative of 20% of the most sensitive lakes in Sweden. By 2010, the ANC in the sensitive lakes was 10 to 50 μeq L^-1 below estimated pre-industrial levels and did not increase much further from 2010 to 2040. Soils at the majority of the modelled catchments continued to lose base cations even after the simulated decline in acid deposition was complete, i.e. after the year 2010. Based on this model prediction, the acidification of the Swedish soils will in general not be reversed by the deposition reduction experienced over the last 10 years and expected to occur by the year 2010.     

Mercury and Organochlorine Contamination in Brown Trout (Salmo Trutta) and Arctic Charr (Salvelinus Alpinus) from High Mountain Lakes in Europe and the Svalbard Archipelago

High concentration of Hg, less volatile PCB congeners and p,p-DDE in Arctic charr from an arctic lake was mainly causedby biomagnification in the food chain where cannibalism was thedriving force. We suggest that low sediment fluxes of Hg, low net production of methyl mercury, and short food chains excludingpiscivory explain the low levels of Hg in the invertebrate feeding fish population in five European high mountain lakes.Concentrations of less volatile PCB congeners in insectivorous fish populations from the European high mountain lakes were mainly influenced by fish age and atmospheric deposition, indicated by the sediment inventory. Atmospheric deposition influenced by local sources may explain the higher concentrationsof pesticides (p,p-DDT, p,p-DDE and -HCH) observedin fish from the Pyrenees compared to the other sites. Theconcentrations of Hg and organochlorines did not exceedthe guidelines for fish consumption, except for Hg levelsin the oldest fish from the arctic lake.     

Changes in Sediment Sources following Wildfire in Mountainous Terrain: A Paired–Catchment Approach,British Columbia,Canada

This paper describes a study examining the potential of mineral magnetic, geochemical and organic properties to determine if a 2003 wildfire in a catchment in British Columbia, Canada, caused a change in the sources of the suspended sediment transported in the channel relative to a nearby unburnt (reference) catchment. The results show that some of the properties offer the potential to determine sediment sources in the unburnt catchment. However, the 2003 wildfire modified the concentrations of some properties and this can either compromise or enhance their ability as tracers in the burnt catchment. At present, the source tracing results are inconclusive. This has implications for the use of certain properties as fingerprints and raises important issues about approaches to sediment source identification.     

Heavy Metal Sediment Load from the City of Stockholm

A transect of upstream lake sitesand downstream coastal sites surrounding the cityof Stockholm, capital of Sweden, wereinvestigated for heavy metals in sediments.Concentrations of Cd, Cu, Hg, Pb and Zn increasedclose to the city. In the most central areas ofStockholm, sediment deposition was increasedabout 5-fold for Cd, Cu, Hg and Pb and 3-fold forZn, as compared to the surrounding areas. Thesediment load from the city was estimated bycorrecting for a background concentration. It canbe concluded that most of the load of Hg and Pbwas trapped in the sediments close to the citywhile Ni, Cu, Cd and Zn to a higher degree weretransported through the archipelago towards theBaltic Sea.     

Combining AHP with GIS for landfill site selection: A case study in the Lake Beyşehir catchment area (Konya,Turkey)

Landfills are the most common method for the disposal of municipal solid waste (MSW) in Turkey. However, determining the location of landfill sites is a difficult and complex process because it must combine social, environmental and technical parameters. Additionally, it depends on several criteria and regulations. The main objective of this study was to select of a landfill site for the Lake Bey?ehir catchment area. The Bey?ehir Lake is the largest freshwater lake and drinking water reservoir in Turkey, but there is no controlled landfill site in the region. Therefore, the landfill site should be determined such that the lake is protected. To determine the most suitable landfill site, an analytical hierarchy process (AHP) was combined with a geographic information system (GIS) to examine several criteria, such as geology/hydrogeology, land use, slope, height, aspect and distance from settlements, surface waters, roads, and protected areas (ecologic, scientific or historic). Each criterion was evaluated with the aid of AHP and mapped by GIS. Data were assorted into four suitability classes within the study area, i.e., high, moderate, low and very low suitability areas, which represented 3.24%, 7.55%, 12.70% and 2.81%, of the study area, respectively. Additionally, 73.70% was determined to be completely unsuitable for a landfill site. As a result, two candidate landfill sites are suggested and discussed. The final decision for landfill site selection will require more detailed field studies.     

