Greenhouse Experimental Methods Towards in-situ Burial and Restoration of Contaminated Sites in Submerged Wetlands

Abstract

As a result of commercial and industrial activit ies conducted in the absence of environmental regulations and enforcement in the past, sediments contaminated by organic compounds, heavy metals, and other potentially to xic chemicals have accu mulated in many of the world's deepwater and wet land environ ments. These sediment-borne contaminants can eventually become incorporated into aquatic food webs and adversely affect ecological receptors like benthic organisms and fish, and u ltimately pose a risk to hu man health. This laboratory research tested a commercial product AquaBlok TM (patented, composite-aggregate technology comprised of a solid core, an outer layer of clay material, and polymers) as an in-situ capping technology that could be used to remediate and/or manage contaminated sediments in the New Jersey Hackensack Meadowlands, a superfund site. In a greenhouse setting, tubs containing representative Meadowland marsh soil and water were capped with AquaBlok. This research not only examined the potential use of this product as an in-situ capping material and possible substrate for flora co lonization, but also examined the imp rovements of the same patented, clay mineral-based composite aggregate technology (SubmerSeed TM ) as an alternative to tradit ional means of wetland p lant propagation. At the end of a two-year period, both the sediment/cap and vegetation plant tissues were examined for metallic contaminants (including Cd, Cr, Cu, Pb, Hg, and Zn). Overall, capping provided a less contaminated substrate. Results indicated that AquaBlok cap alone did not allow contaminants in the sediment belo w to breakthrough. Nevertheless, vegetation colonization was restricted to a limited number of plant species. Furthermore, plants growing in AquaBlok were less robust with lower dry weight and s maller root system than plants growing in uncapped sediments despite the fact that their tissue contained smaller amounts of metallic contaminants. The improvements of the clay mineral-based composite aggregate technology (Sub merSeeds) as an alternative to trad itional means of plant propagation worked very well in successfully delivering aquatic plant seeds into permanently inundated conditions.