PRELIMINARY FINDINGS OF OIL-SOLIDS INTERACTION IN EIGHT ALASKAN RIVERS

Abstract

ABSTRACT The formation of oil-mineral aggregates in rivers with high concentrations of suspended solids could be an important mechanism for transferring oil from a surface slick into the water column. Seven glacier-fed rivers in south-central Alaska were sampled three times in the summer of 1999 and tested to see how suspended solids in the water would interact with crude oil. Oil-mineral aggregates formed with all samples, which lead to the conclusion that similar oil-solids interaction should occur if oil is spilled into other glacier-fed rivers. The amount of oil associated with the solids after mixing was roughly proportional to the concentration of suspended solids in the samples. The oil-loading results ranged between 0.01 and 0.45 g oil/g solid, with most of the measurements falling between 0.03 and 0.24 g oil/g solid. The average loading for all tests was 0.13 g oil/g solid, which is consistent with the findings of a similar study done in 1998 on the Yukon River. This result indicates that the suspended solids in the streams studied—especially the larger Yukon, Copper, and Lowe Rivers—have a large oil-holding capacity and would be capable of scavenging a considerable volume of oil. The exact quantity would depend on several factors, including the volume and dimensions of the slick, concentration of suspended solids, and current velocity of the river. Historical data on stream flow, suspended-solids concentration, and particle-size distribution were gathered and used in conjunction with the laboratory oil-solids interaction results to identify the times of the year when such interaction could occur to a significant degree. This data indicated that oil-mineral aggregates are expected to form in all rivers tested, with the most significant periods being during the summer months.