In the framework of the Paris Convention for the prevention of marine pollution, the Dutch government initiated a research programme on environmental effects of discharges of contaminated drill cuttings from platforms in the North Sea. The programme has run since 1985 and includes field surveys at drilling sites in different parts of the Dutch sector. One of the locations investigated is the former drilling site F18.9, situated on the Oyster grounds. The (abandoned) location was visited in 1988, 1 y after the exploratory drilling ended. This paper gives a brief overview of the 1988 study at this discharge site, which was investigated again in 1990 as part of the Bremerhaven Workshop. Chemical analyses of the sediment over a transect in the residual current direction revealed a clear gradient in contamination levels, with oil concentrations ranging from 250 to 450 mg kg-' dry sediment within 250 m and gradually decreasing to < 20 mg kg-' beyond 750 m. Barium concentrations showed a similar pattern. Subtle biological effects, indicated by the absence of a very sensitive species (Montacuta ferruginosa), were found as far as 2 km from the discharge site. Abundance patterns of 2 other sensitive species (Harpinia antennaria and Callianassa subterranea) suggested environmental stress to occur up to 1 or 2 km. Within 750 m from the discharge site an increasing number of species, including the dominant Amphiura filiformis, appeared to decrease in abundance, successively resulting in a reduced total macrofauna abundance and species richness. Typical opportunistic species were observed more frequently only within a radius of 250 m. An alternative measure of diversity ('relative macrofauna abundance') was introduced and its merits are discussed. It is suggested that a combination should be used of community-based parameters (e.g. species richness, relative abundance) and species-based parameters (e.g. presence of opportunistic species, absence of susceptible species) to describe the impact of pollution. In this way 7 accumulating effects were distinguished. At contamination levels > 100 mg oil kg-' dry sediment all defined effects occurred, whereas below 20 mg kg-' the number of effects rapidly decreased.
In order to control the quality of rare earth determinations in environmental matrices, the Standards, Measurements and Testing Programme (formerly Community Bureau of Reference, BCR) of the European Commission has started a project, the final aim of which is to certify four types of matrices (tuna muscle, mussel tissue, aquatic plant and estuarine sediment) for their contents of a range of rare earth elements (Sc, Y and the lanthanides: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). The elements U and Th were added to the study. The first part of this project consisted of an interlaboratory study which aimed to test the feasibility of preparation of environmental reference materials and to detect and remove most of the pitfalls observed in rare earth determinations. This paper presents the preparation of the four matrices for the intercomparison study and for the candidate reference material. The main results are presented of the interlaboratory study that was carried out prior to the certification campaign. This collaborative trial is the first attempt ever carried out at this scale to evaluate the state-of-the-art of rare earth determinations in the environment. Its impact on the improvement of chemical measurements will have positive effects on the comparability of data necessary for environmental monitoring.
During POSER 2 experiments were performed to study the effects of a single addition of mercury (11) chloride on the development of plankton communities enclosed in large plastic bags. containing 1.5 to 30 m3 water and ranging from 3 to 40 m in depth. The experiments lasted 1 and 3 wk. respectively. In one of these experiments the influence of an additional dose of nutrients was studied. During both experiments mercury concentrations in the water decreased after the addition. Part of the mercury was found in the sediment collected on the bottom of the bags during the experiment, but most of the mercury probably volatilized and was lost to the atmosphere. Addition of 1 or 5 yg Hg I-' in the first experiment resulted in lower numbers of bacteria than in the controls. The first experiment was too short to show effects on phytoplankton and zooplankton. Addition of 5 pg Hg 1-' in the second experiment inhibited bacteria and phytoplankton, and increased the mortality of copepods, which formed the principal part of the zooplankton. Our results are comparable to those obtained during other experiments with natural marine plankton communities also enclosed in large plastic bags in fairly different sea areas Addition of nutrients stimulated phytoplankton growth, but had no observable effects on bacteria or zooplankton.