The Effect of Sediment Source Changes on Pollen Records in Lake Sediments

A major focus of palynological research has been to assess the various pathways by which pollen is delivered to sedimentary archives. In open lake systems, the contribution of streamborne pollen to lake sediments is thought to be highly significant. Despite this, little research has attempted to identify changes in the pollen record that might be attributed to changing sediment pathways rather than to changes in vegetation. This research aims to partially redress this gap by examining a dated pollen sequence from Kyre Pool, Worcestershire, England. The results presented in this paper suggest that some changes in sediment source, as determined by a fingerprinting approach, can influence the pollen record reconstructed from a lake sediment profile.     

Functions of Straw for In Situ Remediation of Acidic Mining Lakes

The addition of straw in combination with Carbokalk, a by-product from the sugar-industry, was successfully used to stimulate microbial alkalinity generation in an acidic mining lake. To get detailed information about functions of straw, anenclosure experiment was carried out. Straw bundles were placedat the sediment surface of an acidic mining lake (ML 111) and thephysiochemical conditions and the microbiology of the sediment-water contact zone were studied. Straw was degraded by anaerobic microorganisms and dissolved organic carbon (DOC) leached from straw bundles. Pigmented flagellates responded to the DOC supply in the water column anda considerable amount of algal carbon was transported to the sediment. Straw addition led to microbial reduction of iron andsulfate in the sediment. Sulfate reduction was observed at a pHof 5.5. The pH, however, was not high enough to precipitate H₂S completely. Thus, some H₂S diffused into the watercolumn, where it was reoxidized. Straw did not create orstabilize an anoxic water body above the sediment. Microbial sulfate reduction and pyrite formation only took place in the sediment,whereas iron reduction also took place in the straw. Straw, however, altered the flow conditions above the sediment surfaceand prevented complete mixing of the profundal water. Straw didnot serve as a substratum for a reactive biofilm. We conclude that the most important function of straw for mining lake remediation is to be a long-term nutrient source for microbialalkalinity generation in the sediment.     

Deposition and Fate of Lead in a Forested Catchment, Lesni Potok, Central Czech Republic

The deposition of trace elements and their fate in a forest ecosystemhas been monitored at the experimental site, Lesni Potok catchment (LP), with granite bedrock. The catchment is located 30 km ESE from Prague. Annual bulk Pb-deposition flux F_Pb was 3.41 kg km^-2 a^-1 in 1994 and gradually decreased to 0.49 kg km^-2 a^-1 in 2001. The decrease is comparable with those observed in Germany and in the U.S.A. in the 1970s and 1980s. The total sales ban of leaded gasoline in the Czech Republic since January 2001 was accompanied by a pronounced decrease of F_Pb in a single year. The residual Pb-deposition flux is assigned to both the long-range transport of fine-grained vehicular lead aerosol (with a long residence time in the atmosphere) and to theemissions from power plant boilers burning lignite mined in the Czech northwest coal basin. The F_Pb of lead correlates stronglywith those of As, Cd, Cu, Zn and Be, the typical metals in coal fly ash, at two monitored sites. Topsoil horizons contain elevated concentrations of Pb (53–67 mg kg^-1), which are of anthropogenicorigin. Soils in the riparian areas contain increased concentrations of Pb when compared to soils on the hillslope areas. Significant amounts of Pb were found on a stream substrate and Fe-precipitate sampled from the stream. Low concentrations of Pb in bark and bole wood suggest that the uptake of Pb by vegetation is negligible. The very small surface water outputs (average of 0.002 kg km^-2 a^-1) compared to inputs (average of 1.890 kg km^-2 a^-1) from the LP catchment indicate an ongoing accumulation of Pb in a forested landscape.     

Trends in the Water Chemistry of High Altitude Lakes in Europe

Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984–1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions.