Drivers of atmospheric deposition of polycyclic aromatic hydrocarbons at European high-altitude sites

Polycyclic aromatic hydrocarbons (PAHs) were analysed in bulk atmospheric deposition samples collected at four European high-mountain areas, Gossenköllesee (Tyrolean Alps), Redon (Central Pyrenees), Skalnate Pleso (High Tatra Mountains), and Lochnagar (Grampian Mountains) between 2004 and 2006. Sample collection was performed monthly in the first three sites and biweekly in Lochnagar. The number of sites, period of study and sampling frequency provide the most comprehensive description of PAH fallout in high mountain areas addressed so far. The average PAH deposition fluxes in Gossenköllesee, Redon and Lochnagar ranged between 0.8 and 2.1µgm−2month−1, and in Skalnate Pleso it was 9.7µgm−2month−1, showing the influence of substantial inputs from regional emission sources. The deposited distributions of PAHs were dominated by parent phenanthrene, fluoranthene and pyrene, representing 32%–60% of the total. The proportion of phenanthrene, the most abundant compound, was higher at the sites of lower temperature, Gossenköllesee and Skalnate Pleso, showing higher transfer from gas phase to particles of the more volatile PAHs. The sites with lower insolation, e.g. those located at lower altitude, were those with a higher proportion of photooxidable compounds such as benz[a]anthracene. According to the data analysed, precipitation is the main driver of PAH fallout. However, when rain and snow deposition were low, particle settling also constituted an efficient driver for PAH deposition. Redon and Lochnagar were the two sites receiving the highest amounts of rain and snow and the fallout of PAH fluxes was related to this precipitation. No significant association was observed between long-range backward air trajectories and PAH deposition in Lochnagar, but in Redon PAH fallout at higher precipitation was essentially related to air masses originating from the North Atlantic, which were dominant between November and May (cold season). In these cases, particle-normalised PAH fallout was also associated with higher precipitation as these air masses were concurrent with lower temperatures, which enhanced gas to particle partitioning transfer. In the warm season (June–October), most of the air masses arriving at Redon originated from the south and particle deposition was enhanced as consequence of Saharan inputs. In these cases, particle settling was also a driver of PAH deposition despite the low overall PAH content of the Saharan particles. In Gossenköllesee, the site receiving lowest precipitation, PAH fallout was also related to particle deposition. The particle-normalised PAH fluxes were significantly negatively correlated to temperature, e.g. for air masses originating from central and eastern Europe, showing a dominant transfer from gas phase to particles at lower temperatures, which enhanced PAH fallout, mainly of the most volatile hydrocarbons. Comparison of PAH atmospheric deposition and lacustrine sedimentary fluxes showed much higher values in the latter case of 24–100µgm−2yr−1 vs. 120–3000µgm−2yr−1. A strong significant correlation was observed between these two fluxes, which is consistent with a dominant origin related to atmospheric deposition at each site

Blockgletscherabflüsse im Äußeren Hochebenkar: Hydrologie, Wasserchemie und Kieselalgen

Hochebenkar rock glacier is one of the most intensively investigated active rock glaciers of the Austrian Alps with first measurements of flow velocities by Pillewizer in 1938. Since 2007 the discharge of the rock glacier outflows has been studied quantitatively by automatic gauges and chemical analysis is used to determine the water quality of the discharge. Runoff of an active rock glacier reveals a high seasonal variability with varying contributions of snowmelt, precipitation events, groundwater and melting of the internal ice body. Peak values of runoff generally occur in late spring caused by the melting of the seasonal winter snow pack. The major melt phase is characterised by a high daily course of runoff values with maxima at night and minima in the late morning. Cold spells generally interrupt the melt phase several times a year causing runoff and its daily course to decrease. Secondary peaks are linked to summer precipitation events when quickflow causes runoff to increase. By late summer or fall, runoff generally decreases and often ceases in November when air temperatures fall below zero.Solute concentrations tend to increase between the onset of major snowmelt and fall. Electrical conductivity – as a measure of the total ion content of a solution – varies from about 100 µS/cm in early summer to some 400 µS/cm in fall at the automatic gauge run by the Hydrographic Service of Tyrol (2,220 m). Conductivity values may even be higher and reach > 500 µS/cm when measured directly at the rock glacier outflow. Heavy summer precipitation events cause a dilution of the highly concentrated rock glacier streams, and secondary runoff peaks coincide with conductivity minima. The same accounts for those ions that dominate the ion content of the brooks, i.e. sulfate, calcium and magnesium. The seasonal course of the solute concentrations reflects the varying contributions of snowmelt, precipitation, groundwater and melting of the internal ice body. So called reference brooks, i.e. brooks without any impact of an active rock glacier revealed substance concentrations that ranged one order of magnitude below values found in rock glacier impacted brooks. Epilithic diatom assemblages were investigated in rock glacier impacted and not impacted streams at two sites (Hochebenkar and Krummgampen) with varying chemical properties. First results indicated that rock glacier outflows may affect species composition and abundance of epilithic diatoms. In particular, increasing acidity caused the substitution of circumneutral taxa by acidophilous and acidobiontic tax

Sedimente von vier Hochgebirgsseen unter unterschiedlichem Einfluß von Permafrost