A Dutch programme was carried out to study the distribution of discharged washed and unwashed oil-containing cuttings in the sediment and waterphase and their effects on selected test species In the Dutch part of the North Sea. The distribution of OBM cuttings in sediment around drilling locations was related to the total amount of oil discharged in the water column. Increased oil contents were found over a range of 1000 to 5000 m in residual current direction. Total oil contents remained high at locations where unwashed OBM cuttings were discharged. At one location oil was found in high concentrations upto 6 years after discharge of OBM cuttings, especially due to the persistence of the oil fractions "Other peaks" and "UCM". Washing persistence of the oil fractions "Other peaks" and "UCM". Washing of OSM cuttings resulted in lower amounts of oil discharged, lower concentrations in the sediment In the vicinity of the platform (upto 100 m), equal concentrations at 250 m but higher concentrations upto at more than 500 m off the platform when compared with unwashed cuttings and the respective amount of oil discharged. However, within one year, degradation of oil seems to have taken place at one of the washed sites at 5000 m. place at one of the washed sites at 5000 m. During discharge in the watercolumn, oil was taken up by Mytilus adulis from washed cuttings as well as from unwashed cuttings. Leaching of oil from the sediment into the waterphass was measurable in the field for only a limited period of time, less than a year after discharge. Several sediment-inhabiting species were tested on their response to oil contamination. Four species tested in experimental boxcosm set-ups, Echinocardium cordatum, Amphiura filiformis, Lagis koreni and Nucula turgida responded to elevated contamination levels by increased mortality. Boxcosm experiments supported the conclusion derived from the results of field studies on the macrofauna distribution around drilling sites, i.e. the NOEC-value should be estimated in the order of 1 - 10 mg oil kg dry sediment. For boxcosms taken at unwashed and washed sites one year after discharge this was confirmed. Preliminary results of a boxcosm experiment with sediment where discharge of unwashed OBM cuttings had taken place 6 years before, the NOEC-value seemed to have increased. Experimental boxcosms enable assessment of possible adverse effects of experimentally treated drilled cuttings or other toxic substances on the (macro)benthic infauna. Adverse effects were also seen at one of the washed sites using a short-term bioassay test with the sediment-inhabiting amphipod Bathyporeia sarsi. Introduction Since the start of drilling activities in the North Sea, in the late 1960's, water-based drilling muds (WBM) were used initially, but at the and of the 1970's oil-based muds (OBM) were introduced. Technical and economical advantages of OSM have increased their use and, as a consequence, the amount of oil discharged. Since regulations have forbidden the use of diesel oil muds because of its high toxicity, OBM based on low-aromatic oil compounds are currently in use. Separation procedures, aimed to regain as much oil from the drilling cuttings as possible, do not prevent disposal of more or less toxic material. Hence, these activities are subject of concern with respect to their impact on the marine environment. In the framework of the Paris Convention (1980), the Dutch Ministry of Transport and Public Works (RWS, North Sea Directorate) has initiated in 1985 a research programme on the Dutch Continental Shelf to study the effects of discharged oil-containing cuttings and discharged waterbased muds/drilling fluids on the sediment, its infauna and selected test species. This project is also financed by the Ministry of Housing, Physical Planning and Environment (VROM) and the Ministry of Economic Affairs (EZ, State Supervision of Mines). The study is carried out by the Netherlands Institute of Sea Research (NIOZ) for the biological part of the project and the TNO Laboratory for Applied Marine part of the project and the TNO Laboratory for Applied Marine Research, responsible for the chemical part. The main object of the programme is to detect biological effects and to get insight into the extent of such effects in both spatial and temporal scales, and to support a scientifically based management of offshore mining activities. The following goals were formulated:To optimize methods and to select suitable techniques and parameters (chemical and biological) for the research-monitoring programme in the vicinity of operational and deserted drilling locations.To assess temporal and spatial trends of possible adverse effects of oil-based muds (OBM), considering:biological effects on macrobenthic infauna, in terms of diversity and abundance, andchemical effects in terms of elevated concentrations of oil components, barium and heavy metals in sediment sand in the waterphase (by use of Active Biological Monitoring (ABM). P. 329
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