Monitoring Re-Suspension and Transport of Dioxin Contaminated Sediment to Evaluate the Recovery of a Shallow Urban Creek Post Sediment Remediation

Lisa Richman,Eric Reiner,Liad Haimovici,Terry Kolic,Sladjana Besevic

doi:10.4236/jep.2016.73039

Abstract

Pringle Creek, identified as the source of dioxin/furan (PCDD/F) contamination to a Lake Ontario harbour was remediated in 2008. Surface sediment collected in 2013 near the floodplain remediation was no longer contaminated (∑17PCDD\Fs ∑17PCDD\Fs 2900 pg/g dw). Nevertheless, sediment ∑17PCDD/F concentrations were lower in 2013 than pre-remediation suggesting that cleaner sediment was being deposited in the creek. Core data confirmed the decrease in sediment contamination through time since the most contaminated sediment was buried. Prior to the development of a remediation strategy for the harbour, the transport of bed-load and suspended sediment contaminated with PCDD/F was assessed. The challenge was the shallow water depth (0.6 m) throughout the creek thereby requiring non-standard sediment traps designed for this study. Suspended sediment collected in traps in 2014 showed residual contamination at the remediated site (∑17PCDD\Fs: 380 pg/g dw; TEQ (TEF fish) ∑17PCDD\Fs concentration for suspended sediment at the creek mouth was 2200 pg/g (SD 260 pg/g dw) indicating PCDD/F contributions to the harbour. However, congener patterns in bottom sediment and suspended sediment near the remediated site and extending about 100 m downstream were similar to background upstream patterns consistent with atmospheric deposition as the source rather than the historical source which indicated that floodplain remedial actions were successful.

Highlights

Contaminant data for Whitby Harbour and Pringle Creek sediment and floodplain soil collected by the Ontario Ministry of Environment and Climate Change (MOECC) from 1993-2013 identified the creek and harbour as being contaminated with polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F)
The surface sediment (0 - 10 cm) PCDD/F core data showed that contamination remained in the lower section of Pringle Creek (Stations S7 to S11), and in a pond on the west bank (Figure 1 & Figure 3(a))
Congener patterns maintained the pattern of the historical source further downstream, concentrations of PCDD/F at stations with historical data, were lower in 2013 than pre-remediation which suggested that cleaner sediment was being deposited (Figure 3(a) & Figure 4)

Summary

Introduction

Contaminant data for Whitby Harbour and Pringle Creek sediment and floodplain soil collected by the Ontario Ministry of Environment and Climate Change (MOECC) from 1993-2013 identified the creek and harbour as being contaminated with polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F). These findings were significant, the presence of high concentrations of the seventeen 2,3,7,8-substituted PCDD/Fs. These findings were significant, the presence of high concentrations of the seventeen 2,3,7,8-substituted PCDD/Fs Since these compounds are bioaccumulative and depending on the congeners present, this can be acutely toxic in fish, wildlife and humans [1] [2]. For comparison ∑17PCDD\Fs concentrations for Lake Erie and Lake Ontario ranged from 30 to 10,000 pg/g with a lake wide average TEQ at 19 pg/g to 110 pg/g respectively [8]

Methods

Results

Conclusion