30 research outputs found
Glaciers as a temporary reservoir of persistent organic pollutants: Incorporation, transport, and release
Winter greenhouse gas emissions (CO2, CH4 and N2O) from a sub-alpine grassland
Although greenhouse gas emissions during winter contribute significantly to annual balances, their quantification is still highly uncertain in snow-covered ecosystems. Here, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were measured at a subalpine managed grassland in Switzerland using concentration gradients within the snowpack (CO2, CH4, N2O) and the eddy covariance method (CO2) during the winter 2010/2011. Our objectives were (1) to identify the temporal and spatial variation of greenhouse gases (GHGs) and their drivers, and (2) to estimate the GHG budget of the site during this specific season (1 December–31 March, 121 days). Mean winter fluxes (December–March) based on the gradient method were 0.77 ± 0.54 μmol m−2 s−1 for CO2 (1.19 ± 1.05 μmol m−2 s−1 measured by eddy covariance), −0.14 ± 0.09 nmol m−2 s−1 for CH4 and 0.23 ± 0.23 nmol m−2 s−1 for N2O, respectively. In comparison with the CO2 fluxes measured by eddy covariance, the gradient technique underestimated the effluxes by 50%. While CO2 and CH4 fluxes decreased with the progressing winter season, N2O fluxes did not follow a seasonal pattern. The major variables correlating with the fluxes of CO2 and CH4 were soil temperature and snow water equivalent, which is based on snow height and snow density. N2O fluxes were only explained poorly by any of the measured environmental variables. Spatial variability across the valley floor was smallest for CO2 and largest for N2O. During the winter season 2010/2011, greenhouse gas fluxes ranged between 550 ± 540 g CO2 m−2 estimated by the eddy covariance approach and 543 ± 247 g CO2 m−2, −0.4 ± 0.01 g CH4 m−2 and 0.11 ± 0.1 g N2O m−2 derived by the gradient technique. Total seasonal greenhouse gas emissions from the grassland were between 574 ± 276 and 581 ± 569 g CO2 eq. m−2, with N2O contributing 5% to the overall budget and CH4 reducing the budget by 0.1%. Cumulative budgets of CO2 were smaller than emissions reported for other subalpine meadows in the Swiss Alps and the Rocky Mountains. Further investigations on the GHG exchange of grasslands in winter are needed in order to (1) deepen our currently limited knowledge on the environmental drivers of each GHG, (2) to thoroughly constrain annual balances, and (3) to project possible changes in GHG flux magnitude with expected shorter and warmer winter periods.ISSN:1810-6277ISSN:1810-628
Polychlorinated Biphenyls in a Temperate Alpine Glacier: 1. Effect of Percolating Meltwater on their Distribution in Glacier Ice
Polychlorinated Biphenyls in Glaciers. 2. Model Results of Deposition and Incorporation Processes
In previous work, Alpine glaciers have been identified as a secondary source of persistent organic pollutants (POPs). However, detailed understanding of the processes organic chemicals undergo in a glacial system was missing. Here, we present results from a chemical fate model describing deposition and incorporation of polychlorinated biphenyls (PCBs) into an Alpine glacier (Fiescherhorn, Switzerland) and an Arctic glacier (Lomonosovfonna, Norway). To understand PCB fate and dynamics, we investigate the interaction of deposition, sorption to ice and particles in the atmosphere and within the glacier, revolatilization, diffusion and degradation, and discuss the effects of these processes on the fate of individual PCB congeners. The model is able to reproduce measured absolute concentrations in the two glaciers for most PCB congeners. While the model generally predicts concentration profiles peaking in the 1970s, in the measurements, this behavior can only be seen for higher-chlorinated PCB congeners on Fiescherhorn glacier. We suspect seasonal melt processes are disturbing the concentration profiles of the lower-chlorinated PCB congeners. While a lower-chlorinated PCB congener is mainly deposited by dry deposition and almost completely revolatilized after deposition, a higher-chlorinated PCB congener is predominantly transferred to the glacier surface by wet deposition and then is incorporated into the glacier ice. The incorporated amounts of PCBs are higher on the Alpine glacier than on the Arctic glacier due to the higher precipitation rate and aerosol particle concentration on the former. Future studies should include the effects of seasonal melt processes, calculate the quantities of PCBs incorporated into the entire glacier surface, and estimate the quantity of chemicals released from glaciers to determine the importance of glaciers as a secondary source of organic chemicals to remote aquatic ecosystems
Understanding and Predicting the Fate of Semivolatile Organic Pesticides in a Glacier-Fed Lake Using a Multimedia Chemical Fate Model.
