Transport of Suspended-Sediment-Bound Toxaphene in the Mississippi River

Abstract

Suspended sediment samples from ∼30 locations along the Mississippi River and six of its major tributaries were collected during July and August 2002 and March 2003 to investigate the distribution and transport of toxaphene in the Mississippi River. The concentration of toxaphene was measured, and the load of toxaphene carried by the river at each site was calculated using water discharge and suspended sediment concentrations. Results indicate that toxaphene is widespread throughout the Mississippi River Basin with the highest concentrations and loads observed for samples collected in the Lower Mississippi River. Among the tributaries, the Yazoo River carried the largest load, amounting to ∼21% of the estimated load carried by the Mississippi River just below Vicksburg, MS. The majority of the contamination is most likely from nonpoint source runoff from agricultural lands. We also found evidence of a localized toxaphene source in the vicinity of Memphis, perhaps coming from the Wolf River. From our data we estimate that between 200 and 1000 kg of toxaphene were released into the Gulf of Mexico in 2002 from the main stem of the Mississippi River.

An 80‐year record of sediment quality in the lower Mississippi River

“…Detections of other organochlorine pesticides were infrequent, probably because the detection levels were high relative to reported concentrations in lower Mississippi River sediments. The toxaphene concentration, for example, in Mississippi River suspended sediment collected immediately downstream from Lake Whittington was 5.9 µg kg −1 in 2002–2003 (Raff and Hites, ), much lower than the reporting level for toxaphene (200 µg kg −1 ) for the method used in this study. Chlordane compounds ( cis ‐ and trans ‐chlordane and trans ‐nonachlor) were also not detected (reporting levels of 0.5–2 µg kg −1 ), and dieldrin was detected in only three samples (maximum concentration was an estimated 0.56 µg kg −1 ) (Supporting Information Table S3).…”

Nonpoint Sources

“…Runoff losses of foliar-applied pesticides were small relative to washoff amounts but were sensitive to runoff timing relative to washoff. Raff and Hites (2004) evaluated the transport of suspended-sediment-bound toxaphene in the Mississippi River. Results indicated toxaphene was widespread throughout the Mississippi River basin.…”

A preliminary assessment of the spatial sources of contemporary suspended sediment in the Ohio River basin, United States, using water quality data from the NASQAN programme in a source tracing procedure

“…Integrated and cost‐effective management of sediment‐associated environmental problems relies heavily on an understanding of the spatio‐temporal dynamics of key catchment sediment sources (Collins et al , 2001). Sediment represents a significant vector contributing to the transfer and fate of many substances, including organic carbon, agricultural chemicals and industrial toxic contaminants (Catt et al , 1998; Winger and Lasier, 1998; Rostad et al , 1999; Warren et al , 2003; Raff and Hites, 2004; Rostad and Daniel, 2007). Enhanced sediment pressures are responsible for degrading freshwater habitats, detrimentally affecting aquatic biota and contributing to health risks associated with bacterial pulses (Packman and Mackay, 2003; Greig et al , 2005; Bennett and Rhoton, 2009; Ochs et al , 2010).…”

“…Horowitz et al, 2001). Data assembled by NASQAN have been used to assess the up-to-date status and temporal change in concentrations and loads of nitrogen, phosphorus, carbon, dissolved solids, selected pesticides and suspended sediment (Raff and Hites, 2004;Turner and Rabalais, 2004) in major rivers and to explore possible linkages with key river basin attributes including land use and associated change (Julien, 2002;Knox, 2006;Meade and Moody, 2009) as well as river channel management (Smith and Winkley, 1996;Meade, 2004).…”