RELEASE OF CHLOROCATECHOLS FROM A CONTAMINATED SEDIMENT

The release of chlorocatechols from a naturally contaminated sediment has been examined. A true steady state was not reached even after 20 cycles with buffered deionized water, and the chlorocatechols were bound in varying degrees to particulate matter which could be removed from the extracts by centrifugation at 100000g, or by dialysis: >70% of the trichlorocatechols and tetrachlorocatechol was contained in particulate material (>0.2 and <10 mum). Release was unaffected by temperature in the range 4-22-degrees-C and only slightly diminished by increased salinity. The amounts of 3,4,5-trichlorocatechol and tetrachlorocatechol released at pH 11 were greater than those released at pH 7. For the chlorocatechols examined, there was a linear relation between the amount released at pH 7 and the pK(a) of the catechol. Addition of metal-complexing agents to the medium increased the amount of chlorocatechols released, and there was a linear relation between the amount of tetrachlorocatechol and the amounts of iron and aluminum released. The role of these metal cations was supported by experiments which showed that chlorocatechols were effectively partitioned from the aqueous phase onto solid phases consisting of goethite, pseudoboehmite, ferrous sulfide, or ferric hydroxide. The environmental consequences of the mobilization of these potentially toxic chlorocatechols from the sediment phase into the overlying water mass are discussed.