GEOCHEMISTRY OF CARBON STABLE ISOTOPES IN SHATT AL-ARAB RIVER AND KHOR AL- ZUBAIR ESTUARY, SOUTH IRAQ

摘要

24 samples of Mollusc shells from Shatt AL-Arab river and Khor AL-Zubairestuary were analyzed in order to determine the concentration of carbon stableisotope and also to clarify the factors that control the geochemical distribution ofcarbon isotopes in these two different environments. The carbon stable isotope weremeasured using the closed tube method, in which shell samples are combusted tocarbon dioxide for carbon isotope analysis. The carbon dioxide samples are analyzedon a Finnigan Mat 251 isotope ratio mass spectrometer equipped with a triple collectorand controlled by an Apple Iie microcomputer. Measurements are made relative toseveral working standards {Norit (–24‰), NBS-22 (–29‰)}, and several secondary lightmethane standards at –43.4‰ and –62.6‰. All values are reported versus PDB. Theseanalyses are conducted in the department of Oceanography in Texas A&M University.This study indicates that the differences in carbon stable isotopes were due to threefactors: environmental conditions, under which these three molluscs are lived, chemistryof the water in Shatt AL-Arab and Khor AL-Zubair and feeding quality of these ofthese molluscs. The factors are close related with another important factor that it is thepollution present in these two different environments.