ABSTRACT

Approximately 350 water samples were collected along 17,000 miles of tanker routes in the Pacific Ocean. Analysis of these samples for nonvolatile (C14+) hydrocarbons gave a median concentration of 1.6 parts per billion (ppb) for the surface and 0.9 ppb in the subsurface at -10 m. Somewhat higher concentrations were observed for one voyage. The hydrocarbons were mixtures which seemed to be of both petroleum and biogenic origin. Data are presented for water along the routes: San Francisco/Cook Inlet, San Francisco/Vancouver/ Panama Canal, and San Francisco/Singapore.

INTRODUCTION

Preservation of the marine environment is of great social concern and the object of considerable study at the present time. One phase of this study deals with the role of hydrocarbons in coastal and open ocean water. To help in the evaluation of this role it is important to know the baseline condition of today's oceans.

Numerous areas of the Atlantic Ocean have been studied. The techniques employed gave concentrations of nonvolatile (C14+) hydrocarbons in water at depths of 1 to 10 meters. A preponderance of measurements give median concentrations of 1 to 4 parts per billion (ppb, g/l) for large areas of the North and South Atlantic (1,2,3,4,5). In the most extensive study (3,4), the median content was 4 ppb with values from 1.3 ppb to 13 ppb falling within one standard deviation from the mean. Barbier, et al (6) reported values up to 45 ppb at two stations near Dakar, Africa, while Wade and Quinn (7) observed a range of 13 to 239 ppb in the Sargasso Sea. Compositional data by Monaghan, et aI, show hydrocarbons to be complex mixtures of saturates and aromatics. Areas of the Baltic Sea (8), Mediterranean (4), and Indian Ocean (4) have also been studied.

Little is known about hydrocarbons in the Pacific Ocean, however, where only limited study of nonvolatile hydrocarbons has been reported (9,10). Volatile hydrocarbons (C1C4) were measured by Swinnerton and Lamontagne (11) and some tar ball measurements have been carried out by Wong, Green, and Cretney (12).

In order to obtain baseline data on the Pacific Ocean, an extensive study was carried out to measure and characterize nonvolatile hydrocarbons. Additional insight was obtained from an extractable organic measurement which includes the hydrocarbons and other liquids such as esters and acids. In carrying out this program, surface and subsurface water was sampled along 17,000 miles of tanker routes. Approximately 350 samples were collected and analyzed.

SAMPLING AND ANALYSIS

The principal analytical measurement of this study involved the total dispersed nonvolatile hydrocarbons in 8 liters of ocean water. To accomplish this, it was generally necessary to observe concentrations which ranged from <1 to 8 ppb. Thus, the quantity of involved hydrocarbon was from <8 to 64 micrograms--an extremely small quantity to accurately measure. It was of paramount importance, for example, to minimize and monitor contamination by the ubiquitous hydrocarbon. This was accomplished through extensive use of sample and analytical blanks as described elsewhere (13).

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