A paleolimnological survey of high mountain lakes in North- and South-Tyrol was conducted within the Interreg project Permaqua (permafrost and its effects on water balance and mountain water ecology) aiming at econstructing the ecological evolution of lakes in permafrost regions since the end of the Little ice Age (~1850), and to investigate possible effects of permafrost thawing on lake geochemistry and biology. Sediment cores from four lakes located above ~2500 m a.s.l. on crystalline bedrock were radioistopically dated (210Pb, 226Ra, 137Cs and 241Am and 14C) and analyzed for lithological (wet density, water and organic content), geochemical (principal elements and heavy metals), and biological (diatom abundance and speceis composition) proxies. All the cores studied showed lithological and biological changes between the end of the Little Ice Age and the first decades of the 20th century. Concentrations of heavy metals increased in the studied cores during the last ~ 150 years and reached highest values after the 1990s. On the contray, changes in diatom species composition which typically characterize many lower lakes of the northern hemisphere after the economic development in the 1960s were not recorded in the lakes investigated. However, it is not possible to explain these changes as completely related to the presence of active rock glaciers in the lake catchments. The long-term changes of biological and chemical indicators observed in the studied sediment cores appear to be the results of a set of combined factors, such as geochemistry, weathering, or catchment characteristics

Sediments of high mountain lakes as records of long-term environmental changes

A limnological and paleolimnological survey of high mountain lakes in North- and South- Tyrol was conducted within the Interreg Project Permaqua (Permafrost and its effects on water balance and mountain water ecology) aiming at reconstructing the ecological evolution of lakes in permafrost regions since the end of the Little Ice Age (~1850), and investigating potential effects of permafrost thawing on lake geochemistry and biology. In fact, recent studies conducted in the Central Alps outlined potential effects of rock glacier thawing on the ecological quality of headwaters. Sediment cores from four lakes located above ~2500 m a.s.l. on crystalline bedrock were radioisotopically dated, and analysed for lithological, geochemical, and biological proxies. All cores studied showed major lithological and biological changes between the end of the Little Ice Age and the first decades of the 20th century. Concentrations of heavy metals increased in the studied cores during the last ~150 years and reached highest values after the 1990s. On the contrary, changes in diatom species composition which typically characterize many low-land lakes of the northern hemisphere after the economic development in the 1960s were not recorded in the lakes investigated. Although it is not possible to explain the observed changes as directly related to the presence of active rock glaciers in the lake catchments, it seems likely that long-term changes of biological and chemical indicators observed in the studied sediment cores are due to a combination of factors, such as geochemistry, weathering, or catchment characteristics

Temperature modulated effects of nutrients on phytooplankton changes in a mountain lake

Piburger See, a dimictic mountain lake in Austria, experienced moderate cultural eutrophication in the 1950s. Lake restoration led to a re-oligotrophication with a decrease in seasonal phytoplankton biovolume until the late 1990s, but a reversed trend appeared since the early 2000s. We hypothesize that recent phytoplankton changes are triggered by changes in lake nitrogen and silica concentrations, and we expect climate-related factors to modulate the trophic status of Piburger See. Phytoplankton data were analyzed by non-metric multidimensional scaling (NMDS) applied on biovolume of morpho-functional groups, combined with correlation analyses of environmental variables. Since the 2000s, short-term changes in phytoplankton of Piburger See were explained by varying concentrations and ratios of nitrogen and silica, while the inter-annual variability in phytoplankton species composition was rather attributed to superimposed rising water temperature and lake thermal stability. Our results underline the co-dominant role of phosphorus and nitrogen as phytoplankton drivers in lakes that experience periods of nitrogen limitation. The combined impact of nutrients and climate on phytoplankton development can thus mimic short-term increases in the trophic level of less productive lake

Temperature modulated effects of nutrients on phytoplankton changes in a mountain lake

Piburger See, a dimictic mountain lake in Austria, experienced moderate cultural eutrophication in the 1950s. Lake restoration led to a re-oligotrophication in the 1990s with a decrease in seasonal phytoplankton biovolume until the late 1990s, but a reversed trend from the early 2000s onwards. We hypothesize that recent changes in phytoplankton biomass and functional structure are triggered by changes in lake nitrogen and silica concentrations, and we expect climate-related factors to modulate the trophic status of Piburger See. Phytoplankton data were analyzed by non-metric multidimensional scaling (NMDS) applied on biovolume of morpho-functional groups, combined with correlation analyses of environmental variables. Since the 2000s, short-term changes in phytoplankton of Piburger See were explained by varying concentrations and ratios of nitrogen and silica, while the inter-annual variability in phytoplankton species composition was rather attributed to superimposed rising water temperature and lake thermal stability. Our results underline the co-dominant role of phosphorus and nitrogen as phytoplankton drivers in lakes that experience periods of nitrogen limitation. The combined impact of nutrients and climate on phytoplankton development can thus mimic short-term increases in the trophic level of less productive lake

Evidence of rock glacier melt impacts on water chemistry and diatoms in high mountain streams

A first study of high alpine freshwaters at Hochebenkar and Krumgampen (Oetztal Alps, Tyrol, Austria) revealed pronounced differences in the concentration of major ions, heavy metals, species composition and biodiversity of epilithic diatoms in streams emerging from two active (i.e. ice containing) rock glaciers and in adjacent unaffected reference streams. The clear-water streams impacted by active rock glaciers are characterized by high electrical conductivity (EC) values, but differ in acidity, heavy metal concentrations and by the proportion of circumneutral and acidobiontic diatoms. On the contrary, all reference streams exhibit low EC and circumneutral to slightly acidic pH values characteristic for surface waters on bedrock composed of paragneiss and micaschist, with no detectable heavy metals and a diatom composition typical for high altitude softwater streams. The high ion concentrations in streams emerging from rock glaciers are attributed to a seasonally increasing release of melt waters from active rock glacier