Transport of Dioxins and Furans Through Geotextiles During Sediment Dewatering

疏浚的海洋沉积物通常在放置或处置之前脱水。被多氯二苯并对二恶英和多氯二苯并呋喃(俗称二恶英和呋喃)污染的沉积物，由于其毒性，给脱水和处置带来了独特的挑战。这一问题在整个加拿大都很普遍；加拿大财政部(2017年)列出了157个联邦登记的污染场地，其中含有多氯二苯并二恶英和/或多氯联苯污染的沉积物。在大多数司法管辖区，通过颗粒物缔合存在于水中的多氯二苯并二恶英的含量即使很低(即皮克)也是不可接受的。使用土工合成管(即土工管)对沉积物进行脱水正成为普遍做法，但通过土工管运输多氯二苯并二恶英/二恶英的风险尚未得到很好的了解或量化。这一研究计划的长期目标是更好地了解在使用地质管进行沉积物脱水过程中，PCDD/Fs通过颗粒物的迁移和去向。文献表明，土壤水系统中的颗粒态有机质与二恶英/二恶英密切相关。这项研究计划将结合实验室和现场研究来评估在土管降水过程中颗粒物的传输，从而评估PCDD/F的传输。将开发新的预测方法来设计涉及PCDD/F的土管脱水系统。初步研究将集中在实验室实验，以确定在脱水过程中，PCDD/F通过土管中的颗粒物传输的主要机制。实验室实验将使用受污染的海洋沉积物，并将使用实验室规模的脱水技术进行物理测试。在这些测试过程中保留的沉积物将进行物理特性分析。流出物中的颗粒物也将使用类似的方法进行表征(即评估脱水过程中的颗粒传输)。还将评估不同土工布和滤饼发展对颗粒物质运输的作用。将评估在脱水过程中从沉积物中迁移多氯二苯并二恶英的关键机制。这部分工作将涉及在沉积物中添加多氯二苯并二恶英，并评估降水过程中多氯二苯并二恶英/氟的迁移情况。这项工作还将涉及评估现有的过滤性能模型，以预测在不同运行条件下的土管脱水过程中多氯二苯并二恶英的迁移情况。多氯二苯并二恶英/氟化物污染沉积物的实地脱水试验将提供与实验室结果进行比较的机会，并将根据这些实地试验对研究中开发的预测工具进行评估。该研究项目还将支持包括2名博士、2名硕士和4名本科生在内的多名HQP的培训。

Dredged marine sediment is often dewatered prior to placement or disposal. Sediments contaminated with polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, commonly known as dioxins and furans (PCDD/Fs), present unique challenges for dewatering and disposal due to their toxicity. This issue is prevalent across Canada; the Treasury Board of Canada (2017) lists 157 federally registered contaminated sites with PCDD/Fs and/or PCB contaminated sediments. PCDD/Fs present at even very small levels (i.e. picogram) in water via particulate matter association are not acceptable in most jurisdictions. Dewatering of sediment using geosynthetic tubes (i.e. geotubes) is becoming common practice, yet the risks associated with PCDD/F transport via geotubes is not well understood or quantified. The long-term objective of this research program is to better understand the transport and fate of PCDD/Fs via particle matter during sediment dewatering using geotubes. It is well established in the literature that PCDD/Fs are strongly associated with particulate organic matter in soil water systems. This research program will use a combination of lab and field studies to assess particulate matter transport, and hence PCDD/F transport, during geotube dewatering. New predictive approaches will be developed for designing geotube dewatering systems involving PCDD/Fs.The initial research will focus on lab experiments to identify the dominant mechanisms responsible for PCDD/F transport via particle matter from geotubes during dewatering. Lab experiments will use contaminated marine sediments and will involve physical testing using bench scale dewatering techniques. The sediment retained during these tests will be physically characterized. The particulate matter in the effluent will also be characterized using similar methods (i.e. to assess particle transport during dewatering). The role of different geotextiles and filter cake development on the transport of particle matter will also be assessed. Key mechanisms will be evaluated with respect to transport of PCDD/Fs from sediment during dewatering. This portion of the work will involve spiking of sediment PCDD/Fs and evaluating PCDD/F transport during dewatering. The work will also involve evaluating existing filtration performance models to predict the transport of PCDD/Fs during geotube dewatering under differing operational conditions. A field dewatering trial of PCDD/F contaminated sediment will provide opportunity for comparison to lab findings and predictive tools developed in the research will be assessed based on these field trials. This research program will also support the training of several HQP including 2 doctoral, 2 masters and 4 undergraduate students.