During the years 1970-1972 the Nipisi, Rainbow, and Old Peace River pipeline spills occurred in the Lesser Slave Lake area of northern Alberta. The Nipisi spill was by far the largest of the three spills and is also one of the largest land spillsin Canadian history. The most recent field survey was conducted in 1995 in order to determine which cleanup methods were most successful and to provide up-to-date information about any changes in residual oil and vegetative recovery 25 years after thespills. The comprehensive chemical analysis data of the Nipisi samples indicate that (a) the Nipisi samples can be categorized into three groups plus the background group, according to the contamination level and degradation degree of the samples; (b)degradation of residual oil of surface samples (0-4 cm) had clearly occurred, and the weathered percentages of this group of samples were estimated to be in the range of 15-43; (c) subsurface samples (10-40 cm) exhibited great quantities of oil even 25years after the spills, indicating that the natural recovery rates were slow for this group of samples; (d) the extent of contamination and degree of degradation correlated strongly with sample depth; (e) oil trends were similar across the site, eventhough different treatments had been used after the spill at the site.
展开▼
