Mark A. Tumeo

Effectiveness of a biosurfactant in removing weathered crude oil from subsurface beach material

Abstract The University of Alaska Fairbanks Environmental Technology Laboratory is conducting ongoing research into the effectiveness of a biosurfactant, PES-51®, in removing weathered crude oil from beach material. A field test was conducted from 1 to 7 July 1993 in Sleepy Bay on La Touche Island in Prince William Sound. The results of chemical analysis of the beach material before and after treatment show that diesel range petroleum hydrocarbons are completely removed to levels below the detection limit of 0.5 mg kg−1. Semivolatile petroleum hydrocarbons were reduced an average of 70%. The microbial data collected indicate that no inhibition of microbial activity in sediments is caused by treatment. The numbers and activity of hydrocarbon-degrading organisms were enhanced immediately following treatment and for about a month afterwards. There was no evidence of dissolved hydrocarbons or increased microbiological activity in seawater samples, providing evidence that oil was not transported offshore during the treatment process.

The Meaning of Stochasticity, Randomness and Uncertainty in Environmental Modeling

The concepts of ‘uncertainty’ ‘randomness’ and’ stochasticity’ are being debated and discussed in great detail in the modeling literature. These issues are especially pertinent when comparing various stochastic methods or when calibrating and validating probabilistic models. This paper reviews the use and meaning of ‘uncertainty’,’ stochasticity’ and ‘randomness’ in the area of environmental modeling and proposes working definitions for the use of these terms and the term ‘error’ when reporting modeling work. There is no assumption on the part of the author as to the definitiveness of the suggested definitions. Instead, they are offered as “straw-persons” that are to be discussed, debated and changed as the necessary consensus develops in the modeling community.