Search

Your search keyword '"Snowball, Ian"' showing total 41 results
Start Over Author "Snowball, Ian" Publisher elsevier bv
41 results on '"Snowball, Ian"'

3. Capping fiberbank sediments to reduce persistent organic pollutants (POPs) fluxes : A large-scale laboratory column experiment

Author

Dahlberg, Anna-Karin, Wiberg, Karin, Snowball, Ian, Lehoux, Alizée, Dahlberg, Anna-Karin, Wiberg, Karin, Snowball, Ian, and Lehoux, Alizée

Abstract

Deposits of contaminated wood fiber waste (fiberbanks), originating from sawmills and pulp and paper industries, have been found in the aquatic environment in boreal countries. In-situ isolation capping has been proposed as a remediation solution because it has the potential to prevent dispersal of persistent organic pollutants (POPs) from this type of sediment. However, knowledge about the performance of such caps when placed on very soft (un-consolidated), gaseous organic rich sediment is scarce. We investigated the effectiveness of conventional in-situ capping to limit POPs fluxes to the water column from contaminated fibrous sediments that produce gas. A controlled, large-scale laboratory column (40 cm diameter, 2 m height) experiment was performed over 8 months to study changes in sediment-to-water fluxes of POPs and particle resuspension before and after capping the sediment with crushed stones (& GE;4 mm grain size). Two different cap thicknesses were tested (20 and 45 cm) on two types of fiberbank sediment with different fiber type composition. Results showed that capping fiberbank sediment with a 45 cm gravel cap reduced the sediment-to-water flux by 91-95% for p,p'-DDD, o,p'-DDD, by 39-82% for CB-101, CB-118, CB-138, CB-153, CB-180 and by 12-18% for HCB, whereas for less hydrophobic PCBs, capping was largely ineffective (i.e. CB-28 and CB-52). Although cap application caused particle resus-pension, the long-term effect of the cap was reduced particle resuspension. On the other hand, substantial sediment consolidation released large volumes of contaminated pore water into the overlying water body. Importantly, both sediment types produced large amount of gas, observed as gas voids forming inside the sediment and gas ebullition events, which increased pore water advection and affected the structural integrity of the cap. This may limit the practical applicability of this method on fiberbank sediments.

Published
2023
Full Text
View/download PDF

7. Palaeoenvironmental implications from Lower Volga loess - Joint magnetic fabric and multi-proxy analyses

Author

Költringer, Chiara, Bradák, Balázs, Stevens, Thomas, Almqvist, Bjarne, Banak, Adriano, Lindner, Martin, Kurbanov, Redzhep, Snowball, Ian, Költringer, Chiara, Bradák, Balázs, Stevens, Thomas, Almqvist, Bjarne, Banak, Adriano, Lindner, Martin, Kurbanov, Redzhep, and Snowball, Ian

Abstract

Magnetic fabric (MF) investigations complemented by geochemical and grain surface analyses of the understudied and controversial marine isotope stage (MIS) 5 b, 4 and 3 loess deposits in the Lower Volga region, Russia show that the material has been transported and deposited by wind and to a large extent experienced post-depositional reworking. Grain surface features suggest that the material was glacially ground and fluvially transported prior to final aeolian deposition as loess. Secondary magnetic fabrics in the loess reveal pedogenic and cryogenic processes and a generally cold environment with brief shifts to warmer climate during late MIS 5 and MIS 3. Palaeowind reconstructions derived from preserved primary aeolian MF, indicate locally influenced westerly and north-westerly flow as part of a wider scale westerly wind pattern, similar to modern day winter conditions. We suggest that the climate of the last glacial in the Northern Caspian Lowland was cold and dry, with higher windspeeds and less variability during MIS 4 compared to MIS 3.

Published
2021
Full Text
View/download PDF

8. Is 'deep-water formation' in the Baltic Sea a key to understanding seabed dynamics and ventilation changes over the past 7,000 years?

Author

Moros, Matthias, Kotilainen, Aarno Tapio, Snowball, Ian, Neumann, Thomas, Perner, Kerstin, Meier, H. E. Markus, Leipe, Thomas, Zillen, Lovisa, Damste, Jaap S. Sinninghe, Schneider, Ralph, Moros, Matthias, Kotilainen, Aarno Tapio, Snowball, Ian, Neumann, Thomas, Perner, Kerstin, Meier, H. E. Markus, Leipe, Thomas, Zillen, Lovisa, Damste, Jaap S. Sinninghe, and Schneider, Ralph

Abstract

Numerous hydro-acoustic studies of the seabed of the Baltic Sea have revealed the unusual occurrence of sediment contourite drifts and re-suspension at greater water depths. In addition, radiocarbon dating of bulk sediments indicates significant age reversals. We present new geophysical, sediment proxy data (including extensive radiocarbon dating) and hydrographic measurements, which are combined with results of numerous marine geological studies performed during the last decades. These data indicate that a deep-water formation process significantly affected the seabed dynamics during regional climatically cold phases during the last c. 7,000 years. We propose that, during the colder periods (e.g. the Little Ice Age), newly formed bottom waters likely caused widespread re-suspension of organic carbon-rich laminated sediments that were deposited during the preceding warm periods in shallower areas, and this material was transported to and re-deposited in the deeper parts of the Baltic Sea sub-basins. In our scenario, a topographic feature, known as the Baltic Sea Klint, acted as a hydrographic barrier for deep-water formed in the northern Baltic. Thus, during the cold periods increased lateral matter influx from the northern Baltic led to the accumulation of much thicker macroscopically homogenous clayey sediments in sub-basins north of the Klint. Moreover, deep-water formation produced bottom currents that led to the formation of sediment contourite drifts at water depths of> 200 m in the Bothnian Sea, the Aland Deep and northern central Baltic Sea sub-basins. Bottom water ventilation in the Baltic Sea is generally assumed to be determined solely by the inflow of oxygen-rich, saline water from the North Sea, but we challenge this assumption and postulate that deep-water formation is a key process that ventilates the bottom waters of the Baltic Sea during climatically cold periods with substantial implications for its sedimentary archive.

Published
2020
Full Text
View/download PDF

11. Is ‘deep-water formation’ in the Baltic Sea a key to understanding seabed dynamics and ventilation changes over the past 7,000 years?

Author

Moros, Matthias, primary, Kotilainen, Aarno Tapio, additional, Snowball, Ian, additional, Neumann, Thomas, additional, Perner, Kerstin, additional, Meier, H.E. Markus, additional, Leipe, Thomas, additional, Zillén, Lovisa, additional, Sinninghe Damsté, Jaap S., additional, and Schneider, Ralph, additional

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results