Gregory S. Durell

Determining produced water originating polycyclic aromatic hydrocarbons in North Sea waters : Comparison of sampling techniques

Abstract A field study was carried out in the Norwegian sector of the North Sea during May and June 1997. The purpose was to measure the concentration of produced water originating polycyclic aromatic hydrocarbons (PAH) in seawater and to compare different sampling techniques for use in future monitoring programs. Three methods were used for direct water sampling: (1) in situ large volume sampling of particulate and dissolved hydrocarbons onto filters and XAD resins, (2) solid phase extraction (SPE) using polystyrene-divinylbenzene disks, (3) whole bulk water sampling. In addition, sampling by semi-permeable membrane devices (SPMDs) and blue mussels (Mytilus edulis) was used to obtain a 4 weeks average of the concentration of the target compounds in seawater. The samples were processed and analysed by GC–MS for determination of PAH concentrations. The measured concentrations were generally found to be low, and in many cases below the limits of detection. The comparison of sampling techniques showed that blue mussels and SPMDs are suitable for measuring PAH in both near- and far-field seawater. In situ large volume water sampling was also suitable for a wide range of PAH concentrations, but this technique was limited by high break-through of the low-molecular weight compounds, such as naphthalenes. The small sampling volumes limited the SPE and whole water sampling techniques, resulting in potential detection limit problems. These grab-sampling techniques may, however, be suitable for monitoring in the near-field areas around the platforms.

Concentrations of chlorinated pesticides and PCBs in microlayer and seawater samples collected in open-ocean waters off the U.S. East Coast and in the Gulf of Mexico

Abstract Microlayer and surface seawater samples, collected during four surveys in 1985 and 1987 to open-ocean waters off the United States middle and south East Coast and in the Gulf of Mexico, were analyzed for selected chlorinated pesticides and polychlorinated biphenyls (PCBs). Analytes detected by gas chromatography-electron capture detection (GC-ECD) were confirmed by analysis with a different gas chromatographic column or detector or both. Of the 27 filter and filtrate microlayer samples collected during the surveys, only one contained pesticides or individual PCB congeners above method detection limits ranging from 0.1 to 1.0 ng 1 −1 . Most PCB congeners and pesticides were not detected in any of the 24 open-ocean surface seawater samples, even at method detection limits of 0.5-3.0 pg 1 −1 , which were achieved by processing 9001 of seawater. Lindane was detected at concentrations in the range of 0:01-0.15 ng 1 -1 in nearly every seawater filtrate sample taken off the Southeast Coast and in the Gulf of Mexico. Chlordane was the other pesticide found predominantly in Gulf of Mexico samples at concentrations of 0.004-0.034 ng 1 −1 . Only a few sample contained very low concentrations of DDTs and their degradation products. No more than four to five individual PCB congeners were detected in any seawater sample; none of the samples possessed an Aroclor pattern. Previous literature on concentrations of pesticides and PCBs in open-ocean waters is reviewed. Most literature values for pesticides (almost exclusively DDTs and their degradation products) and PCBs in microlayer and surface seawater samples are 10–20 years old. Concentrations of PCBs and DDT identified in the earlier studies were significantly higher than their concentrations in samples collected in our 1985 and 1987 surveys. These observations may reflect an actual decline in PCB and DDT levels in the open ocean or improvement in analytical methods, including confirmation of analyte identities. In the earlier studies, PCBs and pesticides were determined by a single-column, single-detector analysis (i.e. GC-ECD): confirmation analysis of identified analytes was not performed.

Bioaccumulation of petroleum hydrocarbons in arctic amphipods in the oil development area of the Alaskan Beaufort Sea.

An objective of a multiyear monitoring program, sponsored by the US Department of the Interior, Bureau of Ocean Energy Management was to examine temporal and spatial changes in chemical and biological characteristics of the Arctic marine environment resulting from offshore oil exploration and development activities in the development area of the Alaskan Beaufort Sea. To determine if petroleum hydrocarbons from offshore oil operations are entering the Beaufort Sea food web, we measured concentrations of hydrocarbons in tissues of amphipods, Anonyx nugax, sediments, Northstar crude oil, and coastal peat, collected between 1999 and 2006 throughout the development area. Mean concentrations of polycyclic aromatic hydrocarbons (PAH), saturated hydrocarbons (SHC), and sterane and triterpane petroleum biomarkers (StTr) were not significantly different in amphipods near the Northstar oil production facility, before and after it came on line in 2001, and in amphipods from elsewhere in the study area. Forensic analysis of the profiles (relative composition and concentrations) of the 3 hydrocarbon classes revealed that hydrocarbon compositions were different in amphipods, surface sediments where the amphipods were collected, Northstar crude oil, and peat from the deltas of 4 North Slope rivers. Amphipods and sediments contained a mixture of petrogenic, pyrogenic, and biogenic PAH. The SHC in amphipods were dominated by pristane derived from zooplankton, indicating that the SHC were primarily from the amphipod diet of zooplankton detritus. The petroleum biomarker StTr profiles did not resemble those in Northstar crude oil. The forensic analysis revealed that hydrocarbons in amphipod tissues were not from oil production at Northstar. Hydrocarbons in amphipod tissues were primarily from their diet and from river runoff and coastal erosion of natural diagenic and fossil terrestrial materials, including seep oils, kerogens, and peat. Offshore oil and gas exploration and development do not appear to be causing an increase in petroleum hydrocarbon contamination of the Beaufort Sea food web.