SUMMARY OF EFFECTS OF SURFACE APPLICATIONS OF BIOSOLIDS ON SOIL, CROPS, GROUND WATER, AND STREAMBED SEDIMENT NEAR DEER TRAIL, COLORADO, 1999–2003
During 1999–2003, the U.S. Geological Survey, in cooperation with Metro Wastewater Reclamation District and North Kiowa Bijou Groundwater Management District, studied natural geochemical conditions and the effects of biosolids applications to the Metro Wastewater Reclamation District
properties near Deer Trail, Colo., because of public concern about potential contamination of soil, crops, ground water, and surface water from biosolids applications. Parameters analyzed for each monitoring component included arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium,
and zinc (the nine trace elements regulated by Colorado Department of Public Health and Environment for biosolids), gross alpha and gross beta radioactivity, and plutonium, as well as other parameters.
Concentrations of the nine regulated trace elements in biosolids were relatively uniform
and did not exceed applicable regulatory standards. Elevated concentrations of bismuth, mercury, phosphorus, and silver would be the most likely inorganic biosolids signature to indicate that soil or streambed sediment have been affected by biosolids. Molybdenum and tungsten, and to a lesser
degree antimony, cadmium, cobalt, copper, mercury, nickel, phosphorus, and selenium, would be the most likely inorganic “biosolids signature” to indicate ground water or surface water has been affected by biosolids.
Soil data indicate that two applications of biosolids have
had no measurable effect on the concentration of the constituents monitored.
Wheat-grain data were insufficient to determine any measurable effects from biosolids. Comparison with similar data from other parts of North America where biosolids were not applied indicates similar concentrations.
quality throughout the study area varied over time at each site and from site to site at the same time. Concentrations of inorganic constituents in ground water commonly exceeded some of the Colorado water-quality standards and had some upward trends. However, there is not conclusive evidence
that ground water of the study area has been impaired by the biosolids applications.
Few paired streambed-sediment samples could be collected during 1999 through 2003 because runoff was infrequent in the designated biosolids-applied and control basins. No appropriate sediment regulatory
standards are available for these sediment data, but trace-element concentrations are consistent with concentrations in uncontaminated soil. Concentrations of ammonia plus organic nitrogen, organic carbon, copper, lead, mercury, and silver were significantly (alpha < 0.10) greater in sediment
of the biosolids-applied basin than that of the control basin.
A signature based not on inorganic- or radioactive-constituent concentrations is needed to help differentiate the effects of biosolids from the effects of natural geochemistry on all the monitoring components. Some other property
or chemical presence, such as pharmaceutical or other anthropogenic organic compounds, that is not possibly characteristic of natural soil, rock, ground water, surface water, or sediment of the area is needed to determine if biosolids could possibly have affected concentrations in the study
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