SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS
VOCs and Nutrients
Concentrations of herbicides, insecticides, volatile organic compounds, and
nutrients detected in ground and surface waters of the Trinity River Basin Study
Unit
[mg/L,
micrograms per liter; %, percent; <, less than; --, not measured; mg/L,
milligrams per liter; trade names might vary]
EXPLANATION
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Freshwater-chronic criterion for the protection of aquatic life a Drinking-water standard or guideline a Range of surface-water detections in all 20 Study Units Range of ground-water detections in all 20 Study Units Detection in the Trinity River Basin Study Unit |
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Volatile
organic compound |
Rate |
Concentration, in mg/L
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1,1-Dichloroethene (Vinylidene chloride) |
-- 1% |
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1,2,4-Trimethylbenzene (Pseudocumene) |
-- 1% |
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Benzene |
-- 1% |
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Chlorobenzene (Monochlorobenzene) |
-- 1% |
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Chloroethene (Vinyl Chloride) |
-- 1% |
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Dimethylbenzenes (Xylenes (total)) |
-- 1% |
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total Trihalomethanes |
-- 3% |
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Trichloroethene (TCE) |
-- 3% |
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Trichlorofluo- |
-- 1% |
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cis-1,2-Dichloro (ethene) |
-- 1% |
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trans-1,2-Dichloro (ethene) |
-- 1% |
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Volatile
organic compound |
Rate |
Concentration, in mg/L
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Methyl tert-butyl etherd (MTBE) |
-- 4% |
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Tetrachloroethene (Perchloroethene) |
-- 1% |
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Nutrient |
Rate |
Concentration, in mg/L
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Dissolved ammonia |
90% 92% |
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Dissolved ammonia plus organic nitrogen as nitrogen |
91% 41% |
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Dissolved phosphorus as phosphorus |
77% 66% |
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Dissolved nitrite plus nitrate |
87% 50% |
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a Selected water-quality standards and guidelines (Gilliom and others, in press).
b Rates of detection are based on the number of analyses and detections in the Study Unit, not on national data. Rates of detection for herbicides and insecticides were computed by counting only detections equal to or greater than 0.01 mg/L to facilitate equal comparisons among compounds, which had widely varying detection limits. For herbicides and insecticides, a detection rate of "<1%" means that all detections are less than 0.01 mg/L, or the detection rate rounds to less than 1%. For other compound groups, all detections were counted and minimum detection limits for most compounds were similar to the lower end of the national ranges shown. Method detection limits for all compounds in these tables are summarized in (Gilliom and others, in press).
c Detections of these compounds are reliable, but concentrations are determined with greater uncertainty than for the other compounds and are reported as estimated values (Zaugg and others, 1995).
d The guideline for methyl tert-butyl ether is between 20 and 40 mg/L; if the tentative cancer classification C is accepted, the lifetime health advisory will be 20 mg/L (Gilliom and others, in press).
e Selected sediment-quality guidelines (Gilliom and others, in press).
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