Toxicity assessment of complex contaminant mixtures in Louisiana sediments
Description
Identification of methods for determining the severity of pollution is vital for successful assessment of environmental damage and guiding of remediation efforts. Development of these methods is often difficult due to issues regarding speciation and distribution of contaminants among phases ranging in bioavailability. Contaminant mixtures introduce further complexity as synergism and/or antagonism between components may occur. Despite the generality and importance of these questions, approaches for analyzing them are less developed than many other aspects of environmental science. In this study, combination of field toxicity tests (to study potential effects on biota), field chemistry data (for contaminant quantification), and evaluation of partitioning (for bioavailability analysis) was used to assess contaminant hazards in two Louisiana waterways (the LaBranche wetlands and Bayou St. John). The main objective was to develop means for identifying the most hazardous pollutants responsible for observed toxicity, while a secondary objective involved examination of correlation between toxicity and concentration A mathematical algorithm was developed that computes the toxicity of mixtures with large numbers of components acting in an additive manner using concentration and MicrotoxRTM toxicity data obtained from the mixture constituents as inputs. Various methods for utilizing this data to account for speciation and bioavailability were investigated to determine the most accurate method for calculating toxicity. Comparison of field toxicity to the computed response was performed to identify the presence of possible mixture interactions, identified as a departure from additivity. A prioritization scheme was also developed to identify components contributing most to the overall observed toxic effect Results of this investigation show that integration of field toxicity tests, contaminant concentration, and partitioning data with mathematical analysis is a powerful tool for prioritizing pollutants and determining the presence of interactive effects. This integrated approach provides a more comprehensive evaluation of pollutant impact since biological, toxicological, and chemical factors are taken into account. Utilization of this technique may reduce effort spent by environmental personnel since emphasis of contaminant monitoring could focus on primary pollutants rather than on all contaminants. This could lead to more effective use of resources for pollutant monitoring as well as means for improvement of remediation strategies