Melting glaciers release previously ice-entrapped chemicals to the surrounding environment. As glacier melting accelerates under future climate warming, chemical release may also increase. This study investigated the behavior of semivolatile pesticides over the course of one year and predicted their behavior under two future climate change scenarios. Pesticides were quantified in air, lake water, glacial meltwater, and streamwater in the catchment of Lake Brewster, an alpine glacier-fed lake located in the Southern Alps of New Zealand. Two historic-use pesticides (endosulfan I and hexachlorobenzene) and three current-use pesticides (dacthal, triallate, and chlorpyrifos) were frequently found in both air and water samples from the catchment. Regression analysis indicated that the pesticide concentrations in glacial meltwater and lake water were strongly correlated. A multimedia environmental fate model was developed for these five chemicals in Brewster Lake. Modeling results indicated that seasonal lake ice cover melt, and varying contributions of input from glacial melt and streamwater, created pulses in pesticide concentrations in lake water. Under future climate scenarios, the concentration pulse was altered and glacial melt made a greater contribution (as mass flux) to pesticide input in the lake water
Polychlorinated Biphenyls in a Temperate Alpine Glacier: 2. Model Results of Chemical Fate Processes
We present results from a chemical
fate model quantifying incorporation
of polychlorinated biphenyls (PCBs) into the Silvretta glacier, a
temperate Alpine glacier located in Switzerland. Temperate glaciers,
in contrast to cold glaciers, are glaciers where melt processes are
prevalent. Incorporation of PCBs into cold glaciers has been quantified
in previous studies. However, the fate of PCBs in temperate glaciers
has never been investigated. In the model, we include melt processes,
inducing elution of water-soluble substances and, conversely, enrichment
of particles and particle-bound chemicals. The model is validated
by comparing modeled and measured PCB concentrations in an ice core
collected in the Silvretta accumulation area. We quantify PCB incorporation
between 1900 and 2010, and discuss the fate of six PCB congeners.
PCB concentrations in the ice core peak in the period of high PCB
emissions, as well as in years with strong melt. While for lower-chlorinated
PCB congeners revolatilization is important, for higher-chlorinated
congeners, the main processes are storage in glacier ice and removal
by particle runoff. This study gives insight into PCB fate and dynamics
and reveals the effect of snow accumulation and melt processes on
the fate of semivolatile organic chemicals in a temperate Alpine glacier
A Temperate Alpine Glacier as a Reservoir of Polychlorinated Biphenyls: Model Results of Incorporation, Transport, and Release
In previous studies, the incorporation of polychlorinated biphenyls (PCBs) has been quantified in the accumulation areas of Alpine glaciers. Here, we introduce a model framework that quantifies mass fluxes of PCBs in glaciers and apply it to the Silvretta glacier (Switzerland). The models include PCB incorporation into the entire surface of the glacier, downhill transport with the flow of the glacier ice, and chemical fate in the glacial lake. The models are run for the years 1900−2100 and validated by comparing modeled and measured PCB concentrations in an ice core, a lake sediment core, and the glacial streamwater. The incorporation and release fluxes, as well as the storage of PCBs in the glacier increase until the 1980s and decrease thereafter. After a
temporary increase in the 2000s, the future PCB release and the PCB concentrations in the glacial stream are estimated to be small but persistent throughout the 21st century. This study quantifies all relevant PCB fluxes in and from a temperate Alpine glacier over two centuries, and concludes that Alpine glaciers are a small secondary source of PCBs, but that the aftermath of
environmental pollution by persistent and toxic chemicals can endure for decades
Understanding and Predicting the Fate of Semivolatile Organic Pesticides in a Glacier-Fed Lake Using a Multimedia Chemical Fate Model
Melting
glaciers release previously ice-entrapped chemicals to
the surrounding environment. As glacier melting accelerates under
future climate warming, chemical release may also increase. This study
investigated the behavior of semivolatile pesticides over the course
of one year and predicted their behavior under two future climate
change scenarios. Pesticides were quantified in air, lake water, glacial
meltwater, and streamwater in the catchment of Lake Brewster, an alpine
glacier-fed lake located in the Southern Alps of New Zealand. Two
historic-use pesticides (endosulfan I and hexachlorobenzene) and three
current-use pesticides (dacthal, triallate, and chlorpyrifos) were
frequently found in both air and water samples from the catchment.
Regression analysis indicated that the pesticide concentrations in
glacial meltwater and lake water were strongly correlated. A multimedia
environmental fate model was developed for these five chemicals in
Brewster Lake. Modeling results indicated that seasonal lake ice cover
melt, and varying contributions of input from glacial melt and streamwater,
created pulses in pesticide concentrations in lake water. Under future
climate scenarios, the concentration pulse was altered and glacial
melt made a greater contribution (as mass flux) to pesticide input
in the lake water
Polychlorinated Biphenyls in Glaciers. 1. Deposition History from an Alpine Ice Core
We present a highly time-resolved
historical record of polychlorinated
biphenyls (PCBs) from an Alpine ice core (Fiescherhorn glacier, Switzerland).
Introduced in the 1940s, PCBs were widely used industrial chemicals.
Because of their persistence they are still found in the environment,
long after their production phase-out. The Fiescherhorn ice core record
covers the entire time period of industrial use of PCBs, that is,
1940–2002. The total concentration of six PCBs varies from
0.5 to 5 ng L<sup>–1</sup> and reveals a temporal trend, with
an 8-fold increase from the early 1940s to the peak value in the 1970s.
The level in 2002 is comparable to the concentration in the 1940s,
when PCBs were introduced into the market. The time trend of PCBs
associated with the particulate fraction closely follows the trend
found in the dissolved fraction, but the absolute values are a factor
of 10 lower. In addition to changing emissions, fluctuations in the
PCB record were explained by variabilty in convective transport and
postdepositional processes such as surface melting. Concentrations
of PCBs are in agreement with data from seasonal snow samples in the
Alps, but are a factor of 100 higher than concentrations measured
in the Arctic. Contrasting time trends and congener patterns between
the Alpine and Arctic region indicate the importance of atmospheric
transport and postdepositional effects