Evidence for partial degradation of toxaphene in the aquatic environment

1995

The historical input of toxaphene to Lake Ontario has been determined. We analyzed total toxaphene concentrations in eight Lake Ontario sediment cores by electron capture gas chromatographic mass spectrometry and found that toxaphene maximizes in 1973 ( 6 yr with a horizon date of 1945 ( 6 yr. The maximum toxaphene flux to Lake Ontario sediment was 22 ( 8 µg/m 2 yr in about 1973, and the total toxaphene load in the lake is 10 ( 3 t. By comparing the toxaphene burdens for the cores, we conclude that toxaphene is deposited to Lake Ontario sediment from both the Niagara River and from the atmosphere. We also found that toxaphene is slowly dechlorinated after deposition in Lake Ontario sediment.

Section: Resultsmentioning

confidence: 99%

Historical Input and Degradation of Toxaphene in Lake Ontario Sediment

Howdeshell

1995

“…Because toxaphene concentrations near the Great Lakes approached detection limits in other studies and because concentrations in the South have been shown to be relatively high, different sample volumes were collected over the same time period at the different sites. A typical sample from Arkansas and Texas was about 400 m 3 of air, and one from Indiana and Michigan was about 1400 m 3 . Site operators at each site performed the sampling and shipped the samples to Indiana University for analysis.…”

Section: Atmosphericmentioning

confidence: 99%

Atmospheric Transport of Toxaphene from the Southern United States to the Great Lakes Region

James

2002

Toxaphene was used extensively as an insecticide on cotton in the southern United States until its use was restricted in 1982. Toxaphene has been found in the water and fishes from the Great Lakes, and several authors have qualitatively linked this observation to atmospheric transport from the southern United States, although no detailed field study has been done to confirm this suggestion. We implemented a sampling network to measure the gas-phase concentrations of toxaphene near Lake Michigan at Sleeping Bear Dunes, MI; Bloomington, IN; Lubbock, TX; and Rohwer, AR. The toxaphene concentrations referenced to 288 K were 11 +/- 1, 25 +/- 1, 160 +/- 3, and 950 +/- 30 pg/ m3, respectively. We combined these concentration data with a nonparametric, backward trajectory, multiple regression model of the following form: ln(P) = a0 + a1/T + a2theta where P is the partial pressure of toxaphene (in atm) in a given sample, T is the atmospheric temperature at the sampling site during sampling (in degrees Kelvin), and theta is 0 if the backward trajectory comes from the north and 1 if the trajectory comes from the south. The parameters of this model were generally significant, giving a temperature coefficient (a1) corresponding to 45 +/- 8 kJ/mol and a positive directional coefficient (a2) of 0.6 +/- 0.2 (except for Texas, which was not significant). The positive sign and magnitude of the directional coefficient indicates that the sources of toxaphene are located south of the sampling sites. We also compared the chemical behavior of toxaphene in the atmosphere and found that the congener ratios were similar at the different sampling sites but slightly different from various toxaphene standards.

“…Toxaphene was produced by the photochlorination of camphene, an isomerization product of α-pinene, which was obtained from softwood tree stumps (). First used as a piscicide in the 1950s in the upper Midwest and Canada ( , ), toxaphene's primary use shifted to the southern United States to control insects on cotton. It was also used on soybeans and peanuts and as a flea dip for livestock ( − ).…”

Section: Introductionmentioning

confidence: 99%

Radial Dilution Model for the Distribution of Toxaphene in the United States and Canada on the Basis of Measured Concentrations in Tree Bark

McDonald

2002

Toxaphene was a highly chlorinated pesticide that was used in the United States from the 1950s until its restriction and ban in the 1980s. It was primarily used on cotton in the southern United States, and perhaps as a result, toxaphene is found in high concentrations in the southern United States. Toxaphene has also been detected at remote locations, such as in the high Canadian Arctic. However, these and other studies focused on selected regions of the United States and Canada, which only allowed for a limited interpretation of these data. We report here the concentrations of toxaphene measured in 46 tree bark samples collected in the United States and Canada. Concentrations were found to be greatest in the Mississippi River Valley along the borders of southern Missouri and Arkansas. We created a simple model based on radial dilution from a central location in the south central United States to describe toxaphene concentrations in tree bark and in air throughout the United States and Canada. The toxaphene concentrations were successfully described by this inverse square distance model. A bark-atmosphere partition coefficient for toxaphene was also calculated that was similar to literature-derived octanol-air partition coefficients. High concentrations of toxaphene still exist in areas where it was heavily used but decline rapidly with distance.