Sources and remediation for mercury contamination in aquatic systems: a literature review

Runoff of particle bound pollutants from urban impervious surfaces studied by analysis of sediments from stormwater traps.

The environmental impact of metallic contaminants in soils and
sediments is dependent both on the chemical speciation of the metal and the
response of the matrix to biological and physicochemical conditions. These
factors are responsible for the mobilisation of the metal from the solid into
the aquatic phase and hence transport within the immediate vicinity, impacting
on the rate of dispersal, dilution, uptake and transfer into living systems.
The impact of changing environmental conditions on the contaminant inventory
can be to enhance or moderate these phenomena, with subsequent consequences
for the broader risk assessment of the contaminants. Remediation of metallic
contaminants can only be brought about by their removal from the site or by
establishing conditions which favour their retention in the solid phase. A
wide range of in situ and ex situ approaches are available
and a summary overview is presented. The examples show assessment at both
the field and laboratory scale and demonstrate an equally wide range of success
in achieving remediation targets. This can be attributed to limitations in
ensuring that the desired conditions for the initial removal or immobilisation
process are met and maintained over a suitable period of time. Three areas
are reviewed which include: the transport and release of metallic contaminants
in estuarine sediments and the assessment of their potential to impact on
biota; terrestrial contamination systems involving the release of chromium
from waste ore contaminating urban environments; the response of metal-contaminated
wastes to changing environmental conditions and the impact of natural bioremediation.
The focus of the discussion is to highlight the generation of reliable speciation
information and the problems associated with impact and risk assessment. Particular
issues of concern are the laboratory to field scale evaluation of contaminant
behaviour and the approach used to assess the reliability of remediation options.
In conclusion, part of a recent initiative in risk assessment and the development
of pilot scale experimental systems to study long-term behaviour are addressed
as future goals to fill gaps in current research.

The relevance of speciation in the remediation of soils and sediments contaminated by metallic elements—an overview and examples from central scotland, uk

Mercury contaminated sediment sites-an evaluation of remedial options.

The sediment to water diffusive flux of PAHs and PCBs was measured under field conditions with a novel infinite-sink benthic flux chamber that deployed semipermeable membrane devices (SPMD) as a sorbing material. Fluxes were measured before and after in situ capping of sediments in Oslo Harbour with clean clay. The fluxes of native pyrene and PCB 52 from uncapped contaminated sediment measured with the flux chamber were 0.3−1.6 μg m−2 d−1 and 2−8 ng m−2 d−1, respectively. Fluxes from the capped sediment were reduced by 93−97%. The in situ measured fluxes were compared to fluxes independently calculated from freely dissolved concentrations in pore water and overlying water, measured using equilibrium passive samplers, diffusive boundary layer (DBL) thickness, measured by an alabaster dissolution method and literature values of diffusion coefficients. Measured fluxes from the uncapped sediment agreed well with calculated fluxes, the median of the ratio of the measured flux over the calculated flux was 0.9 w...

Field Measurement of Diffusional Mass Transfer of HOCs at the Sediment-Water Interface

During the past 60-70 years, contaminated sediments from local rivers have been settling in the harbour basin of Oslo. This contamination, combined with that from other harbour activities, has developed into a serious pollution problem with both organic and inorganic contaminants. Since 1992 dredging activities have been restricted until the effect of dredging was determined and a safe disposal was found for the sediments. Because of this restriction, a conflict situation arose in terms of decreasing sailing depths, and dispersal of large quantities of contaminated sediments into the water column each day from ship traffic. A complete plan of action to remediate Oslo Harbour was started in 1994 and delivered to the State Pollution Control Authority (SFT) in August 1996. An evaluation of environmental risks connected to the remediation work has been carried out along with the determination of the requirements for the monitoring programme during and after the work. Preliminary evaluation of dredging techniques indicates that mechanic/hydraulic equipment will cause the least dispersion of sediment. Several options for treatment of the sediments have been evaluated. Study results point out that conditioning prior to disposal of the sediments in a confined disposal site in the harbour area, is the most cost effective solution. Seven disposal sites with a capacity of 0.5 mill. m 3 have been identified. Two of the sites are integrated with a subsea road tunnel crossing the harbour basin. The other disposal sites will serve as new dock area after closure.

Per Ø. Halvorsen

Papers

Remediation of contaminated sediments in oslo harbour, norway

Remediation of contaminated sediments in Oslo Harbour, Norway