Abstract
Sediments from a waste pit in Houston Ship Channel (HSC) were characterized using a number of molecular markers of natural organic matter fractions (e.g., pyrogenic carbon residues, PAHs, lignins), in addition to dioxins, in order to test the hypothesis that the dispersal and mobility of dioxins from the waste pit in the San Jacinto River is minimal. Station SG-6, sampled at the site of the submerged waste pit, had the highest dioxin/furan concentrations reported for the Houston Ship Channel/Galveston Bay (HSC/GB) system (10,000–46,000 pg/g), which translated into some of the highest reported World Health Organization Toxic Equivalents (TEQs: 2000–11,000 pg/g) in HSC sediments. Using a multi-tracer approach, this study confirmed our hypothesis that sludges from chlorinated pulps are a very likely source of dioxins/furans to this pit. However, this material also contained large quantities of additional hydrophobic organic contaminants (PAHs) and pyrogenic markers (soot-BC, levoglucosan), pointing to the co-occurrence of petroleum hydrocarbons and combustion byproducts. Comparison of dioxin/furan signatures in the waste pit with those from sediments of the HSC and a control site suggests that the remobilization of contaminated particles did not occur beyond the close vicinity of the pit itself. The dioxins/furans in sediments outside the waste pit within the HSC are rather from other diffuse inputs, entering the sedimentary environment through the air and water, and which are comprised of a mixture of industrial and municipal sources. Fingerprinting of waste pit dioxins indicates that their composition is typical of pulp and paper sources. Measured pore water concentrations were 1 order of magnitude lower than estimated values, calculated from a multiphase sorption model, indicating low mobility of dioxins within the waste pit. This is likely accomplished by co-occurring and strong sorbing pyrogenic and petrogenic residues in the waste pit, which tend to keep dioxins strongly sorbed to particles.
Highlights
The 50 mile long Houston Ship Channel (HSC) connects the San Jacinto River Basin to Galveston Bay (GB) and the Gulf of Mexico
Some 210Pbxs profiles (Fig. 23 Supplementary Information (SI)) confirm episodic deposition events over a longer time frame and as such are unsuitable for use in determining a sediment mass accumulation rates (MAR)
The unique and diverse environmental forensics approach presented in this paper, which used organic biomarkers to distinguish possible contamination sources, could be used in other contaminated sites, including super fund sites, to identify the sources and mobility of polychlorinated dibenzodioxins and furans (PCDD/Fs) or similar contaminants
Summary
The 50 mile long Houston Ship Channel (HSC) connects the San Jacinto River Basin to Galveston Bay (GB) and the Gulf of Mexico. Primary sources of dioxins to the environment include the production of herbicides (Stellman et al, 2003), bleaching processes in pulp and paper mills, metal smelting, and the incineration of municipal and industrial waste (Fiedler, 1996; Hagenmaier et al, 1992; Sonnenberg and Nichols, 1995; Wilken et al, 1992). Dioxins are toxic and have a tendency to bioaccumulate in fish and benthic invertebrates (Wenning et al, 1992). These compounds are persistent in the environment due to their very long half-life and increasing number of sources (Wenning et al, 1992). The mobility and bioavailability of these compounds has been a subject of considerable concern (Louchouarn and Brinkmeyer, 2009)
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