Toxic heavy metals in ground water of a portion of the Front Range mineral belt

Abstract

A study of toxic trace metal distribution in ground waters of the Front Range mineral belt, Colorado and adjacent areas was completed in order to determine the relationship of water quality to mineralization and the magnitude of potential health effects. A total of 149 samples were collected and analyzed for arsenic, cadmium, copper, iron, lead, manganese, mercury, silver, and zinc. Field determinations of pH, Eh, and specific conductance were also made. The trace element data exhibited a lognormal distribution and are described utilizing the geometric mean and geometric deviation. Four populations were recognized in the samples; 1) samples in the mineral belt with plumbing contamination, 2) samples in the mineral belt without plumbing contamination, 3) samples outside the mineral belt with plumbing contamination, and 4) samples outside the mineral belt without plumbing contamination. Differences in these populations for several elements are observed utilizing the t test. Utilizing the observed data distributions, geochemical abundance estimates are made for the four recognized populations. The data distributions are corrected for analytical error, corrected for determinations below the detection limit and expressed as a predicted central 95% range for each element in each population. The corrected geometric mean, corrected geometric deviation, along with the U.S. Public Health Service limit for each element determined are used to determine the probability of ground water exceeding the specified limit for each constituent. Ground waters in the mineral belt are estimated to exceed the U.S. Public Health Service limit in 14% of the samples for Cd, 1% for Cu, 51% for Fe, 74% for Mn, 2% for Hg, and 9% for Zn. Ground waters outside the mineral belt have a similar probability of exceeding the limit for Hg and lesser probabilities for all other elements.