Assessment of polynuclear aromatic hydrocarbons ecotoxicity threshold in marine sediments through in situ input/decay measurements

Abstract

: The ability of decomposers to process variable amounts of xenobiotics in the marine sediment is a useful aggregate indicator of their capacity to prevent their accumulation and eventual ecotoxic effects. Since decomposition processes depend on environmental factors at the sediment which are difficult to mimic in laboratory systems, in situ evaluations in undisturbed sediments are of great interest. A method and its results are presented to evaluate the decomposition rates of PAHs (polynuclear aromatic hydrocarbons) in coastal undisturbed marine sediments at different levels of pollution input. The method is based on the application of pulse chromatography concepts to interpret trap and bed sediment monitoring data obtained at regular time intervals, using models of the water column as an anisotropic carrying medium. The results are for a 14 month data series from moderately polluted sediments near an urban site and at a more distant nearly pristine site on the south Atlantic coast. QSAR (quantitative structure activity relations) indicate that decay rates increase with higher UV absorption and lipidic solubility. At low levels of total PAH input to the sediments (<0.05 μg day(-1) g(-1)), decomposition mechanisms effectively process these compounds within a few days. At higher input levels (up to 0.12 μg day(-1) g(-1)), decomposition lags behind the inputs by approximately 25% and PAHs accumulate in the sediment. In situ estimates of the PAH input/decay ratios provide reliable ecosystem indicators of a safe threshold for anthropogenic inputs of PAHs to the marine environment and a basis for receptor-based standards aimed at their regulation.

Time and space issues in ecotoxicology: Population models, landscape pattern analysis, and long‐range environmental chemistry

“…It has been suggested [139] that some ecosystems could be managed in ways that would promote the decomposition of critical pollutants, like polycyclic aromatic hydrocarbon and methylmercury in some wetlands where the degree of flooding could be controlled [140]. Management of aquatic ecosystems to enhance polycyclic aromatic hydrocarbon decomposition requires a knowledge of the environmental conditions that regulate the speed of degradation and the use of mass-balance modeling, as done by Su et al [141] in the case of the Lower Fox River (MI, USA) and in shallow coastal marine sediments [142].…”

Time and Space Issues in Ecotoxicology: Population Models, Landscape Pattern Analysis, and Long-Range Environmental Chemistry

“…It has been suggested [139] that some ecosystems could be managed in ways that would promote the decomposition of critical pollutants, like polycyclic aromatic hydrocarbon and methylmercury in some wetlands where the degree of flooding could be controlled [140]. Management of aquatic ecosystems to enhance polycyclic aromatic hydrocarbon decomposition requires a knowledge of the environmental conditions that regulate the speed of degradation and the use of mass-balance modeling, as done by Su et al [141] in the case of the Lower Fox River (MI, USA) and in shallow coastal marine sediments [142].…”