Method development for long-term monitoring of heavy metals in mussel shells by laser-ablation inductively-coupled-plasma mass-spectrometry

Heavy metal pollution is a growing concern as growing worldwide population and industrial processes increase pollution levels in most environments. High metal concentrations throughout ecosystems pose a serious threat to wild-life and human health. Methods to monitor rising threat levels of metals are a primary concern for monitoring overall ecosystem health. Mechanisms which spread pollution must be intimately understood because of the persistence of heavy metals. Heavy metal contamination in the Tar Creek superfund site provides a great case study to selectively observe differences in heavy metals concentrations both upstream and downstream of mining activity. Thus, research is able to identify natural and man-made point sources of pollution.;The abilities of bivalves to filter-feed and sediment-feed provide a unique monitoring tool for analyzing heavy metals. Mussels are constantly filtering the environment around them. A mussel's seasonal and annual growth layers provide an excellent sample media for obtaining historical records of environmental data. Many species of mussels are found in most freshwater ecosystems throughout the United States. Mussels have low migration rates, live for a suitable amount of time, and leave relic shells. These features make mussels very practical for monitoring heavy metal pollution.;Various studies were conducted to obtain insight into developing methods for using LA-ICP-MS as a tool for monitoring heavy metals in mussel shells. Surface laser ablations, compared at additional depths, resulted in a more than 20% increase in signal intensity. Theoretical and experimental designs show signal changes as a function of depth. Mussel tissue and shell digestions were found to be best when using approximately 1.0 mL of hydrogen peroxide and 1.0 mL of nitric acid for each 0.1 grams of sample. Mussel tissue was found to have greater heavy metal concentrations than shells. Shells were found to average a 96% weight of calcium carbonate; however, the organic layers contained the greatest concentrations of heavy metals per weight.