The measurement and evaluation of certain trace metal concentrations in the nearshore environment of the northwest Gulf of Mexico and Galveston Bay

As a study preliminary to a future long-range program to establish water quality standards this research was directed towards the determination of manganese, nickel, copper, zinc, and lead in the nearshore environment. A method utilizing filtration, ion exchange, persulfate oxidation, and hydrofluoric acid digestion in conjunction with atomic absorption spectroscopy was developed. A total of 66 water and 20 sediment samples from Galveston Bay, the Gulf of Mexico, and the Mississippi River were analyzed. The data indicate that these metals are distributed in at least three definable fractions. They are (1) soluble-reactive (ionic) - that fraction available for direct uptake by the ion exchange resin without prior alteration of their chemical state, (2) filterable-nonreactive (particulate) - that fraction retained by a 0.3 micron pore size glass fiber filter, and (3) soluble-nonreactive - the fraction which penetrates both the filter and the ion exchange resin. The only metals which yielded a consistent soluble-nonreactive fraction were nickel and copper. The method was not effective for soluble-nonreactive manganese and lead. No values were obtained for particulate zinc due to an intense silicon interference encountered in the atomic absorption phase of the determinations. In Galveston Bay the ranges of the observed ionic values were: < 0.1 to 174 μg/1 manganese, < 0.1 to 5.92 μg/1 nickel, < 0.1 to 1.00 μg/1 copper, 2.50 to 25 μg/1 zinc, and < 0.1 μg/1 lead. The ranges of the particulate values were: 5.04 to 84 μg/1 manganese, < 0.1 to 3.74 μg/1 nickel, 0.24 to 5.94 μg/1 copper, and 1.62 to 4.80 μg/1 lead. ..