|dc.identifier.citation||Hoffman, E., Lyons, J., Boxall, J., Robertson, C. , Lake, C.B., and Walker, T.R. 2017. Spatio-temporal assessment (quarter century) of pulp mill metal(loid) contaminated sediment to inform remediation decisions, Journal of Environmental Monitoring and Assessment, 189: 257. https://doi.org/10.1007/s10661-017-5952-0.||en_US
|dc.description.abstract||A bleached kraft pulp mill in Nova Scotia has
discharged effluent wastewater into Boat Harbour, a former
tidal estuary within Pictou Landing First Nation since
1967. Fifty years of effluent discharge into Boat Harbour
has created >170,000 m3 of unconsolidated sediment,
impacted by inorganic and organic contaminants, including
metal[loid]s, polycyclic aromatic hydrocarbons
(PAHs), dioxins, and furans. This study aimed to characterize
metal(loid)-impacted sediments to inform decisions
for a $89 million CAD sediment remediation program.
The remediation goals are to return this impacted aquatic
site to pre-mill tidal conditions. To understand historical
sediment characteristics, spatiotemporal variation covering
~quarter century, of metal(loid) sediment concentrations
across 103 Boat Harbour samples from 81 stations and
four reference locations, were assessed by reviewing secondary
data from 1992 to 2015. Metal(loid) sediment
concentrations were compared to current Canadian freshwater
and marine sediment quality guidelines (SQGs).
Seven metal(loid)s, As, Cd, Cr, Cu, Pb, Hg, and Zn,
exceeded low effect freshwater and marine SQGs; six,
As, Cd, Cr, Pb, Hg, and Zn, exceeded severe effect freshwater
SQGs; and four, Cd, Cu, Hg, and Zn, exceeded
severe effect marine SQGs. Metal(loid) concentrations
varied widely across three distinct temporal periods.
Significantly higherCd, Cu, Pb, Hg, and Zn concentrations
were measured between 1998 and 2000, compared to
earlier, 1992–1996 and more recent 2003–2015 data.
Most samples, 69%, were shallow (0–15 cm), leaving
deeper horizons under-characterized. Geographic information
system (GIS) techniques also revealed inadequate
spatial coverage, presenting challenges for remedy decisions
regarding vertical and horizontal delineation of contaminants.
Review of historical monitoring data revealed
that gaps still exist in our understanding of sediment
characteristics in Boat Harbour, including spatial, vertical
and horizontal, and temporal variation of sediment contamination.
To help return Boat Harbour to a tidal estuary,
more detailed sampling is required to better characterize
these sediments and to establish appropriate reference
(background) concentrations to help develop costeffective
remediation approaches for this decades-old