TRACE-ELEMENT SPECIATION AND BEHAVIOR IN THE TIDAL DELAWARE RIVER

Measurements of dissolved As, Cr, Cu, and Se using species-selective t echniques were made in the tidal freshwater Delaware River at four sit es in July 1991, January 1992, and March 1992. Concentrations of disso lved As, Ct, and Sr were generally higher in July than in March or Jan uary. Copper concentrations were relatively constant. Both As and Cu i ncreased in concentration in the region of Philadelphia. Measurements of As, Cd, Cr, Cu, Pb, Ni, Se, and Zn in seston were made during the J uly 1991 and March 1992 sampling using both a total digest and a serie s of sequential Leaches. A large fraction of most of the elements, in the order Cd > Zn > Ph Cu > Ni greater than or equal to As > Cr > Se, was solubilized by weak acid. The remainding fraction, for elements wh ere the acid leach was not complete, was released by a rigorous digest ion with concentrated acids. Based on estimates of similar rivers, Ph and Zn appear to he substantially enriched in Delaware River seston co mpared to other rivers draining, the same geological provinces. Arseni c, Se, and Cd in seston may be moderately enriched.