7046 ‎(2)‎

• UCREFRP Catalog Number: 7046
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Final Report\
• USFW Year: 1992.
• Copyright Material: NO

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industrial sources of copper pollution include smelting and refining (EP A 1980a). Copper may enter
natural waters directly as emuent or by atmospheric fallout of pollutants produced by industry.
Precipitation of atmospheric fallout may be a significant source of copper to the aquatic environment
in industrial and mining areas (EPA 1980a). Total copper concentrations in the Dolores River
ranged from <0.01 - 0.32 mg/l. Based on the range of water hardness in the Dolores River the EPA
criteria states that freshwater aquatic organisms should not be affected unacceptably if the I-hour
average concentration does not exceed 0.024 - 0.142 mg/l more than once every 3 years on the
average (depending on hardness). However, these values do not apply to situations where a locally
important species is sensitive. When 41 genera of freshwater species were tested for sensitivity to
copper, Ptychocheilus was found to be most sensitive. Copper became acutely toxic to squawfish at
concentrations of 0.016 mg/l at a hardness of 50 mg/l. In the Dolores River in 1990-1991, the upper
limit for preservation of aquatic life was exceeded five-fold Although high levels of water hardness
temper its toxicity, copper may still be present in high enough levels to adversely affect native fish
species, especially Colorado squawfish. Concentrations of copper in the Dolores River in 1990-1991
were substantially higher than reported in 1960 (Table 42). Total copper measured just above the
San Miguel confluence in 1960 peaked at 0.010 mg/l (USPHS 1961), compared to a high of 0.32 near
this location in 1991. Copper levels in the San Miguel were similar in both studies (<0.2 mgll).

Concentrations of iron in the Dolores River in 1990-1991 ranged from 0.2 - 267 mgll. The EPA
has set 1.0 mg/l as the maximum acceptable level of iron for freshwater aquatic life (EP A 1986). This
value was exceeded in 25 of 28 water samples taken on the Dolores River in 1990-1991. The highest
concentration of iron was found on Trip 5 above the confluence of the San Miguel River, and was
267 times the maximum value set by the EP A for protection of freshwater aquatic life. Iron
concentrations in both the Dolores and San Miguel rivers measured in 1990-1991 were higher than
levels recorded in 1960 (USPHS 1961), as well as 1986 (ERI 1986) (Table 42). In 1960, total iron
was 0.08 mg/l in the Dolores River just above the San Miguel confluence, compared to a high of 267
mg/l for the same area in 1991. Although specific criteria were set by EP A, they do not state possible
adverse effects of unacceptable iron levels on fish.

Lead may reach the aquatic environment through precipitation, fallout of lead dust, roadway
runoff, and industrial and municipal wastewater discharges (EPA 1980b). The solubility of lead
compounds in water is inversely related to pH. Concentrations of <0.01 - 0.36 mg/l were measured
in the Dolores River in 1990-1991. Based on the Dolores River water hardness, freshwater species
should not be affected unacceptably if I-hour average concentration does not exceed 0.124 - 1.36 mg/l
(depending on water hardness) more than once every 3 years on average (EP A 1986). Lead
concentrations in the Dolores River never exceeded the upper limit and, based on these criteria, lead
in this system did not appear to be problematic. Total lead in the Dolores and San Miguel rivers
(ERI 1986) were similarly low (Table 42).

Zinc is not found free in nature, but occurs as sulfide, oxide, or carbonate complexes (EP A
198Oc). Zinc is readily transported in most natural waters. Variables affecting its mobility include
concentration and composition of suspended and bed sediments, concentrations of dissolved and
particulate iron and manganese, pH, salinity, and concentrations of zinc. Total zinc in the Dolores
River in 1990-1991 was 0.01 - 1.20 mg/l. EP A criteria for zinc specifies that concentrations should
not exceed 0.421 - 2012 mg/l (based on water hardness) at any time (EP A 1986). Like lead, zinc in
the Dolores River appeared to be at acceptable levels.. ERI (1986) also reported low levels of zinc
in the Dolores and San Miguel rivers in 1986 (Table 42).

Aluminum in the Dolores River ranged from 6.2 - 57 mg/l in 1991. No EP A criteria for
freshwater life are established for aluminum. Concentrations of this element exceeding 1.5 mgll