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6.0 SURFACE -WATER QUALITY -- Continued <br />6.4 Metals <br />Large Concentrations of Total Recoverable Metals Are Associated <br />with Large Concentrations of Suspended Sediment <br />Iron and aluminum are the dominant metals found with suspended sediment. <br />Concentrations of total recoverable metals in- <br />crease with concentrations of suspended sediment <br />during high streamflow. Of those metals analyzed, <br />total recoverable iron and aluminum were dominant. <br />Total recoverable manganese, zinc, copper, and lead <br />occurred in intermediate concentrations; total recov- <br />erable nickel, chromium, cobalt, molybdenum, mer- <br />cury, and cadmium were present in smaller concen- <br />trations. The data indicate the metals primarily are <br />associated with the suspended sediment rather than <br />in the dissolved form. Data for concentrations of <br />sediment and total recoverable metals are available at <br />the eight streamflow- gaging stations shown in figure <br />6.4 -1. The drainage basins of all stations except <br />station 9 are underlain by the Raton and Poison <br />Canyon Formations. The drainage basin of station 9 <br />is underlain by igneous and metamorphic rocks and <br />rocks of Permian and Pennsylvanian age located in <br />the Culebra Range. <br />Maximum total recoverable iron concentrations <br />ranged from 43,000 µg /L (micrograms per liter) at <br />station 9 to 930,000 µg /L at station 16. Maximum <br />.1 <br />total recoverable aluminum concentrations ranged <br />from 100,000 µg /L at station 9 to 800,000 µg /L at <br />station 16. Concentrations of total recoverable iron <br />and aluminum during low -flow periods were less <br />than 150 µg /L at all stations. <br />Analysis of data collected for sediment and total <br />recoverable metals at the eight streamflow- gaging <br />stations in figure 6.4 -1 indicates that a general rela- <br />tionship exists between some metals and sediment <br />concentrations. The relationships, which are illus- <br />trated for station 12 (Purgatoire River at Madrid, <br />Colo.) in figure 6.4 -2, can be used to estimate the <br />concentration of selected total recoverable metals <br />from sediment concentration at this station. For <br />example, assume a water sample at station 12 had a <br />suspended- sediment concentration of 50,000 milli- <br />grams per liter. The estimated total recoverable iron <br />concentration is approximately 540,000 µg /L. A <br />statistical summary of selected metals analyzed is <br />shown in table 6.4 -1. The maximum values occurred <br />during storm runoff. <br />