“…Elemental analysis has been commonly applied to isolated humic substances (Huffman and Stuber, 1985;Peschel and Wildt, 1988;Thurman and Malcolm, 1981), and therefore comparison with published data for "typica]" natura] waters is possible. 'H NMR spectroscopy has also been previously applied to humic substances (Grasso et at., 1990;Thorn, 1987;Wershaw, 1985), along with 13CNMR spectroscopy on both liquid samples (Ruggiero et a!., 1979;Thorn, 1987) and solid samples (Tao et at., 1994). 'H NMR was chosen for this work because the low organic content of the samples of interest precluded the isolation of sufficient material for 13CNMR analysis, which requires significantly greater amounts of sample than the more sensitive 'H NMR technique.…”