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Open-File Report 01-282

Sediment-Deposition Rates and Organic Compounds in Bottom Sediment at Four Sites in Lake Mead, Nevada, May 1998

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Table 8. Dioxin concentrations in bottom-sediment cores at three sites in Lake Mead, May 1998

[Abbreviations: TCDD, tetrachlorodibenzo-p-dioxin; PeCDD, pentachlorodibenzo-p-dioxin; HxCDD, hexachlorodibenzo-p-dioxin; HpCDD, heptachlorodibenzo-p-dioxin; OCDD, octachlorodibenzo-p-dioxin. Symbols: <, less than; *, estimated (reported when the compound has passed all criteria used to identify its presence and only the concentration is estimated). All concentrations are in picograms per gram]

Depth interval (centimeters)

Total TCDDs

2,3,7,8 TCDD

Total PeCDD

1,2,3,7,8 PeCDD

Total HxCDD

1,2,3,4,7,8 HxCDD

1,2,3,6,7,8 HxCDD

1,2,3,7,8,9 HxCDD

Total HpCDD

1,2,3,4,6,7,8 HpCDD

OCDD

Site 1: Las Vegas Bay -- shallow

5-10

39

<0.88

<5.8

<0.61

<3.4

<0.66

<1.5

<1.1

19

*10

72
15-20 17 <.80 <5.9 <2.4 <1.8 <.50 <.98 <1.2 <4.9 <4.3 34
25-30 13 <.59 <6.1 <2.7 <1.8 <.97 <1.1 <.97 <4.5 <4.5 28
35-40 12 <.38 <3.9 <.86 <2.6 <.56 <1.4 <1.3 5.7 *5.7 20
55-60 5.3 <.66 <2.7 <2.3 <2.0 <1.9 <2.0 <1.8 <2.3 <2.3 *10
75-80 .86 <.62 <1.3 <1.3 <1.8 <1.7 <1.8 <1.6 <1.7 <1.7 *8.6
95-100 1.5 <.55 <2.4 <1.9 <3.4 <1.7 <1.7 <1.6 23 10 93

Site 2: Las Vegas Bay -- deep

5-10

20

<.72

<6.4

<2.5

<3.6

<.98

<1.5

<1.6

7.5

*7.5

44
15-20 22 *.98 5.2 <1.7 9.6 <1.5 <2.7 <3.0 16 9.7 35
25-30 21 *.97 9.6 <1.9 10 <1.4 <3.1 <2.7 17 10 40
35-40 7.5 <.57 <3.8 <1.4 <1.7 <.39 <.96 <1.1 <3.4 <3.4 15
55-60 1.3 <.69 <4.6 <.86 <1.0 <.96 <1.0 <.92 <2.3 <2.3 *12
75-80 2.4 <.51 <5.5 <.86 <1.1 <.86 <.86 <.82 <4.4 <2.8 26
95-100 <.82 <.44 <5.5 <.55 <.89 <.86 <.89 <.82 <.99 <.61 <2.5

Site 4: Colorado and Virgin Rivers confluence (pre-impoundment)

3-6

<.76

<.76

<2.0

<1.6

<1.6

<1.5

<1.6

<1.5

<1.8

<1.5

<11
9-12 <.69 <.69 <1.8 <1.7 <1.5 <1.5 <1.5 <1.4 <1.0 <1.0 <3.6
15-18 <.58 <.58 <1.7 <1.7 <1.3 <1.3 <1.3 <1.2 <1.2 <1.2 <5.8
21-24 <.52 <.52 <2.4 <2.4 <1.8 <1.8 <1.8 <1.6 <1.4 <1.4 <9.8
45-50 <.66 <.66 <2.2 <1.8 <1.7 <1.5 <1.7 <1.5 <1.0 <1.0 <3.2
65-70 <.64 <.61 <2.5 <1.7 <1.6 <1.5 <1.6 <1.5 <1.4 <1.4 <5.8