WSP07583

• File Number: 8270.200
• Description: Selenium
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 1/1/1996
• Author: USGS
• Title: Detailed Study of Selenium and Other Constituents in Water-Bottom Sediment-Soil-Alfalfa and Biota Associated with Irrigation Drainage - Uncompahgre Project Area and in the Grand Valley - 1991-93
• Water Supply Pro - Doc Type: Report/Study

Selenium in alfalfa from unit Qr was not significantly
different from selenium concentrations in alfalfa
from alluvium overlying Mancos Shale (Qm),
although the flood-plain alluvial soils contained
only about 21 percent of total selenium and about
38 percent of the water-extractable selenium as did
the soils on alluvium overlying Mancos Shale. In
addition, the correlation of total selenium in alfalfa
with water-extractable selenium in soils on unit Qr is
0.77, which is much higher than the same correlation
for all samples of 0.47 (Stewart and others, 1993).
Results from analysis of variance (ANOVA)
indicate that selenium distribution in the
Uncompahgre Project is not unifonn among geologic
units or within geologic units. The percent of the
variance for total and water-extractable selenium in
soil and total selenium in alfalfa that are accounted for
by each of the four levels in the ANOVA sampling

60

55

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Z40
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o
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en
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Z
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:;
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I-
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lU 10
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lU
0.. 5

o

AMONG GEOLOGIC
UNITS

AMONG
TOWNSHIPS

design (Stewart and others, 1993; Crock and others,
1994) are shown in figure 7. The ANOVA results in
figure 7 show the variance among geologic units and
the variance within geologic unit at the township,
section, and within section scale. Fifty-seven percent
of the variance in total selenium in soil was accounted
for by geologic units. By contrast, only 30 percent of
the total variance in water-extractable selenium in soil
is accounted for by geologic units; differences among
sections in the same geologic unit accounted for more
of the total variance in water-extractable selenium
than did differences among geologic units.
Ranges of selenium concentration were much
greater in alfalfa from the alluvial units Qm (soils
overlying Mancos Shale) and Qr (soils on recent
flood-plain alluvium) than the ranges for the other
geologic units-Kd (soils derived from Dakota
Sandstone), Km (soils derived from Mancos Shale,

_ TOTAL SELENIUM. SOil
[=:J WATER.EXTRACTABLE SELENIUM, SOIL
~ TOTAL SELENIUM, ALFALFA

AMONG
SECTIONS

WITHIN
SECTIONS

Figure 7. Percent of variance in selenium concentrations in soils and alfalfa for different levels in the
sampling design.

20 Detailed Study 01 Selenium end Other Conatltuentaln W818r, BoliO';' Sediment, Soli, Alfelfa, and Biota A8Ioclated with
Irrigation Drainage In the Uncompahgre Prolact AI1I8 and In the Grand Valley, Waat-cantral Colorado, 199t-93