Evaluation of the effects of coal fly ash amendments on the toxicity of a contaminated marine sediment

Abstract

Approaches for cleaning-up contaminated sediments range from dredging to in situ treatment. In the present report, we discuss the effects of amending reference and contaminated sediments with coal fly ash to reduce the bioavailability and toxicity of a field sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). Six fly ashes and a coconut charcoal were evaluated in 7 d whole sediment toxicity tests with a marine amphipod (Ampelisca abdita) and mysid (Americamysis bahia). Fly ashes with high carbon content and the coconut charcoal showed proficiency at reducing toxicity. Some of the fly ashes demonstrated toxicity in the reference treatments. It is suspected that some of this toxicity is related to the presence of ammonia associated with fly ashes as a result of post-oxidation treatment to reduce nitrous oxides emissions. Relatively simple methods exist to remove ammonia from fly ash prior to use and fly ashes with low ammonia content are available. Fly ashes were also shown to effectively reduce overlying water concentrations of several PAHs. There was no evidence of the release of the metals cadmium, copper, nickel or lead from the fly ashes. A preliminary 28 d polychaete bioaccumulation study with one of the high carbon fly ashes and a reference sediment was also performed. Although preliminary, there was no evidence of adverse effects to worm growth or lipid content, or the accumulation of PAHs or mercury from exposure to the fly ash. These data show fly ashes with high carbon contents may represent viable remedial materials for reducing the bioavailability of organic contaminants in sediments.

Influences of multiwalled carbon nanotubes and plant residue chars on bioaccumulation of polycyclic aromatic hydrocarbons by Chironomus plumosus larvae in sediment

“…Because of their strong sorption capacities, both CNTs and black carbon have been suggested as potential remediation materials to reduce the bioavailability of HOCs in sediments or soils [7,[13][14][15]. Petersen et al [6] reported that 0.3% CNT amendment in soils decreased pyrene bioaccumulation by earthworm Eisenia fetida.…”

Activated carbon amendment to remediate contaminated sediments and soils: a review

“…The time of AC treatment varied from two minutes (Sun and Ghosh, 2007) to 780 days (Tomaszewski et al, 2007). In some articles, this information was not available (Voparil et al, 2004;Cornelissen et al, 2006a;Burgess et al, 2009). The work of Sun and Ghosh (2007) was specifically investigating the time of AC treatment.…”

“…Therefore, researchers started to use alternative carbon material like e.g. biochar (Yu et al, 2009), coke breeze (Zimmerman et al, 2004;Millward et al, 2005), waste AC (Guo et al, 1991), fly ash (Burgess et al, 2009), and many more. Further drawbacks and side effects of AC amendment, such as the stability of the AC material, physical alteration of the matrices, direct or indirect harmful effects on, and nutrient availability to organisms will be discussed in "Factors potentially reducing the efficiency of AC amendment and other side effects" section.…”

Mercury capture by native fly ash carbons in coal-fired power plants

“…The levels of PAH associated with a fly ash are, however, a very strong function of the temperature and excess oxygen used in combustion [46], and the levels from pulverized coal combustion power plants are typically quite low (Wornat et al [47] found levels of typical 2- to 3-ring PAH in the range of ppb and below). In fact, these inherent PAH levels are usually sufficiently low, suggesting that coal combustion fly ashes might themselves be useful for binding (adsorbing) PAH from other sources and residing in marine sediments [48]. Fly ash has also been considered as an inexpensive adsorbent for water or soil treatment, such as for adsorption of aromatic acid dyes [49].…”