Stable isotopic analysis of organic carbon in water and sediment from the Houston Ship Channel, Texas, USA.
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In July 1986 water and sediment samples were collected at 14 stations along the Houston Ship Channel. The stable isotope ratios (13C/12C) of dissolved, particulate and sediment organic carbon are useful in estimating the degree and extent of petrochemical pollution. Comparisons of the 1986 water sample data with those from the same stations 18 years earlier support other evidence that water quality in the Houston Ship Channel has improved. While the mean 13C value for POC was virtually unchanged, the mean 13C value for DOC increased from -32 per mil in 1968 to -27 per mil in 1986, as would be expected if petrochemical pollution had decreased. The weight percent organic compound, the C:N ratio and the isotopic evidence of petrochemicals in the sediment decreased as distance along the channel from the inland turning basin increased. In 5 sediment samples, between 20 and 60 weight percent of the organic compound was extractable using methanol-toluene; the 13C values of the extracted organic matter fall between -28 and -26 per mil.