POLAR ORGANIC COMPOUNDS IN PORE WATERS FROM THE CHESAPEAKE BAY IMPACT CRATER

Pore waters from the Chesapeake Bay Impact Crater cores were procured by squeezing or centrifuging. Very small aliquots of pore water, only 100 microliters, from various depths within the core were taken for analysis by direct injection electrospray ionization/mass spectrometry. Pore water samples were analyzed without filtration or fractionation, in positive and negative mode, for polar organic compounds. Positive mode ionizes polar organic compounds almost universally, whereas the negative mode is specific for acidic polar organic compounds. Changes in the dissolved organic carbon with depth as determined by full scan mass spectrometry were investigated. Increasing salt concentrations with depth were compensated for by sequential dilution of the samples. Using the specificity of negative mode, ions indicative of drilling mud fluids were not found in spectra from the Chesapeake Bay Impact Crater pore waters. High intensities of ions from sulfate, sulfonate, and phenolate overshadowed the broad envelope of ions more typical of natural dissolved organic matter. The number-average molecular weight, weight-average molecular weight, and polydispersity, typical terms used to describe natural dissolved organic matter, were relatively consistent and independent of depth.